The CYP2A5 (mouse ortholog of human CYP2A6) was found upregulated under various conditions causing liver injury, such as nicotine/smoke exposure, liver cancer, hepatic infection or heavy metals and solvent exposure, and tightly regulated by nuclear factor erythroid 2-like 2 (Nrf2), a transcription factor activated under redox stress [61]. Here, CYP2A6 is linked to liver cancer.