PDCD1 and cancer: Programmed death ligand-1 (PD-L1; also known as B7-H1 or CD274) is a 33 kDa type 1 transmembrane protein that binds programmed cell death protein-1 (PD-1) on T cells to create one of the major immune checkpoints, thereby suppressing activation, expansion, and acquisition of effector functions of TILs and enabling cancer cells to evade T cell-mediated immune surveillance [1].