CD274 and cancer: Programmed death-ligand 1 (PD-L1, CD274) is a B7 homologous family immune co-signaling molecule that interacts with programmed death-1 (PD-1), a receptor on T cells and natural killer cells, to inactivate both T and natural killer cells, thus attenuate anti-tumor immune responses and allow tumors to evade immune surveillance (Fig. 3A).62, 63, 64 Drugs that block PD-1 or PD-L1 promote endogenous anti-tumor immunity and have been considered the common standard of care for cancer treatment due to their broad spectrum of activity.62