**4. Immunomodulatory molecules as new therapeutic targets for RCC**

Among the standard drugs for metastatic RCC treatment, the most effective regimens include the combination of targeted therapy agents and antiangiogenic agents (tyrosine kinase inhibitors, such as sorafenib, sunitinib, pazopanib, and axitinib), or an antiangiogenic antibody routinely employed in combination with interferon alpha (bevacizumab) [106, 107], and antiproliferative agents (mTOR inhibitors, such as temsirolimus and everolimus) [106, 107]. Despite the effectiveness of these therapies, resistance to antiangiogenic therapy almost always occurs and are associated with high toxicity and, consequently, serious adverse events.

Considering all knowledge previously mentioned in this chapter, it is not surprising that agents altering the immune response in order to prevent tumor growth and metastases have gained space in this scenario [12, 14, 108]. Known as immunomodulators, these molecules have been studied for some time now [109]. Among the first representatives of this class are IL-2 and interferon-alpha (IFN-α). IL-2 is a naturally occurring cytokine, which have antitumor activity by the induction of proliferation of NK cells, lymphokine-activated killer cells (LAKs), and other cytotoxic cells [110, 111]. IFN-α is also a molecule that had its clinical effect for the treatment of RCC demonstrated years ago [109, 112]. It is a pleiotropic cytokine with immunomodulatory activities that is able to induce the differentiation of monocytes into highly activated DCs, which are particularly effective in recognizing complex antigens and inducing T- and B-cell immunity and thus participate in the generation of antitumor T-cell immunity [112]. However, cytokine immunotherapies work effectively only in a minority of RCC patients and currently are not considered for the standard treatment of RCC due to their high toxicity.

In this context, cytokines have been exploited. Combination therapy using an antihuman IL-6R antibody with interferon has been suggested as a novel therapeutic approach for the treatment of RCC. Besides, an IL-6R-neutralizing antibody, tocilizumab, in combination with sorafenib suppressed tumor growth and inhibits angiogenesis *in vivo* more efficiently than sorafenib alone [113, 114]. Similarly, infliximab, an anti-TNFα monoclonal antibody that prevents TNFα binding to its receptors, TNFR1 (p55 receptor) and TNFR2 (p75 receptor) and causes cell death via complement-mediated lysis through interaction with membrane-bound TNF, has been considered for RCC treatment [115]. However, treatments with anti-TNFα monoclonal antibody showed varying results in independent studies, probably due to reactions given by this cytokine to different conditions, environmental and genetic factors and/ or other unknown or unexplained factors [116]. Besides anti-TNFα strategies, targeting IL-1β has also been reported as possible therapy for RCC [117].

Obviously, here we emphasize intracellular events in tumor cells. However, while some processes take place within the tumor cells, others would occur in the stroma: it is the synergism between these responses that contributes to the progression of the disease. RCC and other tumors interact with the surrounding tumor stroma through a variety of cytokines, chemokines, and growth factors [84]. The tumor chemotactic environment recruits inflammatory cells including neutrophils, macrophages, and lymphocytes. Although initially these cells may have a protective antitumoral role, as displayed by neutrophils, which have a higher cytotoxic activity against poorly metastatic cells, secondarily neutrophils could contribute to cancer progression. Leukocytes can produce cytokines, growth factors, and MMPs that enhance growth, proliferation, and angiogenesis, as exemplified by the TAMs, which release growth and angiogenic factors (e.g., VEGF) and basic fibroblast growth factor [105]. Thus, cellular communication by paracrine and autocrine chemokine/cytokine signaling contributes for the survival and growth of metastatic cells. In other words, stroma cells may support tumors at the same time

28 Evolving Trends in Kidney Cancer

as that tumor cells in turn modulate the microenvironment within which they reside.

**4. Immunomodulatory molecules as new therapeutic targets for RCC**

occurs and are associated with high toxicity and, consequently, serious adverse events.

Among the standard drugs for metastatic RCC treatment, the most effective regimens include the combination of targeted therapy agents and antiangiogenic agents (tyrosine kinase inhibitors, such as sorafenib, sunitinib, pazopanib, and axitinib), or an antiangiogenic antibody routinely employed in combination with interferon alpha (bevacizumab) [106, 107], and antiproliferative agents (mTOR inhibitors, such as temsirolimus and everolimus) [106, 107]. Despite the effectiveness of these therapies, resistance to antiangiogenic therapy almost always

Considering all knowledge previously mentioned in this chapter, it is not surprising that agents altering the immune response in order to prevent tumor growth and metastases have gained space in this scenario [12, 14, 108]. Known as immunomodulators, these molecules have been studied for some time now [109]. Among the first representatives of this class are IL-2 and interferon-alpha (IFN-α). IL-2 is a naturally occurring cytokine, which have antitumor activity by the induction of proliferation of NK cells, lymphokine-activated killer cells (LAKs), and other cytotoxic cells [110, 111]. IFN-α is also a molecule that had its clinical effect for the treatment of RCC demonstrated years ago [109, 112]. It is a pleiotropic cytokine with immunomodulatory activities that is able to induce the differentiation of monocytes into highly activated DCs, which are particularly effective in recognizing complex antigens and inducing T- and B-cell immunity and thus participate in the generation of antitumor T-cell immunity [112]. However, cytokine immunotherapies work effectively only in a minority of RCC patients and currently are not considered for the standard treatment of RCC due to their high toxicity.

In this context, cytokines have been exploited. Combination therapy using an antihuman IL-6R antibody with interferon has been suggested as a novel therapeutic approach for the treatment of RCC. Besides, an IL-6R-neutralizing antibody, tocilizumab, in combination with sorafenib suppressed tumor growth and inhibits angiogenesis *in vivo* more efficiently than sorafenib alone [113, 114]. Similarly, infliximab, an anti-TNFα monoclonal antibody that prevents TNFα binding to its receptors, TNFR1 (p55 receptor) and TNFR2 (p75 receptor) and causes cell death via complement-mediated lysis through interaction with membrane-bound Promising candidates for RCC treatment have also been designed to specifically target chemokines and their receptors. One of the most widely studied compounds is AMD3100 which is thought to specifically block CXCR4 signaling [118] and that acts directly in RCC tumor [91] cells as well as local antitumor immune response, by impairing Tregs function [119], know to suppress a whole range of immune cells including B cells, NK cells, NKT cells, CD4+ or CD8+ T cells, monocytes, and DCs [119]. Also, many other chemokine antagonists have also shown potential for clinical application in cancer treatment and could be useful for RCC treatment in the future. For example, anti-CXCR7-12G8 and CCX77, CXCR7 inhibitors or CTCE-9908, which is a peptide analog of CXCL12 and an active inhibitor of the ligand, has shown promising results as well as tolerated drug that stabilized disease in early clinical trials for late-stage cancer patients [12, 120].

Recently, antibodies that inhibit T-cell coinhibitory receptors have emerged as therapeutic promises not only in the treatment of RCC but also in other tumors by inhibiting T-cell regulatory activity and increasing the antitumor immune response [14, 121]. Nivolumab and pembrolizumab (anti-PD-1) [14, 122], avelumab, and durvalumab (anti-PD-L1) are in latestage clinical development for a number of indications [14, 123], besides the first in its class, ipilimumab (anti-CTLA-4), already approved for use in a number of indications [14, 124].

Finally, the close relationship between cancer and immune system has suggested that current drug therapies used to treat inflammatory diseases or particular types of cancers could function as inhibitors of chemokine signaling and could therefore be redirected toward the treatment of other cancers [12, 116]. This hypothesis needs to be tested by further preclinical and clinical investigation, which elucidates how these drugs would act at molecular and systemic levels.
