Macrophage in Tumor Control

**3**

**Chapter 1**

**Abstract**

tumor growth and propagation.

**1. Introduction**

Role of Macrophages in Solid

*Sibi Raj, Vaishali Chandel, Sujata Maurya and Dhruv Kumar*

Cancer cells undergo several complex processes to grow and evolve. For their survival, they manipulate the entire system and acquire the ability to gain all the energy demands from the host system itself. Tumor associated macrophages (TAMs) are macrophages abundantly present in the tumor micro environment (TME) and essentially plays a critical role in coordination with the tumor cells helping them to progress and metastasize. One of the key hallmarks in tumor cells is elevated metabolic processes such as glycolysis, fatty acid oxidation, mitochondrial oxidation, and amino acid metabolism. Macrophages help cancer cells to achieve this metabolic demand through a series of signaling events including mTOR, Akt, and PI3K pathways. The M2-like phenotype of macrophages leads to the tumorous macrophage phenotype along with the tumor cells to support tumor growth through metabolic dysregulation. Focusing upon the area of macrophage-mediated tumor metabolism in solid tumors has been a new area that provides new effective targets to treat cancer. This chapter discusses the role of macrophages in tumor metabolism and cancer progression. Targeting TAMs in tumor microenvironment through metabolic axis could be a potential therapeutic option to control the solid

**Keywords:** macrophages, hypoxia, TME, PD-1, OXPHOS, tumor microenvironment

The slow pace development of solid tumors inside a human body involves a lot of complex process. It is not only the genetic mutations that play important role but also the so-called tumor microenvironment (TME), which is a silent player enhancing this process. TME has complex players such as the T-cells, dendritic cells, and macrophages in the solid tumor [1]. Among these, macrophages have three types of classification namely tumor-associated macrophages (TAMs), tissueresident macrophages, and myeloid-derived suppressor cells (MDSCs). The most abundant tumor infiltrating immune cells in the tumor microenvironment are TAMs. These TAMs are classified into two subtypes namely M1 or M2 macrophages. Macrophages have a role in defense as well as homeostasis of cells by acquiring the capacity of phagocytosis. TAMs have reportedly been associated with several functions such as tumor initiation, progression, and metastasis with secretion of supporting factors such as cytokines, growth factors, inflammatory substrates, and proteolytic enzymes. As macrophages are known to be associated with tumor progression, understanding different signaling complexes has been an important field. The major signaling molecules involved are cytokines, growth factors,

Tumor Metabolism

### **Chapter 1**

## Role of Macrophages in Solid Tumor Metabolism

*Sibi Raj, Vaishali Chandel, Sujata Maurya and Dhruv Kumar*

### **Abstract**

Cancer cells undergo several complex processes to grow and evolve. For their survival, they manipulate the entire system and acquire the ability to gain all the energy demands from the host system itself. Tumor associated macrophages (TAMs) are macrophages abundantly present in the tumor micro environment (TME) and essentially plays a critical role in coordination with the tumor cells helping them to progress and metastasize. One of the key hallmarks in tumor cells is elevated metabolic processes such as glycolysis, fatty acid oxidation, mitochondrial oxidation, and amino acid metabolism. Macrophages help cancer cells to achieve this metabolic demand through a series of signaling events including mTOR, Akt, and PI3K pathways. The M2-like phenotype of macrophages leads to the tumorous macrophage phenotype along with the tumor cells to support tumor growth through metabolic dysregulation. Focusing upon the area of macrophage-mediated tumor metabolism in solid tumors has been a new area that provides new effective targets to treat cancer. This chapter discusses the role of macrophages in tumor metabolism and cancer progression. Targeting TAMs in tumor microenvironment through metabolic axis could be a potential therapeutic option to control the solid tumor growth and propagation.

**Keywords:** macrophages, hypoxia, TME, PD-1, OXPHOS, tumor microenvironment

### **1. Introduction**

The slow pace development of solid tumors inside a human body involves a lot of complex process. It is not only the genetic mutations that play important role but also the so-called tumor microenvironment (TME), which is a silent player enhancing this process. TME has complex players such as the T-cells, dendritic cells, and macrophages in the solid tumor [1]. Among these, macrophages have three types of classification namely tumor-associated macrophages (TAMs), tissueresident macrophages, and myeloid-derived suppressor cells (MDSCs). The most abundant tumor infiltrating immune cells in the tumor microenvironment are TAMs. These TAMs are classified into two subtypes namely M1 or M2 macrophages. Macrophages have a role in defense as well as homeostasis of cells by acquiring the capacity of phagocytosis. TAMs have reportedly been associated with several functions such as tumor initiation, progression, and metastasis with secretion of supporting factors such as cytokines, growth factors, inflammatory substrates, and proteolytic enzymes. As macrophages are known to be associated with tumor progression, understanding different signaling complexes has been an important field. The major signaling molecules involved are cytokines, growth factors,

chemokines, and transforming growth factors beta, vascular endothelial growth factor, and platelet-derived growth factor. Several murine tumor models have reported TAMs as the major source for tumor-promoting factor like IL-6 [2]. The VEGF-A factor produced via TAMs specifically helps tumor cells with angiogenesis switch providing new blood vessels for tumor progression. TAMs have certain immunosuppressive functions apart from their strong inflammatory properties. Macrophages are poor producers of IL-12 but highly produce IL-10 and TGF-β with the help of STAT-3 activation [3]. The membrane-derived PDL-1 is activated on the surface of TAMs by IL-10 and TNF-A. Thus, PDL-1A has a prominent role in inhibiting the activated T-effector cells via the PD-1 receptor. TAMs are also widely reported to suppress therapeutic conditions such as chemotherapy, irradiation, and angiogenic inhibitors.

TAMs are associated with major metabolic changes associated with solid tumor progression. Macrophages can have a sudden change in their function while having a pathogen attack inside the host. The metabolic network inside a tumor cell has been a rich area of study as to decode the signaling molecules and find novel targets for the cure of cancer. Glycolysis is one such heavily activated pathway acquired by cancer cells to have sufficient energy and other key metabolites to progress and survive. TAMs highly elevate the process of glycolysis through HIF-1 stabilization and Akt/mTOR pathway [4]. Glycolysis in cancer cells also acts as intermediate for other cellular mechanisms such as the pentose phosphate pathway, TCA cycle, lipid metabolism, and amino acid metabolism. TAMs are also associated with increased OXPHOS despite having abrupt TCA cycle. Together with increased glycolytic flux and narrowed pathway of TCA cycle, OXPHOS promotes the accumulation of succinate and citrate in LPS/IFN-Ƴ-activated macrophages. This accumulation of succinate leads to a major change in track of pathways by activating the HIF1-alpha subunit factor, which is otherwise in normal conditions inactivated by prolyl hydrolase enzymatic activity. This enhances production of pyruvate through glycolysis, which leads the macrophages to activate inflammatory cytokine production and the abrupt TCA cycle enhances the anti-microbial activity. Other metabolic functions such as the lipid metabolism are actively supported by the macrophages. These macrophages act as a source for synthesizing lipid mediators and fulfill the energy requirements in solid tumors. Macrophages utilize glycerides in lipoproteins as their major source of free fatty acids. This process is indicated by the increased production of lipoprotein lipase (LPL) in activated macrophages. M2-like macrophages have shown to have elevated consumption of amino acids in the form of glutamine as well as fatty acids [5]. An important mechanism of tumor suppression by macrophages through immunosuppressive phenotype helps solid tumors to evolve and grow. This mode of suppressed immunosurveillance in TAMs is mostly led by non-saturated fatty acid metabolism in macrophages. Mitochondrial respiration takes place with the help of lipid droplets, which regulates the catabolic process of free fatty acids (FFAs). mTOR signaling pathway has been reported to play an important role in suppressed immunosurveillance of TAMs. The mTORC1 responsibly is involved in the regulation of de novo lipid synthesis with the help of sterolresponsive element binding protein transcription factors.

Cancer cells and tumor microenvironment has a co-existing phenomenon which supports their growth and metastasis. As macrophages are one of the major immune cells actively present in the tumor microenvironment, the complex signaling procedure involved between the two is of utmost interest. CSF1 is one such major kind of cytokines that comes into play between TAMs and cancer cells to induce an immunosuppressive function to support tumor growth. The CSF-1 induction recruits the monocyte-derived macrophages toward the tumor surface and polarizes it to a M2-like phenotype, which is coupled to fatty acid oxidation [6]. This leads to the

**5**

treat certain types of cancer.

**2. Macrophages**

*Role of Macrophages in Solid Tumor Metabolism DOI: http://dx.doi.org/10.5772/intechopen.93182*

secretion of variety of immunosuppressive factors such as epidermal growth factor (EGF). Interestingly, the metabolic influence of TAMs on solid tumors is not unidirectional. Under hypoxia or increased lactate levels, TAMs secrete various cytokines associated with metabolic systems such as IL6, TNF, C-C motif chemokine ligand 5 (CCL5), and CCL18 [7]. These chemokines in particular promote metabolic processes like glycolysis as well as key glycolytic enzymes such as hexokinase-II, lactate dehydrogenase A (LDH-A), glucose-6-phosphate dehydrogenase etc. One of the major factors involved in cancer cells is anaerobic glycolysis or the famous Warburg effect. Hypoxia-inducible factor-1A (HIF-1A) is one of the key factors that activates aerobic glycolysis and thus stabilizes the long noncoding RNA from lactate-exposed TAMs to cancer cells. The main players in the immune system against tumors like the helper CD 4+ T-cells, cytotoxic CD 8+ T-cells, and natural killer (NK) cells on activation rely on elevated glycolytic metabolism, which in turn supports the tumor cells for their energy demands. On a similar note, Treg cells rely majorly on oxidative phosphorylation for bioenergetic demands. Interestingly this glucose dependency of both tumor and immune cells mediates the TAMs to limit the glycolytic flux in effector cells. This is mainly done through the expression of CD274, which is also known as PDL-1 and is an immunosuppressive molecule. Moreover, PDL-1 is upregulated in cellular types like TAMs, endothelial cells, and tumor cells due to the release of interferon gamma from effector cells [8]. This interaction delineates the immune effector functions and thus balances the metabolic competition majorly toward tumor progression. Considering the growing knowledge on TAMs and its interaction toward solid tumors have given a green signal toward immune-based therapies to treat cancer. Majorly focusing on the delineation of M2-like macrophages or their depolarization toward M1-like phenotype TAMs. The inhibitor against CSF1R also holds a strong promise toward the treatment of such diseases. Strategies to shift the balance from M2- to M1-like phenotype macrophages are also being done using inhibitors against VEGF-A. Interestingly, considering the factor of co-interaction of TAMs with cancer cell and modulating their metabolism provide a great area to identify potential targets against these diseases. In line with this notion, inhibitors against MTORC1 surprisingly favor tumor progression as glycolysis gets inhibited in hypoxia-coupled TAMs, which ultimately favors tumor growth. The food and drug administration has approved drugs against PDL-1, which is an immune checkpoint blocker, which in turn simulates the immune system against cancer cells. In this reference, several metabolism-related antibodies can be functioned along with immune stimulators to

A sheer claim lead by Elie Metchnikoff stated that in "cellular (phagocytic) theory of immunity" the portion of white corpuscle holds an important significance in the elements of the immune system as well as protect the individuals from the invasion of pathogenic organisms [9]. Furthermore, macrophages show key role in immune responses and immunity, also the defensive role assigned to them is perfect depiction to execute the phagocytosis of pathogen aggregation. These are also held responsible for regulating lymphocyte activation as well as proliferation. With the help of antigens and allogenic cells, macrophages play an important role in the activation process of T- and B-lymphocytes [10]. Apart from these, macrophages also grant defense mechanism against the tumor cells, but studies conducted in the past several years describe the mechanism of tumor cell killed by macrophages [11]. Tumor-associated macrophages (TAMs) initiate and progress human cancers and angiogenesis and are important part of the tumor

### *Role of Macrophages in Solid Tumor Metabolism DOI: http://dx.doi.org/10.5772/intechopen.93182*

*Macrophages*

angiogenic inhibitors.

chemokines, and transforming growth factors beta, vascular endothelial growth factor, and platelet-derived growth factor. Several murine tumor models have reported TAMs as the major source for tumor-promoting factor like IL-6 [2]. The VEGF-A factor produced via TAMs specifically helps tumor cells with angiogenesis switch providing new blood vessels for tumor progression. TAMs have certain immunosuppressive functions apart from their strong inflammatory properties. Macrophages are poor producers of IL-12 but highly produce IL-10 and TGF-β with the help of STAT-3 activation [3]. The membrane-derived PDL-1 is activated on the surface of TAMs by IL-10 and TNF-A. Thus, PDL-1A has a prominent role in inhibiting the activated T-effector cells via the PD-1 receptor. TAMs are also widely reported to suppress therapeutic conditions such as chemotherapy, irradiation, and

TAMs are associated with major metabolic changes associated with solid tumor progression. Macrophages can have a sudden change in their function while having a pathogen attack inside the host. The metabolic network inside a tumor cell has been a rich area of study as to decode the signaling molecules and find novel targets for the cure of cancer. Glycolysis is one such heavily activated pathway acquired by cancer cells to have sufficient energy and other key metabolites to progress and survive. TAMs highly elevate the process of glycolysis through HIF-1 stabilization and Akt/mTOR pathway [4]. Glycolysis in cancer cells also acts as intermediate for other cellular mechanisms such as the pentose phosphate pathway, TCA cycle, lipid metabolism, and amino acid metabolism. TAMs are also associated with increased OXPHOS despite having abrupt TCA cycle. Together with increased glycolytic flux and narrowed pathway of TCA cycle, OXPHOS promotes the accumulation of succinate and citrate in LPS/IFN-Ƴ-activated macrophages. This accumulation of succinate leads to a major change in track of pathways by activating the HIF1-alpha subunit factor, which is otherwise in normal conditions inactivated by prolyl hydrolase enzymatic activity. This enhances production of pyruvate through glycolysis, which leads the macrophages to activate inflammatory cytokine production and the abrupt TCA cycle enhances the anti-microbial activity. Other metabolic functions such as the lipid metabolism are actively supported by the macrophages. These macrophages act as a source for synthesizing lipid mediators and fulfill the energy requirements in solid tumors. Macrophages utilize glycerides in lipoproteins as their major source of free fatty acids. This process is indicated by the increased production of lipoprotein lipase (LPL) in activated macrophages. M2-like macrophages have shown to have elevated consumption of amino acids in the form of glutamine as well as fatty acids [5]. An important mechanism of tumor suppression by macrophages through immunosuppressive phenotype helps solid tumors to evolve and grow. This mode of suppressed immunosurveillance in TAMs is mostly led by non-saturated fatty acid metabolism in macrophages. Mitochondrial respiration takes place with the help of lipid droplets, which regulates the catabolic process of free fatty acids (FFAs). mTOR signaling pathway has been reported to play an important role in suppressed immunosurveillance of TAMs. The mTORC1 responsibly is involved in the regulation of de novo lipid synthesis with the help of sterol-

responsive element binding protein transcription factors.

Cancer cells and tumor microenvironment has a co-existing phenomenon which supports their growth and metastasis. As macrophages are one of the major immune cells actively present in the tumor microenvironment, the complex signaling procedure involved between the two is of utmost interest. CSF1 is one such major kind of cytokines that comes into play between TAMs and cancer cells to induce an immunosuppressive function to support tumor growth. The CSF-1 induction recruits the monocyte-derived macrophages toward the tumor surface and polarizes it to a M2-like phenotype, which is coupled to fatty acid oxidation [6]. This leads to the

**4**

secretion of variety of immunosuppressive factors such as epidermal growth factor (EGF). Interestingly, the metabolic influence of TAMs on solid tumors is not unidirectional. Under hypoxia or increased lactate levels, TAMs secrete various cytokines associated with metabolic systems such as IL6, TNF, C-C motif chemokine ligand 5 (CCL5), and CCL18 [7]. These chemokines in particular promote metabolic processes like glycolysis as well as key glycolytic enzymes such as hexokinase-II, lactate dehydrogenase A (LDH-A), glucose-6-phosphate dehydrogenase etc. One of the major factors involved in cancer cells is anaerobic glycolysis or the famous Warburg effect. Hypoxia-inducible factor-1A (HIF-1A) is one of the key factors that activates aerobic glycolysis and thus stabilizes the long noncoding RNA from lactate-exposed TAMs to cancer cells. The main players in the immune system against tumors like the helper CD 4+ T-cells, cytotoxic CD 8+ T-cells, and natural killer (NK) cells on activation rely on elevated glycolytic metabolism, which in turn supports the tumor cells for their energy demands. On a similar note, Treg cells rely majorly on oxidative phosphorylation for bioenergetic demands. Interestingly this glucose dependency of both tumor and immune cells mediates the TAMs to limit the glycolytic flux in effector cells. This is mainly done through the expression of CD274, which is also known as PDL-1 and is an immunosuppressive molecule. Moreover, PDL-1 is upregulated in cellular types like TAMs, endothelial cells, and tumor cells due to the release of interferon gamma from effector cells [8]. This interaction delineates the immune effector functions and thus balances the metabolic competition majorly toward tumor progression.

Considering the growing knowledge on TAMs and its interaction toward solid tumors have given a green signal toward immune-based therapies to treat cancer. Majorly focusing on the delineation of M2-like macrophages or their depolarization toward M1-like phenotype TAMs. The inhibitor against CSF1R also holds a strong promise toward the treatment of such diseases. Strategies to shift the balance from M2- to M1-like phenotype macrophages are also being done using inhibitors against VEGF-A. Interestingly, considering the factor of co-interaction of TAMs with cancer cell and modulating their metabolism provide a great area to identify potential targets against these diseases. In line with this notion, inhibitors against MTORC1 surprisingly favor tumor progression as glycolysis gets inhibited in hypoxia-coupled TAMs, which ultimately favors tumor growth. The food and drug administration has approved drugs against PDL-1, which is an immune checkpoint blocker, which in turn simulates the immune system against cancer cells. In this reference, several metabolism-related antibodies can be functioned along with immune stimulators to treat certain types of cancer.

### **2. Macrophages**

A sheer claim lead by Elie Metchnikoff stated that in "cellular (phagocytic) theory of immunity" the portion of white corpuscle holds an important significance in the elements of the immune system as well as protect the individuals from the invasion of pathogenic organisms [9]. Furthermore, macrophages show key role in immune responses and immunity, also the defensive role assigned to them is perfect depiction to execute the phagocytosis of pathogen aggregation. These are also held responsible for regulating lymphocyte activation as well as proliferation. With the help of antigens and allogenic cells, macrophages play an important role in the activation process of T- and B-lymphocytes [10]. Apart from these, macrophages also grant defense mechanism against the tumor cells, but studies conducted in the past several years describe the mechanism of tumor cell killed by macrophages [11]. Tumor-associated macrophages (TAMs) initiate and progress human cancers and angiogenesis and are important part of the tumor

microenvironment. Targeting TAMs for therapeutic strategy to cure cancer is still in doubt [12]. Tumor metastasis is the parent cause of the deaths of cancer patients, adding to statement the intrinsic alterations in the tumor cells, but also implicated the cross-talk between cancer cells along with their altered components of microenvironment [12]. Tumor microenvironments (TME) are produced by TAMs, which further initiate the immune checkpoint and produce cytokines, chemokines, growth factors that are produced in T-cells. By doing this, TAMs have the most important functions in facilitating a metastatic cascade of the cancerous cells. At the same time, these trigger couple of more targets and few checkpoint blockade immunotherapies in order to oppose the tumor progression [13].

The term macrophages is generally defined as large bodies or cells that are instituted in the tissues that are present in the stationary forms. These are also regarded as the exceedingly multifaceted or the most versatile cells whose functions are based on their basic area of occupancy. Apart from this confinement, their pathophysiologic as well as physiologic contexts are considered to be very efficient in various studies [14]. Holding this significance in favor of host defense, also in primitive organisms, these tend to not only function as the recognition of the threats but at the same time engulf along with destroying the threats and in the higher organisms, such as humans. Macrophages have important roles in both immune responses whether adaptive or innate to the pathogens and also tend to serve as the mediators of inflammatory processes [15]. Macrophages are liberated as immature monocytes deriving from the bone marrow and further circulate in the blood stream in order to finally migrate into the tissues and also undergo the final differentiation into the resident macrophages that include kupffer cells in the liver, alveolar macrophages in the lung, and osteoclasts in the bone. It is a welldocumented fact that macrophages have immunological and repair functions and are the first ones to arrive at the sites of wounding or infection where they carry out several functions that are assigned to them [16]. For promoting tissue repair, macrophages release proteases, growth factors, and angiogenic factors and for killing pathogens they release reactive oxygen and nitrogen radicals. They also release some chemokines or cytokines to arrange the action and recruitment of other immune cells and present the foreign antigens to cytotoxic T-cells [17]. Usually they are not lethal to cancer cells until they are triggered, for example, interferon gamma (IFN-γ) or lipopolysaccharide (LPS), but once they are triggered, the toxicity of cell is directly exerted toward tumor cells or indirectly via the secretion of factors that promote the anti-tumor functions of other cell types; thus, macrophages have pro- and anti-inflammatory properties, which depend on the signals they receive and the stage of disease they possess, that is the inflammatory balance in the microenvironment. Macrophages have multiple phenotypic expressions, which include removal of debris and tissue remodeling, antigen presentation, regulation of inflammation, target cell cytotoxicity, induction of immunity, thrombosis, and various forms of endocytosis [8].

Well promotion comes that of the tumor-associated macrophages (TAMs), which cover multiple strands of neoplastic tissues that counts in the angiogenesis as well as the vascularization, stroma formation accompanied by dissolution, and modulation that supports tumor cell growth which are a part of important enhancement and inhibition. On being activated TAMs are activated, and further gives rise to neoplastic cell death covering cytotoxicity and apoptosis, or even evokes tumor-destructive reactions led by the alteration of the tumor microvasculature. The primary lesions and metastases are known to group of solid tumors that are contented with the large numbers of tumor well associated of leukocytes. Famous as being the heterogeneous ones in the nature and consisting various as well as variable subsets of t-cells which are mainly the helpers, suppressor and cytotoxic,

**7**

*Role of Macrophages in Solid Tumor Metabolism DOI: http://dx.doi.org/10.5772/intechopen.93182*

**3. Role of macrophage in tumor progression**

As it is becoming clear now, the inflammatory cells survive in the tumor microenvironment and show crucial role in the development of cancer. The best example is TAMs that are important components of the mononuclear leukocyte population of solid tumors and show an indecisive association with tumors. TAMs exhibit several tumorigenesis-promoting functions, which have significant roles in the growth and progression of cancer such as these tend to qualify in providing the cytokines and also when it comes to induce tumor angiogenesis [22]. TAMs produce many types of protein digestive enzymes, growth factors, inflammatory mediators, and cytokines in tumor microenvironment that are the main factors in the metastasis of cancer cells. Not only this, TAMs' function and movement are also regulated in tumor microenvironment by cytokines and hypoxia. Some studies suggest that TAMs come in contact with cancer cells, they alter ECM and promote invasion and metastasis of cancer cell and several studies show the release of natural products by TAMs to inhibit the formation of pro-inflammatory cytokines and growth factors and also correlation with cancer metastasis and poor prognosis in various types of cancers that happen in humans [23]. The tumor in various murine models shows IL-6 (tumor-promoting) as the main source of TAMs, and also that the tumor-related myeloid cell production of IL-6 promotes proliferation in colon cells along with the apoptosis prevention through STAT3 activation. There is a Doppler effect observed in pancreatic cancer, IL-6 derived from myeloid cell initiate tumor

b-cells, these are considered to be the natural killer (nk) cells, and hence are termed macrophages. Significance of these macrophages lies in them making up to 80% of the cell mass in breast cancer patients [18]. Due to being heterogeneous in nature, macrophages possess wide range of phenotypes like M1 and M2 based on their environment stimulation. M1 phenotype is related with active microbe killing and M2 phenotype is related with tissue remodeling and angiogenesis. When these monocytes come in contact with tumor-derived anti-inflammatory molecules (i.e., IL-4, IL-10, prostaglandin E2, and transforming growth factor 1), in tumor cells they mature into M2 or polarized macrophages and produce factors that suppress T-cell proliferation and activity, possess poor antigen presenting ability, adapt scavenging for debris, repairing and remodeling of damaged and wound tissues, and promote angiogenesis [19]. In contrast to this, type I or M1 macrophages are immune effector cells that kill microorganisms and tumor cells. They present antigens and produce high levels of immune stimulatory cytokines. The M2 phenotype appears to be that which dominates in tumors, as TAMs show a similar molecular and functional profile that is characterized by low expression of differentiation-associated macrophage antigens such as carboxypeptidase M and CD51, high constitutive expression of interleukin IL-1 and IL-6, and low levels of tumor necrosis factor [20]. Tumor cells, endothelial cells, fibroblasts, and macrophages in human tumors expressed monocyte chemotactic protein (MCP). MCP and chemokines are TAMs derived from monocytes and are recruited largely by CCL2 (chemokine (C–C motif) ligand 2). MCP-1 highly is expressed in a wide range of tumor types such as meningioma, ovarian carcinoma, glioma, and squamous cell carcinoma of uterine cervix and may be the main determinant of the macrophages as suggested by some studies. Other major chemoattractants like vascular endothelial growth factor (VEGF), CCL3, CCL4, CCL5, CCL8, macrophage-colony stimulating factor (M-CSF or CSF-1), macrophage migration inhibition factor (MIF), and macrophage inflammatory protein-1 alpha(MIP-1) are involved in monocyte uptake into tumors and their levels in tumor mass often correlate positively with TAM numbers in human tumors [21].

### *Role of Macrophages in Solid Tumor Metabolism DOI: http://dx.doi.org/10.5772/intechopen.93182*

*Macrophages*

microenvironment. Targeting TAMs for therapeutic strategy to cure cancer is still in doubt [12]. Tumor metastasis is the parent cause of the deaths of cancer patients, adding to statement the intrinsic alterations in the tumor cells, but also implicated the cross-talk between cancer cells along with their altered components of microenvironment [12]. Tumor microenvironments (TME) are produced by TAMs, which further initiate the immune checkpoint and produce cytokines, chemokines, growth factors that are produced in T-cells. By doing this, TAMs have the most important functions in facilitating a metastatic cascade of the cancerous cells. At the same time, these trigger couple of more targets and few checkpoint blockade

The term macrophages is generally defined as large bodies or cells that are instituted in the tissues that are present in the stationary forms. These are also regarded as the exceedingly multifaceted or the most versatile cells whose functions are based on their basic area of occupancy. Apart from this confinement, their pathophysiologic as well as physiologic contexts are considered to be very efficient in various studies [14]. Holding this significance in favor of host defense, also in primitive organisms, these tend to not only function as the recognition of the threats but at the same time engulf along with destroying the threats and in the higher organisms, such as humans. Macrophages have important roles in both immune responses whether adaptive or innate to the pathogens and also tend to serve as the mediators of inflammatory processes [15]. Macrophages are liberated as immature monocytes deriving from the bone marrow and further circulate in the blood stream in order to finally migrate into the tissues and also undergo the final differentiation into the resident macrophages that include kupffer cells in the liver, alveolar macrophages in the lung, and osteoclasts in the bone. It is a welldocumented fact that macrophages have immunological and repair functions and are the first ones to arrive at the sites of wounding or infection where they carry out several functions that are assigned to them [16]. For promoting tissue repair, macrophages release proteases, growth factors, and angiogenic factors and for killing pathogens they release reactive oxygen and nitrogen radicals. They also release some chemokines or cytokines to arrange the action and recruitment of other immune cells and present the foreign antigens to cytotoxic T-cells [17]. Usually they are not lethal to cancer cells until they are triggered, for example, interferon gamma (IFN-γ) or lipopolysaccharide (LPS), but once they are triggered, the toxicity of cell is directly exerted toward tumor cells or indirectly via the secretion of factors that promote the anti-tumor functions of other cell types; thus, macrophages have pro- and anti-inflammatory properties, which depend on the signals they receive and the stage of disease they possess, that is the inflammatory balance in the microenvironment. Macrophages have multiple phenotypic expressions, which include removal of debris and tissue remodeling, antigen presentation, regulation of inflammation, target cell cytotoxicity, induction of immunity,

immunotherapies in order to oppose the tumor progression [13].

thrombosis, and various forms of endocytosis [8].

Well promotion comes that of the tumor-associated macrophages (TAMs), which cover multiple strands of neoplastic tissues that counts in the angiogenesis as well as the vascularization, stroma formation accompanied by dissolution, and modulation that supports tumor cell growth which are a part of important enhancement and inhibition. On being activated TAMs are activated, and further gives rise to neoplastic cell death covering cytotoxicity and apoptosis, or even evokes tumor-destructive reactions led by the alteration of the tumor microvasculature. The primary lesions and metastases are known to group of solid tumors that are contented with the large numbers of tumor well associated of leukocytes. Famous as being the heterogeneous ones in the nature and consisting various as well as variable subsets of t-cells which are mainly the helpers, suppressor and cytotoxic,

**6**

b-cells, these are considered to be the natural killer (nk) cells, and hence are termed macrophages. Significance of these macrophages lies in them making up to 80% of the cell mass in breast cancer patients [18]. Due to being heterogeneous in nature, macrophages possess wide range of phenotypes like M1 and M2 based on their environment stimulation. M1 phenotype is related with active microbe killing and M2 phenotype is related with tissue remodeling and angiogenesis. When these monocytes come in contact with tumor-derived anti-inflammatory molecules (i.e., IL-4, IL-10, prostaglandin E2, and transforming growth factor 1), in tumor cells they mature into M2 or polarized macrophages and produce factors that suppress T-cell proliferation and activity, possess poor antigen presenting ability, adapt scavenging for debris, repairing and remodeling of damaged and wound tissues, and promote angiogenesis [19]. In contrast to this, type I or M1 macrophages are immune effector cells that kill microorganisms and tumor cells. They present antigens and produce high levels of immune stimulatory cytokines. The M2 phenotype appears to be that which dominates in tumors, as TAMs show a similar molecular and functional profile that is characterized by low expression of differentiation-associated macrophage antigens such as carboxypeptidase M and CD51, high constitutive expression of interleukin IL-1 and IL-6, and low levels of tumor necrosis factor [20]. Tumor cells, endothelial cells, fibroblasts, and macrophages in human tumors expressed monocyte chemotactic protein (MCP). MCP and chemokines are TAMs derived from monocytes and are recruited largely by CCL2 (chemokine (C–C motif) ligand 2). MCP-1 highly is expressed in a wide range of tumor types such as meningioma, ovarian carcinoma, glioma, and squamous cell carcinoma of uterine cervix and may be the main determinant of the macrophages as suggested by some studies. Other major chemoattractants like vascular endothelial growth factor (VEGF), CCL3, CCL4, CCL5, CCL8, macrophage-colony stimulating factor (M-CSF or CSF-1), macrophage migration inhibition factor (MIF), and macrophage inflammatory protein-1 alpha(MIP-1) are involved in monocyte uptake into tumors and their levels in tumor mass often correlate positively with TAM numbers in human tumors [21].

### **3. Role of macrophage in tumor progression**

As it is becoming clear now, the inflammatory cells survive in the tumor microenvironment and show crucial role in the development of cancer. The best example is TAMs that are important components of the mononuclear leukocyte population of solid tumors and show an indecisive association with tumors. TAMs exhibit several tumorigenesis-promoting functions, which have significant roles in the growth and progression of cancer such as these tend to qualify in providing the cytokines and also when it comes to induce tumor angiogenesis [22]. TAMs produce many types of protein digestive enzymes, growth factors, inflammatory mediators, and cytokines in tumor microenvironment that are the main factors in the metastasis of cancer cells. Not only this, TAMs' function and movement are also regulated in tumor microenvironment by cytokines and hypoxia. Some studies suggest that TAMs come in contact with cancer cells, they alter ECM and promote invasion and metastasis of cancer cell and several studies show the release of natural products by TAMs to inhibit the formation of pro-inflammatory cytokines and growth factors and also correlation with cancer metastasis and poor prognosis in various types of cancers that happen in humans [23]. The tumor in various murine models shows IL-6 (tumor-promoting) as the main source of TAMs, and also that the tumor-related myeloid cell production of IL-6 promotes proliferation in colon cells along with the apoptosis prevention through STAT3 activation. There is a Doppler effect observed in pancreatic cancer, IL-6 derived from myeloid cell initiate tumor

development possess from epithelial precursor lesions through STAT3 [16]. In a specific genetic model of colorectal cancer, initiation of tumor starts with the loss of the adenomatous polyposis coli tumor suppressor gene, which results in the activation of β-catenin and further causes the barrier disruption of the epithelium. It allows the products of microbes to penetrate and moreover causes IL-23 macrophage production. In CD4+ T-cells, IL-23 drives Th17 response through IL-6 and IL-17, which initiate colorectal cancer [24].

The proportion of blood capillaries present in the non-infectious tissues mainly rests in an inactivated state in which angiogenesis transiently gets started in the perfect response in favor of certain stimuli. On the contrary, at the time of tumor initiation, an "angiogenic switch" is almost always initiated as well as turned on, which leads to vascularization of new capillaries from the inactivated state. On comparing the normal vascular network, the network of blood capillaries that are present in the tumors are basically identified by the complex and excessive branching of the blood vessels, which are contorted and also become large vessels, show irregular blood flow, microhemorrhage, and leakiness [25]. Macrophages are very particular to switch this angiogenic, that in the case of tumors mainly goes through production of vascular-endothelial growth factor A (VEGF-A) along with placental growth factor (PlGF). Talking of the specificity the blood vessels present in the tumors lacking myeloid cell-derived VEGF-A were less tortuous then having more pericyte coverage as well as the less vessel length. Above mentioned characteristics are consider successfully that show normal blood vessels. These are further counted upon modifying the bioavailability of VEGF-A in the tumors by matrix metalloproteinases processing. Adding to this fact, antibody-mediated neutralization of angiopoietin 2, the ligand for the Tie2 receptor, or macrophage depletion blocks tumor angiogenesis as well as limits tumor progression in a mouse model of breast cancer [26]. Several studies conducted on the patients having cancer in liver cells showed that the marginal macrophage density is different from the macrophage density present inside the tumor of the liver although they are directly associated along with the vascular invasion, tumor multiplicity, and also fibrous capsule formation. Furthermore, there was an important relationship observed between the density of TAMs as well as in the poor prognosis in those patients. According to Hansen et al., CD64+ macrophages (TAMs) are present in high numbers in tumor biopsies before treatment and thus show a negative relation along with clinical outcomes in the patients with the metastatic melanoma who undergo IL-2 based immunotherapy [27].

### **4. Tumor microenvironment**

Tumor microenvironment (TME) changes continuously during the tumor development in parallel with the tumor growth. These changes on the one hand influence the immune cells' function and the complex relationship between tumor cells and these cells, and on the other hand influence its cellular content through the release of several factors, which leads to the accumulation of specific types of immune cells into the TME. Hypoxia and limitation of blood-borne nutrients are a characteristic feature of TME, while being enriched in reactive nitrogen species (RNS), protons, and other by-products released from the activated tumor cell metabolism [28, 29]. It is therefore important for the tumor cells to acclimatize their metabolism in order to survive in oxygen- and nutrients-deprived TME, and to respond to their increased demands of energy depending on their enhanced proliferation rate. The metabolic changes have been described over a century ago as "Warburg phenomenon" or "aerobic glycolysis," where tumor cells exploit glycolysis in order to provide energy regardless of the

**9**

**Figure 1.**

*Role of Macrophages in Solid Tumor Metabolism DOI: http://dx.doi.org/10.5772/intechopen.93182*

and pro-tumorigenic properties [33].

**5. Metabolic reprogramming of TAMs**

**5.1 Glucose metabolism in macrophages**

availability of oxygen [30]. Under hypoxic conditions, the cellular metabolism migrates toward anaerobic glycolysis to generate energy, rather than oxidative phosphorylation (OXPHOS), which plays a major role in terms of adenosine triphosphate (ATP) production [31]. As a consequence of the increased rate of glycolysis, the pyruvate is significantly reduced to lactate. This causes upregulated lactate levels that are released in TME by monocarboxylate transporters (MCTs) and that results in reduction in the pH levels and local acidification, while pH within the tumor remains normal [32]. In TME, this significant reduction in the pH levels causes cytotoxic environment for cells, including immune cells such as macrophages that are activated and recruited to restrict the progression of tumor and eliminate the tumor. This provides survival benefit to the cancer cells [29]. Additionally, the toxic waste, for example, lactic acid has been shown to frame and shape the functional phenotype of recruited macrophages toward more tolerogenic phenotypes and conferring them with proangiogenic

TAMs are involved in multiple processes, which result in the promotion and progression of primary tumor facilitating metastasis. The compartment of TAM via an extensive remodeling of energy metabolism evolves over time (i.e., during treatment response and tumor progression) as well as in space (at various tumor sites) [34]. The variations in TAMs in response to the nutritional needs of solid tumor are very dynamic and TME perturbations have a major influence not only on

TAMs majorly support the progression of tumor by (i) indirectly enhancing the nutrients' availability in the TME, (ii) providing signals to tumor cells, and (iii) mediating immunosuppressive functions. "Neoangiogenesis" is the major

*TAM compartment is highly polarized toward M1-like state. Tumor progression depletes TME for the availability of glucose since it produces significant amount of lactate and polarization toward M2-like state. M2-like TAMs show restricted activity of phagocytes, chemokine, and cytokine secretion that facilitates the neoangiogenesis process, deprive TME of amino acids such as glutamine for T-cell function supporting remodulation of ECM. This metabolic alteration results in tumor growth and progression. (TAM: Tumor-*

*associated macrophages; TME: Tumor microenvironment; ECM: Extracellular matrix).*

the survival of TAM but also on tumor progression [35] (**Figure 1**).

*Role of Macrophages in Solid Tumor Metabolism DOI: http://dx.doi.org/10.5772/intechopen.93182*

*Macrophages*

IL-17, which initiate colorectal cancer [24].

development possess from epithelial precursor lesions through STAT3 [16]. In a specific genetic model of colorectal cancer, initiation of tumor starts with the loss of the adenomatous polyposis coli tumor suppressor gene, which results in the activation of β-catenin and further causes the barrier disruption of the epithelium. It allows the products of microbes to penetrate and moreover causes IL-23 macrophage production. In CD4+ T-cells, IL-23 drives Th17 response through IL-6 and

The proportion of blood capillaries present in the non-infectious tissues mainly rests in an inactivated state in which angiogenesis transiently gets started in the perfect response in favor of certain stimuli. On the contrary, at the time of tumor initiation, an "angiogenic switch" is almost always initiated as well as turned on, which leads to vascularization of new capillaries from the inactivated state. On comparing the normal vascular network, the network of blood capillaries that are present in the tumors are basically identified by the complex and excessive branching of the blood vessels, which are contorted and also become large vessels, show irregular blood flow, microhemorrhage, and leakiness [25]. Macrophages are very particular to switch this angiogenic, that in the case of tumors mainly goes through production of vascular-endothelial growth factor A (VEGF-A) along with placental growth factor (PlGF). Talking of the specificity the blood vessels present in the tumors lacking myeloid cell-derived VEGF-A were less tortuous then having more pericyte coverage as well as the less vessel length. Above mentioned characteristics are consider successfully that show normal blood vessels. These are further counted upon

modifying the bioavailability of VEGF-A in the tumors by matrix metalloproteinases processing. Adding to this fact, antibody-mediated neutralization of angiopoietin 2, the ligand for the Tie2 receptor, or macrophage depletion blocks tumor angiogenesis as well as limits tumor progression in a mouse model of breast cancer [26]. Several studies conducted on the patients having cancer in liver cells showed that the marginal macrophage density is different from the macrophage density present inside the tumor of the liver although they are directly associated along with the vascular invasion, tumor multiplicity, and also fibrous capsule formation. Furthermore, there was an important relationship observed between the density of TAMs as well as in the poor prognosis in those patients. According to Hansen et al., CD64+ macrophages (TAMs) are present in high numbers in tumor biopsies before treatment and thus show a negative relation along with clinical outcomes in the patients with the

Tumor microenvironment (TME) changes continuously during the tumor development in parallel with the tumor growth. These changes on the one hand influence the immune cells' function and the complex relationship between tumor cells and these cells, and on the other hand influence its cellular content through the release of several factors, which leads to the accumulation of specific types of immune cells into the TME. Hypoxia and limitation of blood-borne nutrients are a characteristic feature of TME, while being enriched in reactive nitrogen species (RNS), protons, and other by-products released from the activated tumor cell metabolism [28, 29]. It is therefore important for the tumor cells to acclimatize their metabolism in order to survive in oxygen- and nutrients-deprived TME, and to respond to their increased demands of energy depending on their enhanced proliferation rate. The metabolic changes have been described over a century ago as "Warburg phenomenon" or "aerobic glycolysis," where tumor cells exploit glycolysis in order to provide energy regardless of the

metastatic melanoma who undergo IL-2 based immunotherapy [27].

**4. Tumor microenvironment**

**8**

availability of oxygen [30]. Under hypoxic conditions, the cellular metabolism migrates toward anaerobic glycolysis to generate energy, rather than oxidative phosphorylation (OXPHOS), which plays a major role in terms of adenosine triphosphate (ATP) production [31]. As a consequence of the increased rate of glycolysis, the pyruvate is significantly reduced to lactate. This causes upregulated lactate levels that are released in TME by monocarboxylate transporters (MCTs) and that results in reduction in the pH levels and local acidification, while pH within the tumor remains normal [32]. In TME, this significant reduction in the pH levels causes cytotoxic environment for cells, including immune cells such as macrophages that are activated and recruited to restrict the progression of tumor and eliminate the tumor. This provides survival benefit to the cancer cells [29]. Additionally, the toxic waste, for example, lactic acid has been shown to frame and shape the functional phenotype of recruited macrophages toward more tolerogenic phenotypes and conferring them with proangiogenic and pro-tumorigenic properties [33].

### **5. Metabolic reprogramming of TAMs**

TAMs are involved in multiple processes, which result in the promotion and progression of primary tumor facilitating metastasis. The compartment of TAM via an extensive remodeling of energy metabolism evolves over time (i.e., during treatment response and tumor progression) as well as in space (at various tumor sites) [34]. The variations in TAMs in response to the nutritional needs of solid tumor are very dynamic and TME perturbations have a major influence not only on the survival of TAM but also on tumor progression [35] (**Figure 1**).

### **5.1 Glucose metabolism in macrophages**

TAMs majorly support the progression of tumor by (i) indirectly enhancing the nutrients' availability in the TME, (ii) providing signals to tumor cells, and (iii) mediating immunosuppressive functions. "Neoangiogenesis" is the major

#### **Figure 1.**

*TAM compartment is highly polarized toward M1-like state. Tumor progression depletes TME for the availability of glucose since it produces significant amount of lactate and polarization toward M2-like state. M2-like TAMs show restricted activity of phagocytes, chemokine, and cytokine secretion that facilitates the neoangiogenesis process, deprive TME of amino acids such as glutamine for T-cell function supporting remodulation of ECM. This metabolic alteration results in tumor growth and progression. (TAM: Tumorassociated macrophages; TME: Tumor microenvironment; ECM: Extracellular matrix).*

mechanism of nutritional support to the solid tumor cells by products derived from TAM such as adrenomedullin (AMD), C-X-C motif chemokine ligand 8 (CXCL8), vascular endothelial growth factor A (VEGFA), and CXCL12 [36, 37]. Although the vasculature of tumor is functionally and phenotypically impaired, neoangiogenesis plays a crucial role for the growth of neoplasms in this scenario [38]. TME has been shown to exhibit some degree of hypoxia, which facilitates TAMs' tumor-supporting functions majorly via two mechanisms: First, hypoxic condition supports the upregulation of lipocalin 2 (LCN2), and upregulation of solute carrier family 40 member 1 (SLC40A1 or FPN). This causes the acquisition of an iron donor phenotype by TAMs, therefore enhanced availability of iron in the TME, and thus improved iron uptake by malignant cells and significant proliferation [39]. Wenes et al. investigated the character of metabolically activated hypoxic macrophage in metastasis and the blood vessel morphogenesis. It was observed that hypoxia causes TAMs to upregulate REDD1 (regulated in development and in DNA damage response 1), which causes the inhibition of mTOR, and further glycolysis inhibition. This was linked with an enhanced response to angiogenesis and leaky vessels formation. As a consequence, hypoxic TAMs migrate toward oxidative mode of metabolism coupled with decreased intake of glucose, which causes hyperactivation of endothelial cells and results in metastasis and neoangiogenesis because of the increased availability of glucose in the TME. However, the physiological relevance of such shift in humans has not been proven yet [40]. Under normoxia, TAMs exhibit downregulated activity of succinate dehydrogenase (SDH) and lower glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as compared to normal macrophages, aiding their potential to function on relatively low inputs of nutrients as found in the TME. Interestingly, the activity of GAPDH was observed to be more downregulated in M2-like than M1-like macrophages infiltrating colorectal tumors in humans [41]. In a similar manner, in human gliomas TAMs derived from monocytes showed reduced glucose metabolism than tissue-resident TAMs, which was linked with poor patient survival and escalated immunosuppression in the TME. These observations in TAMs suggest that decreased glycolytic activity elicits progression of tumor via both immunosuppression and nutritional circuitries [42]. Even when a decreased glycolysis metabolism in TAMs spears to favor growth of the tumor in a majority of settings, tissue section analysis and co-culture experiments in TAMs showed that production of lactate by human medullary carcinoma cells causes a shift from OXPHOS to glycolysis, couples to upregulated secretion of interleukin 6 (IL6), lactate and tumor necrosis factor (TNF), ultimately supporting tumor progression [43]. Additionally, proteomic analysis demonstrated that enzymes involved in glycolysis such as hexokinase 2 (HK-II) are increased in TAMs from individuals with pancreatic cancer and macrophages derived from bone marrow exposed to breast carcinoma extracts from individuals suggesting an enhanced rather than decreased capacity in glycolysis [44, 45]. Therefore, glycolysis in TAMs can facilitate tumor progression and growth irrespective of an increased competition for local availability of glucose [44].

Macrophages-mediated metabolic reprogramming in tumor is not only limited to glycolysis. Through the different glycolysis intermediates, glycolysis is directly associated with various other intracellular metabolic pathways. This includes fatty acid (FA) and glutamine metabolism, pentose phosphate pathway (PPP), and amino acid metabolism.

### **5.2 Fatty acid and glutamine metabolism**

M2-like TAMs also display increased consumption of fatty acid and glutamine. The latter represents relatively increased levels of metabolic enzymes and glutamine

**11**

*Role of Macrophages in Solid Tumor Metabolism DOI: http://dx.doi.org/10.5772/intechopen.93182*

transporters expression, observed in both in vitro and in vivo in primary human TAMs [43]. In line with this, another study shows, glutamate ammonia ligase (GLUL) facilitates polarization of M2 by catalytic conversion of glutamate to glutamine, at least in vitro [46]. Therefore, inhibition of GLUL supports the M2-like TAMs repolarization into M1 counterparts along with enhanced flux of glycolysis and availability of succinate, suggesting the role of glutamine metabolism in TAMs regulation. Also, depletion of glutamine restrains polarization of M2-like macrophages in murine as a result of limited availability of a-ketoglutarate for epigenetic reprogramming [47]. A similar outcome ensues *N*-glycosylation inhibition suggesting the limited synthesis of aspartate-dependent UDP-N-acetyl-glucosamine (UDP-GlcNac) [47] and limited glucose-acetyl-CoA, which also plays a crucial role in epigenetic functions [48]. The former is the result of interleukin 4 (IL4)-driven activation of signal transducer and PPARG coactivator 1 beta (PPARGC1B), leading to enhanced epigenetic reprogramming and mitochondrial biogenesis toward fatty acid oxidation (FAO) [49]. Therefore, inhibition of pharmacological FAO reportedly supports repolarization of M1-like and M2-like macrophages [50], while upregulation of fatty acid synthase (FASN) in several subsets of TAM has been shown to favor pulmonary tumorigenesis because of the secretion of colony stimulating factor 1 (CSF1). In such a setting, TAMs have shown to support tumor progression by immunosuppressive cytokine interleukin 10 (IL10) release downstream of peroxisome proliferator-activated receptor delta (PPARD) [50]. The latter observation suggests the crosstalk between immune and metabolic functions in the TME. Some TAMs accumulate intracellular source of lipids in order to support metabolic fitness in tumor [51]. This suggests the alteration in majority of crucial factors involved in lipid metabolism such as monoglyceride lipase (MGLL), abhydrolase domain containing 5 (ABHD5), and acyl-CoA dehydrogenase medium chain (ACADM) [51–53]. Therefore, these observations suggest the major role of TAM

metabolism on their ability to influence tumor progression and growth.

TAMs, exclusively pro-tumorigenic and M2-like macrophages, exhibit increased

utilization of glutamine. This is linked with upregulated levels of intermediates such as uridine diphosphate N-acetylglucosamine, which are needed for N linked glycosylation of M2-like macrophages-associated receptors. Consequently, inhibiting the process of N-glycosylation and glutamine deprivation impairs polarization of M2-like macrophages along with downregulation in the TCA cycle [47]. Additionally, TAM isolated and exposed to glioblastoma cell lines exhibited enhanced gene expression related to metabolism [54]. The metabolism of L-arginine has also been shown to be associated with TAMs function. L-arginine can be used either through arginase metabolic pathway or for the synthesis of NO in macrophages. NO synthesis pathway is the characteristic feature of M1-like macrophages. Arginine is converted to L-citrulline and NO by nitric oxide synthase (iNOS). The NO furthermore downregulates OXPHOS through inhibition of electron transport chain (ETC) and TCA cycle enzymes and increases glycolysis [55, 56]. While on the other hand, expression of arginase (ARG1), enzyme that plays a crucial role in urea cycle, is the characteristic feature of M2-like macrophage, which hydrolyses arginine to urea and ornithine and restricts the availability of arginine for NO synthesis [57, 58]. TAM isolated from human ovarian and murine mammary tumors showed reduced cytotoxic properties linked with a decreased production of NO and a lower expression of iNOS in tumorbearing mice [59, 60]. Another study demonstrated elevated expression of Arg1 in TAMs isolated from murine models. Lactate and hypoxia have been studied to be able to upregulate Arg1 expression [13]. Colegio et al. in lung cancer murine model

**5.3 Amino acid metabolism**

*Role of Macrophages in Solid Tumor Metabolism DOI: http://dx.doi.org/10.5772/intechopen.93182*

*Macrophages*

mechanism of nutritional support to the solid tumor cells by products derived from TAM such as adrenomedullin (AMD), C-X-C motif chemokine ligand 8 (CXCL8), vascular endothelial growth factor A (VEGFA), and CXCL12 [36, 37]. Although the vasculature of tumor is functionally and phenotypically impaired, neoangiogenesis plays a crucial role for the growth of neoplasms in this scenario [38]. TME has been shown to exhibit some degree of hypoxia, which facilitates TAMs' tumor-supporting functions majorly via two mechanisms: First, hypoxic condition supports the upregulation of lipocalin 2 (LCN2), and upregulation of solute carrier family 40 member 1 (SLC40A1 or FPN). This causes the acquisition of an iron donor phenotype by TAMs, therefore enhanced availability of iron in the TME, and thus improved iron uptake by malignant cells and significant proliferation [39]. Wenes et al. investigated the character of metabolically activated hypoxic macrophage in metastasis and the blood vessel morphogenesis. It was observed that hypoxia causes TAMs to upregulate REDD1 (regulated in development and in DNA damage response 1), which causes the inhibition of mTOR, and further glycolysis inhibition. This was linked with an enhanced response to angiogenesis and leaky vessels formation. As a consequence, hypoxic TAMs migrate toward oxidative mode of metabolism coupled with decreased intake of glucose, which causes hyperactivation of endothelial cells and results in metastasis and neoangiogenesis because of the increased availability of glucose in the TME. However, the physiological relevance of such shift in humans has not been proven yet [40]. Under normoxia, TAMs exhibit downregulated activity of succinate dehydrogenase (SDH) and lower glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as compared to normal macrophages, aiding their potential to function on relatively low inputs of nutrients as found in the TME. Interestingly, the activity of GAPDH was observed to be more downregulated in M2-like than M1-like macrophages infiltrating colorectal tumors in humans [41]. In a similar manner, in human gliomas TAMs derived from monocytes showed reduced glucose metabolism than tissue-resident TAMs, which was linked with poor patient survival and escalated immunosuppression in the TME. These observations in TAMs suggest that decreased glycolytic activity elicits progression of tumor via both immunosuppression and nutritional circuitries [42]. Even when a decreased glycolysis metabolism in TAMs spears to favor growth of the tumor in a majority of settings, tissue section analysis and co-culture experiments in TAMs showed that production of lactate by human medullary carcinoma cells causes a shift from OXPHOS to glycolysis, couples to upregulated secretion of interleukin 6 (IL6), lactate and tumor necrosis factor (TNF), ultimately supporting tumor progression [43]. Additionally, proteomic analysis demonstrated that enzymes involved in glycolysis such as hexokinase 2 (HK-II) are increased in TAMs from individuals with pancreatic cancer and macrophages derived from bone marrow exposed to breast carcinoma extracts from individuals suggesting an enhanced rather than decreased capacity in glycolysis [44, 45]. Therefore, glycolysis in TAMs can facilitate tumor progression and growth irrespective of an increased competition for local

Macrophages-mediated metabolic reprogramming in tumor is not only limited to glycolysis. Through the different glycolysis intermediates, glycolysis is directly associated with various other intracellular metabolic pathways. This includes fatty acid (FA) and glutamine metabolism, pentose phosphate pathway (PPP), and

M2-like TAMs also display increased consumption of fatty acid and glutamine. The latter represents relatively increased levels of metabolic enzymes and glutamine

**10**

availability of glucose [44].

amino acid metabolism.

**5.2 Fatty acid and glutamine metabolism**

transporters expression, observed in both in vitro and in vivo in primary human TAMs [43]. In line with this, another study shows, glutamate ammonia ligase (GLUL) facilitates polarization of M2 by catalytic conversion of glutamate to glutamine, at least in vitro [46]. Therefore, inhibition of GLUL supports the M2-like TAMs repolarization into M1 counterparts along with enhanced flux of glycolysis and availability of succinate, suggesting the role of glutamine metabolism in TAMs regulation. Also, depletion of glutamine restrains polarization of M2-like macrophages in murine as a result of limited availability of a-ketoglutarate for epigenetic reprogramming [47]. A similar outcome ensues *N*-glycosylation inhibition suggesting the limited synthesis of aspartate-dependent UDP-N-acetyl-glucosamine (UDP-GlcNac) [47] and limited glucose-acetyl-CoA, which also plays a crucial role in epigenetic functions [48]. The former is the result of interleukin 4 (IL4)-driven activation of signal transducer and PPARG coactivator 1 beta (PPARGC1B), leading to enhanced epigenetic reprogramming and mitochondrial biogenesis toward fatty acid oxidation (FAO) [49]. Therefore, inhibition of pharmacological FAO reportedly supports repolarization of M1-like and M2-like macrophages [50], while upregulation of fatty acid synthase (FASN) in several subsets of TAM has been shown to favor pulmonary tumorigenesis because of the secretion of colony stimulating factor 1 (CSF1). In such a setting, TAMs have shown to support tumor progression by immunosuppressive cytokine interleukin 10 (IL10) release downstream of peroxisome proliferator-activated receptor delta (PPARD) [50]. The latter observation suggests the crosstalk between immune and metabolic functions in the TME. Some TAMs accumulate intracellular source of lipids in order to support metabolic fitness in tumor [51]. This suggests the alteration in majority of crucial factors involved in lipid metabolism such as monoglyceride lipase (MGLL), abhydrolase domain containing 5 (ABHD5), and acyl-CoA dehydrogenase medium chain (ACADM) [51–53]. Therefore, these observations suggest the major role of TAM metabolism on their ability to influence tumor progression and growth.

### **5.3 Amino acid metabolism**

TAMs, exclusively pro-tumorigenic and M2-like macrophages, exhibit increased utilization of glutamine. This is linked with upregulated levels of intermediates such as uridine diphosphate N-acetylglucosamine, which are needed for N linked glycosylation of M2-like macrophages-associated receptors. Consequently, inhibiting the process of N-glycosylation and glutamine deprivation impairs polarization of M2-like macrophages along with downregulation in the TCA cycle [47]. Additionally, TAM isolated and exposed to glioblastoma cell lines exhibited enhanced gene expression related to metabolism [54]. The metabolism of L-arginine has also been shown to be associated with TAMs function. L-arginine can be used either through arginase metabolic pathway or for the synthesis of NO in macrophages. NO synthesis pathway is the characteristic feature of M1-like macrophages. Arginine is converted to L-citrulline and NO by nitric oxide synthase (iNOS). The NO furthermore downregulates OXPHOS through inhibition of electron transport chain (ETC) and TCA cycle enzymes and increases glycolysis [55, 56]. While on the other hand, expression of arginase (ARG1), enzyme that plays a crucial role in urea cycle, is the characteristic feature of M2-like macrophage, which hydrolyses arginine to urea and ornithine and restricts the availability of arginine for NO synthesis [57, 58]. TAM isolated from human ovarian and murine mammary tumors showed reduced cytotoxic properties linked with a decreased production of NO and a lower expression of iNOS in tumorbearing mice [59, 60]. Another study demonstrated elevated expression of Arg1 in TAMs isolated from murine models. Lactate and hypoxia have been studied to be able to upregulate Arg1 expression [13]. Colegio et al. in lung cancer murine model

demonstrated that Arg1fl/fl X Lysmcre/wt mice, with deficient ARG1 in macrophages, developed small-sized tumor as compared to the wild-type mice [33]. In the same study, TAMs exhibited upregulated expression of urea cycle. Additionally, metabolites such as tryptophan and cysteine derived from L-arginine are crucial mediators of myeloid-derived suppressor cells (*MDSC*). These findings highlight the role of nitrogen cycle in TAMs' function [61].

### **6. Signaling cross-talk between macrophages and solid tumor**

Colony stimulating factor 1 (CSF1), the major cytokine, plays an important role in the interplay between TAMs and tumor cells [62]. After binding to its cognate receptor, CSF1 facilitates monocyte-derived macrophages' recruitment to tumor bed and M2-like macrophages polarization. This is accompanied with (1) upregulation of FAO [63] and (2) immunosuppressive and pro-tumorigenic factor secretion, such as IL10 [64] and epidermal growth factor (EGF) [65]. Accordingly, inhibition of colony stimulating factor 1 receptor (CSF1R) with monoclonal antibodies or small molecules supports the M1-like TAMs' accumulation [66]. This is accompanied by glycolysis restoration, mediating therapeutic effects in majority of tumor models. CSF1, VEGFA, and IL34 supporting TAMs' growth is sensitive to chemotherapeutic environmental stress, local pH, nutrient availability, and oxygen tension [33, 62]. Therefore, metabolism of lactate is exclusively relevant not only for metabolic symbiosis between normoxic and hypoxic cancer cells but also for the potential of hypoxic cancer cells to decrease TAMs toward poor M2-like glycolytic profile, exhibiting upregulation of FAO, reduced potential for antigen presentation [67]. Additionally, M2 polarization of TAMs-associated melanoma is elicited by a G-protein-coupled receptor (GPCR) signaling mechanism that senses acidification of TME induced by increased glycolysis in cancer cells [68]. Mathematical modeling accompanied with in vivo experiments revealed the potential of TAMs to support the process of neoangiogenesis. This specific metabolic alteration has additional immunological consequences, as VEGFA favors the immunosuppressive receptors' expression [69]. Upregulated activity of lactate in the TME causing hypoxic nature contributes to the arginine catabolism by arginase 1 (ARG1) and ARG2 over nitric oxide synthase 2 (NOS2), causing enhanced secretion of factors supporting tumor such as polyamines and ornithine by TAMs [33, 69]. The levels of ARG1 can be increased in M2-like TAMs by signals induced by apoptotic cancer cells [70], such as FASN-dependent pathway driven by CSF1 [42] and sphingosine-1-phosphate (S1P). Also, lactate contributes polarization of M2-like macrophages in murine breast cancer models by triggering G-protein-coupled receptor 132 (GPR132) signaling. Accordingly, upregulated levels of GPR132 elicit infiltration in breast cancer by monocyte-derived macrophages, which certainly acquire functions supporting tumor phenotype. Another receptor of lactate, hydroxycarboxylic acid receptor 1 (HCAR1), seems to be upregulated in M1-like TAMs [71]. Additionally, cancer cells' metabolic influence on TAMs is not unidirectional. Therefore, when TAMs are exposed to the hypoxic conditions or upregulated lactate levels, they secrete variety of cytokines such as TNF, IL6, C-C motif chemokine ligand 5 (CCL5), and CCL18 [72]. IL6 supports glucose metabolism by mediating 3-phosphoinositide-dependent protein kinase 1 (PDPK1) potential to phosphorylate CCL5, TNF, phosphoglycerate kinase 1 (PGK), and CCL18 enhances pro-glycolytic factors such as PGK1, HXK2, glucose-6-phosphate dehydrogenase (G6PD), lactate dehydrogenase A (LDHA), vascular cell adhesion molecule 1 (VCAM1), pyruvate dehydrogenase (PDH), pyruvate dehydrogenase kinase 1 (PDK1), and GLUT1 [73]. Apart from these findings, Warburg phenomenon is triggered, both in vitro and in vivo, by transfer of long noncoding RNA of hypoxia

**13**

*Role of Macrophages in Solid Tumor Metabolism DOI: http://dx.doi.org/10.5772/intechopen.93182*

hypoxia in an active manner [37] (**Figure 2**).

*phosphorylation and fatty acid oxidation.*

impairs their effector function (**Table 1**).

**metabolism**

**Figure 2.**

inducible factor 1 subunit alpha (HIF1A) from TAMs exposed to lactate to the tumor cells. Intriguingly, HIF1A have been shown to play a crucial role in exacerbating tumor glycolysis as well as M2 polarization. Furthermore, M2-like TAMs trigger

*Metabolic cross-talk signatures between TAMs and cancer cells. As cancer cells begin to proliferate in an uncontrollable manner, they start consuming elevated levels of glucose and other biosynthetic products to progress. This triggers the release of CSF-1 into the tumor microenvironment, which repolarizes the M1-like phenotype macrophages into M2-like macrophages. The M2-like state then releases several chemokines such as EGF, CCL-5, CCL-18, which act as immunosuppressive molecules. The expensive use of lactate by cancer cells delineates the immune function of T effector cells. Moreover, M2-like macrophages upregulated mitochondrial* 

As now it is very evident that TAMs and tumors have very complex interactions between them, which supports the tumor progression, growth, and metastasis, researches across the globe are widely studying this area and finding novel targets against the immune regulators and metabolic mediators in the system. TAMs are the widely found immune cells in the tumor microenvironment and undergo complex processes to support the tumor growth. M2-like TAM phenotype is highly reported from studies to likely support the tumor progression. This conclusion supports the idea of developing antibodies that intervene with the M2 phenotype macrophage function. CCL2 blocking agents have been a promising antibody against cancer metastasis and cancer death. Therefore, strategies to deplete the M2 phenotype into non-tumorous M1 phenotype have been a promising step toward treating cancer. Drugs associated with metabolic blockers also paved a new method for treating cancer. Drugs such as inhibiting HK-II helped in the inhibition of pro-metastatic M2 phenotype of TAMs. Similarly, drugs inhibiting FAO also appear to be a promising field to target pro-tumoral macrophage as well as tumor metabolism. T-cells are the major players contributing toward immune-mediated cell metabolism, which is also approached as an effective target. PD-1 ligation with T-cells helps in the shift in metabolism from glycolysis to FAO, which maintains the longevity of T-cells and

**7. Therapeutic strategies against macrophages-mediated tumor** 

### **Figure 2.**

*Macrophages*

demonstrated that Arg1fl/fl X Lysmcre/wt mice, with deficient ARG1 in macrophages, developed small-sized tumor as compared to the wild-type mice [33]. In the same study, TAMs exhibited upregulated expression of urea cycle. Additionally, metabolites such as tryptophan and cysteine derived from L-arginine are crucial mediators of myeloid-derived suppressor cells (*MDSC*). These findings highlight the

**6. Signaling cross-talk between macrophages and solid tumor**

Colony stimulating factor 1 (CSF1), the major cytokine, plays an important role in the interplay between TAMs and tumor cells [62]. After binding to its cognate receptor, CSF1 facilitates monocyte-derived macrophages' recruitment to tumor bed and M2-like macrophages polarization. This is accompanied with (1) upregulation of FAO [63] and (2) immunosuppressive and pro-tumorigenic factor secretion, such as IL10 [64] and epidermal growth factor (EGF) [65]. Accordingly, inhibition of colony stimulating factor 1 receptor (CSF1R) with monoclonal antibodies or small molecules supports the M1-like TAMs' accumulation [66]. This is accompanied by glycolysis restoration, mediating therapeutic effects in majority of tumor models. CSF1, VEGFA, and IL34 supporting TAMs' growth is sensitive to chemotherapeutic environmental stress, local pH, nutrient availability, and oxygen tension [33, 62]. Therefore, metabolism of lactate is exclusively relevant not only for metabolic symbiosis between normoxic and hypoxic cancer cells but also for the potential of hypoxic cancer cells to decrease TAMs toward poor M2-like glycolytic profile, exhibiting upregulation of FAO, reduced potential for antigen presentation [67]. Additionally, M2 polarization of TAMs-associated melanoma is elicited by a G-protein-coupled receptor (GPCR) signaling mechanism that senses acidification of TME induced by increased glycolysis in cancer cells [68]. Mathematical modeling accompanied with in vivo experiments revealed the potential of TAMs to support the process of neoangiogenesis. This specific metabolic alteration has additional immunological consequences, as VEGFA favors the immunosuppressive receptors' expression [69]. Upregulated activity of lactate in the TME causing hypoxic nature contributes to the arginine catabolism by arginase 1 (ARG1) and ARG2 over nitric oxide synthase 2 (NOS2), causing enhanced secretion of factors supporting tumor such as polyamines and ornithine by TAMs [33, 69]. The levels of ARG1 can be increased in M2-like TAMs by signals induced by apoptotic cancer cells [70], such as FASN-dependent pathway driven by CSF1 [42] and sphingosine-1-phosphate (S1P). Also, lactate contributes polarization of M2-like macrophages in murine breast cancer models by triggering G-protein-coupled receptor 132 (GPR132) signaling. Accordingly, upregulated levels of GPR132 elicit infiltration in breast cancer by monocyte-derived macrophages, which certainly acquire functions supporting tumor phenotype. Another receptor of lactate, hydroxycarboxylic acid receptor 1 (HCAR1), seems to be upregulated in M1-like TAMs [71]. Additionally, cancer cells' metabolic influence on TAMs is not unidirectional. Therefore, when TAMs are exposed to the hypoxic conditions or upregulated lactate levels, they secrete variety of cytokines such as TNF, IL6, C-C motif chemokine ligand 5 (CCL5), and CCL18 [72]. IL6 supports glucose metabolism by mediating 3-phosphoinositide-dependent protein kinase 1 (PDPK1) potential to phosphorylate CCL5, TNF, phosphoglycerate kinase 1 (PGK), and CCL18 enhances pro-glycolytic factors such as PGK1, HXK2, glucose-6-phosphate dehydrogenase (G6PD), lactate dehydrogenase A (LDHA), vascular cell adhesion molecule 1 (VCAM1), pyruvate dehydrogenase (PDH), pyruvate dehydrogenase kinase 1 (PDK1), and GLUT1 [73]. Apart from these findings, Warburg phenomenon is triggered, both in vitro and in vivo, by transfer of long noncoding RNA of hypoxia

role of nitrogen cycle in TAMs' function [61].

**12**

*Metabolic cross-talk signatures between TAMs and cancer cells. As cancer cells begin to proliferate in an uncontrollable manner, they start consuming elevated levels of glucose and other biosynthetic products to progress. This triggers the release of CSF-1 into the tumor microenvironment, which repolarizes the M1-like phenotype macrophages into M2-like macrophages. The M2-like state then releases several chemokines such as EGF, CCL-5, CCL-18, which act as immunosuppressive molecules. The expensive use of lactate by cancer cells delineates the immune function of T effector cells. Moreover, M2-like macrophages upregulated mitochondrial phosphorylation and fatty acid oxidation.*

inducible factor 1 subunit alpha (HIF1A) from TAMs exposed to lactate to the tumor cells. Intriguingly, HIF1A have been shown to play a crucial role in exacerbating tumor glycolysis as well as M2 polarization. Furthermore, M2-like TAMs trigger hypoxia in an active manner [37] (**Figure 2**).

### **7. Therapeutic strategies against macrophages-mediated tumor metabolism**

As now it is very evident that TAMs and tumors have very complex interactions between them, which supports the tumor progression, growth, and metastasis, researches across the globe are widely studying this area and finding novel targets against the immune regulators and metabolic mediators in the system. TAMs are the widely found immune cells in the tumor microenvironment and undergo complex processes to support the tumor growth. M2-like TAM phenotype is highly reported from studies to likely support the tumor progression. This conclusion supports the idea of developing antibodies that intervene with the M2 phenotype macrophage function. CCL2 blocking agents have been a promising antibody against cancer metastasis and cancer death. Therefore, strategies to deplete the M2 phenotype into non-tumorous M1 phenotype have been a promising step toward treating cancer. Drugs associated with metabolic blockers also paved a new method for treating cancer. Drugs such as inhibiting HK-II helped in the inhibition of pro-metastatic M2 phenotype of TAMs. Similarly, drugs inhibiting FAO also appear to be a promising field to target pro-tumoral macrophage as well as tumor metabolism. T-cells are the major players contributing toward immune-mediated cell metabolism, which is also approached as an effective target. PD-1 ligation with T-cells helps in the shift in metabolism from glycolysis to FAO, which maintains the longevity of T-cells and impairs their effector function (**Table 1**).


**Table 1.**

*Metabolic targets in tumor-associated macrophages.*

Therefore, strategies that target macrophages along with tumor metabolism without encouraging the tumor cell growth have been quite challenging and have provide an effective means to treat the solid tumors.

### **8. Conclusion**

Solid tumors are evolving over the years strongly by acquiring the capability to manipulate the host system to help them attain energy demands to survive and metastasize. One such player helping tumor cells is the macrophages. The polarization of macrophages into tumorous M2 phenotype helps the cancer cells in their glycolytic demands. Metabolic events such as amino acid metabolism and oxidative phosphorylation are triggered in cancer cells. The hypoxia event in cancer cells stimulates the signaling events toward glycolysis increasing glycolytic enzymes such as hexokinase-II, LDH-A, and pyruvate dehydrogenase. Thus, series of research has proved that macrophages has an important role to play in tumor metabolism inside the TME. This kind of immunometabolism has triggered challenges and interest in finding novel targets on this area to cure the disease cancer.

### **Acknowledgements**

We thank our lab members for carefully reading the article and contributing valuable inputs for improving it. V.C., S.R., and D.K. were supported by the Department of Science & Technology-Science and Engineering Research Board (DST-SERB) funded research grant (ECR/2016/001489), Govt. of India.

**15**

**Author details**

Sibi Raj, Vaishali Chandel, Sujata Maurya and Dhruv Kumar\*

Amity University Noida, Uttar Pradesh, India

provided the original work is properly cited.

Amity Institute of Molecular Medicine and Stem Cell Research (AIMMSCR),

\*Address all correspondence to: dhruvbhu@gmail.com; dkumar13@amity.edu

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Role of Macrophages in Solid Tumor Metabolism DOI: http://dx.doi.org/10.5772/intechopen.93182*

*Role of Macrophages in Solid Tumor Metabolism DOI: http://dx.doi.org/10.5772/intechopen.93182*

*Macrophages*

2. CSF1

receptor

**8. Conclusion**

**Table 1.**

**Acknowledgements**

Therefore, strategies that target macrophages along with tumor metabolism without encouraging the tumor cell growth have been quite challenging and have

**S. No. Target Effect References**

Antiangiogenic and antimetastasis effects in melanoma

[74]

[66]

[78]

1 CCL2 Reduce tumor growth and metastasis in prostate and breast cancer

and mammary xenograft

6. HCK Suppression of AAM polarization, enhanced tumor immunity in colon cancer

3. IL4Rα Less aggressive skin tumors [75] 4. STAT3 Inhibited immunosuppressive cytokine profile of AAMs [76] 5. COX2 Suppression of breast cancer metastasis [77]

Solid tumors are evolving over the years strongly by acquiring the capability to manipulate the host system to help them attain energy demands to survive and metastasize. One such player helping tumor cells is the macrophages. The polarization of macrophages into tumorous M2 phenotype helps the cancer cells in their glycolytic demands. Metabolic events such as amino acid metabolism and oxidative phosphorylation are triggered in cancer cells. The hypoxia event in cancer cells stimulates the signaling events toward glycolysis increasing glycolytic enzymes such as hexokinase-II, LDH-A, and pyruvate dehydrogenase. Thus, series of research has proved that macrophages has an important role to play in tumor metabolism inside the TME. This kind of immunometabolism has triggered challenges and interest in

We thank our lab members for carefully reading the article and contributing valuable inputs for improving it. V.C., S.R., and D.K. were supported by the Department of Science & Technology-Science and Engineering Research Board (DST-SERB)-

provide an effective means to treat the solid tumors.

*Metabolic targets in tumor-associated macrophages.*

finding novel targets on this area to cure the disease cancer.

funded research grant (ECR/2016/001489), Govt. of India.

**14**

### **Author details**

Sibi Raj, Vaishali Chandel, Sujata Maurya and Dhruv Kumar\* Amity Institute of Molecular Medicine and Stem Cell Research (AIMMSCR), Amity University Noida, Uttar Pradesh, India

\*Address all correspondence to: dhruvbhu@gmail.com; dkumar13@amity.edu

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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[50] Hossain F, Al-Khami AA, Wyczechowska D, et al. Inhibition of fatty acid oxidation modulates immunosuppressive functions of myeloid-derived suppressor cells and enhances cancer therapies. Cancer Immunology Research.

[51] Xiang W, Shi R, Kang X, et al. Monoacylglycerol lipase regulates cannabinoid receptor 2-dependent macrophage activation and cancer progression. Nature Communications.

[52] Miao H, Ou J, Peng Y, et al. Macrophage ABHD5 promotes

stimulated by the tumor

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2016:88-94

2006;**4**(1):13-24

2015;**3**(11):1236-1247

2018;**9**(1):2574

[47] Jha AK, Huang SCC, Sergushichev A, et al. Network integration of parallel metabolic and transcriptional data reveals metabolic modules that regulate macrophage polarization. Immunity. 2015

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[38] Donnem T, Reynolds AR, Kuczynski EA, et al. Non-angiogenic tumours and their influence on cancer biology. Nature Reviews. Cancer.

[39] Mertens C, Mora J, Ören B, et al. Macrophage-derived lipocalin-2 transports iron in the tumor

microenvironment. OncoImmunology.

[40] Wenes M, Shang M, Di Matteo M, et al. Macrophage metabolism controls tumor blood vessel morphogenesis and metastasis. Cell Metabolism.

[41] Miller A, Nagy C, Knapp B, et al. Exploring metabolic configurations of single cells within complex tissue microenvironments. Cell Metabolism.

[42] Müller S, Kohanbash G, Liu SJ, et al. Single-cell profiling of human gliomas reveals macrophage ontogeny as a basis for regional differences in macrophage activation in the tumor microenvironment. Genome Biology.

[43] Arts RJW, Plantinga TS, Tuit S, et al. Transcriptional and metabolic

[44] Penny HL, Sieow JL, Adriani G, et al. Warburg metabolism in tumorconditioned macrophages promotes metastasis in human pancreatic ductal adenocarcinoma. OncoImmunology.

reprogramming induce an inflammatory phenotype in nonmedullary thyroid carcinoma-induced macrophages. OncoImmunology.

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**18**

colorectal cancer growth by suppressing spermidine production by SRM. Nature Communications. 2016

[53] Niu Z, Shi Q, Zhang W, et al. Caspase-1 cleaves PPARγ for potentiating the pro-tumor action of TAMs. Nature Communications. 2017;**8**(1):766

[54] Choi J, Stradmann-Bellinghausen B, Savaskan N, Regnier-Vigouroux A. Human monocyte-derived macrophages exposed to glioblastoma cells and tumor-associated microglia/macrophages differ in glutamatergic gene expressions. Glia. 2015;**16**(8):1205-1213

[55] Albina JE, Mastrofrancesco B. Modulation of glucose metabolism in macrophages by products of nitric oxide synthase. American Journal of Physiology. Cell Physiology. 1993;**246** (6 pt 1)

[56] Clementi E, Brown GC, Feelisch M, Moncada S. Persistent inhibition of cell respiration by nitric oxide: Crucial role of S-nitrosylation of mitochondrial complex I and protective action of glutathione. Proceedings of the National Academy of Sciences of the United States of America. 1998;**95**(13):7631-7636

[57] Rath M, Müller I, Kropf P, Closs EI, Munder M. Metabolism via arginase or nitric oxide synthase: Two competing arginine pathways in macrophages. Frontiers in Immunology. 2014

[58] MacMicking J, Xie Q, Nathan C. Nitric oxide and macrophage function. Annual Review of Immunology. 1997:323-350

[59] DiNapoli MR, Calderon CL, Lopez DM. The altered tumoricidal capacity of macrophages isolated from tumor-bearing mice is related to reduced expression of the inducible nitric oxide synthase gene. The

Journal of Experimental Medicine. 1996;**183**(4):1323-1329

[60] Klimp AH, Hollema H, Kempinga C, van der Zee AGJ, de Vries EGE, Daemen T. Expression of cyclooxygenase-2 and inducible nitric oxide synthase in human ovarian tumors and tumor-associated macrophages. Cancer Research. 2001;**61**(19):7305-7309

[61] Wu T, Sun C, Chen Z, et al. Smad3 deficient CD11b + Gr1 + myeloidderived suppressor cells prevent allograft rejection via the nitric oxide pathway. Journal of Immunology. 2012;**189**(10):4989-5000

[62] DeNardo DG, Brennan DJ, Rexhepaj E, et al. Leukocyte complexity predicts breast cancer survival and functionally regulates response to chemotherapy. Cancer Discovery. 2011:54-67

[63] Park J, Lee SE, Hur J, et al. M-CSF from cancer cells induces fatty acid synthase and PPARβ/δ activation in tumor myeloid cells, leading to tumor progression. Cell Reports. 2015;**10**(9):1614-1625

[64] Ruffell B, Chang-Strachan D, Chan V, et al. Macrophage IL-10 blocks CD8+ T cell-dependent responses to chemotherapy by suppressing IL-12 expression in intratumoral dendritic cells. Cancer Cell. 2014;**26**(5):623-637

[65] Wyckoff J, Wang W, Lin EY, et al. A paracrine loop between tumor cells and macrophages is required for tumor cell migration in mammary tumors. Cancer Research. 2004;**64**(19):7022-7029

[66] Pyonteck SM, Akkari L, Schuhmacher AJ, et al. CSF-1R inhibition alters macrophage polarization and blocks glioma progression. Nature Medicine. 2013;**19**(10):1264-1272

[67] Allen E, Miéville P, Warren CM, et al. Metabolic symbiosis enables adaptive resistance to anti-angiogenic therapy that is dependent on mTOR signaling. Cell Reports. 2016;**15**(6):1144-1160

[68] Bohn T, Rapp S, Luther N, et al. Tumor immunoevasion via acidosisdependent induction of regulatory tumor-associated macrophages. Nature Immunology. 2018;**19**(12):1319-1329

[69] Carmona-Fontaine C, Deforet M, Akkari L, Thompson CB, Joyce JA, Xavier JB. Metabolic origins of spatial organization in the tumor microenvironment. Proceedings of the National Academy of Sciences of the United States of America. 2017;**114**(11):2934-2939

[70] Galluzzi L, Vitale I, Aaronson SA, et al. Molecular mechanisms of cell death: Recommendations of the nomenclature committee on cell death. Cell Death and Differentiation. 2018;**25**(3):486-541

[71] Chen P, Zuo H, Xiong H, et al. Gpr132 sensing of lactate mediates tumor-macrophage interplay to promote breast cancer metastasis. Proceedings of the National Academy of Sciences of the United States of America. 2017;**114**(3):580-585

[72] Jeong H, Kim S, Hong BJ, et al. Tumor-associated macrophages enhance tumor hypoxia and aerobic glycolysis. Cancer Research. 2019;**79**(4):795-806

[73] Zhang M, Di Martino JS, Bowman RL, et al. Adipocyte-derived lipids mediate melanoma progression via FATP proteins. Cancer Discovery. 2018;**8**(8):1006-1025

[74] Qian B-Z, Li J, Zhang H, Kitamura T, Zhang J, Campion LR, et al. CCL2 recruits inflammatory monocytes to facilitate breast-tumour metastasis. Nature. 2011;**475**:222-225

[75] Linde N, Lederle W, Depner S, Rooijen NV, Gutschalk CM, Mueller MM. Vascular endothelial growth factor-induced skin carcinogenesis depends on recruitment and alternative activation of macrophages. The Journal of Pathology. 2012;**227**:17-28

[76] Edwards J, Emens L. The multikinase inhibitor sorafenib reverses the suppression of IL-12 and enhancement of IL-10 by PGE(2) in murine macrophages. International Immunopharmacology. 2010;**10**:1220-1228

[77] Na Y-R, Yoon Y-N, Son D-I, Seok S-H. Cyclooxygenase-2 inhibition blocks M2 macrophage differentiation and suppresses metastasis in murine breast cancer model. PLoS One. 2013;**8**:e63451

[78] Poh AR, Love CG, Masson F, Preaudet A, Tsui C, Whitehead L, et al. Inhibition of hematopoietic cell kinase activity suppresses myeloid cell-mediated colon cancer progression. Cancer Cell. 2017;**31**:563

**21**

**Chapter 2**

*Alice Grigore*

**Abstract**

differentiation.

**1. Introduction**

checkpoint inhibitors [1].

inhibit T-cell activation and proliferation [2].

Targeting Tumor-Associated

**Keywords:** macrophage polarization, phenolic compounds, saponins,

and novel therapeutic approach in preclinical or clinical cancer research.

polysaccharides, coumarins, anthraquinones, alkaloids, tumor microenvironment

Macrophages represent up to 50% of the cells infiltrating into the tumor microenvironment (TME) and modulation of macrophage polarization is an interesting

An increasing number of studies have also shown that tumor-associated macrophages (TAMs) can antagonize, augment or mediate the antitumor effects of cytotoxic agents, tumor irradiation, anti-angiogenic/vascular damaging agents and

In the tumor microenvironment, TAMs are one of the major contributors in *angiogenesis* by secreting pro-angiogenic factors, such as vascular endothelial growth factor (VEGF), adrenomedullin (ADM), platelet-derived growth factor (PDGF), tumor growth factor-beta (TGF-β) and matrix metalloproteinases (MMPs). Also, TAMs promote tumor cell *invasion and metastasis* by modifying the composition of extracellular matrix and cell-cell junctions and promoting basal membrane disruption. It was demonstrated that macrophages *facilitate the metastasis* by enhancing the ability of cancer cells to enter a local blood vessel and also are involved in *immunosuppression* by inhibiting the T-cell response or by secreting immunosuppressive cytokines and proteases such as IL-10, TGF-β, arginase-1 and prostaglandins, which

Macrophages by Plant Compounds

Macrophages play an important role in cancer development, as they represent almost half of the cells forming the tumor microenvironment. They are called tumor-associated macrophages (TAMs) and most of them are alternative activated macrophages (M2 polarized), promoting cancer progression, angiogenesis and local immunosuppression. Blocking the macrophages recruitment, preventing their activation or turning M2 cells toward M1 phenotype (classic activated macrophage promoting an efficient immune response) is a modern immunotherapeutic approach for fighting cancer. Several studies showed that plant compounds (phenolics, triterpenes, coumarins, etc.) exert antitumor properties, not only by a direct toxical effect to malignant cells but also by influencing macrophage phenotypic

### **Chapter 2**

*Macrophages*

[67] Allen E, Miéville P, Warren CM, et al. Metabolic symbiosis enables adaptive resistance to anti-angiogenic therapy that is dependent on mTOR signaling. Cell Reports. 2016;**15**(6):1144-1160

[75] Linde N, Lederle W, Depner S, Rooijen NV, Gutschalk CM, Mueller MM. Vascular endothelial growth factor-induced skin

and alternative activation of

[76] Edwards J, Emens L. The multikinase inhibitor sorafenib reverses the suppression of IL-12 and enhancement of IL-10 by PGE(2) in murine macrophages. International Immunopharmacology.

2012;**227**:17-28

2010;**10**:1220-1228

carcinogenesis depends on recruitment

macrophages. The Journal of Pathology.

[77] Na Y-R, Yoon Y-N, Son D-I, Seok S-H. Cyclooxygenase-2 inhibition blocks M2 macrophage differentiation and suppresses metastasis in murine breast cancer model. PLoS One. 2013;**8**:e63451

[78] Poh AR, Love CG, Masson F, Preaudet A, Tsui C, Whitehead L, et al. Inhibition of hematopoietic cell kinase activity suppresses myeloid cell-mediated colon cancer progression.

Cancer Cell. 2017;**31**:563

[68] Bohn T, Rapp S, Luther N, et al. Tumor immunoevasion via acidosisdependent induction of regulatory tumor-associated macrophages. Nature Immunology. 2018;**19**(12):1319-1329

[69] Carmona-Fontaine C, Deforet M, Akkari L, Thompson CB, Joyce JA, Xavier JB. Metabolic origins of spatial organization in the tumor microenvironment. Proceedings of the National Academy of Sciences of the United States of America.

[70] Galluzzi L, Vitale I, Aaronson SA, et al. Molecular mechanisms of cell death: Recommendations of the nomenclature committee on cell death. Cell Death and Differentiation.

[71] Chen P, Zuo H, Xiong H, et al. Gpr132 sensing of lactate mediates tumor-macrophage interplay to promote breast cancer metastasis. Proceedings of the National Academy of Sciences of the United States of America.

[72] Jeong H, Kim S, Hong BJ, et al. Tumor-associated macrophages enhance tumor hypoxia and aerobic glycolysis. Cancer Research. 2019;**79**(4):795-806

Bowman RL, et al. Adipocyte-derived lipids mediate melanoma progression via FATP proteins. Cancer Discovery.

[74] Qian B-Z, Li J, Zhang H, Kitamura T, Zhang J, Campion LR, et al. CCL2 recruits inflammatory monocytes to facilitate breast-tumour metastasis.

[73] Zhang M, Di Martino JS,

2018;**8**(8):1006-1025

Nature. 2011;**475**:222-225

2017;**114**(11):2934-2939

2018;**25**(3):486-541

2017;**114**(3):580-585

**20**

## Targeting Tumor-Associated Macrophages by Plant Compounds

*Alice Grigore*

### **Abstract**

Macrophages play an important role in cancer development, as they represent almost half of the cells forming the tumor microenvironment. They are called tumor-associated macrophages (TAMs) and most of them are alternative activated macrophages (M2 polarized), promoting cancer progression, angiogenesis and local immunosuppression. Blocking the macrophages recruitment, preventing their activation or turning M2 cells toward M1 phenotype (classic activated macrophage promoting an efficient immune response) is a modern immunotherapeutic approach for fighting cancer. Several studies showed that plant compounds (phenolics, triterpenes, coumarins, etc.) exert antitumor properties, not only by a direct toxical effect to malignant cells but also by influencing macrophage phenotypic differentiation.

**Keywords:** macrophage polarization, phenolic compounds, saponins, polysaccharides, coumarins, anthraquinones, alkaloids, tumor microenvironment

### **1. Introduction**

Macrophages represent up to 50% of the cells infiltrating into the tumor microenvironment (TME) and modulation of macrophage polarization is an interesting and novel therapeutic approach in preclinical or clinical cancer research.

An increasing number of studies have also shown that tumor-associated macrophages (TAMs) can antagonize, augment or mediate the antitumor effects of cytotoxic agents, tumor irradiation, anti-angiogenic/vascular damaging agents and checkpoint inhibitors [1].

In the tumor microenvironment, TAMs are one of the major contributors in *angiogenesis* by secreting pro-angiogenic factors, such as vascular endothelial growth factor (VEGF), adrenomedullin (ADM), platelet-derived growth factor (PDGF), tumor growth factor-beta (TGF-β) and matrix metalloproteinases (MMPs). Also, TAMs promote tumor cell *invasion and metastasis* by modifying the composition of extracellular matrix and cell-cell junctions and promoting basal membrane disruption. It was demonstrated that macrophages *facilitate the metastasis* by enhancing the ability of cancer cells to enter a local blood vessel and also are involved in *immunosuppression* by inhibiting the T-cell response or by secreting immunosuppressive cytokines and proteases such as IL-10, TGF-β, arginase-1 and prostaglandins, which inhibit T-cell activation and proliferation [2].

TAMs often exhibit an array of activation states. In general, they are skewed away from the "classically" activated, tumoricidal phenotype (sometimes referred to as M1) toward an "alternatively" activated tumor-promoting one (M2) [1]. The classically activated M1 macrophages are stimulated by microbial substrates such as lipopolysaccharide, Toll-like receptor ligands and cytokines such as IFN-γ. They are characterized by secretion of pro-inflammatory cytokines such as interleukins IL-6, IL-12, IL-23 and TNF-α and express high levels of major histocompatibility complex class II (MHC-II), CD68, and CD80 and CD86 costimulatory molecules. The alternatively activated M2 macrophages are stimulated by IL-4 and IL-13, secrete IL-10 and TGF-β and express low levels of MHC-II and feature expression of CD163 and CD206 [3].

Unfortunately, M2 cells are the most representative cells of the TAM population within the tumor promoting genetic instability, local immunosuppression and stem cell nurturing [4] and providing essential support for a malignant phenotype [5].

In the early stages of cancers of the lung, colon and stomach, the macrophages in the normoxic milieu display an M1 phenotype and are associated with good prognosis, but within avascular areas of the tumor, TAMs alter the gene expression profile, favoring a protumor M2 phenotype, correlated with a bad prognosis [6]. In **Table 1** are showed recent conclusions concerning the correlation between TAMs and clinical prognostics in several tumor types. In human breast carcinomas, high TAM density is also associated with poor prognosis [7]. TAMs in renal cell carcinoma show a mixed M1/M2 phenotype. CD68 alone has a poor predictive value, while low CD11+ and high CD206+ as single variables correlated with reduced survival [8]. There is strong evidence for an inverse relationship between TAM density and clinical prognosis in solid tumors of the breast, prostate, ovary and cervix. Type I and II endometrial carcinomas had significantly higher macrophage density in both epithelial and stromal compartments than benign endometrium [9]. Type II cancers have nearly twice the TAM density of type 1 cancers and this difference may be due to M1 macrophage predominance in the stroma of type II cancers [10].

TAMs' distribution pattern could be an independent prognostic factor for the overall survival of gastric cancer patients, invasive front-/stroma-dominant pattern having worse outcomes [11]. Studies have shown that the amount of TAMs in tumor stroma predicts the size, stage and metastasis of the gastric tumor [12]. In lung cancer, M2 subset and TAMs in tumor stroma were associated with worse survival, while M1 subset and TAMs in tumor islet were associated with favorable survival of lung cancer [13].

While most cancer research has focused upon these changes and most therapeutics are directed against these tumor cells, it is now apparent that the non-malignant cells in the microenvironment evolve along with the tumor and provide essential support for their malignant phenotype [5]. The knowledge of TAM activation status may allow the therapeutic targeting of TAMs, once TAMs' targeting/modulating agents pass clinical trials and become widely available [6, 14]. The role of macrophages in tumor progression remains to be fully elucidated, in part due to the contrasting roles they play depending on their polarization [15]. Both the systemic and local environments play a tumor-initiating role through the generation of persistent inflammatory responses to a variety of stimuli [16]. To support this correlative data between macrophage-mediated inflammation and cancer induction, genetic ablation of the anti-inflammatory transcription factor STAT3 in macrophages results in a chronic inflammatory response in the colon that is sufficient to induce invasive adenocarcinoma. However, it is unclear whether macrophages in some inflammatory situations can kill aberrant cells before they become tumorigenic and thus be antitumoral [17].

**23**

**Table 1.**

*Targeting Tumor-Associated Macrophages by Plant Compounds*

**Cancer type TAMs as prognostic factors Reference**

or CD206 alone; high infiltration of TAMs was significantly associated with negative hormone receptor status and malignant phenotype

Invasive front-/stroma-dominant pattern having worse outcomes Although CD68+ TAMs infiltration has the neutral prognostic effects on OS, the M1/M2 polarization of TAMs are predicative factors of prognosis

controversial. M2 subset and TAMs in tumor stroma were associated with worse survival, while M1 subset and TAMs in tumor islet were associated with favorable survival of lung cancer. CD204-positive TAMs are the preferable marker for prognostic prediction in NSCLC

Although the density of total CD68+ TAMs is not associated with overall survival, the localization and M1/M2 polarization of TAMs are potential

cancer and high M1/M2 macrophage ratio in tumor tissues predicted

as a probable prognostic factor, the multiple roles that TAMs play in pancreatic cancer progression have not yet been delineated. Additional mechanistic insight into the pathways that regulate the differentiation of

The density of TAMs has an impact on the overall survival of pancreatic cancer patients. M2-TAMs can be recognized as a prognostic indicator in [18]

[11, 12, 19]

[13, 20, 21]

[22]

[23]

[24, 25]

[8]

[26]

[27]

[28]

[29]

[30]

[31]

[32]

Breast CD68 as a biomarker for TAMs to evaluate the risk is better than CD163

Gastric The amount of TAMs in tumor stroma predicts the size, stage and

Lung The prognostic value of tumor-infiltrating TAMs in lung cancer is still

metastasis of the gastric tumor

prognostic predictors of NSCLC

TAMs from monocytes is required

better prognosis

pancreatic cancer

features of GBMs

Hepatocellular carcinoma

Non-Hodgkin's lymphoma

Hodgkin's lymphoma

Colorectal (CRC)

Squamous cell carcinoma of the head and neck (SCCHN)

Cervix Tumor-infiltrating CD204+ M2 macrophages may predict poor prognosis in patients with cervical adenocarcinoma

Ovarian CD163+ TAM infiltration was associated with poor prognosis of ovarian

Pancreatic Although TAM populations in tumor stroma are high, marking them

Renal CD68 alone has a poor predictive value, while low CD11+ and high

Glioblastoma TAM, accounting for approximately 30% of the GBM bulk cell

Melanoma Independent of their intratumoral distribution, the prevalent

indicator of patients' outcome

adverse outcomes in adult cHL

*TAMs as potential predictive indicators in several tumor types.*

CD206+ as single variables correlated with reduced survival

population, may explain, at least in part, the immunosuppressive

The prognostic value of TAMs in patients with hepatocellular carcinoma (HCC) is still controversial. TAMs could serve as independent predictive indicators and therapeutic targets for HCC. Further trials are needed to elucidate the exact relationship and the underlying mechanism

accumulation of M2 TAMs in MM is statistically confirmed to be a poor

High-density CD68+ and CD163+ TAMs, and also high CD163+/CD68+ TAMs ratio is significantly correlated with poor overall survival

High density of either CD68+ or CD163+ TAMs is a robust predictor of

The role of tumor-associated macrophages (TAMs) in predicting the prognosis of CRC remains controversial. Still, high-density CD68+ macrophage infiltration can be a good prognostic marker

CD68+ marker has no prognostic utility in patients with SCCHN; the

M2-like marker CD163+ predicts poor prognosis

in gastric cancer patients

*DOI: http://dx.doi.org/10.5772/intechopen.92298*

*Macrophages*

and CD206 [3].

cancers [10].

lung cancer [13].

TAMs often exhibit an array of activation states. In general, they are skewed away from the "classically" activated, tumoricidal phenotype (sometimes referred to as M1) toward an "alternatively" activated tumor-promoting one (M2) [1]. The classically activated M1 macrophages are stimulated by microbial substrates such as lipopolysaccharide, Toll-like receptor ligands and cytokines such as IFN-γ. They are characterized by secretion of pro-inflammatory cytokines such as interleukins IL-6, IL-12, IL-23 and TNF-α and express high levels of major histocompatibility complex class II (MHC-II), CD68, and CD80 and CD86 costimulatory molecules. The alternatively activated M2 macrophages are stimulated by IL-4 and IL-13, secrete IL-10 and TGF-β and express low levels of MHC-II and feature expression of CD163

Unfortunately, M2 cells are the most representative cells of the TAM population within the tumor promoting genetic instability, local immunosuppression and stem cell nurturing [4] and providing essential support for a malignant phenotype [5]. In the early stages of cancers of the lung, colon and stomach, the macrophages in the normoxic milieu display an M1 phenotype and are associated with good prognosis, but within avascular areas of the tumor, TAMs alter the gene expression profile, favoring a protumor M2 phenotype, correlated with a bad prognosis [6]. In **Table 1** are showed recent conclusions concerning the correlation between TAMs and clinical prognostics in several tumor types. In human breast carcinomas, high TAM density is also associated with poor prognosis [7]. TAMs in renal cell carcinoma show a mixed M1/M2 phenotype. CD68 alone has a poor predictive value, while low CD11+ and high CD206+ as single variables correlated with reduced survival [8]. There is strong evidence for an inverse relationship between TAM density and clinical prognosis in solid tumors of the breast, prostate, ovary and cervix. Type I and II endometrial carcinomas had significantly higher macrophage density in both epithelial and stromal compartments than benign endometrium [9]. Type II cancers have nearly twice the TAM density of type 1 cancers and this difference may be due to M1 macrophage predominance in the stroma of type II

TAMs' distribution pattern could be an independent prognostic factor for the overall survival of gastric cancer patients, invasive front-/stroma-dominant pattern having worse outcomes [11]. Studies have shown that the amount of TAMs in tumor stroma predicts the size, stage and metastasis of the gastric tumor [12]. In lung cancer, M2 subset and TAMs in tumor stroma were associated with worse survival, while M1 subset and TAMs in tumor islet were associated with favorable survival of

While most cancer research has focused upon these changes and most therapeutics are directed against these tumor cells, it is now apparent that the non-malignant cells in the microenvironment evolve along with the tumor and provide essential support for their malignant phenotype [5]. The knowledge of TAM activation status may allow the therapeutic targeting of TAMs, once TAMs' targeting/modulating agents pass clinical trials and become widely available [6, 14]. The role of macrophages in tumor progression remains to be fully elucidated, in part due to the contrasting roles they play depending on their polarization [15]. Both the systemic and local environments play a tumor-initiating role through the generation of persistent inflammatory responses to a variety of stimuli [16]. To support this correlative data between macrophage-mediated inflammation and cancer induction, genetic ablation of the anti-inflammatory transcription factor STAT3 in macrophages results in a chronic inflammatory response in the colon that is sufficient to induce invasive adenocarcinoma. However, it is unclear whether macrophages in some inflammatory situations can kill aberrant cells before they become tumorigenic and thus be

**22**

antitumoral [17].


### **Table 1.**

*TAMs as potential predictive indicators in several tumor types.*

Targeting a single signaling axis that promotes the immunosuppressive and protumoral functions of macrophages is inadequate as there are multiple signals involved in the communication between tumor cells and TAMs. Identifying and inhibiting key driver pathways, which are critical for both cancer cell survival and TAM activation, may offer therapeutic advantages as they disrupt the vicious positive feedback loop between tumor and TAMs [33]. Prevention of TAM accumulation and reduction of TAM presence by depleting existing TAMs represent novel strategies for an indirect cancer therapy specifically aimed at tumor-promoting cells within the microenvironment, but the challenge with this approach is to find ways for local administration of such drugs to the tumor [15]. Targeting TAM polarity toward an M1 phenotype also became a real immunotherapeutical approach in cancer, recalling responses from both innate and adaptive immune systems, leading to tumor regression [4].

Triple combination of anti-CTLA-4, anti-PD-1 and G47Δ-mIL12 was associated with macrophage influx and M1-like polarization in two glioma models [34]. A combination of a bivalent ganglioside and β-glucan, a yeast-derived polysaccharide, able to differentiate TAMs into an M1 phenotype is currently under investigation in a phase I clinical trial of patients with neuroblastoma [35]. Vadimezan, a fused tricyclic analog of flavone acetic acid, was found to repolarize macrophages in M1 phenotype, and it has been the subject of numerous preclinical studies and clinical trials [36]. Zoledronic acid, a clinical drug for cancer therapy, has been found to inhibit spontaneous mammary carcinogenesis by reverting macrophages from the M2 phenotype to the M1 phenotype [37].

### **2. Herbal compounds in TAM modulation**

Research to date suggests that, despite the potency of cytotoxic anticancer agents and the high specificity that can be achieved by immunotherapy, neither of these two types of treatment is sufficient to eradicate the disease. Moreover, even in standard chemotherapy, there has been efficiency through the introduction into current practice of treatments with combinations of drugs [38]. In general, literature data show that the combination of conventional treatment with natural compounds exerts an additive effect caused by the alternative activation of signaling pathways that induce cell death or increase the activity of the chemotherapeutic agent. The involvement of these natural compounds (alone or in combination therapy) in the immunobiology of cancer is a branch that has not yet been studied but offers major therapeutic opportunities. Herbal compounds have many regulatory effects on macrophage polarization, but the specific mechanisms, signaling pathways and target genes involved remain incompletely understood [39]. Their effects, according to recent research studies, are summarized in **Figure 1**.

Although natural products have historically been a critical source for therapeutic drugs, sometimes natural molecules may suffer from insufficient efficacy, unacceptable pharmacokinetic properties, undesirable toxicity or reduced availability, which impedes their direct therapeutic application. Poor availability of some natural compounds, despite their pharmacological effects, limits their clinical application. In recent years, there has been an increased interest in developing nanoformulations with increased bioavailability and fewer side effects. For instance, TAM-rich tumors, due to their enhanced permeability, demonstrated an elevated retention (>700%) of the nanotherapeutic (poly(d,l-lactic-*co*-glycolic acid)-*b*-poly(ethylene glycol) (PLGA-PEG)), as compared to TAM-deficient tumors [14].

**25**

**2.1 Saponins**

**Figure 1.**

to anticancer drugs [40, 41].

Triterpenic compounds, including corosolic acid, tigogenin, timosaponin AIII, neoaspidistrin and oleanolic acid, suppress the CD163 expression. Corosolic and oleanolic acids change M2 polarization to M1 polarization in human monocytederived macrophages (HMDMs) by suppressing STAT3 and NF-kB activation. The effects of these two compounds were exerted not only on macrophages but also on glioblastoma cells, suppressing tumor cell proliferation and sensitizing tumor cells

*Herbal compounds and their main actions on TAMs in cancer progression.*

M2 polarization was switched also by astragaloside IV (AS-IV, 3-O-β-dxylopyranosyl-6-O-β-d-glucopyranosyl cycloastragenol), a natural saponin extracted from *Astragali* radix, by modulating the AMPK signaling pathway. In the intravenous lung cancer model, AS-IV treatment did not alter the percentage of macrophages but did significantly reduce the number of M2 macrophages [42]. In another study, G-Rh2, a monomeric compound extracted from *Panax ginseng* C. A.

*Targeting Tumor-Associated Macrophages by Plant Compounds*

*DOI: http://dx.doi.org/10.5772/intechopen.92298*

### *Targeting Tumor-Associated Macrophages by Plant Compounds DOI: http://dx.doi.org/10.5772/intechopen.92298*

### **Figure 1.**

*Macrophages*

to tumor regression [4].

M2 phenotype to the M1 phenotype [37].

**2. Herbal compounds in TAM modulation**

to recent research studies, are summarized in **Figure 1**.

Targeting a single signaling axis that promotes the immunosuppressive and protumoral functions of macrophages is inadequate as there are multiple signals involved in the communication between tumor cells and TAMs. Identifying and inhibiting key driver pathways, which are critical for both cancer cell survival and TAM activation, may offer therapeutic advantages as they disrupt the vicious positive feedback loop between tumor and TAMs [33]. Prevention of TAM accumulation and reduction of TAM presence by depleting existing TAMs represent novel strategies for an indirect cancer therapy specifically aimed at tumor-promoting cells within the microenvironment, but the challenge with this approach is to find ways for local administration of such drugs to the tumor [15]. Targeting TAM polarity toward an M1 phenotype also became a real immunotherapeutical approach in cancer, recalling responses from both innate and adaptive immune systems, leading

Triple combination of anti-CTLA-4, anti-PD-1 and G47Δ-mIL12 was associated

Research to date suggests that, despite the potency of cytotoxic anticancer agents and the high specificity that can be achieved by immunotherapy, neither of these two types of treatment is sufficient to eradicate the disease. Moreover, even in standard chemotherapy, there has been efficiency through the introduction into current practice of treatments with combinations of drugs [38]. In general, literature data show that the combination of conventional treatment with natural compounds exerts an additive effect caused by the alternative activation of signaling pathways that induce cell death or increase the activity of the chemotherapeutic agent. The involvement of these natural compounds (alone or in combination therapy) in the immunobiology of cancer is a branch that has not yet been studied but offers major therapeutic opportunities. Herbal compounds have many regulatory effects on macrophage polarization, but the specific mechanisms, signaling pathways and target genes involved remain incompletely understood [39]. Their effects, according

Although natural products have historically been a critical source for therapeutic

drugs, sometimes natural molecules may suffer from insufficient efficacy, unacceptable pharmacokinetic properties, undesirable toxicity or reduced availability, which impedes their direct therapeutic application. Poor availability of some natural compounds, despite their pharmacological effects, limits their clinical application. In recent years, there has been an increased interest in developing nanoformulations with increased bioavailability and fewer side effects. For instance, TAM-rich tumors, due to their enhanced permeability, demonstrated an elevated retention (>700%) of the nanotherapeutic (poly(d,l-lactic-*co*-glycolic acid)-*b*-poly(ethylene glycol) (PLGA-PEG)), as compared to TAM-deficient

with macrophage influx and M1-like polarization in two glioma models [34]. A combination of a bivalent ganglioside and β-glucan, a yeast-derived polysaccharide, able to differentiate TAMs into an M1 phenotype is currently under investigation in a phase I clinical trial of patients with neuroblastoma [35]. Vadimezan, a fused tricyclic analog of flavone acetic acid, was found to repolarize macrophages in M1 phenotype, and it has been the subject of numerous preclinical studies and clinical trials [36]. Zoledronic acid, a clinical drug for cancer therapy, has been found to inhibit spontaneous mammary carcinogenesis by reverting macrophages from the

**24**

tumors [14].

*Herbal compounds and their main actions on TAMs in cancer progression.*

### **2.1 Saponins**

Triterpenic compounds, including corosolic acid, tigogenin, timosaponin AIII, neoaspidistrin and oleanolic acid, suppress the CD163 expression. Corosolic and oleanolic acids change M2 polarization to M1 polarization in human monocytederived macrophages (HMDMs) by suppressing STAT3 and NF-kB activation. The effects of these two compounds were exerted not only on macrophages but also on glioblastoma cells, suppressing tumor cell proliferation and sensitizing tumor cells to anticancer drugs [40, 41].

M2 polarization was switched also by astragaloside IV (AS-IV, 3-O-β-dxylopyranosyl-6-O-β-d-glucopyranosyl cycloastragenol), a natural saponin extracted from *Astragali* radix, by modulating the AMPK signaling pathway. In the intravenous lung cancer model, AS-IV treatment did not alter the percentage of macrophages but did significantly reduce the number of M2 macrophages [42]. In another study, G-Rh2, a monomeric compound extracted from *Panax ginseng* C. A. Mey (ginseng), converts the differentiation of macrophages from M2 to M1 phenotype resulting in the decreased levels of MMPs and VEGF. By blocking the PI3K-Akt signaling pathway, the compound prevented the metastasis of lung cancer (NSCLC) cells [43]. Recently, a novel EV-liked ginseng-derived nanoparticle (GDNP) was tested in melanoma, and it altered M2 polarization both *in vitro* and *in vivo*, depending on TLR4 and MyD88 signaling and contributing to an antitumor response [44].

A potential role of celastrol, a pentacyclic triterpenoid in antimetastasis treatment, was suggested by Yang et al. [45], which found that this compound suppresses M2-like polarization by interfering with STAT6 signaling pathway after stimulation with IL-13. An active role in decreasing macrophage recruitment and tumor angiogenesis was showed for lupeol and stigmasterol in an *in vivo* model [46].

### **2.2 Alkaloids**

Treatment with 9-hydroxycanthin-6-one, a β-carboline alkaloid isolated from the *Ailanthus altissima* stem bark, inhibited the levels of M2 phenotype markers and some cancer-promoting factors, such as MMP-2, MMP-9 and VEGF, in macrophages educated in ovarian cancer–conditioned medium. The compound also decreased the expressions of MCP-1 and RANTES, major determinants of macrophage recruitment at tumor sites, in ovarian cancer cells [47].

A regulatory effect on macrophage differentiation during tumor development exerts phlenumdines E, A, hupermine A and 12-epi-lycopodine-N-oxide isolated from the club moss *Phlegmariurus nummulariifolius* (Blume) Ching, which exhibited an inhibitory effect on IL-10–induced expression of CD163, an M2 phenotype marker, in HMDMs [48].

Sophoridine, a bioactive alkaloid extracted from the seeds of *Sophora alopecuroides* L, was able to reshape gastric cancer immune microenvironment by shifting TAM polarization to M1 and suppressing M2-TAM polarization through TLR4/IRF3 axis [49].

### **2.3 Phenolic compounds**

### *2.3.1 Chalcones*

In a model of azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced colitis-associated tumorigenesis, it was showed that isoliquiritigenin (6′-deoxychalcone) inhibits M2 macrophage polarization depending on the downregulation of the IL-6/STAT3 pathway [50]. The same mechanism was proposed by Sumiyoshi et al. [51], for xanthoangelol and 4-hydroxyderricin, chalcones isolated from *Angelica keiskei* roots. In the *in vivo* study, the antitumor action of xanthoangelol was higher than that of 4-hydroxyderricin and it was proposed that the presence of a 4-free phenolic OH and/or the presence of a longer isoprene moiety in C-3 could be the cause of better activity of xanthoangelol. Reducing breast cancer cells' migration with the aid of M2 macrophages was achieved *in vitro* by the total flavonoid from *Glycyrrhizae Radix et Rhizoma* and isoliquiritigenin. These compounds inhibited gene and protein expression of Arg-1, upregulated gene of HO-1 and protein expression of iNOS, and enhanced the expression of microRNA 155 and its target gene SHIP1 [52].

### *2.3.2 Catechins*

Macrophage infiltration and differentiation of macrophages into tumorpromoting M2 macrophage were decreased by epigallocatechin gallate (EGCG) treatment in murine tumor models and the molecular mechanism proposed was

**27**

*2.3.4 Isoflavones*

*Targeting Tumor-Associated Macrophages by Plant Compounds*

the downregulation of NF-κB pathway [53, 54]. EGCG can be rapidly degraded *in vivo* limiting its clinical application. A peracetate-protected EGCG (Pro-EGCG) synthesized by modification of the reactive hydroxyl groups with peracetate groups proved six times more stability than EGCG and showed greater efficacy in induction of cell death in leukemic cells. Treatment with Pro-EGCG inhibits differentiation of macrophages toward TAMs through decreasing CXCL12 expression in endometrial stromal cells with no influence on the expression level of CD163 and CD206 [55].

Luteolin, 3 0,4 0,5,7-tetrahydroxyflavone, is a common flavonoid derived from various plants and inhibits IL-4–induced phosphorylation of STAT6 and the TAM phenotype, ameliorating the recruitment of monocytes and the migration of lung cancer cells by the reduction of chemokine CCL2 secretion from macrophages [56]. The antitumor mechanism of luteolin in non-small cell lung carcinoma (NSCLC) was mediated by downregulation of TAM receptor tyrosine kinases (RTKs), and it was found to decrease the protein levels of all three TAM RTKs in the A549 and A549/ CisR cells in a dose-dependent manner [57]. In an *in vitro* tumor model, cobalt chloride (CoCl2) was used to simulate hypoxia and it was showed that luteolin decreased the expression of VEGF and MMP-9, which promote angiogenesis. In addition, luteolin also suppressed the activation of HIF-1 and phosphorylated-signal transducer and

The regulation of M2 macrophage repolarization through inhibiting PI3K/Akt signal pathway is the mechanism proposed for baicalein (5,6,7-trihydroxyflavone), a widely used Chinese herbal medicine derived from the root of *Scutellaria baicalensis*. Changing the phenotype of macrophages from M2 to M1 was supported by decreasing of M2-specific marker CD206 correlated to the increased M1-specific marker CD86. Still, the authors of the study suggested that the cytotoxic effect of baicalein on breast cancer cells directly is more pronounced than on TAMs (IC 50 of baicalein for MDA-MB-231 at 24 h, 48 h and 72 h was 79.12/50.10/34.77 μmol/L, for MCF-7 at 24 h, 48 h and 72 h was 49.76/43.73/39.44 μmol/L, for TAM at 24 h, 48 h and 72 h

It has been reported that a novel chrysin (5,7-dihydroxyflavone) analog 8-bromo-7-methoxychrysin has anticancer activities with more potent bioactivity than the lead compound [60]. It also has the capacity to regulate the tumor microenvironment by inhibition of NF-κB activation, suppressing significantly the expression of the M2 macrophage marker CD163 and modulating the secretion

According to traditional Chinese medicine (TCM) theory, herbs with Qi-tonifying character are involved in improving the defense capacity of immune system. Total flavonoids from *Glycyrrhizae Radix et Rhizoma* significantly inhibited the expression of Arg-1 (above 90% at 100 μg/mL), one of the phenotype markers of M2 macrophages, and suppressed M2 polarization of macrophages partly by inactivating STAT6 pathway. The regulation of M1 and M2 markers' expressions

Naringin (4′,5,7 trihydroxyflavanone-7-rhamnoglucoside) exert a potential inhibitory effect on tumor progression by inducing CD169-positive and M1-like macrophages, potentially correlating with cytotoxic T-cell activation [63].

Puerarin [4H-1-benzopyran-4-one, 8-β-d-glucopyranosyl-7-hydroxy-3- (4-hydroxyphenyl)] is the major bioactive ingredient isolated from the root of

activator of STAT3 signaling, particularly within the M2-like TAMs [58].

was 191.5/107.1/41.78 μmol/L, respectively) [59].

was partly due to the enhancement of miR-155 levels [62].

profile of TAM cytokines [61].

*DOI: http://dx.doi.org/10.5772/intechopen.92298*

*2.3.3 Flavonoids*

the downregulation of NF-κB pathway [53, 54]. EGCG can be rapidly degraded *in vivo* limiting its clinical application. A peracetate-protected EGCG (Pro-EGCG) synthesized by modification of the reactive hydroxyl groups with peracetate groups proved six times more stability than EGCG and showed greater efficacy in induction of cell death in leukemic cells. Treatment with Pro-EGCG inhibits differentiation of macrophages toward TAMs through decreasing CXCL12 expression in endometrial stromal cells with no influence on the expression level of CD163 and CD206 [55].

### *2.3.3 Flavonoids*

*Macrophages*

**2.2 Alkaloids**

marker, in HMDMs [48].

TLR4/IRF3 axis [49].

*2.3.1 Chalcones*

*2.3.2 Catechins*

**2.3 Phenolic compounds**

Mey (ginseng), converts the differentiation of macrophages from M2 to M1 phenotype resulting in the decreased levels of MMPs and VEGF. By blocking the PI3K-Akt signaling pathway, the compound prevented the metastasis of lung cancer (NSCLC) cells [43]. Recently, a novel EV-liked ginseng-derived nanoparticle (GDNP) was tested in melanoma, and it altered M2 polarization both *in vitro* and *in vivo*, depending on TLR4 and MyD88 signaling and contributing to an antitumor response [44]. A potential role of celastrol, a pentacyclic triterpenoid in antimetastasis treatment, was suggested by Yang et al. [45], which found that this compound suppresses M2-like polarization by interfering with STAT6 signaling pathway after stimulation with IL-13. An active role in decreasing macrophage recruitment and tumor angiogenesis was

Treatment with 9-hydroxycanthin-6-one, a β-carboline alkaloid isolated from the *Ailanthus altissima* stem bark, inhibited the levels of M2 phenotype markers and some cancer-promoting factors, such as MMP-2, MMP-9 and VEGF, in macrophages educated in ovarian cancer–conditioned medium. The compound also decreased the expressions of MCP-1 and RANTES, major determinants of macro-

A regulatory effect on macrophage differentiation during tumor development exerts phlenumdines E, A, hupermine A and 12-epi-lycopodine-N-oxide isolated from the club moss *Phlegmariurus nummulariifolius* (Blume) Ching, which exhibited an inhibitory effect on IL-10–induced expression of CD163, an M2 phenotype

Sophoridine, a bioactive alkaloid extracted from the seeds of *Sophora alopecuroides* L, was able to reshape gastric cancer immune microenvironment by shifting TAM polarization to M1 and suppressing M2-TAM polarization through

In a model of azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced colitis-associated tumorigenesis, it was showed that isoliquiritigenin (6′-deoxychalcone) inhibits M2 macrophage polarization depending on the downregulation of the IL-6/STAT3 pathway [50]. The same mechanism was proposed by Sumiyoshi et al. [51], for xanthoangelol and 4-hydroxyderricin, chalcones isolated from *Angelica keiskei* roots. In the *in vivo* study, the antitumor action of xanthoangelol was higher than that of 4-hydroxyderricin and it was proposed that the presence of a 4-free phenolic OH and/or the presence of a longer isoprene moiety in C-3 could be the cause of better activity of xanthoangelol. Reducing breast cancer cells' migration with the aid of M2 macrophages was achieved *in vitro* by the total flavonoid from *Glycyrrhizae Radix et Rhizoma* and isoliquiritigenin. These compounds inhibited gene and protein expression of Arg-1, upregulated gene of HO-1 and protein expression of iNOS, and

enhanced the expression of microRNA 155 and its target gene SHIP1 [52].

Macrophage infiltration and differentiation of macrophages into tumorpromoting M2 macrophage were decreased by epigallocatechin gallate (EGCG) treatment in murine tumor models and the molecular mechanism proposed was

showed for lupeol and stigmasterol in an *in vivo* model [46].

phage recruitment at tumor sites, in ovarian cancer cells [47].

**26**

Luteolin, 3 0,4 0,5,7-tetrahydroxyflavone, is a common flavonoid derived from various plants and inhibits IL-4–induced phosphorylation of STAT6 and the TAM phenotype, ameliorating the recruitment of monocytes and the migration of lung cancer cells by the reduction of chemokine CCL2 secretion from macrophages [56]. The antitumor mechanism of luteolin in non-small cell lung carcinoma (NSCLC) was mediated by downregulation of TAM receptor tyrosine kinases (RTKs), and it was found to decrease the protein levels of all three TAM RTKs in the A549 and A549/ CisR cells in a dose-dependent manner [57]. In an *in vitro* tumor model, cobalt chloride (CoCl2) was used to simulate hypoxia and it was showed that luteolin decreased the expression of VEGF and MMP-9, which promote angiogenesis. In addition, luteolin also suppressed the activation of HIF-1 and phosphorylated-signal transducer and activator of STAT3 signaling, particularly within the M2-like TAMs [58].

The regulation of M2 macrophage repolarization through inhibiting PI3K/Akt signal pathway is the mechanism proposed for baicalein (5,6,7-trihydroxyflavone), a widely used Chinese herbal medicine derived from the root of *Scutellaria baicalensis*. Changing the phenotype of macrophages from M2 to M1 was supported by decreasing of M2-specific marker CD206 correlated to the increased M1-specific marker CD86. Still, the authors of the study suggested that the cytotoxic effect of baicalein on breast cancer cells directly is more pronounced than on TAMs (IC 50 of baicalein for MDA-MB-231 at 24 h, 48 h and 72 h was 79.12/50.10/34.77 μmol/L, for MCF-7 at 24 h, 48 h and 72 h was 49.76/43.73/39.44 μmol/L, for TAM at 24 h, 48 h and 72 h was 191.5/107.1/41.78 μmol/L, respectively) [59].

It has been reported that a novel chrysin (5,7-dihydroxyflavone) analog 8-bromo-7-methoxychrysin has anticancer activities with more potent bioactivity than the lead compound [60]. It also has the capacity to regulate the tumor microenvironment by inhibition of NF-κB activation, suppressing significantly the expression of the M2 macrophage marker CD163 and modulating the secretion profile of TAM cytokines [61].

According to traditional Chinese medicine (TCM) theory, herbs with Qi-tonifying character are involved in improving the defense capacity of immune system. Total flavonoids from *Glycyrrhizae Radix et Rhizoma* significantly inhibited the expression of Arg-1 (above 90% at 100 μg/mL), one of the phenotype markers of M2 macrophages, and suppressed M2 polarization of macrophages partly by inactivating STAT6 pathway. The regulation of M1 and M2 markers' expressions was partly due to the enhancement of miR-155 levels [62].

Naringin (4′,5,7 trihydroxyflavanone-7-rhamnoglucoside) exert a potential inhibitory effect on tumor progression by inducing CD169-positive and M1-like macrophages, potentially correlating with cytotoxic T-cell activation [63].

### *2.3.4 Isoflavones*

Puerarin [4H-1-benzopyran-4-one, 8-β-d-glucopyranosyl-7-hydroxy-3- (4-hydroxyphenyl)] is the major bioactive ingredient isolated from the root of traditional Chinese medicine Ge-gen (*Radix Puerariae*) able to suppress the cell invasion and migration probably through inactivating MEK/ERK 1/2 pathway in a model of NSCLC. Also, it was showed that puerarin acts directly on macrophages by increasing M1 macrophage markers (CD197+, iNOS+ and CD40+) and reducing the expression of M2 markers (CD206+, Arg-1+ and CD163+) [64].

Another isoflavone, genistein, can inhibit the increased M2 polarization of macrophages and stemness of ovarian cancer cells by co-culture of macrophages with ovarian cancer stem-like cells through disrupting IL-8/STAT3 signaling axis [65].

### *2.3.5 Phenolic acids*

Chlorogenic acid (5-caffeoylquinic acid, CA), the ester of caffeic acid, is a phenolic compound widely found in plants. It was showed that this compound inhibits growth of G422 glioma *in vivo*, an effect associated with a decrease of M2-like TAMs and recruitment of M1-like TAMs into tumor tissue. Low dose (1 μM) of CA could significantly inhibit the M2 macrophage-induced proliferation of glioma and breast cancer cells, mainly via STAT1 and STAT6 signaling pathways [66]. Oršolić et al. [67] concluded that the antitumor activity of CA is the result of the synergistic activities of different mechanisms by which CA acts on proliferation, angiogenesis, immunomodulation and survival. Mice with Ehrlich ascites tumor (EAT) and treated for 10 days with CA in a dose of 40 and/or 80 mg kg<sup>−</sup><sup>1</sup> showed an increase of the cytotoxic actions of M1 macrophages and inhibition of the tumor growth, probably mediated through its antioxidative activity.

### *2.3.6 Lignans*

Deoxyschizandrin, a major dibenzocyclooctadiene lignan present in *Schisandra chinensis* berries, significantly suppressed CD163 and CD209 expression, inhibiting protumor mediator production as well as M2 polarization in TAM macrophages stimulated by the conditioned medium of A2780 cells [68].

### *2.3.7 Other phenolic compounds*

Several studies focused on a stilbene derivative, resveratrol (3,4′,5-trihydroxystilbene), a widely studied compound that exhibits potent preventive effects on lifestyle-related disorders such as hyperlipidemia, obesity, coronary heart disease and cancer, as well as on aging. In lung cancer tumors, resveratrol induced their sluggish growth by decreasing F4/80 positive expressing cells and M2 polarization (lower expression of M2 markers-IL-10, Arg-1 and CD206), probably by STAT3 suppression [69]. Antitumor and antimetastatic effects of resveratrol (25 and 50 μM) based on the regulation of M2 macrophage activation and differentiation were confirmed by Kimura and Sumiyoshi [70], which also conducted a study for correlation of stilbene structure with biological activity. Among the nine stilbenes examined, 2,3-,3,4-, and 4,4′-dihydroxystilbene inhibited the production of MCP-1 in M2-polarized THP-1 macrophages at a concentration of 50 μM, demonstrating that the inhibitory effects of stilbenes with dihydroxy groups on the production of MCP-1 were greater than those with mono-hydroxyl groups. Dihydroxystilbene at 25 and 50 μM, 3,4-dihydroxystilbene at 50 μM, and 4,4′-dihydroxystilbene at 10, 25 and 50 μM significantly inhibited the production of IL-10 by M2 THP-1 macrophages. The three dihydroxystilbenes, 2,3-, 3,4-, and 4,4′-dihydroxystilbenes, at concentrations of 10–50 μM inhibited p-STAT3 increase during M2 THP-1 macrophage differentiation induced by IL-4 plus IL-13 [71].

**29**

*Targeting Tumor-Associated Macrophages by Plant Compounds*

The resveratrol analogue, HS-1793 (4-(6-hydroxy-2-naphthyl)-1,3-benzenediol), was also shown to elevate the level of IFN-γ production conducting reprograming

Curcumin ((1*E*,6*E*)-1,7-Bis(4-hydroxy-3-methoxyphenyl)hepta-1,6-diene-3,5-dione), a natural phenol and the main active ingredient in turmeric, acts in several ways as a suppressor of macrophage functions. Even though curcumin has previously received considerable attention from researchers as an anti-inflammatory agent, it has a promising future in the area of immunomodulation [73]. Most of the studies on curcumin focused on the anti-inflammatory effect, promoting the conversion of macrophages from M1 to an anti-inflammatory and protective M2 phenotype [73]. Gao et al. [74] demonstrated that curcumin plays a key role in M2 polarization in two ways: (1) via the inhibition of DNA methyltransferase3b (DNMT3b), overexpression of which can promote increased M1 polarization, and (2) via increased phosphorylation of signal transducer and activator of transcription STAT-6, an important transcription factor activated by IL-4 and IL-10. Other studies showed that curcumin also induces TAMs re-polarization from tumor-promoting M2 phenotype toward the more antitumor M1 phenotype in tumor-bearing hosts, mediated by inhibition of STAT3 activity [75]*.* Curcumin administration and delivery to glioblastoma brain tumors (GBM) caused a dramatic re-polarization of TAMs from an M2 to M1 phenotype and tumor remission in 50–60% of GBMbearing mice [76]. Hydrazinocurcumin, a synthetic analog of curcumin encapsulated within nanoparticles, reeducates TAMs to an M1-like phenotype IL-10 low

It was showed that TriCurin, a synergistic formulation of curcumin, resveratrol, and epicatechin gallate (molar ratio C:E:R: 4:1:12.5) can shift TAM polarity in HPV-positive HNSCC by silencing the M2 TAM and activating/recruiting a discrete population of M1 TAM while maintaining a constant number of overall intra-tumor Iba1+ TAM, along with expression of activated STAT3 and induction of activated STAT1 and NF-kB (p65) [77]. Moreover, a liposomal formulation of TriCurin with increased bioavailability (TrLp) was able to cause repolarization of M2-like tumor (GBM)-associated microglia/macrophages to the tumoricidal M1-like phenotype

In a urethane-induced lung carcinogenic model, lung carcinogenesis was ameliorated with increased M1 macrophages and decreased M2 macrophages in the lung interstitial by administration of 6-gingerol ((*S*)-5-hydroxy-1-(4-hydroxy-3 methoxyphenyl)-3-decanone), the main bioactive component in ginger (*Zingiber officinale* Roscoe). M2 macrophage-resetting efficacy of 6-gingerol was confirmed in a Lewis lung cancer allograft model and the mechanism proposed was the reduction of Arg-1 and ROS levels and elevation of L-arginine and NO levels [79].

Also, it was showed that paeoniflorin, one of the major active constituents of *Paeonia lactiflora* Pallas, inhibits the alternative activation of macrophages in subcutaneous xenograft tumors of the C57BL/6 J mice at doses of 40 and 20 mg·kg<sup>−</sup><sup>1</sup>

It was suggested that modulation of TAM polarization was implicated in the antitumor immunostimulatory activity of polysaccharides from *Panax japonicus* (ginseng). The transcription and production of TGF-β and IL-10, two well-known immunosuppressive cytokines secreted by TAMs, were reduced in response to *Panax* polysaccharides and also the number of infiltrated CD168+ M2 TAMs was substantially declined although the number of CD68+ total macrophages in transplanted tumor tissues remained almost unchanged [81]. A significant inhibition of Arg-1 expression (above 90% at 100 μg/mL), one of the phenotype markers of

[80].

and intra-GBM recruitment of activated natural killer cells [78].

*DOI: http://dx.doi.org/10.5772/intechopen.92298*

of TAMs M2 phenotype [72].

IL-12 high TGF-β low [54].

**2.4 Polysaccharides**

*Macrophages*

*2.3.5 Phenolic acids*

*2.3.6 Lignans*

*2.3.7 Other phenolic compounds*

tion induced by IL-4 plus IL-13 [71].

traditional Chinese medicine Ge-gen (*Radix Puerariae*) able to suppress the cell invasion and migration probably through inactivating MEK/ERK 1/2 pathway in a model of NSCLC. Also, it was showed that puerarin acts directly on macrophages by increasing M1 macrophage markers (CD197+, iNOS+ and CD40+) and reducing the

Another isoflavone, genistein, can inhibit the increased M2 polarization of macrophages and stemness of ovarian cancer cells by co-culture of macrophages with ovarian cancer stem-like cells through disrupting IL-8/STAT3 signaling axis [65].

Chlorogenic acid (5-caffeoylquinic acid, CA), the ester of caffeic acid, is a phenolic compound widely found in plants. It was showed that this compound inhibits growth of G422 glioma *in vivo*, an effect associated with a decrease of M2-like TAMs and recruitment of M1-like TAMs into tumor tissue. Low dose (1 μM) of CA could significantly inhibit the M2 macrophage-induced proliferation of glioma and breast cancer cells, mainly via STAT1 and STAT6 signaling pathways [66]. Oršolić et al. [67] concluded that the antitumor activity of CA is the result of the synergistic activities of different mechanisms by which CA acts on proliferation, angiogenesis, immunomodulation and survival. Mice with Ehrlich ascites tumor (EAT) and

of the cytotoxic actions of M1 macrophages and inhibition of the tumor growth,

Deoxyschizandrin, a major dibenzocyclooctadiene lignan present in *Schisandra chinensis* berries, significantly suppressed CD163 and CD209 expression, inhibiting protumor mediator production as well as M2 polarization in TAM macrophages

Several studies focused on a stilbene derivative, resveratrol (3,4′,5-trihydroxystilbene), a widely studied compound that exhibits potent preventive effects on lifestyle-related disorders such as hyperlipidemia, obesity, coronary heart disease and cancer, as well as on aging. In lung cancer tumors, resveratrol induced their sluggish growth by decreasing F4/80 positive expressing cells and M2 polarization (lower expression of M2 markers-IL-10, Arg-1 and CD206), probably by STAT3 suppression [69]. Antitumor and antimetastatic effects of resveratrol (25 and 50 μM) based on the regulation of M2 macrophage activation and differentiation were confirmed by Kimura and Sumiyoshi [70], which also conducted a study for correlation of stilbene structure with biological activity. Among the nine stilbenes examined, 2,3-,3,4-, and 4,4′-dihydroxystilbene inhibited the production of MCP-1 in M2-polarized THP-1 macrophages at a concentration of 50 μM, demonstrating that the inhibitory effects of stilbenes with dihydroxy groups on the production of MCP-1 were greater than those with mono-hydroxyl groups. Dihydroxystilbene at 25 and 50 μM, 3,4-dihydroxystilbene at 50 μM, and 4,4′-dihydroxystilbene at 10, 25 and 50 μM significantly inhibited the production of IL-10 by M2 THP-1 macrophages. The three dihydroxystilbenes, 2,3-, 3,4-, and 4,4′-dihydroxystilbenes, at concentrations of 10–50 μM inhibited p-STAT3 increase during M2 THP-1 macrophage differentia-

showed an increase

expression of M2 markers (CD206+, Arg-1+ and CD163+) [64].

treated for 10 days with CA in a dose of 40 and/or 80 mg kg<sup>−</sup><sup>1</sup>

stimulated by the conditioned medium of A2780 cells [68].

probably mediated through its antioxidative activity.

**28**

The resveratrol analogue, HS-1793 (4-(6-hydroxy-2-naphthyl)-1,3-benzenediol), was also shown to elevate the level of IFN-γ production conducting reprograming of TAMs M2 phenotype [72].

Curcumin ((1*E*,6*E*)-1,7-Bis(4-hydroxy-3-methoxyphenyl)hepta-1,6-diene-3,5-dione), a natural phenol and the main active ingredient in turmeric, acts in several ways as a suppressor of macrophage functions. Even though curcumin has previously received considerable attention from researchers as an anti-inflammatory agent, it has a promising future in the area of immunomodulation [73]. Most of the studies on curcumin focused on the anti-inflammatory effect, promoting the conversion of macrophages from M1 to an anti-inflammatory and protective M2 phenotype [73]. Gao et al. [74] demonstrated that curcumin plays a key role in M2 polarization in two ways: (1) via the inhibition of DNA methyltransferase3b (DNMT3b), overexpression of which can promote increased M1 polarization, and (2) via increased phosphorylation of signal transducer and activator of transcription STAT-6, an important transcription factor activated by IL-4 and IL-10. Other studies showed that curcumin also induces TAMs re-polarization from tumor-promoting M2 phenotype toward the more antitumor M1 phenotype in tumor-bearing hosts, mediated by inhibition of STAT3 activity [75]*.* Curcumin administration and delivery to glioblastoma brain tumors (GBM) caused a dramatic re-polarization of TAMs from an M2 to M1 phenotype and tumor remission in 50–60% of GBMbearing mice [76]. Hydrazinocurcumin, a synthetic analog of curcumin encapsulated within nanoparticles, reeducates TAMs to an M1-like phenotype IL-10 low IL-12 high TGF-β low [54].

It was showed that TriCurin, a synergistic formulation of curcumin, resveratrol, and epicatechin gallate (molar ratio C:E:R: 4:1:12.5) can shift TAM polarity in HPV-positive HNSCC by silencing the M2 TAM and activating/recruiting a discrete population of M1 TAM while maintaining a constant number of overall intra-tumor Iba1+ TAM, along with expression of activated STAT3 and induction of activated STAT1 and NF-kB (p65) [77]. Moreover, a liposomal formulation of TriCurin with increased bioavailability (TrLp) was able to cause repolarization of M2-like tumor (GBM)-associated microglia/macrophages to the tumoricidal M1-like phenotype and intra-GBM recruitment of activated natural killer cells [78].

In a urethane-induced lung carcinogenic model, lung carcinogenesis was ameliorated with increased M1 macrophages and decreased M2 macrophages in the lung interstitial by administration of 6-gingerol ((*S*)-5-hydroxy-1-(4-hydroxy-3 methoxyphenyl)-3-decanone), the main bioactive component in ginger (*Zingiber officinale* Roscoe). M2 macrophage-resetting efficacy of 6-gingerol was confirmed in a Lewis lung cancer allograft model and the mechanism proposed was the reduction of Arg-1 and ROS levels and elevation of L-arginine and NO levels [79].

Also, it was showed that paeoniflorin, one of the major active constituents of *Paeonia lactiflora* Pallas, inhibits the alternative activation of macrophages in subcutaneous xenograft tumors of the C57BL/6 J mice at doses of 40 and 20 mg·kg<sup>−</sup><sup>1</sup> [80].

### **2.4 Polysaccharides**

It was suggested that modulation of TAM polarization was implicated in the antitumor immunostimulatory activity of polysaccharides from *Panax japonicus* (ginseng). The transcription and production of TGF-β and IL-10, two well-known immunosuppressive cytokines secreted by TAMs, were reduced in response to *Panax* polysaccharides and also the number of infiltrated CD168+ M2 TAMs was substantially declined although the number of CD68+ total macrophages in transplanted tumor tissues remained almost unchanged [81]. A significant inhibition of Arg-1 expression (above 90% at 100 μg/mL), one of the phenotype markers of

M2 macrophages, was also observed for the ethanol extract of Ginseng *Radix et Rhizoma* [62]. Recently, Chen et al. [82], showed that water extract of Ginseng and Astragalus could be a novel option for integrative cancer therapies due mainly to their ability to regulate macrophage polarization.

In a murine model of sarcoma, immunotherapy with IAPS-2 (acidic polysaccharide, namely IAPS-2, from the root of *Ilex asprella*) demonstrated that it could significantly inhibit the growth of tumors via modulating the function of TAMs and increase the animal survival rate [83]. Similar results were obtained with an aqueous extract of *Trametes robiniophila* Murr (Huaier), a sandy beige mushroom found on the truck of trees and has been widely used in TCM for approximately 1600 years for its antitumor, antiangiogenic and immunomodulatory effects. Huaier not only modulates the macrophage polarization but also could inhibit the macrophage-induced angiogenesis by decreasing the expression of VEGF, MMP2 and MMP9, thus inhibiting the formation of new blood vessels in tumor [84].

### **2.5 Coumarins**

Esculetin (6,7-dihydroxycoumarin) and fraxetin (6-methoxy-7,8-dihydroxycoumarin) (50, 75 and 100 μM) inhibited the production of IL-10, MCP-1 and TGF-β-1 in macrophages and the phosphorylation of STAT 3 without affecting its expression during the differentiation of M2 macrophages. Esculetin also suppressed the increased production of these cytokines during M2 macrophage differentiation at 10–100 μM. On the other hand, daphentin (7,8-dihydroxycoumarin) had no such effects, revealing that coumarins with two hydroxyl groups at the 6 and 7 positions (esculetin) or coumarins with a methoxy group at the 6 and two hydroxyl groups at the 7 and 8 positions (fraxetin) are more active, exhibiting antitumor and antimetastatic actions in osteosarcoma LM8 cells [85]. The antitumor and antimetastatic actions of esculetin may be due to the dual actions at tumor and TAM sites: inhibition of the expression of cyclin D 1 and CDK4 in osteosarcoma LM8 cells, and also decreasing the STAT 3 phosphorylation in macrophages. In the case of fraxetin, the effects are partly attributed to the inhibition of M2 macrophage differentiation [85].

A classical formula of traditional Chinese medicine (TCM) to alleviate lung cancer–related symptoms is Bu-Fei decoction (BFD), consisting of six herbal Chinese medicines-*Codonopsis pilosula*, S*chisandra chinensis*, *Rehmannia glutinosa*, *Astragalus* sp., *Aster* sp. and *Morus* sp.-but it has not been established whether it induces an antitumor effect or it modulates the tumor microenvironment. The result of an *in vivo* study revealed that BFD successfully interrupted the interaction between tumor cells and TAMs by inhibiting the expression of two important markers: IL-10 (correlated with late stage (stage II, III and IV), lymph node metastases, pleural invasion, lymphovascular invasion and poor differentiation in NSCLC patients) and PD-L1 (correlated with poor prognosis in a number of human cancers, including breast cancer, kidney cancer and NSCLCs) [86].

### **2.6 Anthraquinones**

It has been shown that emodin (6-methyl-1,3,8-trihydroxyanthraquinone), the active ingredient of several Chinese herbs including Rhubarb (*Rheum palmatum*), inhibits the growth of a variety of tumors and enhances the responsiveness of tumors to chemotherapy agents. In breast cancer, emodin directly inhibited macrophage infiltration and M2 polarization in the tumors, independent of tumor size [87]. Previously, Jia et al. [88], showed that emodin is not cytotoxic to breast cancer cells

**31**

lating the action of XIAOPI formula [97].

M1 [96].

*Targeting Tumor-Associated Macrophages by Plant Compounds*

for patients with M2 macrophage-driven diseases [89].

**2.7 Other herbal compounds/preparations**

enhancing its radiosensitivity [91].

at concentration achieved *in vivo* (up to 30 μM) and it failed to affect macrophage infiltration in primary tumors. In contrast to its lack of effects on primary tumors, emodin dramatically suppressed lung metastasis by diminishing phosphorylation of STAT6 and C/EBPβ signaling upon IL-4 stimulation [88]. Further, it was showed that emodin suppresses the activation of multiple signaling pathways, including NF-kB, IRF5, MAPK, STAT1 or STAT6, and IRF4, depending on the environmental settings. It acts mostly on M2 polarization, suggesting that emodin could be most beneficial

In oral squamous cell carcinoma (OSCC) animal models, highly pure super critical CO2 leaf extract of *Azadirachta indica* (Neem) induces an M1 phenotype in TAMs *in vivo*, and the primary active component, nimbolide (a limonoid tetranortriterpenoid with an α,β-unsaturated ketone system and a δ-lactone ring) has significant anticancer activity in established OSCC xenografts [90]. β-Elemene, a widely known sesquiterpene, regulated the polarization of macrophages from M2 to M1, inhibiting the proliferation, migration and invasion of lung cancer cells and

Onionin A (ONA), a natural low molecular weight compound containing sulfur isolated from onions, inhibited the EOC cell-induced M2 polarization of HMDMs, and STAT3 activation was significantly inhibited by ONA treatment in all cell lines [92]. Adjunctive treatment with Withaferin A, the most abundant constituent of *Withania somnifera* (Ashwagandha) root extract, reduced myeloid cell-mediated immune suppression and polarized immunity toward a tumor-rejecting type 1

Traditional Chinese medicine provides pharmacologically efficient preparates such as KSG-002, a hydroalcoholic extract of radices *Astragalus membranaceus* and *Angelica gigas* at 3: 1 ratio that suppresses breast cancer growth and metastasis through targeting NF-κB–mediated TNF α production in macrophages [94] and SH003, mixed extract from *Astragalus membranaceus*, *Angelica gigas* and *Trichosanthes kirilowii* Maximowicz that suppresses highly metastatic breast cancer

Traditional Chinese medicine Jianpi Yangzheng Decoction (JPYZ) used for improving the quality of life and prolonging the survival of gastric cancer patients

CXCL-1 was also found to be a cytokine secreted by tumor-associated macrophage, which recruits myeloid-derived suppressor cells to form pre-metastatic niche and led to liver metastasis from colorectal cancer. The current study demonstrated that after administration of XIAOPI formula (consisting of 10 herbs including *Epimedium brevicornum*, *Cistanche deserticola*, *Leonurus heterophyllus*, *Salvia miltiorrhiza*, *Curcuma aromatica*, *Rhizoma Curcumae*, *Ligustrum lucidum*, *Radix Polygoni Multiflori preparata*, *Crassostrea gigas* and *Carapax trionycis*), the density of TAMs decreased significantly and the level of CXCL-1 was also inhibited in both mouse plasma and cellular supernatants. When CXCL-1 cytokine was co-administrated with XIAOPI formula, the antimetastatic property of XIAOPI formula was blocked, indicating that CXCL-1 might be the principal gene involved in the network regu-

was more effective compared with Jianpi Yangzheng Xiaozheng Decoction (JPYZXZ) for inducing the phenotypic change in macrophages from M2 to M1. JPYZXZ inhibits the gastric cancer EMT more effectively than JPYZ, but JPYZ primarily works to regulate the phenotypic change in macrophages from M2 to

phenotype, facilitating the development of antitumor immunity [93].

growth and metastasis by inhibiting STAT3-IL-6 signaling path [95].

*DOI: http://dx.doi.org/10.5772/intechopen.92298*

*Macrophages*

**2.5 Coumarins**

macrophage differentiation [85].

**2.6 Anthraquinones**

ing breast cancer, kidney cancer and NSCLCs) [86].

M2 macrophages, was also observed for the ethanol extract of Ginseng *Radix et Rhizoma* [62]. Recently, Chen et al. [82], showed that water extract of Ginseng and Astragalus could be a novel option for integrative cancer therapies due mainly to

In a murine model of sarcoma, immunotherapy with IAPS-2 (acidic polysaccharide, namely IAPS-2, from the root of *Ilex asprella*) demonstrated that it could significantly inhibit the growth of tumors via modulating the function of TAMs and increase the animal survival rate [83]. Similar results were obtained with an aqueous extract of *Trametes robiniophila* Murr (Huaier), a sandy beige mushroom found on the truck of trees and has been widely used in TCM for approximately 1600 years for its antitumor, antiangiogenic and immunomodulatory effects. Huaier not only modulates the macrophage polarization but also could inhibit the macrophage-induced angiogenesis by decreasing the expression of VEGF, MMP2 and MMP9, thus inhibiting the formation of new blood vessels in tumor [84].

Esculetin (6,7-dihydroxycoumarin) and fraxetin (6-methoxy-7,8-dihydroxycoumarin) (50, 75 and 100 μM) inhibited the production of IL-10, MCP-1 and TGF-β-1 in macrophages and the phosphorylation of STAT 3 without affecting its expression during the differentiation of M2 macrophages. Esculetin also suppressed the increased production of these cytokines during M2 macrophage differentiation at 10–100 μM. On the other hand, daphentin (7,8-dihydroxycoumarin) had no such effects, revealing that coumarins with two hydroxyl groups at the 6 and 7 positions (esculetin) or coumarins with a methoxy group at the 6 and two hydroxyl groups at the 7 and 8 positions (fraxetin) are more active, exhibiting antitumor and antimetastatic actions in osteosarcoma LM8 cells [85]. The antitumor and antimetastatic actions of esculetin may be due to the dual actions at tumor and TAM sites: inhibition of the expression of cyclin D 1 and CDK4 in osteosarcoma LM8 cells, and also decreasing the STAT 3 phosphorylation in macrophages. In the case of fraxetin, the effects are partly attributed to the inhibition of M2

A classical formula of traditional Chinese medicine (TCM) to alleviate lung cancer–related symptoms is Bu-Fei decoction (BFD), consisting of six herbal Chinese medicines-*Codonopsis pilosula*, S*chisandra chinensis*, *Rehmannia glutinosa*, *Astragalus* sp., *Aster* sp. and *Morus* sp.-but it has not been established whether it induces an antitumor effect or it modulates the tumor microenvironment. The result of an *in vivo* study revealed that BFD successfully interrupted the interaction between tumor cells and TAMs by inhibiting the expression of two important markers: IL-10 (correlated with late stage (stage II, III and IV), lymph node metastases, pleural invasion, lymphovascular invasion and poor differentiation in NSCLC patients) and PD-L1 (correlated with poor prognosis in a number of human cancers, includ-

It has been shown that emodin (6-methyl-1,3,8-trihydroxyanthraquinone), the active ingredient of several Chinese herbs including Rhubarb (*Rheum palmatum*), inhibits the growth of a variety of tumors and enhances the responsiveness of tumors to chemotherapy agents. In breast cancer, emodin directly inhibited macrophage infiltration and M2 polarization in the tumors, independent of tumor size [87]. Previously, Jia et al. [88], showed that emodin is not cytotoxic to breast cancer cells

their ability to regulate macrophage polarization.

**30**

at concentration achieved *in vivo* (up to 30 μM) and it failed to affect macrophage infiltration in primary tumors. In contrast to its lack of effects on primary tumors, emodin dramatically suppressed lung metastasis by diminishing phosphorylation of STAT6 and C/EBPβ signaling upon IL-4 stimulation [88]. Further, it was showed that emodin suppresses the activation of multiple signaling pathways, including NF-kB, IRF5, MAPK, STAT1 or STAT6, and IRF4, depending on the environmental settings. It acts mostly on M2 polarization, suggesting that emodin could be most beneficial for patients with M2 macrophage-driven diseases [89].

### **2.7 Other herbal compounds/preparations**

In oral squamous cell carcinoma (OSCC) animal models, highly pure super critical CO2 leaf extract of *Azadirachta indica* (Neem) induces an M1 phenotype in TAMs *in vivo*, and the primary active component, nimbolide (a limonoid tetranortriterpenoid with an α,β-unsaturated ketone system and a δ-lactone ring) has significant anticancer activity in established OSCC xenografts [90]. β-Elemene, a widely known sesquiterpene, regulated the polarization of macrophages from M2 to M1, inhibiting the proliferation, migration and invasion of lung cancer cells and enhancing its radiosensitivity [91].

Onionin A (ONA), a natural low molecular weight compound containing sulfur isolated from onions, inhibited the EOC cell-induced M2 polarization of HMDMs, and STAT3 activation was significantly inhibited by ONA treatment in all cell lines [92].

Adjunctive treatment with Withaferin A, the most abundant constituent of *Withania somnifera* (Ashwagandha) root extract, reduced myeloid cell-mediated immune suppression and polarized immunity toward a tumor-rejecting type 1 phenotype, facilitating the development of antitumor immunity [93].

Traditional Chinese medicine provides pharmacologically efficient preparates such as KSG-002, a hydroalcoholic extract of radices *Astragalus membranaceus* and *Angelica gigas* at 3: 1 ratio that suppresses breast cancer growth and metastasis through targeting NF-κB–mediated TNF α production in macrophages [94] and SH003, mixed extract from *Astragalus membranaceus*, *Angelica gigas* and *Trichosanthes kirilowii* Maximowicz that suppresses highly metastatic breast cancer growth and metastasis by inhibiting STAT3-IL-6 signaling path [95].

Traditional Chinese medicine Jianpi Yangzheng Decoction (JPYZ) used for improving the quality of life and prolonging the survival of gastric cancer patients was more effective compared with Jianpi Yangzheng Xiaozheng Decoction (JPYZXZ) for inducing the phenotypic change in macrophages from M2 to M1. JPYZXZ inhibits the gastric cancer EMT more effectively than JPYZ, but JPYZ primarily works to regulate the phenotypic change in macrophages from M2 to M1 [96].

CXCL-1 was also found to be a cytokine secreted by tumor-associated macrophage, which recruits myeloid-derived suppressor cells to form pre-metastatic niche and led to liver metastasis from colorectal cancer. The current study demonstrated that after administration of XIAOPI formula (consisting of 10 herbs including *Epimedium brevicornum*, *Cistanche deserticola*, *Leonurus heterophyllus*, *Salvia miltiorrhiza*, *Curcuma aromatica*, *Rhizoma Curcumae*, *Ligustrum lucidum*, *Radix Polygoni Multiflori preparata*, *Crassostrea gigas* and *Carapax trionycis*), the density of TAMs decreased significantly and the level of CXCL-1 was also inhibited in both mouse plasma and cellular supernatants. When CXCL-1 cytokine was co-administrated with XIAOPI formula, the antimetastatic property of XIAOPI formula was blocked, indicating that CXCL-1 might be the principal gene involved in the network regulating the action of XIAOPI formula [97].

### **3. Conclusions**

Macrophages, as key players in the tumor microenvironment, play essential roles in maintenance and progression of malignant state. Due to their plasticity, these cells balance between pro- and antitumoral effects in close correlation to specific factors. Recent immunotherapeutic strategies focus on tumor-associated macrophages in two main directions: to inhibit protumor macrophages and their suppressive effects (CCL2 inhibitors, trabectedin, zoledronic acid, JAK/STAT inhibitors, etc.) and to activate TAMs to an antitumor phenotype (TLR and CD40 agonists, PI3kδ inhibitor, VEGF and Ang2 inhibitors, etc.).

Several natural compounds/herbal extracts were studied as therapeutic/supportive agents for macrophage modulation in different types of cancers, most of them being able to change M2 polarization (protumoral) to M1 polarization (antitumoral). They belong to various classes of herbal compounds: saponins (corosolic and oleanolic acids, astragaloside, ginsenosides, celastrol, etc.), alkaloids (9-hydroxycanthin-6-one, phlenumdines E, A, hupermine A and 12-epilycopodine-N-oxide, sophoridine, etc.), flavonoids and polyphenolcarboxylic acids (isoliquiritigenin, xanthoangelol and 4-hydroxyderricin, baicalein, naringin, genistein, deoxyschizandrin, chlorogenic acid, curcumin, 6-gingerol and paeoniflorin), polysaccharides (isolated from various vegetal sources), coumarins (esculetin, fraxetin, etc.), and anthraquinones (emodin). This action is most probably achieved by downregulation of the STAT3, STAT 6 and NF-kB pathways with consecutive modulation of the secretory profile of TAM cytokines.

TCM supports the dual approach of cancer therapy, to destroy cancer cells on one hand and to improve patients' immunological status on the other hand. For several preparations such as Jianpi Yangzheng Decoction, Bu-Fei decoction and XIAOPI formula, research studies proved the correlation between cancer cells and tumor microenvironment and the effective intervention of these herbal products in delaying/breaking the tumorigenic process.

Low solubility of some herbal compounds limits their clinical application and it conducted to designing of new analogs with improved bioavailability-ginsengderived nanoparticles, peracetate-protected EGCG, chrysin and resveratrol analogs.

By now, many herbal compounds have been shown to exhibit antitumor effects in various cancer types. Further, more researches need to be focused on the influence of these valuable compounds/preparations on modulation of the tumor microenvironment, as key element in the relation of tumor-host.

### **Acknowledgements**

This research was financially supported by the Ministry of Research and Innovation in the frame of the project PN.16.41.01.01/2018, CORE Program.

**33**

**Author details**

Bucharest, Romania

National Institute for Chemical-Pharmaceutical Research and Development,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: alicearmatu@yahoo.com

provided the original work is properly cited.

Alice Grigore

*Targeting Tumor-Associated Macrophages by Plant Compounds*

*DOI: http://dx.doi.org/10.5772/intechopen.92298*

*Targeting Tumor-Associated Macrophages by Plant Compounds DOI: http://dx.doi.org/10.5772/intechopen.92298*

*Macrophages*

**3. Conclusions**

PI3kδ inhibitor, VEGF and Ang2 inhibitors, etc.).

modulation of the secretory profile of TAM cytokines.

microenvironment, as key element in the relation of tumor-host.

delaying/breaking the tumorigenic process.

**Acknowledgements**

Macrophages, as key players in the tumor microenvironment, play essential roles in maintenance and progression of malignant state. Due to their plasticity, these cells balance between pro- and antitumoral effects in close correlation to specific factors. Recent immunotherapeutic strategies focus on tumor-associated macrophages in two main directions: to inhibit protumor macrophages and their suppressive effects (CCL2 inhibitors, trabectedin, zoledronic acid, JAK/STAT inhibitors, etc.) and to activate TAMs to an antitumor phenotype (TLR and CD40 agonists,

Several natural compounds/herbal extracts were studied as therapeutic/supportive agents for macrophage modulation in different types of cancers, most of them being able to change M2 polarization (protumoral) to M1 polarization (antitumoral). They belong to various classes of herbal compounds: saponins (corosolic and oleanolic acids, astragaloside, ginsenosides, celastrol, etc.), alkaloids (9-hydroxycanthin-6-one, phlenumdines E, A, hupermine A and 12-epilycopodine-N-oxide, sophoridine, etc.), flavonoids and polyphenolcarboxylic acids (isoliquiritigenin, xanthoangelol and 4-hydroxyderricin, baicalein, naringin, genistein, deoxyschizandrin, chlorogenic acid, curcumin, 6-gingerol and paeoniflorin), polysaccharides (isolated from various vegetal sources), coumarins (esculetin, fraxetin, etc.), and anthraquinones (emodin). This action is most probably achieved by downregulation of the STAT3, STAT 6 and NF-kB pathways with consecutive

TCM supports the dual approach of cancer therapy, to destroy cancer cells on one hand and to improve patients' immunological status on the other hand. For several preparations such as Jianpi Yangzheng Decoction, Bu-Fei decoction and XIAOPI formula, research studies proved the correlation between cancer cells and tumor microenvironment and the effective intervention of these herbal products in

Low solubility of some herbal compounds limits their clinical application and it conducted to designing of new analogs with improved bioavailability-ginsengderived nanoparticles, peracetate-protected EGCG, chrysin and resveratrol analogs. By now, many herbal compounds have been shown to exhibit antitumor effects in various cancer types. Further, more researches need to be focused on the influence of these valuable compounds/preparations on modulation of the tumor

This research was financially supported by the Ministry of Research and Innovation in the frame of the project PN.16.41.01.01/2018, CORE Program.

**32**

### **Author details**

Alice Grigore National Institute for Chemical-Pharmaceutical Research and Development, Bucharest, Romania

\*Address all correspondence to: alicearmatu@yahoo.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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**38**

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TriCurin, a synergistic formulation of curcumin, resveratrol, and epicatechin gallate, repolarizes tumor-associated macrophages and triggers an immune response to cause suppression of HPV+ tumors. Cancer Immunology, Immunotherapy. 2018;**67**(5):761-774. DOI: 10.1007/s00262-018-2130-3

[78] Mukherjee S, Baidoo JNE, Sampat S, Mancuso A, David L, Cohen LS. Liposomal TriCurin, a synergistic combination of curcumin, epicatechin gallate and resveratrol, repolarizes tumor-associated microglia/macrophages, and eliminates glioblastoma (GBM) and GBM stem cells. Molecules. 2018;**23**;(1). pii: E201. DOI: 10.3390/molecules23010201

[79] Yao J, Du Z, Li Z, Zhang S, Lin Y, Li H, et al. 6-Gingerol as an arginase inhibitor prevents urethane-induced lung carcinogenesis by reprogramming tumor supporting M2 macrophages to M1 phenotype. Food & Function. 2018;**9**(9):4611-4620. DOI: 10.1039/ c8fo01147h

[80] Wu Q, Chen GL, Li YJ, Chen Y, Lin FZ. Paeoniflorin inhibits macrophage-mediated lung cancer metastasis. Chinese Journal of Natural Medicines. 2015;**13**(12):925-932. DOI: 10.1016/S1875-5364(15)30098-4

[81] Shu G, Jiang S, Mu J, Yu H, Duan H, Deng X. Antitumor immunostimulatory activity of polysaccharides from *Panax japonicus* C. A. Mey: Roles of their effects on CD4 + T cells and tumor associated macrophages. International Journal of Biological Macromolecules. 2018;**111**:430-439. DOI: 10.1016/j. ijbiomac.2018.01.011

[82] Chen Y, Bi L, Luo H, Jiang Y, Chen F, Wang Y, et al. Water extract of ginseng and astragalus regulates macrophage polarization and synergistically enhances DDP's anticancer effect. Journal of Ethnopharmacology.

2019;**232**:11-20. DOI: 10.1016/j. jep.2018.12.003

[83] Li Q, Hao Z, Hong Y, He W, Zhao W. Reprogramming tumor associated macrophage phenotype by a polysaccharide from Ilex asprella for sarcoma immunotherapy. International Journal of Molecular Sciences. 2018;**19**(12). pii: E3816. DOI: 10.3390/ ijms19123816

[84] Li Y, Qi W, Song X, Lv S, Zhang H, Yang Q. Huaier extract suppresses breast cancer via regulating tumor-associated macrophages. Scientific Reports. 2016;**6**:20049. DOI: 10.1038/srep20049

[85] Kimura Y, Sumiyoshi M. Antitumor and antimetastatic actions of dihydroxycoumarins (esculetin or fraxetin) through the inhibition of M2 macrophage differentiation in tumorassociated macrophages and/or G 1 arrest in tumor cells. European Journal of Pharmacology. 2015;**746**:115-125. DOI: 10.1016/j.ejphar.2014.10.048

[86] Pang L, Han S, Jiao Y, Jiang S, He X, Li P. Bu Fei decoction attenuates the tumor associated macrophage stimulated proliferation, migration, invasion and immunosuppression of non-small cell lung cancer, partially via IL-10 and PD-L1 regulation. International Journal of Oncology. 2017;**51**:25-38. DOI: 10.3892/ ijo.2017.4014

[87] Iwanowycz S, Wang J, Hodge J, Wang Y, Yu F, Fan D. Emodin inhibits breast cancer growth by blocking the tumor-promoting feedforward loop between cancer cells and macrophages. Molecular Cancer Therapeutics. 2016;**15**(8):1931-1942. DOI: 10.1158/1535-7163.MCT-15-0987

[88] Jia X, Yu F, Wang J, Iwanowycz S, Saaoud F, Wang Y, et al. Emodin suppresses pulmonary metastasis of breast cancer cells accompanied with

**41**

*Targeting Tumor-Associated Macrophages by Plant Compounds*

KSG-002, suppresses breast cancer growth and metastasis by targeting NF-κ B-Dependent TNF α production in macrophages. Evidence-Based Complementary and Alternative Medicine. 2013;**2013**:728258. DOI:

[95] Choi YK, Cho SG, Woo SM, Yun YJ, Park S, Shin YC, et al. Herbal extract SH003 suppresses tumor growth and metastasis of MDA-MB-231 breast cancer cells by inhibiting STAT3-IL-6 signaling. Mediators of Inflammation. 2014;**2014**:492173. DOI:

10.1155/2013/728258

10.1155/2014/492173

jep.2019.02.003

[96] Wu J, Zhang XX, Wang M, Wang HX, Wang YH, Li C, et al. The effect of Jianpi Yangzheng Xiaozheng decoction and its components on gastric cancer. Journal of Ethnopharmacology. 2019;**10**(235):56-64. DOI: 10.1016/j.

[97] Wang N, Zheng Y, Gu J,

10.1038/s41598-017-15030-3

Cai Y, Wang S, Zhan F, et al. Networkpharmacology-based validation of TAMS/CXCL-1 as key mediator of XIAOPI formula preventing breast cancer development and metastasis. Scientific Reports. 2017;**7**(1):14513. DOI:

*DOI: http://dx.doi.org/10.5772/intechopen.92298*

[89] Iwanowycz S, Wang J, Altomare D, Hui Y, Fan D. Emodin bidirectionally modulates macrophage polarization and epigenetically regulates macrophage memory. The Journal of Biological Chemistry. 2016;**291**(22):11491-11503.

DOI: 10.1074/jbc.M115.702092

[90] Morris J, Gonzales CB, De La Chapa JJ, Cabang B, Fountzilas C, Patel M, et al. The highly pure neem leaf extract, SCNE, inhibits tumorigenesis in oral squamous cell carcinoma via disruption of pro-tumor inflammatory cytokines and cell signaling. Frontiers in Oncology. 2019;**9**:890. DOI: 10.3389/

[91] Yu X, Xu M, Li N, Li Z, Li H, Shao S, et al. β-Elemene inhibits tumorpromoting effect of M2 macrophages in lung cancer. Biochemical and

Biophysical Research Communications. 2017;**490**(2):514-520. DOI: 10.1016/j.

[92] Tsuboki J, Fujiwara Y, Horlad H, Shiraishi D, Nohara T, Tayama S, et al. Onionin a inhibits ovarian cancer progression by suppressing cancer cell proliferation and the protumour function of macrophages. Scientific Reports. 2016;**6**:29588. DOI: 10.1038/

[93] Sinha P, Ostrand-Rosenberg S. Myeloid-derived suppressor cell function is reduced by Withaferin a, a potent and abundant component of *Withania somnifera* root extract. Cancer Immunology, Immunotherapy. 2013;**62**(11):1663-1673. DOI: 10.1007/

[94] Woo SM, Choi YK, Cho SG, Park S, Ko SG. A new herbal formula,

decreased macrophage recruitment and M2 polarization in the lungs. Breast Cancer Research and Treatment. 2014;**148**(2):291-302. DOI: 10.1007/

s10549-014-3164-7

fonc.2019.00890

bbrc.2017.06.071

srep29588

s00262-013-1470-2

### *Targeting Tumor-Associated Macrophages by Plant Compounds DOI: http://dx.doi.org/10.5772/intechopen.92298*

decreased macrophage recruitment and M2 polarization in the lungs. Breast Cancer Research and Treatment. 2014;**148**(2):291-302. DOI: 10.1007/ s10549-014-3164-7

*Macrophages*

c8fo01147h

TriCurin, a synergistic formulation of curcumin, resveratrol, and epicatechin gallate, repolarizes tumor-associated macrophages and triggers an immune response to cause suppression of HPV+ tumors. Cancer Immunology, Immunotherapy. 2018;**67**(5):761-774. DOI: 10.1007/s00262-018-2130-3

2019;**232**:11-20. DOI: 10.1016/j.

[83] Li Q, Hao Z, Hong Y, He W, Zhao W. Reprogramming tumor associated macrophage phenotype by a polysaccharide from Ilex asprella for sarcoma immunotherapy. International

Journal of Molecular Sciences. 2018;**19**(12). pii: E3816. DOI: 10.3390/

[84] Li Y, Qi W, Song X, Lv S, Zhang H, Yang Q. Huaier extract suppresses breast cancer via regulating tumor-associated macrophages. Scientific Reports. 2016;**6**:20049. DOI: 10.1038/srep20049

[85] Kimura Y, Sumiyoshi M. Antitumor

and antimetastatic actions of dihydroxycoumarins (esculetin or fraxetin) through the inhibition of M2 macrophage differentiation in tumorassociated macrophages and/or G 1 arrest in tumor cells. European Journal of Pharmacology. 2015;**746**:115-125. DOI: 10.1016/j.ejphar.2014.10.048

[86] Pang L, Han S, Jiao Y, Jiang S, He X, Li P. Bu Fei decoction attenuates the tumor associated macrophage stimulated proliferation, migration, invasion and immunosuppression of non-small cell lung cancer, partially via IL-10 and PD-L1 regulation. International Journal of Oncology. 2017;**51**:25-38. DOI: 10.3892/

[87] Iwanowycz S, Wang J, Hodge J, Wang Y, Yu F, Fan D. Emodin inhibits breast cancer growth by blocking the tumor-promoting feedforward loop between cancer cells and macrophages. Molecular Cancer Therapeutics. 2016;**15**(8):1931-1942. DOI: 10.1158/1535-7163.MCT-15-0987

[88] Jia X, Yu F, Wang J, Iwanowycz S, Saaoud F, Wang Y, et al. Emodin suppresses pulmonary metastasis of breast cancer cells accompanied with

jep.2018.12.003

ijms19123816

ijo.2017.4014

[78] Mukherjee S, Baidoo JNE, Sampat S, Mancuso A, David L, Cohen LS. Liposomal TriCurin, a synergistic combination of curcumin, epicatechin gallate and resveratrol, repolarizes tumor-associated

microglia/macrophages, and eliminates glioblastoma (GBM) and GBM stem cells. Molecules. 2018;**23**;(1). pii: E201. DOI: 10.3390/molecules23010201

[79] Yao J, Du Z, Li Z, Zhang S, Lin Y, Li H, et al. 6-Gingerol as an arginase inhibitor prevents urethane-induced lung carcinogenesis by reprogramming tumor supporting M2 macrophages to M1 phenotype. Food & Function. 2018;**9**(9):4611-4620. DOI: 10.1039/

[80] Wu Q, Chen GL, Li YJ, Chen Y, Lin FZ. Paeoniflorin inhibits macrophage-mediated lung cancer metastasis. Chinese Journal of Natural Medicines. 2015;**13**(12):925-932. DOI: 10.1016/S1875-5364(15)30098-4

[81] Shu G, Jiang S, Mu J, Yu H, Duan H, Deng X. Antitumor immunostimulatory activity of polysaccharides from *Panax japonicus* C. A. Mey: Roles of their effects on CD4 + T cells and tumor associated macrophages. International Journal of Biological Macromolecules. 2018;**111**:430-439. DOI: 10.1016/j.

[82] Chen Y, Bi L, Luo H, Jiang Y, Chen F, Wang Y, et al. Water extract of ginseng and astragalus regulates macrophage polarization and synergistically enhances DDP's anticancer effect. Journal of Ethnopharmacology.

ijbiomac.2018.01.011

**40**

[89] Iwanowycz S, Wang J, Altomare D, Hui Y, Fan D. Emodin bidirectionally modulates macrophage polarization and epigenetically regulates macrophage memory. The Journal of Biological Chemistry. 2016;**291**(22):11491-11503. DOI: 10.1074/jbc.M115.702092

[90] Morris J, Gonzales CB, De La Chapa JJ, Cabang B, Fountzilas C, Patel M, et al. The highly pure neem leaf extract, SCNE, inhibits tumorigenesis in oral squamous cell carcinoma via disruption of pro-tumor inflammatory cytokines and cell signaling. Frontiers in Oncology. 2019;**9**:890. DOI: 10.3389/ fonc.2019.00890

[91] Yu X, Xu M, Li N, Li Z, Li H, Shao S, et al. β-Elemene inhibits tumorpromoting effect of M2 macrophages in lung cancer. Biochemical and Biophysical Research Communications. 2017;**490**(2):514-520. DOI: 10.1016/j. bbrc.2017.06.071

[92] Tsuboki J, Fujiwara Y, Horlad H, Shiraishi D, Nohara T, Tayama S, et al. Onionin a inhibits ovarian cancer progression by suppressing cancer cell proliferation and the protumour function of macrophages. Scientific Reports. 2016;**6**:29588. DOI: 10.1038/ srep29588

[93] Sinha P, Ostrand-Rosenberg S. Myeloid-derived suppressor cell function is reduced by Withaferin a, a potent and abundant component of *Withania somnifera* root extract. Cancer Immunology, Immunotherapy. 2013;**62**(11):1663-1673. DOI: 10.1007/ s00262-013-1470-2

[94] Woo SM, Choi YK, Cho SG, Park S, Ko SG. A new herbal formula, KSG-002, suppresses breast cancer growth and metastasis by targeting NF-κ B-Dependent TNF α production in macrophages. Evidence-Based Complementary and Alternative Medicine. 2013;**2013**:728258. DOI: 10.1155/2013/728258

[95] Choi YK, Cho SG, Woo SM, Yun YJ, Park S, Shin YC, et al. Herbal extract SH003 suppresses tumor growth and metastasis of MDA-MB-231 breast cancer cells by inhibiting STAT3-IL-6 signaling. Mediators of Inflammation. 2014;**2014**:492173. DOI: 10.1155/2014/492173

[96] Wu J, Zhang XX, Wang M, Wang HX, Wang YH, Li C, et al. The effect of Jianpi Yangzheng Xiaozheng decoction and its components on gastric cancer. Journal of Ethnopharmacology. 2019;**10**(235):56-64. DOI: 10.1016/j. jep.2019.02.003

[97] Wang N, Zheng Y, Gu J, Cai Y, Wang S, Zhan F, et al. Networkpharmacology-based validation of TAMS/CXCL-1 as key mediator of XIAOPI formula preventing breast cancer development and metastasis. Scientific Reports. 2017;**7**(1):14513. DOI: 10.1038/s41598-017-15030-3

**43**

**Chapter 3**

**Abstract**

cytokines

**1. Introduction**

Functional Biomaterials Modulate

Macrophage in the Tumour

*Tsung-Meng Wu, Kuang-Teng Wang, Hisang-Lin Tsai,* 

The inflammation response requires the cooperation of macrophages with immune cell function and active factors, such as cytokines and chemokines. Through this response, these factors are involved in the immune response to affect physiological activities. Macrophages can be categorized into two types: 'M1' and 'M2'. M1 macrophages destroy the pathogen through phagocytosis activation, ROS production, and antigen-presenting, among other functions. M2 macrophages release cellular factors for tissue recovery, growth, and angiogenesis. Studies have determined that tumour tissue presents with numerous macrophages, termed tumour-associated macrophages. Tumour cells and peripheral stromal cells stimulate the tumour associated with macrophages (M2) to produce factors that regulate angiogenesis. Modulating the balance of the M1 and M2 function has already gained interest as a potentially valuable immune disease therapy. However, applications of the immunotherapy in clinical treatments are still not clear with regard to the cellular working mechanism. Therefore, we summarized the functions of common

**Keywords:** macrophage, polarization, tumour micro-environment, biomaterials,

Inflammation has been demonstrated to be a critical factor in the induction of immune disease. Immunotherapy is a novel therapeutic approach for anti-inflammation, which could help avoid drug resistance. However, findings have indicated that the balance of inflammation and anti-inflammation is crucial. Cellular ROS are produced by stress to clear pathogen infections [1]. The inflammatory response involves macrophages, dendritic cells, and M cells, which are crucial protectors. These cells present partial antigens to enhance the T-cell activation and cytokine production, which modulate the host micro-environment. Cytokines are produced

Immunotherapy was developed as an approach to rectify the imbalanced inflammation. Immunotherapy was hypothesized as a possible alternative therapy applied in the early phase of clinical therapy and immunomodulation in the early stages of immune disease. The common immunotherapy employs natural functional

biomaterials involved in the modulation of the macrophage.

and released as signals to regulate the immune cell function.

Micro-environment

*Fan-Hua Nan and Yu-Sheng Wu*

### **Chapter 3**

## Functional Biomaterials Modulate Macrophage in the Tumour Micro-environment

*Tsung-Meng Wu, Kuang-Teng Wang, Hisang-Lin Tsai, Fan-Hua Nan and Yu-Sheng Wu*

### **Abstract**

The inflammation response requires the cooperation of macrophages with immune cell function and active factors, such as cytokines and chemokines. Through this response, these factors are involved in the immune response to affect physiological activities. Macrophages can be categorized into two types: 'M1' and 'M2'. M1 macrophages destroy the pathogen through phagocytosis activation, ROS production, and antigen-presenting, among other functions. M2 macrophages release cellular factors for tissue recovery, growth, and angiogenesis. Studies have determined that tumour tissue presents with numerous macrophages, termed tumour-associated macrophages. Tumour cells and peripheral stromal cells stimulate the tumour associated with macrophages (M2) to produce factors that regulate angiogenesis. Modulating the balance of the M1 and M2 function has already gained interest as a potentially valuable immune disease therapy. However, applications of the immunotherapy in clinical treatments are still not clear with regard to the cellular working mechanism. Therefore, we summarized the functions of common biomaterials involved in the modulation of the macrophage.

**Keywords:** macrophage, polarization, tumour micro-environment, biomaterials, cytokines

### **1. Introduction**

Inflammation has been demonstrated to be a critical factor in the induction of immune disease. Immunotherapy is a novel therapeutic approach for anti-inflammation, which could help avoid drug resistance. However, findings have indicated that the balance of inflammation and anti-inflammation is crucial. Cellular ROS are produced by stress to clear pathogen infections [1]. The inflammatory response involves macrophages, dendritic cells, and M cells, which are crucial protectors. These cells present partial antigens to enhance the T-cell activation and cytokine production, which modulate the host micro-environment. Cytokines are produced and released as signals to regulate the immune cell function.

Immunotherapy was developed as an approach to rectify the imbalanced inflammation. Immunotherapy was hypothesized as a possible alternative therapy applied in the early phase of clinical therapy and immunomodulation in the early stages of immune disease. The common immunotherapy employs natural functional

materials including triterpenoids and polysaccharides. Studies have demonstrated that functional polysaccharides can promote macrophage differentiation into M1 or M2, and the ratio modulates the host micro-environment through cytokine secretion.

Polysaccharides such as beta-glucan are considered to be biological response modifiers (BRMs) that activate macrophages and modulate the inflammation response. Findings have indicated that beta-glucan combines with receptors expressed on the macrophage cell surface, such as Toll-like receptor. Once combined, alveolar macrophages, Kupffer cells, Langerhans cells, mesangial cells, and microglial are activated through toll-like receptor 4–mediated signalling pathways to modulate the immune response.

### **2. Macrophage activation**

Macrophages are present in almost all tissues and coordinate developmental, metabolic, and immunological functions, thereby contributing to the maintenance of homeostasis. Macrophages have a complex role in tissues and act on lipopolysaccharide (LPS), interferon-γ (IFN-γ), and interleukin (IL)-4 to polarize the M0 into M1. Macrophages are activated by exposure to various stimuli. The stimuli that act on macrophages are categorized into danger, homeostatic, metabolic, and modulatory signals. Danger signals include pathogen-associated molecular patterns, such as LPS. Tissue macrophage exposure to danger signals results in an inflammatory response. Findings have indicated that tumour environments contain numerous transmitters, such as M-CSF, IL-6, IL-10, TGF-β, and COX-2, which induce tumour megakaryocytes to differentiate into M2 macrophages, which, in addition to having poorer antigen-presenting and cytotoxic abilities, also secrete factors that inhibit immune cells, resulting in an enhanced immune inhibitory effect of the tumour environment as shown in **Figure 1**. We investigated the modulation of M1 and M2 in the tumour environment by using immunomodulators to delay or inhibit the tumour to identify alternative approaches to reduce the side effect of tumour chemotherapy. Inflammation is a crucial adaptive response for animals, and the mechanism involves a complex interaction of molecular mediators. The functions of immune cells in a micro-environment are mediated by responses that occur at all levels of biological organization [2]. This process involves cooperation among cells and mediators, and the classical immune response varies based on a wide range of factors, including the stage of the inflammation process, the tissue or organ involved, and whether the inflammation is acute and resolving or chronic and nonresolving [3]. The inflammation process involves vascular permeabilization, active migration of blood cells, and passage of plasma constituents into injurious tissue [4]. Studies have demonstrated that the infiltration of immune cells during the inflammation process plays a crucial role in atherosclerosis [5]. Blood leukocytes are mediators of host defences and inflammation localized in the earliest lesions of atherosclerosis in experimental animals. The study of inflammation in atherosclerosis provided new insights into the mechanisms underlying the recruitment of leukocytes [6]. Recently, studies have indicated that inflammation plays a role in Alzheimer disease (AD) [7]. Inflammatory components involved in AD neuroinflammation include brain cells (such as microglia and astrocytes), the complement system, and cytokines and chemokines [8]. Regarding cancer development [9], proinflammatory cytokines, including chemokines; matrix metallopeptidase (MMP)-9; vascular endothelial growth factor (VEGF); and IL-1α, IL-1β, IL-6, IL-8, and IL-18, are primarily regulated by the transcription factor nuclear factor (NF)-kB, which is active in most tumours and is induced by carcinogens [10]. Cutaneous wound repair

**45**

**Figure 1.**

*Functional Biomaterials Modulate Macrophage in the Tumour Micro-environment*

is a tightly regulated and dynamic process involving blood clotting, inflammation, new tissue formation, and tissue remodeling [11]. Thrombin is the protease involved in blood coagulation. Thrombin deregulation can lead to haemostatic abnormalities, which range from subtle subclinical to life-threatening coagulopathies (i.e., during septicaemia) [12]. Inflammation and blood coagulation is part of the innate host protection mechanism against vascular injury, infection, or other wounds. Cells of the innate immune system, endothelial cells, and platelets are actively involved in acute and chronic inflammation; they release proinflammatory mediators and recruit leukocytes [13]. The protease-activated receptor (PAR) family serves as sensor of serine proteinases in the blood clotting system in the target cells involved in inflammation. Activation of PAR-1 by thrombin and of PAR-2 by factor leads to a rapid expression and exposure of both adhesive proteins that mediate an acute inflammatory reaction and of the tissue factor that initiates the blood coagulation cascade on the membrane of endothelial cells [14]. In this process, cooperation among cells and mediators occurs, and a wide range of factors are involved in the classical immune response: (1) the stage of the inflammation process; (2) the tissue or organ involved; and (3) whether the inflammation is acute and resolving or chronic and nonresolving [15]. The inflammation process involves vascular permeability, active migration of blood cells, and the passage of plasma constituents into injurious tissue [4]. Studies on the infiltration of immune cells have demonstrated that the inflammation process plays a crucial role in atherosclerosiss [5]. Blood leukocytes, mediators of host defences and inflammation, localize in the earliest lesions of atherosclerosis in experimental animals. The study of inflammation in atherosclerosis has provided numerous new insights into the mechanisms underlying the recruitment of leukocytes [6]. Studies have reported that inflammation is involved in Alzheimer's disease (AD) [7]. Inflammatory components involved in AD neuroinflammation include brain cells (such as microglia and astrocytes), the complement system, and

*Macrophages can be categorized into two types: 'M1' and 'M2'. M1 macrophages destroy the pathogen through phagocytosis activation, ROS production, and antigen-presenting, among other functions. M2 macrophages release cellular factors for tissue recovery, growth, and angiogenesis. We thought that the regulation of* 

*DOI: http://dx.doi.org/10.5772/intechopen.92429*

*macrophage is beneficial to reduce the auto-immune disease.*

*Functional Biomaterials Modulate Macrophage in the Tumour Micro-environment DOI: http://dx.doi.org/10.5772/intechopen.92429*

#### **Figure 1.**

*Macrophages*

secretion.

to modulate the immune response.

**2. Macrophage activation**

materials including triterpenoids and polysaccharides. Studies have demonstrated that functional polysaccharides can promote macrophage differentiation into M1 or M2, and the ratio modulates the host micro-environment through cytokine

Polysaccharides such as beta-glucan are considered to be biological response modifiers (BRMs) that activate macrophages and modulate the inflammation response. Findings have indicated that beta-glucan combines with receptors expressed on the macrophage cell surface, such as Toll-like receptor. Once combined, alveolar macrophages, Kupffer cells, Langerhans cells, mesangial cells, and microglial are activated through toll-like receptor 4–mediated signalling pathways

Macrophages are present in almost all tissues and coordinate developmental, metabolic, and immunological functions, thereby contributing to the maintenance of homeostasis. Macrophages have a complex role in tissues and act on lipopolysaccharide (LPS), interferon-γ (IFN-γ), and interleukin (IL)-4 to polarize the M0 into M1. Macrophages are activated by exposure to various stimuli. The stimuli that act on macrophages are categorized into danger, homeostatic, metabolic, and modulatory signals. Danger signals include pathogen-associated molecular patterns, such as LPS. Tissue macrophage exposure to danger signals results in an inflammatory response. Findings have indicated that tumour environments contain numerous transmitters, such as M-CSF, IL-6, IL-10, TGF-β, and COX-2, which induce tumour megakaryocytes to differentiate into M2 macrophages, which, in addition to having poorer antigen-presenting and cytotoxic abilities, also secrete factors that inhibit immune cells, resulting in an enhanced immune inhibitory effect of the tumour environment as shown in **Figure 1**. We investigated the modulation of M1 and M2 in the tumour environment by using immunomodulators to delay or inhibit the tumour to identify alternative approaches to reduce the side effect of tumour chemotherapy. Inflammation is a crucial adaptive response for animals, and the mechanism involves a complex interaction of molecular mediators. The functions of immune cells in a micro-environment are mediated by responses that occur at all levels of biological organization [2]. This process involves cooperation among cells and mediators, and the classical immune response varies based on a wide range of factors, including the stage of the inflammation process, the tissue or organ involved, and whether the inflammation is acute and resolving or chronic and nonresolving [3]. The inflammation process involves vascular permeabilization, active migration of blood cells, and passage of plasma constituents into injurious tissue [4]. Studies have demonstrated that the infiltration of immune cells during the inflammation process plays a crucial role in atherosclerosis [5]. Blood leukocytes are mediators of host defences and inflammation localized in the earliest lesions of atherosclerosis in experimental animals. The study of inflammation in atherosclerosis provided new insights into the mechanisms underlying the recruitment of leukocytes [6]. Recently, studies have indicated that inflammation plays a role in Alzheimer disease (AD) [7]. Inflammatory components involved in AD neuroinflammation include brain cells (such as microglia and astrocytes), the complement system, and cytokines and chemokines [8]. Regarding cancer development [9], proinflammatory cytokines, including chemokines; matrix metallopeptidase (MMP)-9; vascular endothelial growth factor (VEGF); and IL-1α, IL-1β, IL-6, IL-8, and IL-18, are primarily regulated by the transcription factor nuclear factor (NF)-kB, which is active in most tumours and is induced by carcinogens [10]. Cutaneous wound repair

**44**

*Macrophages can be categorized into two types: 'M1' and 'M2'. M1 macrophages destroy the pathogen through phagocytosis activation, ROS production, and antigen-presenting, among other functions. M2 macrophages release cellular factors for tissue recovery, growth, and angiogenesis. We thought that the regulation of macrophage is beneficial to reduce the auto-immune disease.*

is a tightly regulated and dynamic process involving blood clotting, inflammation, new tissue formation, and tissue remodeling [11]. Thrombin is the protease involved in blood coagulation. Thrombin deregulation can lead to haemostatic abnormalities, which range from subtle subclinical to life-threatening coagulopathies (i.e., during septicaemia) [12]. Inflammation and blood coagulation is part of the innate host protection mechanism against vascular injury, infection, or other wounds. Cells of the innate immune system, endothelial cells, and platelets are actively involved in acute and chronic inflammation; they release proinflammatory mediators and recruit leukocytes [13]. The protease-activated receptor (PAR) family serves as sensor of serine proteinases in the blood clotting system in the target cells involved in inflammation. Activation of PAR-1 by thrombin and of PAR-2 by factor leads to a rapid expression and exposure of both adhesive proteins that mediate an acute inflammatory reaction and of the tissue factor that initiates the blood coagulation cascade on the membrane of endothelial cells [14]. In this process, cooperation among cells and mediators occurs, and a wide range of factors are involved in the classical immune response: (1) the stage of the inflammation process; (2) the tissue or organ involved; and (3) whether the inflammation is acute and resolving or chronic and nonresolving [15]. The inflammation process involves vascular permeability, active migration of blood cells, and the passage of plasma constituents into injurious tissue [4]. Studies on the infiltration of immune cells have demonstrated that the inflammation process plays a crucial role in atherosclerosiss [5]. Blood leukocytes, mediators of host defences and inflammation, localize in the earliest lesions of atherosclerosis in experimental animals. The study of inflammation in atherosclerosis has provided numerous new insights into the mechanisms underlying the recruitment of leukocytes [6]. Studies have reported that inflammation is involved in Alzheimer's disease (AD) [7]. Inflammatory components involved in AD neuroinflammation include brain cells (such as microglia and astrocytes), the complement system, and

cytokines and chemokines [8]. Regarding cancer development, proinflammatory cytokines, including chemokines, MMP-9, VEGF, and IL-1α, IL-1β, IL-6, IL-8, and IL-18, are primarily regulated by the transcription factor NF-kB, which is active in most tumours and is induced by carcinogens [9, 10]. Macrophages play a crucial role in inflammation process, tumour growth, and tumour progression by induced angiogenesis. Studies have reported that promotion of angiogenesis with the production of proangiogenic factors, such as TGFβ, VEGF, PDGF, members of the fibroblast growth factors family, and angiogenic chemokines [16], and the development of breast cancer and several other human tumours was correlated with macrophage infiltration [17]. VEGF-C production by tumour-associated macrophages (TAMs) was reportedly involved in peritumoral lymphangiogenesis and the subsequent dissemination of cancer cells with formation of lymphatic metastasis [18]; moreover, macrophage colony-stimulating factor (M-CSF) and VEGF actively recruit circulating blood monocytes at the tumour site [19].

### **3. Polysaccharide function on the immunomodulation**

Evidence has indicated that acetyl-xylogalactan extracted from *Sarcodia suieae* induced macrophage polarization through the IL-1β, TNF, and Malt-1 expression [20]. Nakanishi et al determined that celecoxib can alter the immune inhibitory effects of the tumour micro-environment by promoting the transformation of TAMs into M1 macrophages, leading to inhibited tumour growth [21]. In 1968, Ikekawa et al. reported that the fruiting body extracts from *Lentinus edodes*, *Trametes versicolor*, *Ganoderma tsugae*, *Flammulina velutiper,* and *Tricholoma matsutake* demonstrated significant antitumour activities in transplanted Sarcoma 180 tumour cells [22, 23]. Studies have reported that *Antrodia camphorata*-derived beta-glucan demonstrated inhibitory effects on tumour growth in Sarcoma 37, Sarcoma 180, Erlich ascites sarcoma, Yoshida sarcoma, and LLC1 transplanted tumour [24]. Daily intake of *A. comphorata*-derived beta-glucan for 18 consecutive days was demonstrated to slow tumour growth and reduce the rate of metastasis [25]. Cytotoxic T-cell activity and tumour occurrence rate were investigated and the results revealed that daily oral intake of *Grifola frondosa*-derived beta-glucan or Lentinan can enhance cytotoxic T-cell activity and reduce tumour occurrence rate [26]. Furthermore, the addition of conditioned medium with tumour cells into the progenitors of dendritic cells was determined to further inhibit the maturation of dendritic cells and lower the antigen-presenting capability of the dendritic cells [27]. Studies have reported that tumour cells secrete M-CSF, thereby inhibiting dendritic and T-cell differentiation and antitumour ability [27–30]. In the tumour environment, the amounts of M1 and M2 macrophages are not equal [31]. Tumour environments are known to contain a large number of transmitters such as M-CSF, IL-6, IL-10, TGF-β, and COX-2, which induce tumour megakaryocytes to differentiate into M2 macrophages, which have poorer antigen-presenting and cytotoxic abilities and secrete factors that inhibit immune cells, resulting in an enhanced immune inhibitory effect of the tumour environment [16, 32–41]. M2 macrophages in tumour-bearing mice enhance tumour growth and immune inhibitory effects. M2 macrophages also secrete cytokines, such as IL-10 and TGF-β, in high quantities, which attract noncytotoxic Treg-cells and Type 2 helper T cells to congregate in tumour tissues, which in turn inhibit the differentiation and normal functions of T cells, including their cytotoxic ability, which further leads to T-cell apoptosis [38, 40, 42–44]. The Th1 and Th2 polarization is built on cytokine patterns, which begin when the antigen-presenting cells interact with the naive T cells and polarize into type 1 and type 2 cells in response to the type of antigen encountered [45]. Th1 and Th2 cells secrete different cytokines.

**47**

**4. Conclusion**

*Functional Biomaterials Modulate Macrophage in the Tumour Micro-environment*

polysaccharides, have been isolated from the extract of *G. lucidum* [50].

cial aspects of inflammation, including inhibition of tumour growth.

Immunotherapy is being developed and presents certain advantages of alternative medicine because immunomodulation factors, such as mushroom beta-glucan, antimicrobial peptides, and triterpenoid, represent a novel therapeutic approach for cancer therapy and may provide an alternative to deal with the problem of drug resistance. However, exploring current insights into tumour biology and tumour micro-environment is complex and involves chemistry, biology, instrumentation, and formulation science. Therefore discovering a novel, more effective tumourtargeting treatment is difficult. Immunotherapy is hypothesized to be an alternative

therapy that could be applied in the early phase of clinical tumour therapy.

Antimicrobial peptides are effective components of innate immunity that are widely present in the biological system. Hepcidin is a 25-amino acid antibiotic peptide synthesized in the liver, which is reportedly responsible for regulating iron balance and recycling in humans and mice. Studies on 0–100 μg/mL concentrations of hepcidin incubated with HT1080, Hep-G2, and HeLa for 24 h revealed higher growth inhibition ratios after treatment with 70 μg/mL hepcidin in HT1080 cells. Hepcidin was very effective at inhibiting the growth of fibrosarcoma cells [51, 52]. Studies on tachyplesin, an antimicrobial peptide present in leukocytes of the horseshoe crab (*Tachypleus tridentatus*), demonstrated that tachyplesin was able to inhibit the growth of TSU tumour cells on the chorioallantoic membrane of chicken embryos and B16 tumour cells in syngeneic mice. Tachyplesin also blocked the proliferation of both tumour and endothelial cells in culture in a dose-dependent manner, whereas proliferation was relatively unaffected in nontumorigenic cell lines Cos-7 and NIH-3T3 [53]. D-K4R2L9 is a peptide with 15 amino acid residues, comprising of Leu, Lys, and Arg residues, which binds to and lyses B16-F10 mouse melanoma cells in culture at concentrations that do not harm normal 3T3 fibroblasts or erythrocytes, thereby preventing intravenous-injected D122 lung carcinoma cells from forming lung tumours in mice [54, 55]. Another antimicrobial peptide, bovine lactoferricin (LfcinB), is a 25-amino acid, highly basic peptide with a disulphide bridge between two cysteines; thus, LfcinB is a cyclic twisted antiparallel β-sheet solution structure. The effects of LfcinB on neuroblastoma growth were investigated in vivo, which revealed that SH-SY-5Y xenografts in nude rats were significantly inhibited after injections of 1.0 or 2.0 mg of LfcinB compared with untreated controls [56]. Related research has demonstrated that antimicrobial peptides can activate specific innate immune responses and lead to immunomodulatory effects in the host when there is a risk of damage. Furthermore, the antimicrobial peptides are proposed to modulate the host's immune system through inflammatory responses and stimulate the benefi-

Th1 cells are dependent on IL-2, IFN-γ, and TNF, which are involved in cell-mediated immunity against pathogens. Th2 cells are mostly dependent on IL-4 and IL-5, which stimulate the production of IgE antibodies and eosinophil responses, resulting in allergic diseases [46, 47]. An imbalanced Th1/Th2 immune response is linked to certain hypersensitivity disorders such as allergy, asthma, and hay fever [48]; therefore, studies have suggested that using BRM to restore the balance between Th1 and Th2 immune response could be a treatment option for the IgE-dependent hypersensitivity [49]. *Ganoderma lucidum* is a medicinal mushroom, which has been widely used for hundreds of years as a folk medicine in oriental countries such as China and Japan for its immunomodulating and antitumour effects. Numerous biological available substances with immunity enhancement effects, in particular

*DOI: http://dx.doi.org/10.5772/intechopen.92429*

### *Functional Biomaterials Modulate Macrophage in the Tumour Micro-environment DOI: http://dx.doi.org/10.5772/intechopen.92429*

Th1 cells are dependent on IL-2, IFN-γ, and TNF, which are involved in cell-mediated immunity against pathogens. Th2 cells are mostly dependent on IL-4 and IL-5, which stimulate the production of IgE antibodies and eosinophil responses, resulting in allergic diseases [46, 47]. An imbalanced Th1/Th2 immune response is linked to certain hypersensitivity disorders such as allergy, asthma, and hay fever [48]; therefore, studies have suggested that using BRM to restore the balance between Th1 and Th2 immune response could be a treatment option for the IgE-dependent hypersensitivity [49]. *Ganoderma lucidum* is a medicinal mushroom, which has been widely used for hundreds of years as a folk medicine in oriental countries such as China and Japan for its immunomodulating and antitumour effects. Numerous biological available substances with immunity enhancement effects, in particular polysaccharides, have been isolated from the extract of *G. lucidum* [50].

Antimicrobial peptides are effective components of innate immunity that are widely present in the biological system. Hepcidin is a 25-amino acid antibiotic peptide synthesized in the liver, which is reportedly responsible for regulating iron balance and recycling in humans and mice. Studies on 0–100 μg/mL concentrations of hepcidin incubated with HT1080, Hep-G2, and HeLa for 24 h revealed higher growth inhibition ratios after treatment with 70 μg/mL hepcidin in HT1080 cells. Hepcidin was very effective at inhibiting the growth of fibrosarcoma cells [51, 52]. Studies on tachyplesin, an antimicrobial peptide present in leukocytes of the horseshoe crab (*Tachypleus tridentatus*), demonstrated that tachyplesin was able to inhibit the growth of TSU tumour cells on the chorioallantoic membrane of chicken embryos and B16 tumour cells in syngeneic mice. Tachyplesin also blocked the proliferation of both tumour and endothelial cells in culture in a dose-dependent manner, whereas proliferation was relatively unaffected in nontumorigenic cell lines Cos-7 and NIH-3T3 [53]. D-K4R2L9 is a peptide with 15 amino acid residues, comprising of Leu, Lys, and Arg residues, which binds to and lyses B16-F10 mouse melanoma cells in culture at concentrations that do not harm normal 3T3 fibroblasts or erythrocytes, thereby preventing intravenous-injected D122 lung carcinoma cells from forming lung tumours in mice [54, 55]. Another antimicrobial peptide, bovine lactoferricin (LfcinB), is a 25-amino acid, highly basic peptide with a disulphide bridge between two cysteines; thus, LfcinB is a cyclic twisted antiparallel β-sheet solution structure. The effects of LfcinB on neuroblastoma growth were investigated in vivo, which revealed that SH-SY-5Y xenografts in nude rats were significantly inhibited after injections of 1.0 or 2.0 mg of LfcinB compared with untreated controls [56]. Related research has demonstrated that antimicrobial peptides can activate specific innate immune responses and lead to immunomodulatory effects in the host when there is a risk of damage. Furthermore, the antimicrobial peptides are proposed to modulate the host's immune system through inflammatory responses and stimulate the beneficial aspects of inflammation, including inhibition of tumour growth.

### **4. Conclusion**

Immunotherapy is being developed and presents certain advantages of alternative medicine because immunomodulation factors, such as mushroom beta-glucan, antimicrobial peptides, and triterpenoid, represent a novel therapeutic approach for cancer therapy and may provide an alternative to deal with the problem of drug resistance. However, exploring current insights into tumour biology and tumour micro-environment is complex and involves chemistry, biology, instrumentation, and formulation science. Therefore discovering a novel, more effective tumourtargeting treatment is difficult. Immunotherapy is hypothesized to be an alternative therapy that could be applied in the early phase of clinical tumour therapy.

*Macrophages*

ing blood monocytes at the tumour site [19].

**3. Polysaccharide function on the immunomodulation**

cytokines and chemokines [8]. Regarding cancer development, proinflammatory cytokines, including chemokines, MMP-9, VEGF, and IL-1α, IL-1β, IL-6, IL-8, and IL-18, are primarily regulated by the transcription factor NF-kB, which is active in most tumours and is induced by carcinogens [9, 10]. Macrophages play a crucial role in inflammation process, tumour growth, and tumour progression by induced angiogenesis. Studies have reported that promotion of angiogenesis with the production of proangiogenic factors, such as TGFβ, VEGF, PDGF, members of the fibroblast growth factors family, and angiogenic chemokines [16], and the development of breast cancer and several other human tumours was correlated with macrophage infiltration [17]. VEGF-C production by tumour-associated macrophages (TAMs) was reportedly involved in peritumoral lymphangiogenesis and the subsequent dissemination of cancer cells with formation of lymphatic metastasis [18]; moreover, macrophage colony-stimulating factor (M-CSF) and VEGF actively recruit circulat-

Evidence has indicated that acetyl-xylogalactan extracted from *Sarcodia suieae* induced macrophage polarization through the IL-1β, TNF, and Malt-1 expression [20]. Nakanishi et al determined that celecoxib can alter the immune inhibitory effects of the tumour micro-environment by promoting the transformation of TAMs into M1 macrophages, leading to inhibited tumour growth [21]. In 1968, Ikekawa et al. reported that the fruiting body extracts from *Lentinus edodes*, *Trametes versicolor*, *Ganoderma tsugae*, *Flammulina velutiper,* and *Tricholoma matsutake* demonstrated significant antitumour activities in transplanted Sarcoma 180 tumour cells [22, 23]. Studies have reported that *Antrodia camphorata*-derived beta-glucan demonstrated inhibitory effects on tumour growth in Sarcoma 37, Sarcoma 180, Erlich ascites sarcoma, Yoshida sarcoma, and LLC1 transplanted tumour [24]. Daily intake of *A. comphorata*-derived beta-glucan for 18 consecutive days was demonstrated to slow tumour growth and reduce the rate of metastasis [25]. Cytotoxic T-cell activity and tumour occurrence rate were investigated and the results revealed that daily oral intake of *Grifola frondosa*-derived beta-glucan or Lentinan can enhance cytotoxic T-cell activity and reduce tumour occurrence rate [26]. Furthermore, the addition of conditioned medium with tumour cells into the progenitors of dendritic cells was determined to further inhibit the maturation of dendritic cells and lower the antigen-presenting capability of the dendritic cells [27]. Studies have reported that tumour cells secrete M-CSF, thereby inhibiting dendritic and T-cell differentiation and antitumour ability [27–30]. In the tumour environment, the amounts of M1 and M2 macrophages are not equal [31]. Tumour environments are known to contain a large number of transmitters such as M-CSF, IL-6, IL-10, TGF-β, and COX-2, which induce tumour megakaryocytes to differentiate into M2 macrophages, which have poorer antigen-presenting and cytotoxic abilities and secrete factors that inhibit immune cells, resulting in an enhanced immune inhibitory effect of the tumour environment [16, 32–41]. M2 macrophages in tumour-bearing mice enhance tumour growth and immune inhibitory effects. M2 macrophages also secrete cytokines, such as IL-10 and TGF-β, in high quantities, which attract noncytotoxic Treg-cells and Type 2 helper T cells to congregate in tumour tissues, which in turn inhibit the differentiation and normal functions of T cells, including their cytotoxic ability, which further leads to T-cell apoptosis [38, 40, 42–44]. The Th1 and Th2 polarization is built on cytokine patterns, which begin when the antigen-presenting cells interact with the naive T cells and polarize into type 1 and type 2 cells in response to the type of antigen encountered [45]. Th1 and Th2 cells secrete different cytokines.

**46**

*Macrophages*

### **Competing interests**

The authors declare no competing interests.

### **Author details**

Tsung-Meng Wu1 , Kuang-Teng Wang1 , Hisang-Lin Tsai<sup>2</sup> , Fan-Hua Nan3 and Yu-Sheng Wu1 \*

1 Department of Aquaculture, National Pingtung University of Science and Technology, Pingtung, Taiwan

2 Surgery Medical College of Kaohsiung Medical University, Kaohsiung, Taiwan

3 Department of Aquaculture, National Taiwan Ocean University, Keelung, Taiwan

\*Address all correspondence to: wuys0313@mail.npust.edu.tw

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**49**

*Functional Biomaterials Modulate Macrophage in the Tumour Micro-environment*

[10] Aggarwal BB, Shishodia S, Sandur SK, Pandey MK, Sethi G. Inflammation and cancer: How hot is the link? Biochemical Pharmacology.

[11] Muller AK, Meyer M, Werner S. The roles of receptor tyrosine kinases and their ligands in the wound repair process. Seminars in Cell & Developmental Biology.

[12] Danckwardt S, Hentze MW, Kulozik AE. Pathologies at the nexus of blood coagulation and inflammation: Thrombin in hemostasis, cancer, and beyond. Journal of Molecular Medicine.

[13] Strukova S. Blood coagulationdependent inflammation. Coagulation-

inflammation-dependent thrombosis. Frontiers in Bioscience (Elite Edition).

[14] Dugina TN, Kiseleva EV, Chistov IV, Umarova BA, Strukova SM. Receptors of the par-family as a link between blood coagulation and inflammation. Biochemistry (Moscow). 2002;**67**:65-74

inflammation & allergy—Drug targets. Inflammation & Allergy Drug Targets.

Locati M, Allavena P, Sica A. Macrophage

polarized m2 mononuclear phagocytes. Trends in Immunology. 2002;**23**:549-555

[17] Leek RD, Lewis CE, Whitehouse R, Greenall M, Clarke J, Harris AL. Association of macrophage infiltration with angiogenesis and prognosis in invasive breast carcinoma. Cancer Research. 1996;**56**:4625-4629

dependent inflammation and

[15] Zaenker KS. Journal of

[16] Mantovani A, Sozzani S,

polarization: Tumor-associated macrophages as a paradigm for

2006;**72**:1605-1621

2012;**23**:963-970

2013;**91**:1257-1271

2006;**11**:59-80

2009;**8**:1

*DOI: http://dx.doi.org/10.5772/intechopen.92429*

Carrillo NJTPJ. Reactive oxygen species generated in chloroplasts contribute to tobacco leaf infection by the necrotrophic fungus *Botrytis cinerea*. The Plant Journal. 2017;**92**:761-773

[2] Allavena P, Sica A, Solinas G, Porta C, Mantovani A. The inflammatory microenvironment in tumor progression: The role of tumor-associated macrophages.

[3] Punchard NA, Whelan CJ, Adcock I. The journal of inflammation. Journal of Inflammation (London). 2004;**1**:1

[4] Maslinska D, Gajewski M. Some aspects of the inflammatory process. Folia Neuropathologica.

[5] Sbarsi I, Falcone C, Boiocchi C, Campo I, Zorzetto M, De Silvestri A, et al. Inflammation and atherosclerosis: The role of tnf and tnf receptors polymorphisms in coronary artery disease. International Journal of Immunopathology and Pharmacology.

[6] Libby P, Ridker PM, Maseri A. Inflammation and atherosclerosis. Circulation. 2002;**105**:1135-1143

[7] Schott JM, Revesz T. Inflammation in alzheimer's disease: Insights from immunotherapy. Brain.

[8] Rubio-Perez JM, Morillas-Ruiz JM. A

review: Inflammatory process in Alzheimer's disease, role of cytokines. Scientific World Journal. 2012;**2012**:1-15

[9] Gregory CD. Inflammation and cancer revisited: An hypothesis on the oncogenic potential of the apoptotic tumor cell. Autoimmunity.

1998;**36**:199-204

2007;**20**:145-154

2013;**136**:2654-2656

2013;**46**:312-316

Critical Reviews in Oncology/ Hematology. 2008;**66**:1-9

[1] Rossi FR, Krapp AR, Bisaro F, Maiale SJ, Pieckenstain FL,

**References**

*Functional Biomaterials Modulate Macrophage in the Tumour Micro-environment DOI: http://dx.doi.org/10.5772/intechopen.92429*

### **References**

*Macrophages*

**Competing interests**

The authors declare no competing interests.

**48**

**Author details**

Tsung-Meng Wu1

and Yu-Sheng Wu1

, Kuang-Teng Wang1

\*Address all correspondence to: wuys0313@mail.npust.edu.tw

\*

provided the original work is properly cited.

Technology, Pingtung, Taiwan

, Hisang-Lin Tsai<sup>2</sup>

1 Department of Aquaculture, National Pingtung University of Science and

2 Surgery Medical College of Kaohsiung Medical University, Kaohsiung, Taiwan

3 Department of Aquaculture, National Taiwan Ocean University, Keelung, Taiwan

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

, Fan-Hua Nan3

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[2] Allavena P, Sica A, Solinas G, Porta C, Mantovani A. The inflammatory microenvironment in tumor progression: The role of tumor-associated macrophages. Critical Reviews in Oncology/ Hematology. 2008;**66**:1-9

[3] Punchard NA, Whelan CJ, Adcock I. The journal of inflammation. Journal of Inflammation (London). 2004;**1**:1

[4] Maslinska D, Gajewski M. Some aspects of the inflammatory process. Folia Neuropathologica. 1998;**36**:199-204

[5] Sbarsi I, Falcone C, Boiocchi C, Campo I, Zorzetto M, De Silvestri A, et al. Inflammation and atherosclerosis: The role of tnf and tnf receptors polymorphisms in coronary artery disease. International Journal of Immunopathology and Pharmacology. 2007;**20**:145-154

[6] Libby P, Ridker PM, Maseri A. Inflammation and atherosclerosis. Circulation. 2002;**105**:1135-1143

[7] Schott JM, Revesz T. Inflammation in alzheimer's disease: Insights from immunotherapy. Brain. 2013;**136**:2654-2656

[8] Rubio-Perez JM, Morillas-Ruiz JM. A review: Inflammatory process in Alzheimer's disease, role of cytokines. Scientific World Journal. 2012;**2012**:1-15

[9] Gregory CD. Inflammation and cancer revisited: An hypothesis on the oncogenic potential of the apoptotic tumor cell. Autoimmunity. 2013;**46**:312-316

[10] Aggarwal BB, Shishodia S, Sandur SK, Pandey MK, Sethi G. Inflammation and cancer: How hot is the link? Biochemical Pharmacology. 2006;**72**:1605-1621

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Section 2

Macrophage and Infection

Control

### Section 2
