Transformation-associated changes in regulating cell growth and proliferation result in specific nutrient or metabolic enzyme dependencies that are absent in non-transformed cells. Thus, nutrient dependency has recently been shown to be therapeutically exploitable in cancer. On the other hand, cancer cells frequently face nutrient limitation resulting from environmental variations, such as poor vascular supply, enhanced local consumption, dietary restriction and response to therapeutics. As a result, cancer cells become increasingly dependent on adaptive responses to mitigate metabolic stress. Therefore, defining the metabolites and the stress response pathways on which cancer cells depend will facilitate development of better therapeutic strategies that can improve management of cancer patients. For example, glutamine, a versatile biosynthetic substrate in cancer cells, is frequently found depleted in tumor environment when compared to normal surrounding tissues. We recently demonstrated that asparagine, a nonessential amino acid, plays a critical role in regulating tumor cells' adaptation to glutamine depletion, raising the potential to target asparagine bioavailability to treat cancer. However, little is known about how tumor cells sense and respond to asparagine deficiency. In this proposal, we will use lymphoid malignancies as models to explore the role of adaptive amino acid response in tumor cells' response to asparagine availability and its implication in cancer therapy. Our central hypothesis is that: neoplastic lymphocytes rely on de novo biosynthesis to produce asparagine when environmental asparagine becomes limiting. This adaptive program requires both the expression of key biosynthetic enzyme and the availability of glutamine-derived biosynthetic substrates, which can collectively affect oncogenic signaling beyond their roles in biosynthesis. Using biochemical, genetic and translational approaches, we will: (1) determine signaling and chromatin-modifying components regulating cellular adaptation to asparagine deprivation in acute lymphoblastic leukemia (ALL) and (2) determine impact of glutamine/asparagine metabolism on oncogenic MYC function in ALL and MYC-driven B cell lymphoma.
A challenge of targeting metabolic pathways in cancer is that tumor cells engage various adaptive mechanisms to suffice their metabolic demands or bypass their requirement. Using lymphoid malignancies, including acute lymphoblastic leukemia (ALL) and aggressive B cell lymphoma, as models, we will determine the signaling and chromatin-modifying components that dictate ALL cells' adaptation to asparagine limitation and how glutamine/asparagine availability modulates oncogenic MYC function.
