CD274 and melanoma: PD-L1/PD-1 axis plays a pivotal role in inducing anergy of cytotoxic T cells and maintaining immunosuppressive microenvironment [35], which is supported by the efficacy of antibodies targeting PD-1 or PD-L1 in non-small-cell lung cancer (NSCLC), gastric cancer, melanoma and hepatocellular carcinoma [12–14, 36, 37].