The overall goal of this program is to characterize the molecular strategies cancer cells use to adapt to limitations in oxygen and nutrients. Oxygen and nutrient limitation develops as an initiated cancer cell clone accumulates in excess of physiologic numbers supportable by the existing vascular system. In nontransformed cells, either hypoxia and/or nutrient deprivation leads to the initiationof apoptosis to limit cell accumulation, thus helping to maintain organ homeostasis. To persist in such an environment, cancer cells must not only suppress apoptosis but must undergo adaptation to the changes in oxygen or nutrient availability. Although ultimately neoangiogenesis may correct the hypoxia and nutrient depletion, our hypothesis is that cells must still suppress apoptosis and adapt metabolically in order to persist until such a vascular response occurs. Project 1 seeks to characterize the molecular mechanisms that initiate apoptosis in response to hypoxia and nutrient deprivation. Efforts will be focused on characterization of the role of the Bcl-2 family and the PI3 kinase/Akt/TOR/PTEN pathway in regulating this apoptotic response. Using cells deficient in Bax and Bak, genes involved in long-term adaptation to hypoxia and glucose deprivation will be characterized. Project 2 addresses the molecular adaptation to oxygen availability that occurs through production of HIF-dependent transcriptional targets that enhance the rate of glycolysis. One of the major responses to limitations in oxygen is a compensatory inhibition of translation that limits energy expenditure. Oxygen-dependent changes in the activity of the TOR pathway will be studied as well as the molecular strategies utilized to selectively translate HIF-dependent targets under such conditions to allow cells to adapt to a low O2 environment. In Project 3 the ER stress pathway, sometimes referred to as the unfolded protein response, will be studied as a sensor of glucose deprivation. One of the first processes compromised as a result of glucose deprivation is protein glycosylation, a process required for protein export from the ER. Studies in Project 3 will address how the induction of ER stress modulates adaptation to glucose deprivation through the inhibition of translation while coordinately inducing a transcriptional response and the selected translation of adaptive proteins. All three projects will make extensive use of the Metabolic Core which will provide a common set of assays for the analysis of cellular bioenergetics and an Administrative Core which will provide services of administrative oversight, budgetary management, and manuscript preparation. Extensive points of collaboration have already been established between all three projects. We anticipate that our collective efforts will provide novel insights into metabolic changes that characterize the adaptation of transformed cells to survival under conditions of oxygen and nutrient deprivation. Ultimately we hope this information may be used to design novel strategies to specifically treat transformed tumor cells growing under conditions of nutrient and oxygen limitation.
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