PDCD1 and melanoma: Blockade of pathways involving PD-1 and its ligand is a promising treatment for cancers (melanoma, nonsmall cell lung cancer, metastatic renal cell carcinoma, head and neck carcinomas, Hodgkin lymphoma, and urothelial carcinoma) (4), although the role of PD1/programmed death ligand 1 in immune suppression and the mechanism of action of antibodies remain to be better defined.