Studying On The Molecular Mechanism Of A Novel Amonafide Anlogue 8-c Inhibiting Multidrug Resistance In Multidrug Resistant Colon Cancer Cells

Naphthalimides characterized by a high cytotoxic activity upon a variety of cancer cells have been extensively investigated as traditional antitumor drugs for many years. Amonafide is a representative naphthalimide topoll inhibitor, but it is still not widely used because it caused a unpredictable toxicity. Despite this, the simplicity of amonafide, associated with its antitumor activity, offers promise for the rational design of new chemotherapeutic agents.8-c was one of the potent DNA intercalators among the novel naphthalimide-based compounds as the novel amonafide analogues but alleciating the toxicity of the patent compound amonafide. Previous study has reported that amonafide, could circumvent cancer drug resistance (Pgp). However, the effect of amonafide on anti-multidrug resistance in MDR cells has not yet been fully defined. Therefore, we investigated the molecular mechanism by which 8-c induced apoptosis and inhibited multidrug resistance in HCT116/L-OHP cells.We assessed the antitumor activity of 8-c on a panel of established cancer cells by MTT assay. The result demonstrated 8-c had similar effect on MDR and corresponding parental cell lines. The comparable Pgp protein expression level and 8-c content in the HCT116 and HCT116/L-OHP indicated that 8-c have the intrinsic ability to bypass MDR phenotype.8-c induced a time-dependent DNA strand breaks in MDR cells by comet assay. Flow cytometric estimation showed that 8-c produced a dose-dependent increase in the apoptotic cell population. We then investigated the apoptosis-related protein p53, Bcl-2, caspase-3 and cleaved-PARP. The results showed that 8-c induces apoptosis by activating a pre-existing apoptotic pathway. We demonstrated that the inhibition of Bcl-2 expression by transient transfection with miR-1915 mimic significantly suppressed the growth of HCT116/L-OHP cells, providing direct evidence of the involvement of Bcl-2 in multidrug resistance and 8-c-induced cell apoptosis in HCT116/L-OHP cells. Meanwhile,8-c induced decrease in the mRNA and protein of DNA repair protein such as ERCC1. We conclude that 8-c could effectively inhibit multidrug resistance in MDR colon cancer celss, via regulating apoptosis-related pathways and the ability of DNA repair.