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Date of Award
Doctor of Philosophy (PhD)
Gain-of-function mutations in isocitrate dehydrogenase 1 (IDH1) and isocitrate dehydrogenase 2 (IDH2) are frequently observed in glioma and acute myeloid leukemia (AML) cancer cases, respectively. Though the effects of an IDH2 mutation on patient outcome have not yet displayed a consistent trend, IDH1 mutations have an improved patient prognosis in glioma cases. It is now well established that IDH1 and IDH2 mutations lead to the production of the oncometabolite 2-hydroxyglutarate (2-HG), which accumulates to millimolar levels in both in vitro systems as well as in patients. While the precise downstream effects of 2-HG are not yet fully characterized, we present evidence that the process of 2-HG synthesis itself has substantive effects on comprehensive metabolism due to the consumption of cellular resources to synthesize 2-HG. We first used untargeted stable isotope-based metabolomics to determine that 2-HG is not further metabolized in a cell culture system using engineered mutant IDH1 human colorectal cancer cell lines. This result led us to pose the question of how cells compensate for the resources spent on 2-HG production, if the metabolite is not re-incorporated into central carbon metabolism. We next investigated the metabolic cost of 2-HG production in IDH1 mutant cells. We demonstrated that these cells produce 2-HG at the expense of other NADPH-requiring reactions and induce increased pentose phosphate pathway (PPP) activity. We show that synthesis of 2-HG sensitizes cells to redox stress, which is a common line of therapy in the clinic to treat cancer (e.g. radiation, chemotherapy). Interestingly, we found that synthesis of 2-HG in the mitochondria by mutated IDH2 enzyme did not sensitize cells to redox stress from ionizing radiation as synthesis of 2-HG in the cytosol by IDH1 enzyme did. These data suggest that depletion of NADPH in the cytosol has different metabolic effects than depletion of NADPH in mitochondria. Our findings indicate that synthesis of 2-HG is a metabolic weakness and therapeutic opportunity, which is especially notable given the efforts that have surrounded inhibition of mutant IDH1 in the clinic.
Chair and Committee
Gary J. Patti
Milan G. Chheda, Timothy A. Wencewicz, Robert E. Blankenship, Shankar Mukherji,
Gelman, Susan, "Understanding the Impact of IDH Mutations on Cellular Redox Balance" (2019). Arts & Sciences Electronic Theses and Dissertations. 1869.
Available for download on Monday, May 15, 2119