For example, aberrant hypermethylation has been identified in the promoter regions of key tumor-suppressor genes, including MLH1, CDKN2A, and APC in the case of CRC; abnormal histone methylations, including H4K20me3, H3K4me1/2/3, H3K9me3, H3K27me3, and H3K79me2, have been frequently found in CRC tumor samples and cell lines [6]. This evidence concerns the gene CDKN2A and colorectal carcinoma.