IDH1 and glioma: More recently, mutations in the metabolic enzyme isocitrate dehydrogenase 1 (IDH1) have been identified in low-grade glioma and secondary glioblastoma, which were then discovered to form the oncometabolite 2-hydroxyglutarate (2-HG) that demonstrated the capacity to regulate global epigenetic programs in these tumors (3–5).