PROJECT SUMMARY/ABSTRACT – Role of Neutrophil Extracellular Traps in Pancreatic Cancer Pancreatic ductal adenocarcinoma (PDAC) is a devastating malignancy characterized by a fibrotic and immunosuppressive tumor microenvironment that promotes resistance to therapy. Innovative approaches to overcome the pathophysiology in the PDAC tumor microenvironment (TME) that drive treatment resistance are desperately needed. The uniquely fibrotic TME serves as a physical barrier to prevent infiltration of T cells and has limited functional vasculature, which reduces the delivery of chemotherapy. We have recently demonstrated that neutrophil extracellular traps (NETs), in which activated neutrophils release their intracellular contents including DNA, histones and granules into the extracellular space or circulation, are upregulated in pancreatic cancer, driving tumor growth and promoting fibrosis through pancreatic stellate cell (PSC) activation. Protein arginine deiminase 4 (PAD4) is an enzyme that citrullinates histones to allow for unwinding and expulsion from the cell and is required for NET formation, providing a potential therapeutic target for NET inhibition in cancer. PAD4-/- mice have diminished local and systemic NET formation, resulting in limited tumor growth and improved survival in murine orthotopic pancreatic cancer. We have generated preliminary data demonstrating that PDAC mice with genetic ablation of PAD4 have enhanced cytotoxic immune response and increased functional vasculature. The objective of this application is to identify the impactful mechanisms through which NETs promote treatment resistance to immunotherapy and chemotherapy. We will explore the impact of PAD4 ablation on spontaneous transgenic Kras and p53 mediated PDAC. In Aim 1, we will thoroughly evaluate the immune response to PAD4 ablation/inhibition with a focus on how reduction in PSC activation as a result of diminished NETs enhances T cell infiltration and function, promoting response to immunotherapy. In Aim 2, we will evaluate the changes that NETs have on angiogenesis, functional vasculature and delivery of cytotoxic chemotherapy. These studies will support translation of novel therapeutic approaches in combination with standard of care chemotherapy and immunotherapy to maximize treatment response in this devastating disease.