CDKN2A and hepatocellular carcinoma: As shown in Figure 3, we found a statistical difference between HCC tumor tissues and adjacent tissues for p16 methylation in China from 28 studies (OR = 4.88, 95% CI = 3.50–6.81, I2 = 66%, p < 0.00001) and in Japan from 6 studies (OR = 8.43, 95% CI = 3.71–19.19, I2 = 68%, p < 0.00001), but not in Germany from 3 studies (p = 0.12, I2 = 86%).