Abstract 3998: Exploring fibroblast's influence on chemoresistance in PDAC using patient-derived organoids

Abstract Pancreatic adenocarcinoma (PDAC) remains one of the most lethal malignancies, with a 5-year survival rate below 13%. A critical factor in this poor prognosis is the tumor microenvironment (TME), characterized by dense stroma comprising cancer-associated fibroblasts (CAFs), immune cells, and epithelial cells. CAFs secrete inflammatory cytokines like IL-6 and TGF-β and deposit ECM components, particularly collagen, leading to immunosuppression and chemotherapy resistance. This study examines the role of fibroblasts in modulating the efficacy of gemcitabine in PDAC using patient-derived organoids (PDOs). PDOs were co-cultured with either human fibroblasts and tumor cells or tumor cells with fibroblast-conditioned medium. The PDOs were cultured in collagen based matrices, which allows for manipulation of the ECM stiffness, using either a soft or stiff gel condition to mimic the heterogeneity of in vivo environments. Conditioned Medium was collected from fibroblasts grown in either soft or stiff ECM gels. Patient-derived cells were obtained from two patients: one Black (G43) and one White (G46). Results reveal significant differences in response to treatment between the two cells used. G43 is shown to be more sensitive to treatment overall in co-culture and condition medium, when compared to G46. However, when cells are compared to themselves, either in co-culture or conditioned medium, there are differences seen. In particular, G43 cells are more responsive to treatment in conditioned medium, in soft ECM, when compared to co-cultures. However, in stiff ECM conditioned media, this effect is not seen. Indicating that the stiffness of the ECM, rather than just secreted soluble factors alone, is a key driver of tumor cell behavior. The difference between co-culture and conditioned media supports the observations that fibroblast induced mechano-stress, aids in chemotherapy resistance. The results suggest that therapeutic strategies aimed at modulating the physical properties of the tumor microenvironment, such as ECM stiffness, could potentially improve treatment responses in PDAC. Citation Format: Jonathan Barajas, Carolyn Ruiz, Zhi Yang, Edward Agyare, Saun-Joo Yoon, Ba Xuan Hoang, Bo Han. Exploring fibroblast's influence on chemoresistance in PDAC using patient-derived organoids [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 3998.