Abstract Pancreatic ductal adenocarcinoma (PDAC) is highly aggressive and profoundly resistant to immunotherapy, driven by a dense, desmoplastic, and immunosuppressive stroma dominated by cancer-associated fibroblasts (CAFs). CAFs are genetically stable and abundant, making them attractive targets for epigenetic reprogramming to overcome immune exclusion.We hypothesized that epigenetic modulators could reshape CAF-cancer cell interactions, reduce immunosuppression, and enhance responsiveness to immunotherapies, including immune checkpoint blockade and CAR-T cells. Using a 3D PDAC co-culture spheroid model, we screened a panel of clinically relevant epigenetic agents. Transcriptomic profiling revealed drug-induced changes in both tumor and stromal compartments, focusing on CAF subtype reprogramming, stroma-epithelial crosstalk, tumor growth and invasion, immunosuppression, and matrisome remodeling.The CDK7 inhibitor CT7001 emerged as a promising candidate, profoundly altering CAF phenotype, reprogramming CAF subtypes, and modulating stromal gene expression, while reducing epithelial-mesenchymal transition and cell cycle pathways in cancer cells. In an orthotopic PDAC mouse model, CT7001 combined with Gemcitabine significantly extended survival. Notably, treated tumors exhibited increased T-cell infiltration into the otherwise immunologically “cold” PDAC microenvironment, highlighting its potential to sensitize tumors to immunotherapy. Ongoing spatial multiplex imaging and RNA-seq analyses aim to correlate in vivo immune and stromal changes with in vitro findings, supporting rational combination strategies. This epigenetic screening platform provides a predictive framework to evaluate compounds that overcome CAF-mediated immune exclusion and modulate the tumor microenvironment, offering new avenues to enhance PDAC responsiveness to diverse immunotherapies. Citation Format: Celia Martín-Otal, Daire Hanna, Kairbaan Hodivala-Dilke, Angus J. M. Cameron, Oliver Pearce, David Propper. Epigenetic reprogramming of stromal-epithelial crosstalk to improve immunotherapy response in pancreatic ductal adenocarcinoma abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 7936.
Martín-Otal et al. (2026) studied this question.