At the same time, we detected the expression of six down-regulated hub genes in HCC and normal liver tissues by the TCGA database, the results suggested that KLKB1, F9, ALDH8A1, C8B, AFM, and CYP2A6 were all more highly expressed in normal liver tissues than in cancerous tissues (Figure 9A). This evidence concerns the gene CYP2A6 and hepatocellular carcinoma.