In the PD-L1−/− PD-L2−/− mice, PD-L1 expression on the tumor cells is the only source of ligands for PD-1.They found that MC38 tumor growth was similarly robust in PD-L1−/− PD-L2−/− and WT mice, which indicates that engagement of PD-1 by PD-L1 on tumor cells alone is sufficient to suppress antitumor immunity to MC38 tumors. The gene discussed is CD274; the disease is neoplasm.