Metabolic characterization of isocitrate dehydrogenase (IDH) mutant and IDH wildtype gliomaspheres uncovers cell type-specific vulnerabilities

Abstract

BackgroundThere is considerable interest in defining the metabolic abnormalities of IDH mutant tumors to exploit for therapy. While most studies have attempted to discern function by using cell lines transduced with exogenous IDH mutant enzyme, in this study, we perform unbiased metabolomics to discover metabolic differences between a cohort of patient-derived IDH1 mutant and IDH wildtype gliomaspheres.MethodsUsing both our own microarray and the TCGA datasets, we performed KEGG analysis to define pathways differentially enriched in IDH1 mutant and IDH wildtype cells and tumors. Liquid chromatography coupled to mass spectrometry analysis with labeled glucose and deoxycytidine tracers was used to determine differences in overall cellular metabolism and nucleotide synthesis. Radiation-induced DNA damage and repair capacity was assessed using a comet assay. Differences between endogenous IDH1 mutant metabolism and that of IDH wildtype cells transduced with the IDH1 (R132H) mutation were also investigated.ResultsOur KEGG analysis revealed that IDH wildtype cells were enriched for pathways involved in de novo nucleotide synthesis, while IDH1 mutant cells were enriched for pathways involved in DNA repair. LC-MS analysis with fully labeled 13C-glucose revealed distinct labeling patterns between IDH1 mutant and wildtype cells. Additional LC-MS tracing experiments confirmed increased de novo nucleotide synthesis in IDH wildtype cells relative to IDH1 mutant cells. Endogenous IDH1 mutant cultures incurred less DNA damage than IDH wildtype cultures and sustained better overall growth following X-ray radiation. Overexpression of mutant IDH1 in a wildtype line did not reproduce the range of metabolic differences observed in lines expressing endogenous mutations, but resulted in depletion of glutamine and TCA cycle intermediates, an increase in DNA damage following radiation, and a rise in intracellular ROS.ConclusionsThese results demonstrate that IDH1 mutant and IDH wildtype cells are easily distinguishable metabolically by analyzing expression profiles and glucose consumption. Our results also highlight important differences in nucleotide synthesis utilization and DNA repair capacity that could be exploited for therapy. Altogether, this study demonstrates that IDH1 mutant gliomas are a distinct subclass of glioma with a less malignant, but also therapy-resistant, metabolic profile that will likely require distinct modes of therapy.Electronic supplementary materialThe online version of this article (10.1186/s40170-018-0177-4) contains supplementary material, which is available to authorized users.

Glioblastoma utilizes fatty acids and ketone bodies for growth allowing progression during ketogenic diet therapy

“…Recent studies, including one from our own group 12 , have demonstrated that GBMs harboring an isocitrate dehydrogenase 1 (IDH1) mutation represent a metabolically distinct subset of glioma. Because of this, we sought to identify potential differences in FAO utilization between our IDH1 mutant and IDH WT gliomasphere cultures.…”

“…Wildtype metabolic function of these enzymes is primarily restricted to the TCA cycle where they produce alpha-ketoglutarate through the oxidative decarboxylation of isocitrate.However, these enzymes often incur neomorphic gain-of-function mutations that result in the production of 2-hydroxyglutarate (2-HG) 11 , a proposed oncometabolite, along with widespread changes that extend far beyond the TCA cycle. The effects of IDH mutations have been attributed to altered glucose and nucleotide metabolism, DNA repair capacity, and reactive oxygen species (ROS) regulation, to name a few 12,13,14 . Thus, the mutations present in any given tumor (such as EGFR, PTEN, and IDH1) may determine the extent to which it can adjust to declining substrate availability, pathway inhibition, or therapeutic insult.…”

Purine metabolism regulates DNA repair and therapy resistance in glioblastoma

“…We chose to inhibit de novo GTP synthesis ( Fig. 3A) because guanylates were the metabolic pathway most correlated with RT-resistance and most GBMs are thought to rely on de novo nucleotide synthesis rather than nucleotide salvage 29 . Drugs inhibiting de novo GTP synthesis, such as mycophenolic acid (MPA) and its orally bioavailable prodrug mycophenolate mofetil (MMF), are FDA-approved to treat immune-mediated disorders and are being investigated as anticancer therapeutics 30 .…”

Metabolic reprogramming in the pathogenesis of glioma: Update

“…Primary GBM (GBM, IDH wild‐type) and IDH ‐wild‐type LGGs usually exhibit a clinically aggressive behavior in comparison with IDH ‐mutant gliomas . Interestingly, it has been reported that IDH ‐mutant and IDH ‐wild‐type tumor cells are distinguishable by metabolic expression profiles . Thus, understanding how IDH ‐wild‐type diffuse gliomas promote metabolic reprogramming may yield crucial insights into glioma pathogenesis and be important from a therapeutic standpoint.…”

“…21,22 Interestingly, it has been reported that IDH-mutant and IDH-wild-type tumor cells are distinguishable by metabolic expression profiles. 23 Thus, understanding how IDH-wild-type diffuse gliomas promote metabolic reprogramming may yield crucial insights into glioma pathogenesis and be important from a therapeutic standpoint. Recent studies have revealed that the D-2-HG enantiomer L(S)-2-HG is generated by hypoxia in IDH-wild-type tumors and both 2-HG enantiomers can competitively inhibit α-KG-dependent enzymes.…”