To more closely investigate the mechanisms by which cytochrome P450 2E1 activation and the production of reactive oxygen species cause cellular damage, Dai and colleagues (1993) and Chen and Cederbaum (1998) developed recombinant hepatoma-based cell lines that express cytochrome P450 2E1; they called these cell lines E9 and E47 cells (Dai et al. 1993; Chen and Cederbaum 1998). Here, CYP2E1 is linked to hepatocellular carcinoma.