An Inhibitor of Mutant IDH1 Delays Growth and Promotes Differentiation of Glioma Cells Expression data for Xenograft Samples

The recent discovery of mutations in metabolic enzymes has rekindled interest in harnessing the altered metabolism of cancer cells for cancer therapy. One potential drug target is isocitrate dehydrogenase 1 (IDH1) which is mutated in multiple human cancers. Here, we examine the role of mutant IDH1 in fully transformed cells with endogenous IDH1 mutations. A selective R132H-IDH1 inhibitor (AGI-5198) identified through a high-throughput screen dose-dependently blocked the ability of the mutant enzyme (mIDH1) to produce R-2-hydroxyglutarate (R-2HG). Under conditions of near complete R-2HG inhibition, the mIDH1 inhibitor induced demethylation of histone H3K9M3 and expression of genes associated with gliogenic differentiation. Blockade of mIDH1 impaired the growth of IDH1-mutant - but not IDH1-wildtype – glioma cells without appreciable changes in genome wide DNA methylation. These data suggest that mIDH1 may promote glioma growth through mechanisms beyond its well-characterized epigenetic effects. Two xenograft experiments were carried out, one with treatment cohorts of vehicle and 450mg/kg, and the other with vehicle, 150mg/kg/day, and 450mg/kg/day. After the indicated time tumors were harvested and total RNA was extracted and analyzed by the Affymetrix U133 plus 2 array.