From the comparison of DNA methylation levels of the 30 genes in normal tissues and HCC tissues, the DNA methylation levels of some genes in normal tissues were not different from those in HCC tissues with low hypoxia scores but were higher than those in HCC tissues with high hypoxia scores (such as RGS2), and the DNA methylation levels of some other genes were highest in normal tissues, followed by those in HCC tissues with low hypoxia scores, and lowest in HCC tissues with high hypoxia scores (such as CLIC1). The gene discussed is RGS2; the disease is hepatocellular carcinoma.