CDKN2A and hepatocellular carcinoma: Subgroup meta-analysis by geographical populations found that RASSF1A, GSTP1, APC, RUNX3 and PRDM2 hypermethylation was a common risk factor between HCC tumor tissues and adjacent tissues in HCC patients, however, the statistical significance of p16 hypermethylation was only found in China and Japan, but not in Germany.