More than 70% of low-grade gliomas (grades II and III) possess mutations in IDH1 or IDH2. The mutant proteins produce D-2-hydroxyglutarate and inhibit α-ketoglutarate, a cofactor of TET family proteins, and thus inhibit the TET-induced hydroxymethylation of DNA [20–22]. Here, IDH1 is linked to glioma.