GSTP1 and hepatocellular carcinoma: As shown in Table 3, Our meta-analysis showed statistical significance between HCC tumor serums and normal serums for the methylation of all six genes, including RASSF1A (the overall OR = 83.81, 95% CI = 47.35–148.36, p < 0.00001), p16 (the overall OR = 123.15, 95% CI = 49.12–308.74, p < 0.00001), CDH1 (the overall OR = 23.70, 95% CI = 5.39–104.28, p < 0.0001), RUNX3 (the overall OR = 103.92, 95% CI = 16.33–661.45, p < 0.00001), GSTP1 (the overall OR = 21.09, 95% CI = 4.02–110.65, p = 0.0003) and WIF1 (the overall OR = 53.65, 95% CI = 10.62–271.09, p < 0.00001).