Abstract 200: Role of transforming growth factor beta signaling in mediating cancer-stromal interaction and its inhibition by apigenin in ovarian cancer

Abstract Tumor microenvironment (TME) plays crucial roles in regulating tumor progression. Fibroblasts as predominant component in the TME have shown to promote growth of cancer cells. Transforming growth factor beta (TGF-β) regulates many cellular functions, including cell growth, differentiation, and apoptosis in a context-dependent manner. Growing evidence suggests that TGF-β mediates interaction between cancer cells and their associated fibroblasts (CAFs) to facilitate malignant progression. Polyphenols are widely present in plant-based foods and have diverse health promoting effects via modulating multiple cellular signaling pathways in various cell types. The present study investigated if growth-stimulating tumor-stromal interaction is mediated by TGF-β derived from ovarian CAFs and if food polyphenols inhibit this interaction. Ovarian cancer cells, OVCAR3 and OVCAR4, were cultured in conditioned media (CM) derived from CAFs (CAF-CON) in the presence and absence of SB525334 (an inhibitor of TGF-β receptor 1) to test the involvement of TGF-β in CAF-CON-induced cell growth. Effects of mitogen-activated protein kinase and AKT pathways on TGF-β signaling pathways were examined using their specific inhibitors. Various food polyphenols (5 μM) were treated to CAFs while preparing CM and evaluated their effects on TGF-β1 secretion and cancer cell growth induced by CAFs. Further, the effect of apigenin (API), the most effective compound, on TGF-β signaling pathway was evaluated using immunoblotting. OVCAR3 cells were transplanted into SCID mice. Once tumors were palpable, mice were either treated with vehicle control (VEH) or API (2.5 mg/kg bw/day) by oral gavage while concentrated CAF-CON, CM derived from API-treated CAFs (CAF-API), or phosphate buffered saline were injected onto formed tumors. Treatment with SB525334 effectively inhibited CAF-CON-induced growth increase in both OVCAR3 and OVCAR4 cells. Notably, inhibition of p38 activity suppressed CAF-CON-induced activation of Smad3 and AKT in ovarian cancer cells, suggesting that p38 activation induced by CAF-CON enhances TGF-β1 and AKT signaling pathways. Among various CM obtained from CAFs treated with diverse polyphenols, CAF-API exhibited the greatest inhibitory effect on cell proliferation in both OVCAR3 and OVCAR4 cells (> 50% reduction relative to CAF-CON) and the lowest TGF-β1 levels (<40% reduction relative to CAF-CON). Smad activation was induced in the presence of CAF-CON, whereas it was reduced in CAF-API. OVCAR3-derived tumor growth was significantly increased by treatment with CAF-CON (40% relative to VEH) but not with CAF-API or CAF-CON with simultaneous oral administration of API. Therefore, the present study suggests that TGF-β1 contributes to interplay between ovarian cancer cells and their stroma, and API can inhibit this interaction. Citation Format: Hyunjin Seo, Soo-Jung Lee, Somin Lee, Youngjoo Kwon. Role of transforming growth factor beta signaling in mediating cancer-stromal interaction and its inhibition by apigenin in ovarian 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 200.