In addition, Feng revealed that HOXA9, RASSF1 and SFRP1 were more frequently methylated in HBV-positive HCC cases, while CDKN2A were significantly more frequently methylated in HCV-positive HCC cases, suggesting that methylation of these gene promoters may be involved in virus-induced hepatocarcinogenesis [34]. This evidence concerns the gene CDKN2A and hepatocellular carcinoma.