The treatment efficacy of malignant tumors has been greatly improved by the introduction of immune checkpoint inhibitors (ICIs), including programmed cell death protein-1 (PD-1)/programmed cell death-ligand 1 (PD-L1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) monoclonal antibodies [1]. Here, PDCD1 is linked to cancer.