DDRE-20. TARGETING SPHINGOLIPID PATHWAY REVEALS VULNERABILITY IN IDH1^MUT GLIOMA

While central carbon metabolism has been studied extensively in cancer, lipidomic research is sparse. Sphingolipids participate in cellular functions including secondary messengers, lymphocyte trafficking, inflammation, angiogenesis, migration, proliferation, necrosis and apoptosis, thus highlighting the importance of understanding their role to tumor phenotype. Our investigation into metabolic alterations involving sphingolipid pathway in patient-derived IDH1^mut glioma cultures aimed to identify points of metabolic vulnerability.

Dysregulation of sphingolipid metabolism was interrogated for brain tumor cultures via LCMS. Expression of enzymes within the pathway was assessed for IDH^mut 1/2 and IDH^WT glioblastoma patient cohorts via The Cancer Genome Atlas (TCGA) analysis and Western blot for tumor cultures. Biostatic drug response was examined via viability and cytotoxicity assays.

We probed the effect that decreasing D-2HG levels with IDH1^mut inhibitor (AGI5198) treatments had on sphingolipid metabolism in tumor cultures. The probe revealed N,N-dimethylsphingosine (NDMS), and sphingosine were significantly elevated, while sphingosine-1-phosphate (S1P) was downregulated in IDH1^mut cultures following treatment. Drug panel screening revealed that SPHK inhibitor (SPHKi), N,N-dimethylsphingosine in combination with sphingosine triggered lethal dose-dependent response in IDH1^mut cultures; contrary to IDH^WT. Westerns presented differential expression of SPHK1 and SPHK2 in IDH^WT glioblastoma cells, while IDH^mut exclusively expressed SPHK1.

This novel discovery showed how targeting sphingolipid metabolism in IDH1^mut gliomas presents therapeutic implications. Elevated S1P was reported particularly for malignant glioblastomas in prior studies; whereas our research revealed relatively low S1P in the IDH^mut compared with IDH^WT cultures. In addition to reduced or silenced expression of SPHK2, we postulate that S1P levels in IDH^mut gliomas might be closer to a critical threshold allowing treatment with SPHK1i to effectively suspend proliferation and anti-apoptotic defense mechanisms. Our findings revealed that the manipulation of pivotal, endogenous sphingolipids can ultimately trigger apoptosis in IDH^mut gliomas. Future studies will probe these targets in preclinical models.