CYP3A4 and carcinoma: By screening a library of 3200 compounds with known bioactivity in the human carcinoma cell line HepG2 stably transfected with PXR and CYP3A4-luc, which was previously used to detect the activation PXR [9], we identified a series of flavonoids as potent activators of PXR-mediated CYP3A4 promoter activation (Fig. 1).