In the past decades, cancer immunotherapy has revolutionized cancer treatment, with immune checkpoint blockades (ICBs) including programmed cell death protein 1 (PD-1)/programmed cell death protein-ligand 1 (PD-L1)/cytotoxic T lymphocyte associate protein-4 (CTLA-4) being regarded as one of the most promising approaches to treat cancer. Here, PDCD1 is linked to cancer.