CD274 and cancer: Among these, immune checkpoint molecules including the programmed death 1 (PD-1) receptor and its ligands, programmed death ligand 1 (PD-L1) and programmed death ligand 2 (PD-L2), have emerged as important factors involved in immune evasion by tumor cells and monoclonal inhibitors of this signaling pathway show impressive therapeutic responses and favorable safety profiles across a variety of human cancers such as melanoma, lung cancer, renal cell cancer, bladder cancer, and others [3, 4].