Highly recurrent somatic mutations in the isocitrate dehydrogenase (IDH) 1 and 2 enzymes have been identified in a variety of tumor types including GBM and glioma subtypes, acute myelogenous leukemia, chondrosarcoma, and cholangiocarcinoma, among others. Mutant IDH proteins gain a novel function: the production of the “oncometabolite” 2-hydroxyglutarate (2-HG), which accumulates in the tumors of affected patients. The similarity of 2-HG to a-ketoglutarate, a cofactor required for the function of a large number of cellular enzymes, has led to the hypothesis that 2-HG may alter the function of one or more of these enzymes. Current literature has shown that 2-HG is able to inhibit a number of epigenetic factors (i.e. Jmj-domain histone demethylases, and the TET family of methylcytosine oxidases) though most of these studies have been carried out using over-expression systems that can potentially force non-relevant phenotypes. To this end, we explored histone methylation changes in a variety of cells that harbor endogenous heterozygous IDH1/2 mutations. Using an LC-MS based method to detect histone modifications, we profiled IDH MUT vs. WT cells to evaluate which global histone methylation changes correlated with mutant IDH status and whether these changes were widespread or discrete. This unbiased search highlighted IDH-dependent modifications of Histone 3 on Lysine 9 (H3K9) as the histone mark of highest interest for further study. We followed up by assessing the sufficiency and necessity of IDH mutation and 2-HG to alter H3K9 methylation using immunoblotting techniques. Our results suggest that H3K9 methylation is particularly sensitive to mutant IDH and 2-HG, which may give us further insight into the mechanism of how mutant IDH drives tumorgenicity.

Citation Format: Fallon Lin, Veronica Saenz-Vash, Huili Zhai, Joy Fletcher, Mike Acker, David Jiang, John Gounarides, Julian Levell, Raymond Pagliarini. IDH mutations and 2-HG selectively affect histone methylation in the endogenous setting. [abstract]. In: Proceedings of the AACR Special Conference on Chromatin and Epigenetics in Cancer; Jun 19-22, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2013;73(13 Suppl):Abstract nr A20.