Abstract

There is increasing evidence that the expression level of drug metabolic enzymes affects the final cellular response following drug treatment. Moreover, anti-tumour agents may modulate enzymatic activity and/or cellular expression of metabolic enzymes in tumour cells. We investigated the influence of CYP3A4 overexpression on the cellular response induced by the anti-tumour agent C-1311 in hepatoma cells. C-1311-mediated CYP3A4 activity modulation and the effect of CYP3A4 overexpression on C-1311 metabolism were also examined. Experiments were performed using the HepG2 cell line and its CYP3A4-overexpressing variant, Hep3A4. DAPI staining, cell cycle analysis, phosphatidylserine externalization, and senescence-associated (SA)--galactosidase expression were used to monitor the cellular effects following C-1311 exposure. C-1311 cellular metabolism and CYP3A4 activity were investigated by high-performance liquid chromatography. C-1311 metabolism was found to be very low in both hepatoma cell lines and slightly influenced by CYP3A4 expression. Interestingly, C-1311 was an effective inhibitor of CYP3A4 enzymatic activity, with no impact on its protein levels. C-1311 cytotoxicity was significantly lower in Hep3A4 cells than in HepG2 cells. Cell cycle analysis revealed that HepG2 cells underwent a rather stable G2/M arrest, whereas CYP3A4-overexpressing cells accumulated slightly in this compartment. C-1311-treated cells died through apoptosis and necrosis, whereas surviving cells underwent cellular senescence; however, these effects occurred faster and to a greater extent in Hep3A4 cells. Although CYP3A4 did not influence C-1311 metabolism, changes in CYP3A4 levels affected the C-1311-induced cellular response in hepatoma cells. Therefore, inter-patient differences in CYP3A4 levels should be considered when assessing the potential therapeutic effects of C-1311.

Authors (5)