Consistent with these findings, module 2 showed that the PPI in tumor groups and normal groups involved many members in Cytochrome P450, such as CYP3A4, CYP4A11, CYP2B6, CYP2C8, CYP26A1, CYP2A6, and CYP1A2, indicating that some key Cytochrome P450 enzymes had essential functions in HCC. Here, CYP26A1 is linked to hepatocellular carcinoma.