Mutant IDH1 and IDH2 alter glioma metabolism, favoring the reduction of α-ketoglutarate to 2-hydroxyglutarate (2-HG) (17), which in turn inhibits DNA and histone demethylases and establishes a glioma-CpG island hypermethylator phenotype (G-CIMP) (5), featuring hypermethylation at a large number of loci. Here, IDH1 is linked to central nervous system cancer.