Maivel Ghattas et al.[68] suggested the possible involvement of MTHFR promoter methylation and the consequent inactivation of MTHFR, which might be part of a feedback regulation mechanism of MTHFR. Decreased MTHFR level induced DNA hypomethylation and Ding, X. et al.[69] indicated that the methylation rate of PDCD4 promoter is significantly higher in HCC tissues than that in adjacent nontumor tissues. This evidence concerns the gene MTHFR and hepatocellular carcinoma.