TMET-45. Ceramidase Inhibition in Oligodendroglioma Drives Apoptosis and Immune Remodeling

Abstract BACKGROUND The sphingosine-1-phosphate (S1P) to ceramide ratio is a well-established regulator of glioblastoma’s hallmarks, including angiogenesis, resistance to apoptosis, and sustained proliferation. However, this ratio had not been characterized in IDH1mut gliomas. We were the first to demonstrate that IDH1mut gliomas exhibit an inverse S1P:ceramide ratio compared to IDH1 WT glioblastomas, rendering them more susceptible to apoptosis. Leveraging this metabolic vulnerability, we hypothesized that further increased ceramide levels would amplify apoptotic signaling in these tumors. METHODS A focused drug screen targeting ceramide-metabolizing enzymes identified SABRAC as a potent acid ceramidase (AC) inhibitor. Glioma cell sensitivity was assessed via CCK8 assays, and mechanistic studies using Western blot and LC-MS confirmed ceramide accumulation. Apoptosis induction was evaluated by flow cytometry and rescue assays. Raman and fluorescence imaging traced ceramide trafficking from lysosomes to mitochondria. In vivo efficacy was tested in oligodendroglioma-derived intracranial xenografts, and immune modulation was assessed by flow cytometry for MHC-I expression. RESULTS AND CONCLUSIONS We report that inhibition of AC induces apoptosis and extends survival in mice bearing IDH1-mutant oligodendrogliomas. Using patient-derived oligodendroglioma cells, we demonstrated increased cytotoxicity of the AC inhibitor SABRAC in IDH1-mut tumors, with markedly lower sensitivity observed in glioblastoma models. SABRAC activated both the extrinsic and intrinsic apoptotic pathways in an ER stress–independent manner, suggesting that ceramide accumulation directly disrupts mitochondrial membrane integrity. Apoptosis under SABRAC treatment correlated with up to a 30-fold increase in ceramides. Unexpectedly, SABRAC also enhanced MHC-I surface expression on tumor cells, highlighting a potential link between ceramide metabolism and immune modulation. We are conducting additional preclinical studies to elucidate the mechanisms by which AC inhibition modulates the tumor immune microenvironment.