Abstract PR-011: Role of cancer associated fibroblasts in ovarian cancer relapse

Abstract Frequent relapse and development of chemoresistance leads to poor prognosis in ovarian cancer (OC). Cancer stem cells (CSCs) consist of a small subpopulation in the tumor that are typically resistant to cytotoxic chemotherapy and are a potential cause of relapse and chemoresistance. Using patient specimens as well as in vitro models, we determined that CSCs are enriched in a niche adjacent to cancer associated fibroblasts (CAFs) after chemotherapy. Cancer associated fibroblasts (CAFs) are a major constituent of the ovarian cancer tumor microenvironment and are highly enriched in the residual tumors following chemotherapy. Therefore, we studied the role of CAFs in promoting ovarian cancer chemoresistance and disease relapse by providing an optimal microenvironment for CSCs. CAFs isolated from ovarian cancer patient tumors were used in heterotypic 2D or 3D coculture systems with high-grade serous ovarian cancer cell lines or with patient-derived ovarian cancer cells to study their effect on CSCs and chemoresistance. Matched pre-and post-chemotherapy patient tumors were used to confirm our findings. CAFs significantly increased resistance to carboplatin and enriched CSCs by increasing their symmetric division as well as dedifferentiation of bulk ovarian cancer cells. Pre-coculture with CAFs increased in vivo tumor initiation capacity of the ovarian cancer cells by 10-fold. The CSC-CAF crosstalk responsible for CSC induction was found to be mediated by Wnt5a signaling. CRISPR knockdown of Wnt5a in CAFs or treatment with a specific Wnt5a inhibitor abrogated the induction of CSCs by CAFs. Only cancer cells with ROR2 Wnt coreceptor respond to Wnt5a signaling triggered by CAFs and developed into CSCs. Responders were found to signal through a non-canonical Wnt pathway involving the coreceptor ROR2, protein kinase C (PKC), and CAMP Responsive Element Binding Protein 1 (CREB1). Inhibition of each of them prevented CSC induction and functional rescue experiments confirmed the sequence of the Wnt5a-ROR2-PKC-CREB1 axis. Treatment of mouse xenografts was established by co-injection of CAFs and ovarian cancer cells, with the Wnt5a inhibitor sensitized them to carboplatin, and eliminated the CSCs in the residual tumors. Our results indicate that CAF-derived Wnt5a is instrumental in ovarian cancer CSC growth and maintenance. In the long term, our studies will broaden the understanding of the mechanism of CSC maintenance by the tumor microenvironment and contribute towards the development of novel therapeutic approaches to prevent ovarian cancer chemoresistance and relapse. Citation Format: Yiming Fang, Argha Ghosh, Ji Wang, Subramanyam Dasari, Dimitriy Zamarin, Anirban Kumar Mitra. Role of cancer associated fibroblasts in ovarian cancer relapse abstract. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84 (5 Suppl₂): Abstract nr PR-011.