**2. Natural and adaptive immunity in RCC**

The tumor microenvironment is a complex structure composed by several mediators that are involved in the cell signaling. The activation profile of extracellular matrix, fibroblasts, immune cells, blood vessels, and endothelial cells is essential to the pathogenesis of cancer, as well as to define therapeutic approaches [16–18]. Resident nontumor cells or infiltrated cells at tumor sites may even suppress the development of RCC. However, tumor cells can avoid the immune response coordinating changes in these cells and stimulating the secretion of immunosuppressive factors for tumorigenesis, pro-inflammatory cytokines including angiogenic factors, thus ensuring the supply of nutrients by newly formed, blood vessels, which further allow for tumor growth [19, 20].

In addition, the profile of soluble factors, such as cytokines and chemokines, present in the tumor microenvironment may undergo dual polarization allowing either tumor growth (leading to progressive disease) or its suppression (leading to regressive disease). Immune cells could interact with tumor cells, especially through immunosuppression, via cell-cell contact, or by the release of factors that maintain a supportive environment for tumor growth. Through some soluble mediators, such as tumor necrosis factor-alpha (TNFα), immune cells can stimulate other cells, such as fibroblasts, to produce proteolytic enzymes for extracellular matrix remodeling and collagen, facilitating the spread of metastases. It may also stimulate the involvement of endothelial cells, which become able to form new vessels [18, 21, 22]. On the other hand, TNFα, which is mainly produced by macrophages, has also an important role in the recruitment of other immune cells to the tumor site where they will be able to assemble a response against the tumor. Thus, the constant interference of mediators may favor/inhibit an adequate environment for tumor maintenance and growth [18, 21].

According to the cell type where the tumor starts, kidney cancers are classified as renal cell carcinoma (RCC) subdivided in papillary RCC, chromophobe RCC, rare types of RCC, and unclassified RCC. Also, there are transitional cell carcinoma, Wilms' tumor, which almost

Regardless of the category, kidney tumors have been associated with immune dysfunction [1–3, 5]. RCCs are rich in immune infiltrates consisting of T cells, natural killer (NK), DCs, macrophages among others [6, 7]. Different functions are ascribed to the different subsets of leukocytes. While the function of some of these cells is still elusive, like neutrophils which are essential components of the RCC microenvironment, others have well-defined roles in tumor progression. For example, tumor-associated macrophages (TAMs) are known for their immunosuppressive action, which is associated to the secretion of inhibitory cytokines, the generation of reactive oxygen species, regulatory T cells (Treg) development, and the induction of angiogenesis [6, 8, 9]. Likewise, myeloid-derived suppressor cells (MDSCs) have been reported preventing the formation and execution of an effective antitumor immune response by the inhibition of effector T-cell function and the induction of Tregs maturation [6, 7], besides the inhibition of DC maturation and DC-induced T-cell activation and antitumor cytotoxic T lymphocyte (CTL) [10]. The role of the immune system in RCC is not only observed at the cellular level but also through inflammatory mediators, that is, through the action of cytokines and chemokines which act in tumor and stroma cells [11–13]. These mediators in RCC and stroma cells lead to survival, proliferation, and migration and favor angiogenesis and metastasis [11–13]. Thereby, the modulation of immune system effectors has shown therapeutic potential. In fact, strategies involving immune checkpoint inhibitors, immunotherapy, and antagonists of chemokine

Herein, we summarize relevant information about the role of natural and adaptive immunity in the development of RCC. Additionally, we describe cytokine and chemokine intracellular signaling pathways and mention how all knowledge has been useful for identification and

The tumor microenvironment is a complex structure composed by several mediators that are involved in the cell signaling. The activation profile of extracellular matrix, fibroblasts, immune cells, blood vessels, and endothelial cells is essential to the pathogenesis of cancer, as well as to define therapeutic approaches [16–18]. Resident nontumor cells or infiltrated cells at tumor sites may even suppress the development of RCC. However, tumor cells can avoid the immune response coordinating changes in these cells and stimulating the secretion of immunosuppressive factors for tumorigenesis, pro-inflammatory cytokines including angiogenic factors, thus ensuring the supply of nutrients by newly formed, blood vessels, which further

In addition, the profile of soluble factors, such as cytokines and chemokines, present in the tumor microenvironment may undergo dual polarization allowing either tumor growth

always occur in children and renal sarcoma [1–4].

20 Evolving Trends in Kidney Cancer

receptors have proven clinical efficacy [14, 15].

advancement of therapeutic approaches for RCC.

**2. Natural and adaptive immunity in RCC**

allow for tumor growth [19, 20].

Indeed, tissue repair promoted by inflammation is self-limited, and the imbalance on this process may be pathogenic, giving inflammatory cells either a beneficial and/or a detrimental role in the pathogenesis of various diseases, including chronic inflammation and neoplasia [23]. The TAMs have at least two well-described states of polarization, according to immunological competences. While M1 (classically activated) macrophages can inhibit tumor growth, M2 (alternatively activated) macrophages stimulate tumor growth [24–26]. The M1 polarization is functionally characterized by the release of pro-inflammatory cytokines (interleukin [IL]-1β, IL-6, and TNFα) and reactive nitrogen/oxygen species (RNI/ROS) acting as microbicidal and tumoricidal [24]. In the tumor context, some authors suggest that macrophages in the initial phase of tumorigenesis can naturally inhibit tumor growth, eradicate tumor cells, and stimulate the immune response. In contrast, M2 macrophages may favor neoplasia by producing anti-inflammatory cytokines that suppress the cellular response, release vascular endothelial growth factors (VEGFs), responsible for angiogenesis, and release transforming growth factors (TGF-beta) [27].

The different subtypes of T lymphocytes are also recruited into the tumor microenvironment and interact with tumor cells, which may induce tumor cell death, becoming anergic or even suppressing the immune response against the tumor [28, 29]. T CD8+ lymphocytes, also known as cytotoxic T cells, play an important role in the adaptive immunity in response to tumorspecific epitopes. Together with NK and Natural killer T (NKT) cells, T CD8<sup>+</sup> cells induce tumor cell death by apoptosis through the secretion of cytotoxic factor, such as granzymes and perforins. Besides, when the TCD8 lymphocyte is activated, it secretes IFN-gamma and IL2, activating other TCD8 cells and M1 macrophages, skewing the inflammatory response toward a Th1 profile. However, RCC and some types of tumor-infiltrating immune cells, such as MDSCs, present in the tumor microenvironment can suppress antitumor response T cell mediated by the expression of programmed death ligand-1 (PD-L1, also known as B7-H1 or CD274) [30, 31].

CD4 T lymphocyte is endowed with great plasticity, being able to differentiate into Th1, Th2, Th3, Th17, and Treg subtypes. Treg cells play a critical role in the control of the acute phase of the inflammatory response through immunosuppression. High levels of Treg in the tumor microenvironment are considered as poor prognosis for tumors, for example, in renal and pancreatic tumor, due to the recruitment of other immunosuppressive cells and the stimulation of the angiogenic process [29, 32]. MDSCs are involved in chronic inflammation processes, which are recruited by tumor or Treg, increasing immunosuppression in the tumor microenvironment [33]. A common feature of almost all solid tumors is hypoxia that could lead to the stability of the HIF-1α transcription factor (hypoxia-inducible factor-1α). HIF-1α can bind to a hypoxiaresponsive element in the PD-L1 promoter leading to PD-L1 expression, not only on tumor cells but also on MDSCs, macrophages, and DCs within the tumor microenvironment [34].

cytokines are important for equilibrium and elimination phases of tumor control [52]. Several cytokines are involved in the differentiation process of immune cells. Interferon-gamma (INF-gamma) belongs to interferon family and is a natural glycoprotein that shows antiviral, antiproliferative, and immunomodulatory properties. INF-gamma plays a key role in the tumor microenvironment, where it aids in tumor eradication. This cytokine is able to recruit and induce the proliferation of T lymphocytes in the tumor microenvironment, to activate innate immunity cells, rendering them cytotoxic, besides polarizing the Th1 response from T CD4

Role of Immune System in Kidney Cancer http://dx.doi.org/10.5772/intechopen.77379 23

**Figure 1.** Dual role of natural and adaptive immunity in RCC. Innate immune cells (dendritic cells, macrophages, NK cells, neutrophils, and MDSCs) and adaptive immunity (B and T cells) in the tumor microenvironment may undergo dual polarization allowing either tumor growth (leading to progressive disease) or its suppression (leading to regressive disease). Dendritic cells are primed by tumor antigens, which are then presented to T and B cells for adaptive responses. On the other hand, dendritic cells can directly drive tumor angiogenesis through the release of pro-angiogenic cytokines such as TNFα and CXCL8. Similarly, neutrophils in the tumor microenvironment are able to release pro-angiogenic factors and chemokines that could contribute for cancer progression and metastasis. T CD8+ lymphocytes, also known as cytotoxic T cells, play an important role against tumor cells under response to tumor-specific epitopes. However, the PD-L1/PD-1 interaction on CD8+ T-cell surface induces cellular energy suppressing the effector response, leading CD8 T cell to death. Failure of CD8+ T cells to kill tumor cells involves signals from multiple cells including MDSC, Treg, and TAMs. NK cells are characterized by a high cytolytic capacity against transformed cancer cells by the secretion of granzyme and perforin. Tumor cells and fibroblasts also produce survival/growth-promoting chemokines. Metastatic cancer cells are facilitated by the upregulation of particular chemokine receptors (such as CXCR4) by tumor cells, which

enables them to migrate to secondary tissues where the ligands are expressed.

PD-L1 binds with PD-1 present on the cell surface of activated T cells leading to proliferation blockade, dysfunctional response, and T-cell death. CTLA-4 (CTL -associated antigen 4), a receptor also present in T cells, is the best studied inhibitory molecule, well known for its capacity of blocking T cell-mediated immune responses [35, 36]. CTLA-4 competes with CD28 for CD80 or CD86 binding. When the CTLA-4/CD80 or CD86 interaction occurs, the cell becomes anergic and dies. The overexpression of CTLA-4 is involved in several neoplastic, inflammatory, and autoimmune diseases [37]. The inhibition of T response allows for RCC to avoid effectors of immunologic control and facilitates invasion and metastasis. Accordingly, PD-L1 overexpression is related to worse prognosis for metastatic RCC, and it is therefore an important target for drug discovery [38, 39]. New drugs based on monoclonal antibodies, such as anti-PD-1 and anti-CTLA-4, have been strongly explored in clinical trial and proven to be efficacious to combinatorial treatments [39]. Indeed, immunotherapy is a promising therapeutic strategy for different types of cancers, but it is often not sufficient to control tumor growth [40]. Several therapeutic strategies based on innate, adaptive, humoral, or cytokine immune system responses have been studied in order to combat tumor cells in the host [41–45].

Studies using allogeneic DCs in metastatic Renal Cell Carcinoma (mRCC) and melanoma patients are widespread due to the ability of these cells to mediate the cell signaling between the innate and adaptive immune response. As professional antigen-presenting cells (APCs), these cells phagocytose tumor cell particles, process them, and further present their epitopes to further activate effector lymphocytes [46]. APCs play a crucial role in coordinating the immune response, where the imbalance between populations of macrophages, immature, and mature DCs significantly affects the immune response against solid tumors [47]. Both DCs and macrophages can be activated by some microbial stimulus or cytokines in an inflammatory environment. DCs and macrophages could differentiate from monocytes, according to the tissue environment, where cytokines such as IL4 and macrophage colony-stimulating factor granulocytes (GM-CSF) may induce differentiation, followed by TNFα-induced maturation [47]. In the tumor context, the inflammatory profile present at different stages of disease development may contribute to or eradicate the pathogenesis [47]. The International Society for the Biological Therapy of Cancer (iSBTc), together with the Society for Cancer Immunotherapy (SITC), has been discussing the theme with the purpose of advancing the critical understanding of the involvement of inflammation during pathogenesis and cancer treatment [48, 49]. In fact, the dynamics of tumor progression along with immunoedition has been studied for years, through the realization of which cells, molecules, and pathways of the immune system are engaged at different steps of the evolution of cancers. Nonetheless, an integrative picture of the whole process is still missing [50, 51]. Vesely et al. described several interactions between innate and adaptive immunity in cancer, suggesting a dynamic immuno-delivery model, where cells such as M2 macrophages, MDSC, Th17, Treg, and TCD8+ overexpressing CTLA-4 receptor are present in chronic inflammation and favor the processes related to tumor progression [52]. In contrast, NK, NKT, TCD8<sup>+</sup> , TCD4+ , M1 macrophages, DCs, Tγδ cells and IL12 and IFN-gamma cytokines are important for equilibrium and elimination phases of tumor control [52]. Several cytokines are involved in the differentiation process of immune cells. Interferon-gamma (INF-gamma) belongs to interferon family and is a natural glycoprotein that shows antiviral, antiproliferative, and immunomodulatory properties. INF-gamma plays a key role in the tumor microenvironment, where it aids in tumor eradication. This cytokine is able to recruit and induce the proliferation of T lymphocytes in the tumor microenvironment, to activate innate immunity cells, rendering them cytotoxic, besides polarizing the Th1 response from T CD4

A common feature of almost all solid tumors is hypoxia that could lead to the stability of the HIF-1α transcription factor (hypoxia-inducible factor-1α). HIF-1α can bind to a hypoxiaresponsive element in the PD-L1 promoter leading to PD-L1 expression, not only on tumor cells

PD-L1 binds with PD-1 present on the cell surface of activated T cells leading to proliferation blockade, dysfunctional response, and T-cell death. CTLA-4 (CTL -associated antigen 4), a receptor also present in T cells, is the best studied inhibitory molecule, well known for its capacity of blocking T cell-mediated immune responses [35, 36]. CTLA-4 competes with CD28 for CD80 or CD86 binding. When the CTLA-4/CD80 or CD86 interaction occurs, the cell becomes anergic and dies. The overexpression of CTLA-4 is involved in several neoplastic, inflammatory, and autoimmune diseases [37]. The inhibition of T response allows for RCC to avoid effectors of immunologic control and facilitates invasion and metastasis. Accordingly, PD-L1 overexpression is related to worse prognosis for metastatic RCC, and it is therefore an important target for drug discovery [38, 39]. New drugs based on monoclonal antibodies, such as anti-PD-1 and anti-CTLA-4, have been strongly explored in clinical trial and proven to be efficacious to combinatorial treatments [39]. Indeed, immunotherapy is a promising therapeutic strategy for different types of cancers, but it is often not sufficient to control tumor growth [40]. Several therapeutic strategies based on innate, adaptive, humoral, or cytokine immune

but also on MDSCs, macrophages, and DCs within the tumor microenvironment [34].

system responses have been studied in order to combat tumor cells in the host [41–45].

such as M2 macrophages, MDSC, Th17, Treg, and TCD8+

, TCD4+

contrast, NK, NKT, TCD8<sup>+</sup>

22 Evolving Trends in Kidney Cancer

Studies using allogeneic DCs in metastatic Renal Cell Carcinoma (mRCC) and melanoma patients are widespread due to the ability of these cells to mediate the cell signaling between the innate and adaptive immune response. As professional antigen-presenting cells (APCs), these cells phagocytose tumor cell particles, process them, and further present their epitopes to further activate effector lymphocytes [46]. APCs play a crucial role in coordinating the immune response, where the imbalance between populations of macrophages, immature, and mature DCs significantly affects the immune response against solid tumors [47]. Both DCs and macrophages can be activated by some microbial stimulus or cytokines in an inflammatory environment. DCs and macrophages could differentiate from monocytes, according to the tissue environment, where cytokines such as IL4 and macrophage colony-stimulating factor granulocytes (GM-CSF) may induce differentiation, followed by TNFα-induced maturation [47]. In the tumor context, the inflammatory profile present at different stages of disease development may contribute to or eradicate the pathogenesis [47]. The International Society for the Biological Therapy of Cancer (iSBTc), together with the Society for Cancer Immunotherapy (SITC), has been discussing the theme with the purpose of advancing the critical understanding of the involvement of inflammation during pathogenesis and cancer treatment [48, 49]. In fact, the dynamics of tumor progression along with immunoedition has been studied for years, through the realization of which cells, molecules, and pathways of the immune system are engaged at different steps of the evolution of cancers. Nonetheless, an integrative picture of the whole process is still missing [50, 51]. Vesely et al. described several interactions between innate and adaptive immunity in cancer, suggesting a dynamic immuno-delivery model, where cells

present in chronic inflammation and favor the processes related to tumor progression [52]. In

overexpressing CTLA-4 receptor are

, M1 macrophages, DCs, Tγδ cells and IL12 and IFN-gamma

**Figure 1.** Dual role of natural and adaptive immunity in RCC. Innate immune cells (dendritic cells, macrophages, NK cells, neutrophils, and MDSCs) and adaptive immunity (B and T cells) in the tumor microenvironment may undergo dual polarization allowing either tumor growth (leading to progressive disease) or its suppression (leading to regressive disease). Dendritic cells are primed by tumor antigens, which are then presented to T and B cells for adaptive responses. On the other hand, dendritic cells can directly drive tumor angiogenesis through the release of pro-angiogenic cytokines such as TNFα and CXCL8. Similarly, neutrophils in the tumor microenvironment are able to release pro-angiogenic factors and chemokines that could contribute for cancer progression and metastasis. T CD8+ lymphocytes, also known as cytotoxic T cells, play an important role against tumor cells under response to tumor-specific epitopes. However, the PD-L1/PD-1 interaction on CD8+ T-cell surface induces cellular energy suppressing the effector response, leading CD8 T cell to death. Failure of CD8+ T cells to kill tumor cells involves signals from multiple cells including MDSC, Treg, and TAMs. NK cells are characterized by a high cytolytic capacity against transformed cancer cells by the secretion of granzyme and perforin. Tumor cells and fibroblasts also produce survival/growth-promoting chemokines. Metastatic cancer cells are facilitated by the upregulation of particular chemokine receptors (such as CXCR4) by tumor cells, which enables them to migrate to secondary tissues where the ligands are expressed.

lymphocytes [53, 54]. IL1-beta is one of the major cytokines involved in the pro-inflammatory response, which is synthesized by several immune cells, such as monocytes, macrophages, DCs, B lymphocytes, NK cells, among others. It has similar activities as described for TNFα, favoring tumor invasion and the angiogenic process, as well as favoring vascular permeability and facilitating the recruitment of immune system cells to the tumor microenvironment [55]. However, TNFα is the main mediator of the acute inflammatory response, being secreted primarily by macrophages and T cells. TNFα causes vascular endothelial cells to increase the expression of leukocyte integrins inducing chemotaxis. In addition, TNFα also acts on phagocytic cells, which characterizes an autocrine effect, since macrophages, apart from secreting TNFα, may respond to the stimulus itself, releasing IL1-beta [56, 57]. IL12 is secreted primarily by macrophages, DCs, monocytes, and neutrophils. It has action in the activation of cytotoxic NK cells and TCD8 lymphocytes, but its main function in the antitumor activity is involved in the activation and proliferation of T lymphocytes and NK cells, which induces the production of IFN-gamma. Moreover, IL12 and INF-gamma together are able to differentiate T-helper cells into Th1 cells [58, 59]. IL6 is synthesized by mononuclear phagocytes, such as macrophages and also by some activated T cells and by other cell types that are not part of the immune system in response to microorganisms or IL1-beta and TNFα stimuli [60]. IL10 is a cytokine known to be anti-inflammatory, synthesized in the form of monomers of 18–20 kDa, being functional in the form of homodimers. This cytokine can be produced by Th2 lymphocytes, monocytes, and epithelial cells. Its main action is to suppress the synthesis of several inflammatory cytokines such as IL1-beta, TNFα, IL-6, IL-8, and IL-12, as well as hematopoietic growth factors (GM-CSF, G-CFS) and macrophage colony-stimulating factor (M-CFS). In addition, IL-10 can inhibit the synthesis of nitric oxide, gelatinase, and collagenase, avoiding tissue injury [61]. Although its role in the tumor context remains unclear, IL-17 is a pro-inflammatory cytokine secreted by Th17 lymphocytes, which regulates NFkB and MAPK activities. It is constantly involved in the acute phase of inflammatory diseases, such as autoimmune diseases, and it is associated with poor prognosis in patients with RCC [62, 63].

Key pro-inflammatory cytokines in kidney cancer include interleukin-1 beta (IL-1β), IL-6, and TNFα, all of which signal via the type I cytokine receptors that are structurally divergent from other cytokine receptor types [66, 67]. IL-1 signaling starts through its binding to its receptor composed of two subunits, interleukin 1 receptor type I (IL-1RI) and interleukin 1 receptor accessory protein (IL1RAP) [68, 69]. Signaling proceeds with TIR adaptor and MyD88 by recruitment of IL-1R-associated kinases (IRAKs), which promote TNFR-associated factor 6 (TRAF6) polyubiquitination via lysine 63 linkages. Subsequently, TRAF6 interacts with the TAK1/TAB1/TAB2 complex that allows NFκB nuclear translocation (p65/p50) resulting in proinflammatory gene expression [69]. Also, TAK1/TAB1/TAB2 complex triggers the activation of the mitogen-activated protein kinases (MAPKs), c-JunN-terminal kinase (JNK), and p38, which induce the expression of pro-inflammatory genes. Similarly, TNFα binding to TNFR1 results in NFκB nuclear translocation, MAPKs, JNK, and p38, but signaling is coordinated by complex I (TRADD/TRAF2/RIP) [67, 70]. Importantly, TNFα signaling following receptor internalization is thought to be pro-apoptotic, via the formation of complex II (TRADD/FADD/ Pro-Caspase-8) [67]. On the other hand, IL-6 binds to the FIII domains of the IL-6R chains, unleashing its signal via the gp130 proteins [71, 72]. Consequently, Janus kinases (JAKs) are recruited to the receptor, phosphorylating it and themselves, triggering STAT3 activation and

Role of Immune System in Kidney Cancer http://dx.doi.org/10.5772/intechopen.77379 25

transcription of pro-inflammatory genes and intracellular adhesion molecules [64].

HIF-1α-mediated VEGF expression in human RCC cell [79].

Currently, it is not fully understood how the signaling triggered by these cytokines contributes to tumor progression, but high serum levels of these pro-inflammatory cytokines are associated with advanced disease [73]. Some evidence has arisen, as follows. It is well known that angiogenesis is stimulated by inflammatory mediators in the tumor microenvironment, such as those expressed by TAMs [74]. Interestingly, TAMs isolated from RCC tumors express high levels of IL-1β, TNFa, and IL-6 [75]. In addition, mouse models have demonstrated that the inhibition of IL-1β signaling reduced tumor blood vessel formation [76] and IL-1β mediates metalloproteinase-dependent RCC tumor cell invasion through the activation of cytosine-cytosine-adenosineadenosine-thymidine (CCAAT) enhancer binding protein b [67]. Regarding TNFα signaling, many studies associated it to chemokine overexpression in tumor and nontumor cells [77, 78]. Moreover, TNFα plays an important role in the progression of RCC by inducing epithelial to mesenchymal transition and CD44 expression, which may be involved in the resistance to the sunitinib treatment [66]. There is no direct correlation between IL-6R and RCC development; however, RCC cells express high levels of IL-6, and its signaling activity seems necessary for carcinogenesis, tumor progression, and tumor evasion of the immune system. STAT3 activation by IL-6 promotes tumorigenesis by preventing apoptosis while enhancing proliferation, angiogenesis, invasiveness, and immune evasion [79]. For example, activated STAT3 induces

Besides these pro-inflammatory cytokines, other mediators act as crucial players in RCC. Chemotactic cytokines or chemokines are responsible for the recruitment of cells from both the innate and adaptive immune systems to the site of injury or infection [64]. Chemokines induce integrin expression, such as the β2-integrin lymphocyte function-associated antigen (LFA-1), in target leukocytes, thus acting in the arrest of these cells and favoring diapedesis through the endothelium [71]. Despite this, primary chemotaxis action, chemokines, and their receptors are physiological relevant in many biological process, such as the initiation of adaptive immune responses, immune surveillance and the migration, proliferation, and

Taken all these studies together, the dual role of natural and adaptive immunity in RCC is evident (**Figure 1**).
