Acid Ceramidase Inhibition Disrupts Ceramide Homeostasis and Induces Mitochondrial Apoptosis in IDH1-Mutant...

Oligodendroglioma is genetically defined by mutations in isocitrate dehydrogenase 1 or 2 (IDH1/IDH2) and 1p/19q codeletion. We previously showed that in IDH1-mutant oligodendroglioma, the oncometabolite D-2-hydroxyglutarate biases the sphingosine-1-phosphate-to-ceramide rheostat toward ceramides. Taking advantage of this intrinsic metabolic vulnerability, we investigated whether further elevating ceramide levels through inhibition of acid ceramidase could exacerbate this imbalance and promote apoptotic cell death. Analysis of patient datasets demonstrated that acid ceramidase is expressed at higher levels in both low- and high-grade gliomas compared with normal tissue. Pharmacologic inhibition of acid ceramidase with SABRAC preferentially reduced viability in human IDH1-mutant oligodendroglioma cell lines. In these sensitive models, acid ceramidase inhibition markedly increased ceramide levels and induced coordinated sphingolipid remodeling. Subcellular imaging using a fluorescent ceramide analogue demonstrated increased ceramide localization to lysosomes and mitochondria following acid ceramidase inhibition. This was accompanied by cytochrome c redistribution, executioner caspase activation, and caspase-dependent apoptotic cell death, consistent with engagement of intrinsic mitochondrial apoptosis. Transcriptomic and biochemical analyses further revealed activation of endoplasmic reticulum stress and unfolded protein response signaling, including PERK- and IRE1α-associated programs, suggesting coordinated multi-organelle stress responses under sustained ceramide elevation. These mechanistic effects translated into a survival benefit in oligodendroglioma xenograft-bearing mice. Together, these findings suggest that IDH1-mutant oligodendroglioma harbors a pre-existing heightened sensitivity to ceramide stress and identify acid ceramidase as a therapeutically actionable target in this disease.