Neutralizing Stromal NetrinG1 to Intercept Pancreatic Cancer

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PROJECT SUMMARY - PROJECT 2 Most patients with pancreatic cancer (PC) do not survive one year and less than 10% survive five years. This is unfortunate, given the slow rate of growth of PC over many years, and the large window of opportunity for potential intervention prior to diagnosis. Patients with hereditary familial PC (~10% of PC cases), as well as those exposed to mutagens and presenting with predisposing clinical conditions like pancreatitis and new onset of diabetes, are at high risk for PC and would benefit greatly from improved early detection, cancer prevention, and/or interception strategies. The proposed project addresses this unmet need by joining the FCCC Cancer Prevention-Interception Targeted Agent Discovery Program (CAP-IT) at the “Agent Identification and Screening” stage. The proposal is the first, to our knowledge, to employ a stroma-targeting strategy to intercept progression of precancerous tissue to overt PC. This proposal exploits our work in studying desmoplasia – a unique microenvironment enriched in stromal fibroblasts and dense extracellular matrix (ECM) that characterizes PC. We have defined distinct subsets of tumor-promoting and tumor-suppressing fibroblasts (TPFs and TSFs), which can reversibly interconvert in phenotype. We have shown that TPFs arise in early precancerous tissue, and are characterized by expression of Netrin G1 (NetG1). NetG1-dependent signaling is essential for premalignant cells to thrive as tumors. Mechanistically, we have shown that NetG1+ TPFs provide nutritional support to premalignant initiated epithelial cells (IECs) and tumors, allowing them to survive in the nutrient-poor desmoplastic environment and escape immunosurveillance by inducing an immunosuppressive microenvironment. While some support is delivered via TPF secretion of nutrients and chemokines; additional support is provided by the TPF-generated ECM. Critically, we have shown that a commercial monoclonal antibody (mAb) that inhibits NetG1 reverts all of these tumor-promoting properties and intercepts the formation of PC. Although the commercial mAb is sufficient for proof-of-concept experiments, it is not sufficiently potent as a clinical candidate. A large panel of mAbs targeting diverse NetG1 epitopes, with higher binding affinities than the one above-mentioned, has been generated. In Aim 1, we will determine which of the new mAbs functionally reverts TPFs to TSFs, based on the expression of molecular markers that distinguish between the two classes. In Aim 2, co-culture experiments will be used to identify mAbs that reduce the ability of TPFs to provide nutritional support to IECs, and assess whether the same mAbs decrease the ability of the ECM, produced by TPFs, to enhance IEC growth. New IEC models will be engineered that parallel the loss of function genetic variants seen in populations at high risk for PC. In Aim 3, the lead candidate mAbs that can intercept the transition from precancer to cancer in vitro will be evaluated for their toxicity profiles and ability to inhibit formation of PanINs, the precursor of PC, in KC mice, a model of PC. These studies are expected to yield novel agents that target the stroma for PC prevention and/or interception.