PDCD1 and colorectal carcinoma: We then examined that relationship between common immune checkpoint inhibitors and chemotherapy and the prognostic model, which revealing that HAVCR2, the immune checkpoint marker gene, was positively associated with the high-risk group for all four digestive cancers, while other marker genes (CD274, PDCD1, CTLA4, LAG3 and TIGIT) were more significant in some single cancers such as CRC, STAD and LIHC.