Abstract
Abstract Introduction: Earlier we reported that aberrant overexpression of Notch1 in colon cancer patients is responsible for aggressiveness and progression of the disease. Current, therapeutic interventions of notch1 inhibitors that binds catalytic unit of γ-secretase and disrupts the cleavage activity cause gastrointestinal toxicity in clinical trial. Therefore, our study aims to develop a small molecule inhibitor, which inhibits Notch1 signaling but binds outside of γ-secretase’s catalytic unit thereby substantially reducing associated toxicity attributes. Through structure-activity relationship (SAR) studies based on naturally occurring Withaferin A (WA) structure, we have recently identified a WA-difuroate analog ASR458 as one such small molecule. Methods: To analyze the effect of ASR490 on HCT116 and HCT116/Notch1 cells, we performed phenotypic, western blot and in vivo analysis. Results: Notch1 overexpressing CRC cells (HCT/Notch1) showed aggressive cell growth (42%) as compared to HCT116 cells, however, ASR490 treatment inhibited cell growth in both HCT116 (IC50: 600 nM) as well as HCT/Notch1 cells (IC50: 850 nM). ASR458 significantly inhibited Notch1 expression and its downstream events in both the transfected cell lines. As a result, we observed shutdown of pro-survival machinery and induction of pro-apoptotic events (Bax, caspases and PARP) resulting in apoptotic cell death in ASR456 treated HCT116 and Notch1/HCT116 cells. Since Notch1 is responsible for epithelial mesenchyme transition (EMT); we analyzed EMT drivers and readout invasion/migration assays. ASR458 treatment reversed the mesenchymal characteristics by restoring the function of E-cadherin, which resulted in the suppression of invasion and migration in readout assays of HCT116 transfectants. Our ongoing Xenotransplanted mice experiments may suggest whether ASR458 inhibits the growth of HCT116 and HCT116/Notch1 tumors. Conclusion: Restrained gastrointestinal toxicity of Notch1 targeting therapeutics is achievable with novel small molecules displaying a differential binding affinity to γ-secretase. ASR458 inhibits cell growth in Notch1 overexpressing cells and abrogates Notch1 induced EMT. Ongoing molecular docking and in vivo studies may confirm ASR458 binding sites in γ-secretase and validate our in vitro findings respectively. Citation Format: Chendil Damodaran, Ashish Tyagi, Balaji Chandrasekaran, Venkatesh Kolluru, Ibrahim Jojua, Srinivasa Ramisetti, Arun K. Sharma, Murali K. Ankem. A novel small molecule inhibitor to suppress Notch1 activation in CRC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2014.
Published Version
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