ICIs are humanized monoclonal antibodies that can activate T cells and relieve the immune system to recognize and assault cancer cells by targeting cytotoxic T-lymphocyte-associated protein 4 (CTLA4) (CD152), programmed cell death protein 1 (PD-1), or programmed cell death ligand-1 (PD-L1) [4]. Here, PDCD1 is linked to cancer.