Abstract 2331: WNT/β-catenin modulation by activation of the farnesoid X receptor for interception of familial adenomatous polyposis-associated colorectal cancer

Introduction: Familial adenomatous polyposis (FAP) is a hereditary syndrome caused by germline alterations in APC and characterized by the presence of multiple colorectal adenomas that are associated to high risk of colorectal cancer (CRC) development. APC mutations dysregulate WNT signaling leading to aberrant β-catenin activity. The Farnesoid X Receptor (FXR) is a key regulator of bile acid homeostasis and has been identified as a suppressor of intestinal tumorigenesis. FXR downregulation has been shown to exacerbate β-catenin activity, further promoting malignant transformation of intestinal stem cells. Therefore, pharmacologic FXR activation represents a promising preventive strategy for the FAP population. In this study, we investigate the ability of the FXR agonist obeticholic acid (OCA) to restore FXR function and stabilize WNT/β-Catenin signaling for CRC interception in FAP. Methods: The effect of OCA was evaluated on colonic organoids generated from a FAP mouse model (Cdx2-Cre;ApcLoxP/+), 4 different human CRC cell lines, and patient-derived intestinal (duodenal and colonic) organoids from FAP patients. Organoids and cell lines were treated with OCA at different doses and time points followed by analyses of cell viability, apoptosis, and gene expression. Co-culture assays with patient-derived organoids and matched peripheral blood mononuclear cells (PBMCs) were performed to assess immune-related FXR regulation after OCA treatment. Results: OCA treatment led to a time- and dose-dependent decrease in cell viability in both mouse- and patient-derived organoids as well as in human CRC cell lines. In mouse-derived organoids, OCA significantly restored the gene expression levels of FXR (Nrh14) and downstream targets (Nr0b2 and Fabp6), and increased Epcam levels while reducing intestinal stem cells (Lgr5 and Wnt3a), cancer stem cells (Ascl2, Myc, Axin2, and Acox2), proliferation (Ki67), and invasion (Vimentin) markers. Further, FXR restoration by OCA also promoted apoptosis in all CRC cell lines tested in a dose-dependent manner. To further assess the effects of OCA on anti-tumor immune responses, a co-culture experiment using colonic and duodenal organoids from FAP patients and their matched PBMCs, showed that the combination of 10µM OCA with PBMCs significantly reduced cell viability after 48 hours of co-culture. Low and high doses of OCA are currently being analyzed in vivo, alongside single-cell RNA sequencing from co-culture assay to identify epithelial cell clusters affected by OCA exposure. Conclusions: Taken together, our findings reveal that OCA has promising potential to intercept CRC progression in FAP patients, thus providing further support for ongoing clinical trials (NCT05223036) with the FXR agonist OCA in FAP patients. Citation Format: Abel Martel-Martel, Nan Deng, Fahriye Duzagac, Jacklyn V. Thompson, Mahira Zaheer, Araceli Garcia-Gonzalez, Krishna M. Sinha, Eduardo Vilar. WNT/β-catenin modulation by activation of the farnesoid X receptor for interception of familial adenomatous polyposis-associated colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2331.