Breast Cancer Therapeutics Based on Fusarochromanone and EGFR Inhibitors

Abstract

\n Background: Fusarochromanone (FC101) is a small molecule with potent anti-cancer activity. It was originally derived from the fungal plant pathogen, Fusarium equiseti, and it has also been synthesized in non-racemic form in our lab. Numerous studies reveal the promising biological activity of FC101, including potent anti-angiogenic and anti-cancer activity. While FC101 is potent as a single drug treatment across many cancer cell lines, current cancer therapies often incorporate a combination of drugs in order to increase efficacy and decrease the development of drug resistance. In this study, we leverage drug combinations and cellular phenotypic screens to address important questions about FC101’s mode of action and its potential synergies as an anti-cancer therapeutic agent in triple negative breast cancer (TNBC).Method: We hypothesized that FC101’s activity against TNBC is similar to the known mTOR inhibitor, everolimus, because FC101 reduces the phosphorylation of two key mTOR substrates, S6K and S6. Since everolimus synergistically enhances the anti-cancer activities of known EGFR inhibitors (erlotinib or lapatinib) in TNBC, we performed analogous studies with FC101. Phenotypic cellular assays helped assess whether FC101 (in both single and combination treatments) acts similarly to everolimus.Results: FC101 outperformed all other single treatments in both cell proliferation and viability assays. Unlike everolimus, however, FC101 brought about a sustained decrease in cell viability in drug washout studies. None of the other drugs were able to maintain comparable effects upon removal of the treatment agents. Although we observed slightly additive effects when the TNBC cells were treated with FC101 and either EGFR inhibitor, those effects were not truly synergistic in the manner displayed with everolimus. Conclusion: Our results rule out direct inhibition of mTOR by FC101 and suggest that FC101 acts through a different mechanism than everolimus. This lays the foundation for the refinement of our hypothesis in order to better understand FC101’s mode of action as a novel anti-cancer agent.