Metabolic pathways are essential for maintaining cellular homeostasis, and in proliferative cells the demand to accumulate biomass requires metabolic pathway alteration. Indeed, altered bioenergetics is a hallmark of cancer. In contrast to normally proliferating cells, those within a tumor are frequently starved for nutrients due to a combination of increased nutrient consumption and unreliable tumor vasculature. Fluctuations in nutrient availability affect cancer cell metabolism, and may be part of a selective process that occurs during tumorigenesis. Thus, understanding both the altered metabolism of cancer cells and their response to nutrient deprivation will enable identification of metabolic liabilities that can be exploited for cancer therapy. The Possemato lab seeks to understand the pathways that are altered in cancer, the processes that these altered pathways support, and the environmental, genetic, and epigenetic contexts in which these pathways are important. To this end, we focus on four key areas: (1) Iron-cluster biosynthesis, the requirement for which we found to be dependent on environmental oxygen concentration. We are asking whether activation of this pathway is an important step in lung tumorigenesis and can be exploited by increasing the sensitivity of cells to ferroptosis, a type of oxidative cell death. (2) Fluctuations in metabolism that are cell cycle dependent. We utilize traditional cell cycle synchronization methods and a murine liver model of tissue regeneration to identify key metabolic regulators of proliferative metabolism. (3) Serine biosynthesis and the key enzyme PHGDH. We identified PHGDH, now a member of the PAM50 gene set, as being highly expressed and required for the viability of ER-negative breast cancer cells. We are investigating how this pathway supports tumor metabolism and the requirement for individual pathway components across cancer types. (4) Development of novel tools and approaches for future hypothesis generation. We are utilizing a strategy to assay broad classes of phenotypes across hundreds of cell lines simultaneously, as well as engaging in loss of function genetic screening upon restriction of key nutrients.