Cancer immunotherapy stands out as a revolutionary advancement in recent years, including immune checkpoint therapy, exemplified by programmed cell death 1 (PD-1) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) inhibitors, as well as adoptive T-cell therapy (ACT), represented by chimeric antigen receptor T cell (CAR-T) therapy and cancer vaccines. Here, PDCD1 is linked to cancer.