Modified Project Summary/Abstract Section The goal of this project is to establish the role of CCL28 in chronic pancreatitis and use structure-based drug discovery methods to identify small molecule inhibitors of this secreted protein. CCL28 is a mucosal chemokine that promotes tumor growth in a variety of organs by recruiting regulatory T cells (Tregs) that express the G protein-coupled receptor CCR10. Based on our published and preliminary results, we postulate that secretion of the chemokine CCL28 by pancreatic ductal epithelial cells also drives chronic inflammation that progresses to malignant disease. We hypothesize that inhibition of CCL28 activity will alter the pancreatic mucosal microenvironment in a manner that reduces pre-malignant inflammation and enhances the activity of existing chemotherapeutics and immunotherapies. To achieve this objective, we propose three conceptually linked but experimentally independent specific aims. First, we will test our mechanistic hypothesis in animal models of chronic pancreatitis, to demonstrate experimentally that CCL28 activity through CCR10 plays a key role in the fibroinflammatory response in vivo and develop an in vitro model that can be used to screen promising inhibitors (aim 1). Key elements of CCL28 recognition by its G protein-coupled receptor CCR10 will be mapped in detail using NMR and molecular modeling, and we will define the complete intracellular signaling profile of this chemokine receptor using state-of-the-art assay platforms for receptor pharmacology (aim 2). Using the solved NMR structure of CCL28 and knowledge of its sulfotyrosine binding pocket, we will employ a structure-based strategy developed in the Volkman lab that enables the discovery of small molecules that bind a specific chemokine target and inhibit cell migration (aim 3). Collectively, the proposed studies will provide fundamental advances in our understanding of (1) Treg function and pathophysiology in the pancreas, (2) the structural basis for ligand-receptor selectivity and GPCR pharmacology in a largely unexamined chemokine signaling axis, and (3) the druggability of a mucosal chemokine at the tumor-promoting interface of chronic inflammation and neoplasia.