Abstract A043: Paracrine remodeling of normal fibroblasts into glioblastoma-associated states: An immune-enriched stromal model of GBM
Cancer-associated fibroblasts (CAFs) are central orchestrators of tumor progression, stromal remodeling, and immune evasion in glioblastoma. While tumor-derived secretomes can induce CAF-like phenotypes, it remains unknown whether therapy resistance reprograms the secretome to generate CAFs with amplified immunosuppressive and immune-shaping functions. Induced CAFs (i-CAFs) were generated from normal fibroblasts using conditioned media derived from therapy-resistant (R) and therapy-responsive(NR) glioblastoma cells. CAF induction was confirmed by morphological transformation, increased proliferation and migration, and upregulation of ACTA2 (>4-fold) and TGFB1. Secretome-driven mechanisms were interrogated using integrated proteomic profiling and pathway-level bioinformatic analysis. CAFs were incorporated into 3D tumor organoids (30%) using both glioma cell lines and patient-derived samples, and immune modulation was assessed using co-culture systems with primary human immune cells. Secretome exposure induced a stable CAF phenotype with enhanced proliferation, migration, and clonogenicity. Proteomic and pathway analysis identified coordinated activation of metabolic and stromal programs, including glycolysis and lipid metabolism (PGK1, FASN, CPT1A), lactate transport (SLC16A3), and ECM remodeling/contractility networks (LAMA5, PALLD, MYH10). In parallel, stress-response and redox regulators (NQO1, PRDX6, HSPB1) and interferon-associated signaling (STAT1, ISG15, IFITM family) were enriched, indicating a metabolically active and immune-modulatory state. Functionally, CAF incorporation increased tumoroid size, structural integrity, and reduced heterogeneity. Importantly, resistant-derived CAFs exhibited significantly higher monocyte chemotaxis compared to NR-derived CAFs and normal fibroblasts (P < 0.05). CAF-containing systems promoted macrophage polarization toward an immunosuppressive CD206+ phenotype, while targeting stress-associated pathways partially restored CD80+ polarization, with a more pronounced effect in resistant CAF contexts. These findings were recapitulated in patient-derived tumoroids, confirming translational relevance. Glioblastoma secretomes drive fibroblast reprogramming into metabolically reprogrammed, contractile, and immunomodulatory CAFs. Therapy resistance amplifies these effects, enhancing immune recruitment and immunosuppressive polarization. Targeting CAF metabolic and stress-response pathways may represent a strategy to reprogram the tumor microenvironment and restore anti-tumor immunity. Mahdieh Shokrollahi Barough, Maryam sadat Mirlohi, Amir Seyfoori, Meitham Amereh, Patrick B. Walter, Ibrahim Numanagic, Mohsen Akbari. Paracrine remodeling of normal fibroblasts into glioblastoma-associated states: An immune-enriched stromal model of GBM [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Breaking Barriers in the Fight against Rare Cancers; 2026 Jul 18-20; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2026;86(14_Suppl):Abstract nr A043.