TMET-02. Significance of <i>IDH1</i> <i>R132H/+</i> mutation on sphingolipidoma in glioblastoma

Abstract Gliomas are the most common primary brain tumors and are frequently characterized by mutations in the isocitrate dehydrogenase 1 (IDH1) gene, particularly the R132H point mutation. These genetic alterations are among the earliest events in gliomagenesis and result in a neomorphic enzymatic activity that converts α-ketoglutarate to the oncometabolite 2-hydroxyglutarate (2-HG) (Kayabolen et al., 2021). The accumulation of 2-HG inhibits α-ketoglutarate-dependent enzymes, leading to widespread epigenetic and metabolic changes (Dang et al., 2009). This also results in an altered sphingolipid metabolism. Sphingolipids are bioactive lipids that play essential roles in regulating apoptosis, autophagy, and cell survival (Strub et al., 2010) - key processes in cancer progression and therapy response. This study aims to identify specific alterations in bioactive sphingolipids in IDH1-mutant glioma cells and to evaluate their impact on cellular pathways. Experiments were conducted using an isogenic U-87 MG glioma cell line harboring the IDH1R132H/+ mutation, with wild-type IDH1+/+ cells serving as controls. The only difference between the two cell lines is the single point mutation at codon 132, ensuring high comparability. Lipid extractions were performed using a methanol/chloroform-based protocol followed by alkaline hydrolysis to remove glycerolipids. Samples were analyzed by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS), with quantification based on internal standards and external calibration curves (Prell et al., 2024). The results revealed distinct differences in the sphingolipid profiles of wild-type and mutant cells, particularly in the ratios of ceramides to dihydroceramides. These changes suggest a potential role of IDH1 mutations in regulating pathways related to autophagy and apoptosis. Future investigations will assess whether pharmacological inhibition of mutant IDH1 can modulate these sphingolipid ratios and induce cell death in glioma cells. These findings may contribute to the development of novel therapeutic approaches targeting IDH1-mutant gliomas by exploiting vulnerabilities in their altered lipid metabolism.