(a) Western blots for myc-tagged human isocitrate dehydrogenase 1 (IDH1-myc) or R132H mutant (R132H-myc) in stably transfected U87MG human glioblastoma cells, (b) Metabolite profiles from cells expressing R132H IDH1 or WT IDH1 detected by LC-MS scanning for species between 110–1000 m/z (M-H+). Red spots labeled A, B, and C represent species assigned to 2HG, dehydro-2HG, and 2HG-sodium adduct respectively. Spectrometric details supporting the identification of species “A” as 2HG are shown in the right panel, (c) Cells expressing R132H IDH1 contain elevated levels of 2HG. Data were normalized by cell number and expressed as fold difference relative to parental values. Error bars depict one standard deviation (SD) from the mean of 3 independent experiments, (d) Cells expressing R132H IDH1 display time-dependent accumulation of 2HG in cell culture media, normalization was as described in (c). Errors bars depict one SD from the mean of four independent experiments.