Specifically, they demonstrated that DNA hypomethylation and the repressive histones H3K9me3 and H3K27me3 are both involved in the upregulation of the CTLA4 and TIGIT genes, whereas only the repressive histones are involved in the upregulation of the PDCD1 and HAVCR2 genes (coding for PD-1 and Tim-3) in CRC tumor tissues. Here, CTLA4 is linked to colorectal carcinoma.