The liver-selective hepatotoxin diethylnitrosamine (DEN) (Tolba et al., 2015) undergoes CYP2E1-mediated oxidation (Kang et al., 2007) to become a genotoxin (Bakiri and Wagner, 2013), leading to hepatocyte apoptosis and tissue damage that can progress to cirrhosis and HCC (Tolba et al., 2015). The gene discussed is CYP2E1; the disease is Cirrhosis.