PDCD1 and melanoma: Blockade of cytotoxic T-lymphocyte–associated antigen 4 (CTLA-4) and programmed death 1 (PD-1) or the PD-1 ligand, PD-L1 have achieved survival rates of 30–50% in various cancers such as non-small cell lung carcinoma (NSCLC), melanoma, and bladder cancer4,5.