PDCD1 and melanoma: Antibodies targeting inhibitory receptors including cytotoxic T lymphocyte-associated Antigen 4 (CTLA-4) and programmed cell death 1 (PD-1) successfully relieve inhibition and enhance T cell effector function, leading to improved clinical efficacy in treating several solid tumors (3), including advanced melanoma, non-small-cell lung cancer, renal cell carcinoma and metastatic bladder cancer (4).