Abstract 1763: NEO2734, a novel dual bromodomain and histone acetyltransferase inhibitor, in the treatment of colorectal cancer

Abstract

Abstract Background: Oncogenic c-MYC activation is seen in a broad spectrum of cancers and is often associated with more aggressive disease and/or poor outcomes. c-MYC expression is often driven by transcriptional super-enhancers which depend on histone modifications to function. We report the results of our studies on the novel suppressor of histone reading and writing, NEO2734, and the effects on colorectal cancer cells. Methods: Commercially and publicly available colorectal cancer cell lines were used under standard culture conditions. All small molecule treatments were performed with DMSO as the primary solvent and dilutions made in aqueous solution. Commonly employed techniques such as MTS viability assays, immunofluorescent 2-D microscopy, siRNA knockdown, western blotting, and single-color flow cytometry were used. Results: NEO2734, a dual BET/bromodomain inhibitor and p300/CBP inhibitor, reduced cell growth more than the BET inhibitor OTX-015 and the p300/CBP inhibitor CPI-637. NEO2734 potently induced cell death and markers of apoptosis such as PUMA and TRAIL2/DR5. Inhibition of the caspase by zVAD-fmk eliminated the induction of cell death by NEO2734. Knockdown or knockout of the death proteins PUMA or DR5 additively reduced the amount of NEO2734-induced apoptosis. NEO2734 reduced the expression of downstream targets c-MYC, acetylated histone H3, and acetylated histone-H4. Strikingly, NEO2734 significantly upregulated the ER stress markers BiP and ATF3. NEO2734 also activated immunogenic cell death in vitro, as measured by HMGB1 release and membrane localization of calreticulin. Finally, examination of a panel of cell lines revealed SPOP mutant colorectal cancer cells to be exquisitely sensitive to growth inhibition by NEO2734. Conclusions: NEO2734 causes growth inhibition and apoptosis of colorectal cancer cells. NEO2734 is more potent than single-target BET inhibitors. Anticipated targets such as c-MYC and acetylated histone are confirmed. NEO2734 appears to trigger cell death through both PUMA and TRAIL mediated apoptosis. NEO2734 also activates ER stress and immunogenic cell death. Work is ongoing to confirm the mechanism of apoptosis and test rational drug combinations such as with chemotherapy and immunotherapy. Citation Format: Chaoyuan Kuang, Manbo Cai, Denise Risnik, Francis Giles, Lin Zhang. NEO2734, a novel dual bromodomain and histone acetyltransferase inhibitor, in the treatment of colorectal cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1763.