Immunotherapy in Metastatic Renal Cell Carcinoma: A Comprehensive Review

Table 1

Proposed mechanisms of tumor mediated immune evasion.

Effects of tumor mediated immune evasion on T cells	Molecular mechanisms underlying tumor effects on T cells
Direct deletion of immune effector cells	Expression of death inducing ligand (Fas)
	Secretion of immunosuppressive cytokines: IL-10, TGFβ
Direct tolerization of tumor reactive T cells	Cross presentation of tumor antigens by bone marrow APCs
	B7-H1 expression by tumor and induction of T cell apoptosis
Inhibition of T cell activation or induction of anergy	Lack of expression of costimulatory molecules (CD 28 on T cells, B7 ligands on APCs)
	Overexpression of inhibitory costimulatory molecules CTLA-4, PD-1, and PD-1 ligands

IL: interleukin, TGF: tissue growth factor, APCs: antigen-presenting cells, B7-H1: B7-homolog 1, CTLA-4: cytotoxic T lymphocyte antigen, PD1: programmed death-1, PD-L1: programmed death-ligand 1, and VEGF: vascular endothelial growth factor.