Figure 4 shows that the gene and protein expression levels of catalase, glutathione peroxidase (GPx) and superoxide dismutase (SOD) decreased in HCCs (Hepa1-6 and HepG2 cells) with increasing SOE concentration. This effect may have contributed to the apoptotic effect of SOE on hepatoma cells [16,17]. This evidence concerns the gene CAT and hepatocellular carcinoma.