For example, CYP2E1 expression is higher in breast tumors (Kapucuoglu et al. 2003), in the MGC-803 human gastric cancer cell line (Wang et al. 2020), in the esophageal mucosa of patients with esophageal squamous cell carcinoma (Bergheim et al. 2007), and in adjacent nontumor tissues from hepatocellular carcinoma patients (Ho et al. 2004), than in their normal counterparts. This evidence concerns the gene CYP2E1 and esophageal squamous cell carcinoma.