Given that PD-1 is highly expressed on lymphocytes infiltrating human tumors and circulating tumor-specific T cells [42], and together with that PD-L1 expression is correlated with prognosis in many cancers, which suggests that PD-L1 expression is a mechanism for tumor immune evasion [24,28,31], it is reasonable to consider the blockade of the PD-1/PD-L1 interaction may be a promising anticancer immunotherapy. This evidence concerns the gene CD274 and cancer.