Indeed, mutated IDH1 transforms isocitrate into D-2-hydroxy-ketoglutarate (D2-HG), which inhibits the dioxygenase activity of TETs, leading to an accumulation of methylated cytosine residues and the occurrence of the so-called glioma hypermethylator phenotype (G-CIMP) [51,52]. The gene discussed is IDH1; the disease is central nervous system cancer.