Cancer cell adaptation to metabolic stress

University Of Pennsylvania, Philadelphia PA

Investigators

Linked publications & trials

Abstract

The overallgoal of this program is to characterize the molecular strategies cancer cells use to adapt to limitations in oxygen and nutrients. Oxygen and nutrientlimitationdevelopsas an initiatedcancer cell clone accumulates in excess of physiologicnumberssupportable by the existingvascular system. In nontransformedcells, either hypoxiaand/or nutrientdeprivation leads to the initiationof apoptosis to limitcell accumulation,thus helpingto maintain organ homeostasis. To persist in such an environment, cancer cells must not only suppressapoptosis but must undergo adaptation to the changes in oxygen or nutrient availability. Although ultimatelyneoangiogenesis may correct the hypoxiaand nutrient depletion, our hypothesis is that cellsmust stillsuppressapoptosls and adapt metabolically inorder to persist untilsuch a vascular responseoccurs. Project 1 seeks to characterize the molecular mechanisms that initiate apoptosisin responseto hypoxia and nutrient deprivation. Effortswill be focused on characterization of the role of the Bcl-2 family and the PI3 kinase/Akt/TOR/PTEN pathway in regulatingthis apoptotic response. Using cellsdeficient in Bax and Bak, genes involvedin long-term adaptation to hypoxia and glucose deprivation will be characterized. Project 2 addresses the molecular adaptation to oxygen availability that occurs through productionof 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 O_environment. In Project 3 the ER stress pathway, sometimes referred to as the unfolded protein response, will be studiedas 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 specificallytreat transformed tumor cells growing under conditions of nutrient and oxygen limitation.