Abstract 6612: Targeting CPT-1-mediated fatty acid oxidation causes radiation sensitization in glioblastoma.

Abstract Background: Glioblastoma (GBM) is the most common primary brain tumor in adults and has a median survival of less than two years despite surgery, chemotherapy, and radiotherapy. A subpopulation of glioma stem-like cells (GSCs) survives radiation and repopulates the tumor. Recent studies have shown that GSCs rely heavily on mitochondrial fatty-acid oxidation (FAO) for ATP production, NAD+ regeneration, and redox balance. Carnitine-palmitoyl-transferase-1 (CPT-1) catalyzes the rate limiting step of FAO by shuttling long-chain fatty acids into the mitochondrial matrix. We therefore hypothesized that pharmacologic inhibition of CPT-1 will limit GSC metabolism and sensitize GSCs to radiation. Methods: Human GBM cell line U-118 and a patient-derived GSC line (GNS144) were treated for 72 h with perhexiline (5 µM), etomoxir (10 µM), or vehicle control.Cells then received a single fraction of 0, 2, 4, 6, or 8 Gy. Cell viability was measured 48 h later. Sphere formation assays were performed 7-14 days after radiation; sphere number and mean diameter were recorded. Immunoblotting was performed to evaluate for stem cell markers CD44, Nestin, and Vimentin. All experiments were performed in triplicate; statistical significance was assessed by two-way ANOVA with Tukey post-hoc test (p < 0.05). Results: Perhexiline + radiation and etomoxir + radiation produced a dose dependent decline in cell viability compared with radiation alone (p < 0.001). Combination treatment reduced sphere number by 55-70 % across the 4-8 Gy range (p ≤ 0.005) and lowered mean sphere diameter by 30 % (p ≤ 0.005). Immunoblotting analysis showed a 2-fold reductions in CD44, Nestin, and Vimentin expression in the drug + radiation arms versus radiation alone (p < 0.01). Conclusions: These results suggest that inhibition of CPT-1-mediated FAO with perhexiline or etomoxir enhances radiation induced cell death, suppresses sphere forming capacity, and downregulates key GSC markers in both standard and patient-derived GBM models. These findings should be investigated further and suggest that CPT-1 blockade could be integrated with current standard of care regimens to overcome stem cell driven radiation resistance. Citation Format: Kenneth M. Austin, Tingting Huang, Todd Miller, Kelli B. Pointer. Targeting CPT-1-mediated fatty acid oxidation causes radiation sensitization in glioblastoma [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 6612.