Immunotherapy in Metastatic Renal Cell Carcinoma: A Comprehensive Review

Figure 1

Mechanism of action of immune checkpoint inhibitors. PD-1 is expressed on activated T cells and when it binds to its ligand PD-L1 on tumor cells leads to T cell exhaustion. CTLA-4 competes with CD28 (costimulatory T cell molecule) for B7 ligands (CD80 and CD86 that are not shown in the figure) and upon activation decreases T cell proliferation as well as activity. Blockade of CTLA-4 (by anti-CTLA-4) and PD-1 (anti-PD-1) or PD-L1 stimulates effector T cells to produce antitumor responses. Adapted by permission from Macmillan Publishers Ltd. [37], copyright (Jan 2014). PD-1: programmed death-1, PD-L1: programmed death-ligand 1, MHC: major histocompatibility complex, TCR: T cell receptor, and CTLA-4: cytotoxic T lymphocyte antigen.