Oncogenic Isocitrate Dehydrogenase Mutations: Mechanisms, Models, and Clinical Opportunities

Heterozygous mutations in catalytic arginine residues of isocitrate dehydrogenases 1 and 2 (IDH1 and IDH2) are common in glioma, acute myeloid leukemia, chondrosarcoma, cholangiocarcinoma, and angioimmunoblastic T-cell lymphoma. The mutant enzymes acquire a neomorphic activity that converts alpha-ketoglutarate (alpha-KG) to D-2-hydroxyglutarate (D2HG), a rare metabolite. In cells and tissues expressing mutant IDH, D2HG concentrations are highly elevated. D2HG may act as an oncometabolite by inhibiting a class of alpha-KG-dependent enzymes involved in epigenetic regulation, collagen synthesis, and cell signaling. Knock-in mouse models of IDH1 mutations have shed light on these mechanisms and will provide valuable animal models for further investigation. Significance: Mutations in IDH1 and IDH2 promote the development of a number of malignancies. These active site mutations cause a gain-of-function leading to the accumulation of the rare metabolite D2HG. Mouse models of these mutations should provide insights into the mechanisms driving tumorigenesis and facilitate evaluation of new treatments. (C) 2013 AACR.