The role of CCR6 in Pancreatic Cancer and Tregs

Abstract public domain (NIH RePORTER)

PROJECT SUMMARY Pancreatic cancer has a dismal average life expectancy of around six months, in large part due to the marked immunosuppression surrounding the tumor preventing an anti-tumor immune response (1,2). A mediator of the pancreatic cancer immunosuppression is regulatory T cells (Tregs) (3). Tregs are a known pro-tumorigenic population within pancreatic cancer tumors but complete depletion of Tregs results in accelerated tumor progression, indicating that there is a delicate balance of Tregs needed (4,5). The goal of this proposal is to use in vitro assays to characterize the population of CCR6+ Tregs that show increased immunosuppressive capabilities. Further, the effects of CCL20, the only chemokine ligand for CCR6, will be assessed on its ability to shape Treg function. Next, the impact of CCR6-CCL20 signaling will be tested using in vivo models of pancreatic cancer with the aim of striking the balance needed for targeting some, but not all, Tregs to achieve an anti-tumor immune response. My preliminary data show that CCR6+ Tregs are enriched within pancreatic cancer tumors and they possess superior suppressive abilities compared to CCR6- Tregs. CCL20 is upregulated in pancreatic cancer and is associated with a worse prognosis and thus poses as an attractive target to overcome local immunosuppression (6). The central hypothesis of this proposal is that CCL20 induces a “super suppressor” phenotype on CCR6+ Tregs and these super suppressor CCR6+ Tregs are responsible for the CCL20-mediated pro-tumorigenic effects seen in PDAC. Our lab has been a leader in defining the role of chemokines in cancer and is thus perfectly suited to pursue this question. Utilizing inducible Tregs, bulk sequencing, and functional assays, I will extensively characterize the mechanisms in the immunosuppressive arsenal of CCR6+ super suppressor Tregs. Additionally, I will use in vivo models of pancreatic cancer to explore the impact of CCL20-CCR6 in pancreatic cancer progression and on the tumor microenvironment through extensive analysis with flow cytometry and single nucleus RNA sequencing (snRNA-seq). This would be the first study to perform snRNA-seq on in vivo models of pancreatic cancer, an urgent need due to snRNA-seq’s ability to better capture the large fibroblast populations present within pancreatic cancer compared to single cell RNA sequencing (7,8). Lastly, I will test the ability of a novel compound, generated by our group, that inhibits CCR6 chemotaxis to function within pancreatic cancer tumors (9). Collectively, these data will give greater insight into Treg function, increase understanding of how the immunosuppressive pancreatic cancer microenvironment forms, evaluate the ability of a prominent preclinical model of pancreas cancer to accurately recapitulate human disease, and investigate the efficacy of a novel pharmacological compound.

Public health relevance public domain (NIH RePORTER)

PROJECT NARRATIVE Avoiding immune destruction is a hallmark of cancer that is especially prominent within pancreatic cancer tumors (10,11). The proposed studies will investigate of a population of highly functional regulatory T cells to determine their mechanisms of immune suppression and their impact in pancreatic cancer. The data generated from these studies will have implications in the study of autoimmune disease and other types of cancer, providing critical information for not only the development of these diseases but also in the design of new therapeutics.