PDCD1 and neoplasm: Programmed cell-death ligand 1(PD-L1) is an immunosuppressive molecule mainly expressed on the surface of tumor cells [1], which inhibits anti-tumor function of T cells by activating programmed cell-death protein 1 (PD-1)/PD-L1 signaling pathway in the tumor microenvironment (TME) and causes immune escape of tumor cells [2, 3].