The use of checkpoint inhibitors has shown benefits for the anti-tumor response in various cancers but has also resulted in toxicity that differed from the side effects of conventional anticancer treatments such as cytotoxic chemotherapy; treatment with anti-CTLA-4 or anti-PD-1 antibodies are associated with inflammatory side effects, named together as immune-related adverse effects (irAEs) (27). Here, PDCD1 is linked to cancer.