CDKN2A and hepatocellular carcinoma: As shown in Figure 5, we found a statistical difference between HCC tumor tissues and normal tissues for p16 methylation in China from 15 studies (OR = 21.31, 95% CI = 11.10–40.94, I2 = 0%, p < 0.00001), in Japan from 6 studies (OR = 9.20, 95% CI = 4.58–18.51, I2 = 0%, p < 0.00001) and in Germany from 3 studies (OR = 30.43, 95% CI = 7.32–126.41, I2 = 41%, p < 0.00001).