CD274 and neoplasm: PD-L1 (B7-H1) is a transmembrane protein expressed by T cells, B cells, and various tumor cells.153 Binding of PD-L1 with PD-1 on the surface of CTLs can inhibit the proliferation of CTLs and suppress the secretion of CTL cytokines such as IL-2, thereby affecting the function of CTLs and promoting TIE.146 The overexpression of PD-L1 on the surface of tumor cells through different mechanisms can enhance immunosuppression and promote immune escape.