Liu 3 speculated that the low CPS1 gene expression in HCC may be related to DNA methylation; in addition, Liu proved that the CpG island hypermethylation of CPS1 gene is a key mechanism for the low CPS1 enzyme expression in the liver cell carcinoma, and two CpG island hypermethylation sites were found in the vicinity of the promoter region. This evidence concerns the gene CPS1 and hepatocellular carcinoma.