PDCD1 and renal cell carcinoma: Immune checkpoint inhibitors (ICIs) targeting programmed cell death-1 (PD-1), programmed cell death ligand-1 (PD-L1), and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) are a major class of immuno-oncology therapeutics that have significantly improved the prognosis of advanced renal cell carcinoma (RCC) [1].