Abstract 7109: Fasn inhibition enhances the efficacy of chemotherapy by inhibiting DNA damage response in colorectal cancer

Abstract Altered lipid metabolism plays a significant role in progression of colorectal cancer, however, its role in chemotherapy resistance remains poorly understood. We previously identified FASN, the rate limiting enzyme in de novo lipogenesis, as an important regulator of colorectal cancer progression. However, TVB-3664, a potent and specific small molecule inhibitor of FASN, showed limited effect in reducing tumor burden in pre-clinical studies as a stand-alone therapy. Therefore, the goal of this study is to evaluate the combinatorial efficacy of TVB-3664 in improving the therapeutic indices of standard chemotherapy in colorectal cancer. Using a combination of colon cancer cell lines and patient derived organoids we showed that TVB-3664 potentiates chemotherapy drug-induced double-strand DNA breaks (DSBs) and apoptotic cell death by altering histone acetylation levels. In addition, TVB-3664 treatment blocked DNA damage response (DDR) by decreasing ATM expression and Chk1/2 phosphorylation. Mechanistically, inhibition of FASN prevents the activation of both DSB repair pathways, namely homologous recombination (HR) and classical non-homologous end joining (NHEJ), by blocking BRCA1 and 53BP1 recruitment to γH2AX foci, respectively. Moreover, we found that the inhibitory effect of TVB-3664 on DNA repair requires ACLY-dependent acetylation as genetic or pharmacological inhibition of ACLY attenuates TVB-3664-inducded DNA damage. Functionally, combining TVB-3664 with irinotecan synergistically decreased xenograft tumor growth and significantly delayed tumor relapse after withdrawal of therapy. Taken together, we identified a novel mechanism by which FASN inhibitors improve the efficacy of conventional chemotherapy by blocking DNA damage response to delay tumor recurrence and overcome a major challenge in treating colorectal cancer patients. Citation Format: Moumita Banerjee, Yekaterina Zaytseva, Sumati Hasani, Piotr Ryachahou, Tadahide Izumi, B. Mark Evers, Tianyan Gao. Fasn inhibition enhances the efficacy of chemotherapy by inhibiting DNA damage response in colorectal cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 7109.