IDH1 and central nervous system cancer: Within the numbering of the human IDH2 sequence, mutations in Arg172 (an analog of frequently mutated Arg132 of cytosolic IDH1 [56]) are detected in gliomas [23, 36, 37], and mutations in Arg172 and Arg140 (which is adjacent in the active site to Arg172 [50]) are found in AML [57].