Stromal metabolism promotes therapeutic resistance in pancreatic cancer

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ABSTRACT Pancreatic ductal adenocarcinoma (PDA) is a devastating disease with a five-year survival rate below 10%. Modern advances in chemotherapy and immunotherapy have yet to provide effective treatments. While oncogenic mutations in Kras are nearly universal in PDA, to date Kras remains undruggable. Clearly, new strategies are needed to develop more effective strategies to improve outcomes for patients with PDA. Metabolic pathways utilized by PDA cells present attractive targets to exploit therapeutically. The cells in a pancreatic tumor are nutrient-deprived and persist in a hypoxic environment. High intratumoral pressure caused by excessive extracellular matrix deposition from the cancer-associated fibroblasts (CAFs) prevents proper vascularization, nutrient delivery, and waste removal. Predictably, PDA cells hijack normal metabolic pathways to meet the biosynthetic and energetic demands required to survive and proliferate. According to this framework, several agents that target pancreatic tumor metabolism are being explored in clinical trials. However, PDA cells also support their metabolic demands via interaction with non-malignant cells. Thus, strategies targeting tumor metabolism must also take into consideration the role of the diverse cell types in the tumor microenvironment. Consistent with previous work, we observed that inhibition of mitochondrial metabolism is profoundly growth inhibitory to PDA cells in culture. Yet, we more recently found that PDA tumors are resistant to mitochondrial- targeted therapies in vivo. Through a series of biochemical and metabolomic co-culture studies, we found that pancreatic CAFs promotes resistance to mitochondrial inhibition. We then identified pyruvate as the single factor in CAF media that restored PDA cell proliferation upon mitochondrial inhibition. In this research proposal, we will define how pyruvate is made and released by CAFs and how pyruvate is obtained and utilized by PDA cells to promote resistance to mitochondrial inhibitors. We will also test the hypothesis that pyruvate release is a CAF property engaged by signaling pathways promoted within pancreatic tumors. These studies will be accomplished using metabolomics techniques in combination with inhibitors of metabolism and signal transduction. In parallel, we will disrupt this pyruvate crosstalk pathway in human patient-derived organoid models and in orthotopic transplant mouse models to determine the translation value. The application of insights from these studies could have an immediate impact on patients, as mitochondrially-targeted therapies are being tested in clinical trials for PDA and other cancers. A means to predict activity of mitochondrially- targeted agents based on tumor CAF content or CAF properties would increase the utility of these agents.