The goal of this research proposal is to determine the mechanism(s) by which mutant isocitrate dehydrogenase 1 (IDH1) causes brain tumors to be less aggressive. The most common type of brain tumor is the diffusely infiltrative glioma;these tumors cannot be completely excised surgically, and are difficult to treat with radiation and chemotherapy. Thus, infiltrative gliomas are incurable. A specific point mutation in IDH1 (and a less common analogous mutation in IDH2) has been found to be quite frequent in these gliomas. When present, it is a powerful favorable prognostic factor, being strongly associated with longer patient survival. Mutant IDH1 has recently been shown to produce a novel compound, 2-hydroxyglutarate (2-HG). However, the effects of mutant IDH1 and 2-HG on glioma cells are unknown. Other work showed that 2-HG causes oxidative stress in nonneoplastic tissue models, and our preliminary data indicate that 2-HG is toxic to glioma cells and induces autophagy, ERK activation, and reactive oxygen species production. We therefore hypothesize that the improved survival imparted by mutant IDH1 in diffuse gliomas is due to 2-HG-induced production of reactive oxygen species, leading to oxidative damage and cell death. We also hypothesize that the cell death is primarily by autophagy, a form of programmed cell death involving lysosomes that has been shown to be prominent in many gliomas. To test these hypotheses, glioma cells will be treated with 2-HG or transfected with mutant IDH1, and multiple well-described markers of autophagy and reactive oxygen species will be measured. Response of glioma cells to autophagy and reactive oxygen species modulation will be assessed. For patient-derived tumor biopsies and human-mouse xenografts, immunohistochemical markers of autophagy and oxidative stress will be quantified and correlated with IDH mutation status. Success in this project would determine whether mutant IDH1 causes increased oxidative stress and autophagy in gliomas, thereby producing a less aggressive glioma compared to tumors that are wild type for IDH1. This knowledge could then be exploited to develop novel ways of treating gliomas. I am fortunate to have been mentored by exceptional scientists and physicians, thus instilling in me a desire to pursue a career that synthesizes what I have learned as a scientist and neuropathologist.My graduate and postdoctoral work in neuroscience and my work in neuro-oncology have given me a diverse array of techniques and approaches that will be used in this project. My current position as an Assistant Professor in the Department of Pathology in the University of Kentucky offers the ideal opportunity to pursue my goal of being an independent investigator. I have nine person-months (75%) of guaranteed protected time for research, separate laboratory space that has been fully equipped, a full-time technician to increase output, and sufficient funds to conduct experiments for the next four years. All this has been put in place by my chairman, Dr. Paul Bachner, independent of my success in securing extramural funding. I also benefit from a collaborative environment, superb mentorship by Drs. Natasha Kyprianou, Arie Perry, and Jeremy Rich, and excellent technical resources. Now that I have completed my clinical training, the funding provided by this K08 award would allow me to develop as an independent investigator. Furthermore, the project described in this proposal provides a superb opportunity to discover why mutant IDH1 imparts a more favorable survival in patients afflicted with gliomas, in turn helping to identify pathways and targets for effective therapeutic interventions.
This research explores why mutant isocitrate dehydrogenase 1, an abnormal enzyme found in many brain tumors, is such a powerful marker of longer patient survival. Discovering why this is so will help find new ways to treat these incurable tumors.
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