DNMT1 and hepatocellular carcinoma: In relation to liver cancer, despite an early research on 51 HCC tissue samples found a less frequent RARβ promoter methylation [145], in a subsequent study, the RARβ2 promoter hypermethylation was found as induced by HBV in HCC through the up-regulation of the DNA methyltransferases 1 and 3a, resulting in the RARβ2 down-regulation [147].