Immune checkpoint inhibitors (ICIs), could reduce the immunosuppression in the tumor microenvironment and reactivate the antitumor function of T cells through inhibiting the cytotoxic T lymphocyte-associated protein 4 (CTLA-4) and PD-1/PD-L1 pathway (programmed cell death-1 and programmed cell death receptor ligand-1 pathway) (9–13). The gene discussed is PDCD1; the disease is neoplasm.