(180d) Role of Redox Balancing and Reactive Oxygen Species in the Metabolic Phenotype of Tumor Cells

Reprogramming of glucose and glutamine metabolism is a key event in malignant transformation. However, the functional significance and molecular mechanisms underlying these adaptations are only now starting to emerge. Tumor metabolism is considered ?wasteful? from the carbon and energetic standpoint because it produces large amounts of lactate, even when oxygen is readily available to support respiration. However, an often overlooked role of central metabolism is to supply reductant in the form of NADPH, which is typically the limiting resource in anabolic processes such as lipid and nucleotide biosynthesis. Furthermore, rapidly proliferating cells must tightly regulate reactive oxygen species (ROS) accumulation in order to avoid DNA damage while maintaining activation of MAPK signaling cascades. These critical metabolic functions require continuous production of cytosolic NADPH to effectively modulate ROS levels.

We are applying systems approaches to elucidate the role of cell-wide metabolic reprogramming to maintain redox homeostasis while optimizing intracellular ROS levels in tumor cells. We will present results from 13C metabolic flux analysis (MFA) applied to both normal FL5.12 B-cells and P493-6 lymphoma cells. These cell lines have been genetically modified to overexpress key oncoproteins including Akt or Myc as well as important metabolic enzymes such as Glut1 or hexokinase. This approach allows us to quantify how specific oncogenic signals redirect metabolic fluxes through NADPH- and ROS-producing pathways. We have observed that increased expression of the Myc oncoprotein results in a dose-dependent increase in ROS accumulation in P493-6 cells, which is associated with increased growth and upregulation of both glucose and glutamine metabolism. We will present results from 13C MFA studies aimed at elucidating the global metabolic alterations underlying these phenotypes, as well as how they respond to targeted interventions.