PDCD1 and renal cell carcinoma: The use of ipilimumab (anti-CTLA-4 mAb) either alone or in combination with nivolumab (anti-PD-1 mAb) is currently approved for the treatment of melanoma, colorectal cancer (CRC), hepatocellular carcinoma (HCC), non-small cell lung cancer (NSCLC), and renal cell carcinoma (RCC) (44).