IDH1R132H/− gliomas have lower D-2HG than IDH1R132H/WT gliomas. A, Two anaplastic astrocytomas WHO grade III (A3) which progressed to glioblastomas WHO grade IV (sGBM) demonstrate loss of the wild type IDH1 allele and decreased levels of D-2HG. Mutant IDH1R132H is CAT (His); wild type IDH1 is CGT (Arg). B, D-2HG levels in human gliomas with wild type IDH1 (WT/WT), heterozygous IDH1 mutation (R132H/WT), or IDH1 mutation with loss of wild type IDH1 (R132H/−). LGG, lower grade glioma WHO grade II or III.