Targeting IDH1-Mutated Oligodendroglioma with Acid Ceramidase Inhibitors

Abstract

Oligodendroglioma is genetically defined as a tumor harboring isocitrate dehydrogenase 1 or 2 mutations (IDH1mut/IDH2mut)and 1p/19q co-deletions. Previously, we reported that in IDH1mut gliomas, D-2HG, the product of IDH1 mutant enzyme produces an increase in monounsaturated fatty acid levels that are incorporated into ceramides, tilting the S1P-to-ceramide rheostat toward apoptosis. Herein, we exploited this imbalance to further induce and IDHmut-specific glioma cell death. We report for the first time that the inhibition of acid ceramidase (AC) induces apoptosis and provides a benefit in mice survival in IDH1mut oligodendroglioma. We demonstrated an IDH1mut-specific cytotoxicity of SABRAC, an irreversible inhibitor of AC, in patient-derived oligodendroglioma cells. Exploring the mechanism of action of this drug, we found that SABRAC activates both extrinsic and intrinsic apoptosis in an ER stress-independent manner, pointing to a direct action of AC-related ceramides in mitochondria permeability. The activation of apoptosis detected under SABRAC treatment was associated with up to 30-fold increase in some ceramide levels and its derivatives from the salvage pathway. We propose that this novel enzyme, AC, has the potential to increase survival in oligodendroglioma with IDH1mut and should be considered in the future.