,37 As a promising therapeutic technique in immunotherapy, immune checkpoint inhibitors (ICIs) have been acknowledged to be involved in conquering tumor microenvironment immunosuppression and enhancing the immunological anti-cancer responses by blocking inhibitory immune checkpoints,38,39,40,41 such as cytotoxic T lymphocyte antigen-4 (CTLA4)42 and programmed cell death protein 1 (PD-1),43 which have shown survival benefits in clinical trials. Here, PDCD1 is linked to cancer.