CYP2E1 and liver cancer: The CYPs mRNA expression in HepG2 cell is based on HepG2 cell model, serum pharmacological method, UPLC method, and MTT assay for reasons as follow: first, HepG2 cells, the human liver cancer cell with different gene expression profiles, are known to constitutively express CYP1A2, CYP2E1, and CYP3A4 (Ooi et al., 2011).