CD274 and carcinoma: Inhibiting PD-1 or PD-L1 can contribute to antitumor immunity and induce carcinoma regression by various pathways, including (1) reinvigorating lymphocyte activity and cytotoxic cytokine release; (2) activating and proliferating CD8+ T-cells specific to tumor antigens; (3) dislodging the apoptosis of lymphocytes induced by PD-1/PD-L1 interaction; and (4) boosting the immune discrimination of tumor cells [30,31].