Aerobic glycolysis, or the Warburg Effect, is the fundamental metabolic phenotype of cancer and promotes proliferation and apoptosis evasion (1, 2). Cancer cells consume excess glucose compared to normal tissue. Instead of oxidizing glucose in the mitochondria, cancer cells waste the majority of the carbon as lactate. It is unknown why proliferating cells are addicted to this pathway. Recent studies have demonstrated that the Warburg Effect provides rapid cytosolic ATP for plasma membrane bioenergetic processes (3). In addition to metabolism, these cells remodel ATP dependent Ca2+ transport by altering ATPase expression (4). It therefore is likely the metabolic phenotype of cancer is linked to Ca2+ alterations. For example, inhibition of glycolysis but not mitochondrial metabolism causes a rise in intracellular Ca2+ (5). The central hypothesis of this proposal is that the Warburg Effect is activated during oncogenesis to fuel ATPases and actively buffer the rise cytosolic Ca2+ to promote cell proliferation. However there are many Ca2+ ATPases which vary in their chemical properties and location in the cell. It is not known how specific ATPases influence cancer metabolism. In the DeBerardinis Lab, a thorough metabolic characterization of 81 lung cancer cell lines identified two ATPases associated with the Warburg Effect. The first is the ER specific SERCA3 whose expression negatively correlates with aerobic glycolysis. Loss of SERCA3 is suggested as a marker of increased lung cancer susceptibility (6). In addition to SERCA3, our correlation analyses indicated that expression of the plasma membrane specific PMCA4 was associated with decreased glucose oxidation. The objective of this proposal is to investigate how SERCA3 and PMCA4 quantitatively influence the metabolic phenotype of lung cancer cell lines using a combination of metabolomics and metabolic flux analysis (MFA). MFA is a powerful computational platform to analyze how cancer metabolism is affected by altered protein expression. MFA will be applied to uncover how SERCA3 and PMCA4 expression is linked to proliferation, carbon allocation, and metabolic flux in lung cancer. MFA will also aid in calculating the total amount of glucose metabolism that is dedicated to managing Ca2+ levels. Lastly, these in vitro models of cancer metabolism will be examined in vivo through the use of mouse xenografts. The expected outcome of these studies is a comprehensive understanding of the Warburg Effect and Ca2+ regulation. This knowledge will aid in identifying key metabolic nodes which induce Ca2+ vulnerabilities in lung cancer. A principal goal of this proposal is to train me to become an independent researcher in cancer metabolism. I will combine my skills in mathematical models of metabolism with new molecular biology and in vivo tools to prepare myself for a career as a principal investigator in metabolic mechanisms of disease.
Cancer is a disease marked by both reprogrammed metabolism and changes in Ca2+ homeostasis (1, 2). I hypothesize that these two processes are intimately related, and that the enhanced glucose consumption in cancer cells exists largely to accommodate altered Ca2+ dynamics and to enable pathological cell proliferation. I believe that understanding how metabolism influences Ca2+ signaling will produce new therapeutic opportunities in cancer.
