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High CYP3A4 expression sensitizes tumor cells to certain antitumor agents while for others it can lower their therapeutic efficacy. We have elucidated the influence of CYP3A4 overexpression on the cellular response induced by antitumor acridine derivatives, C-1305 and C-1748, in two hepatocellular carcinoma (HepG2) cell lines, Hep3A4 stably transfected with CYP3A4 isoenzyme, and HepC34 expressing empty vector. The compounds were selected considering their different chemical structures and different metabolic pathways seen earlier in human and rat liver microsomes C-1748 was transformed to several metabolites at a higher rate in Hep3A4 than in HepC34 cells. In contrast, C-1305 metabolism in Hep3A4 cells was unchanged compared to HepC34 cells, with each cell line producing a single metabolite of comparable concentration. C-1748 resulted in a progressive appearance of sub-G1 population to its high level in both cell lines. In turn, the sub-G1 fraction was dominated in CYP3A4-overexpressing cells following C-1305 exposure. Both compounds induced necrosis and to a lesser extent apoptosis, which were more pronounced in Hep3A4 than in wild-type cells. In conclusion, CYP3A4-overexpressing cells produce higher levels of C-1748 metabolites, but they do not affect the cellular responses to the drug. Conversely, cellular response was modulated following C-1305 treatment in CYP3A4-overexpressing cells, although metabolism of this drug was unaltered.

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 have 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 have also been examined. With the HepG2 cell line and its CYP3A4-overexpressing variant, Hep3A4, experiments involving DAPI staining, cell cycle analysis, phosphatidylserine externalisation and senescence-associated (SA)-β-galactosidase expression, were used to monitor the effects of C-1311 exposure. C-1311 cellular metabolism and CYP3A4 activity were investigated by high-performance liquid chromatography. C-1311 metabolism was very low in both hepatoma cell lines and slightly influenced by CYP3A4 expression. Interestingly, in HepG2 cells, C-1311 was an effective modulator of CYP3A4 enzymatic activity, being the inhibitor of this isoenzyme in Hep3A4 cells. Cell cycle analysis showed that HepG2 cells underwent a rather stable G(2) /M arrest following C-1311 exposure, whereas CYP3A4-overexpressing cells accumulated only slightly in this compartment. C-1311-treated cells died by apoptosis and necrosis, whereas surviving cells underwent senescence; however, these effects occurred faster and more intensely in Hep3A4 cells. Although CYP3A4 did not influence C-1311 metabolism, changes in CYP3A4 levels affected the C-1311-induced response in hepatoma cells. Therefore, inter-patient differences in CYP3A4 levels should be considered when assessing the potential therapeutic effects of C-1311.

The interactions of C-1305 (5-dimethylaminopropylamino-8-hydroxy-6H-v-triazolo[4,5,1-de]acridin-6-one) with DNA were studied using differential pulse voltammetry and UV-vis spectroscopy. C-1305 interacts with dsDNA in two ways: by intercalation and by binding to the minor-groove. For the intercalation at physiological pH (7.4) the values of the binding constant, K1, and the binding-site size, n1, equal 3.36×105 M−1 and 2.5, respectively. For the weak interactions the K2 and n2 parameters equal 0.18×105 M−1 and 4. In the presence of excess NaCl the weak interactions do not vanish, therefore they are assigned to the minor groove binding. Substantial and complex is the influence of pH.

Normal pulse-, square wave-, differential pulse- and cyclic voltammetries were used in electroanalytical characterization of C-1311, an antitumor drug that undergoes the phase-II of clinical trials. The results obtained give a possibility of electrochemical investigation of the interactions between the drug and double stranded DNA (dsDNA). Spectroelectrochemical investigations (in situ UV-vis) revealed that unusual oscillations of the C-1311 absorbance appear after cyclic polarization of the transparent electrodes in moderate pH. The oscillations disappear in the presence of dsDNA (C-1311 binds to dsDNA).

Given poor prognosis of pancreatic cancer, there is a strong need for the development of novel therapeutic agents and discovery of new molecular targets. Changes in lipid metabolism can affect nume...