APC and hepatocellular carcinoma: Controversially, DNA hypermethylation at CpG islands promotes the silencing of tumor suppressor genes, and many hypermethylated gene promoters, such as the promoter regions of adenomatous polyposis coli (APC) gene and cyclin-dependent kinase inhibitor 2A (CDKN2A) gene, have enabled researchers to distinguish tumor tissues from non-tumor liver tissues in patients with HCC [30].