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Photoactivation of Mutant Isocitrate Dehydrogenase 2 Reveals Rapid Cancer-Associated Metabolic and Epigenetic Changes.

ABSTRACT: Isocitrate dehydrogenase is mutated at a key active site arginine residue (Arg172 in IDH2) in many cancers, leading to the synthesis of the oncometabolite (R)-2-hydroxyglutarate (2HG). To investigate the early events following acquisition of this mutation in mammalian cells we created a photoactivatable version of IDH2(R172K), in which K172 is replaced with a photocaged lysine (PCK), via genetic code expansion. Illumination of cells expressing this mutant protein led to a rapid increase in the levels of 2HG, with 2HG levels reaching those measured in patient tumor samples, within 8 h. 2HG accumulation is closely followed by a global decrease in 5-hydroxymethylcytosine (5-hmC) in DNA, demonstrating that perturbations in epigenetic DNA base modifications are an early consequence of mutant IDH2 in cells. Our results provide a paradigm for rapidly and synchronously uncloaking diverse oncogenic mutations in live cells to reveal the sequence of events through which they may ultimately cause transformation.

SUBMITTER: Walker OS

PROVIDER: S-EPMC4821487 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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Photoactivation of Mutant Isocitrate Dehydrogenase 2 Reveals Rapid Cancer-Associated Metabolic and Epigenetic Changes.

Walker Olivia S OS Elsässer Simon J SJ Mahesh Mohan M Bachman Martin M Balasubramanian Shankar S Chin Jason W JW

Journal of the American Chemical Society 20160112 3

Isocitrate dehydrogenase is mutated at a key active site arginine residue (Arg172 in IDH2) in many cancers, leading to the synthesis of the oncometabolite (R)-2-hydroxyglutarate (2HG). To investigate the early events following acquisition of this mutation in mammalian cells we created a photoactivatable version of IDH2(R172K), in which K172 is replaced with a photocaged lysine (PCK), via genetic code expansion. Illumination of cells expressing this mutant protein led to a rapid increase in the l ...[more]

PMID: 26761588

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Project description: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.

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Photoactivation of Mutant Isocitrate Dehydrogenase 2 Reveals Rapid Cancer-Associated Metabolic and Epigenetic Changes.

Publications

Photoactivation of Mutant Isocitrate Dehydrogenase 2 Reveals Rapid Cancer-Associated Metabolic and Epigenetic Changes.

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