CD274 and cancer: Among the immune checkpoint molecules, programmed death 1 (PD-1), a member of the B7 family of cosignaling molecules, and its associated ligand PD-L1 have drawn considerable attention as therapeutic targets in several types of cancers, and inhibitors for the PD-1/PD-L1 axis are often combined with novel anti-cancer agents to maximize their therapeutic efficacy [6–10].