Date of Award

Summer 6-27-2025

Embargo Period

6-30-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Pharmacology

Additional Department

Microbiology and Immunology

College

College of Graduate Studies

First Advisor

Nathan Dolloff

Second Advisor

John O'Bryan

Third Advisor

Michael Ostrowski

Fourth Advisor

Anand Mehta

Fifth Advisor

David Long

Abstract

Pancreatic ductal adenocarcinoma (PDAC) has one of the lowest 5-year survival rates of all cancers, and limited treatment options exist. Immunotherapy is effective in some cancer types, but the immunosuppressive tumor microenvironment (TME) of PDAC is a barrier to effective immunotherapy. CXCR2+ myeloid-derived suppressor cells (MDSCs) are abundant in PDAC tumors in humans and in mouse models. MDSCs suppress effector cell function, making them attractive targets for restoring anti-tumor immunity. The studies outlined in this dissertation (1) link tumor-intrinsic oncogenic signaling to dysregulated myeloid activity in PDAC, (2) describe a rationally designed fusion protein and potent inhibitor of CXCR2+ myeloid cell migration in PDAC, and (3) explore CXCL1-Fc as a modular platform for CXCR2-targeted therapeutics. We utilize cytokine arrays and quantitative ELISA to show that the most abundant soluble factors released from a genetically diverse set of human and mouse PDAC cells are CXCR2 ligands, including CXCL8, CXCL5, and CXCL1. Using engineered cell models, we showed that expression of CXCR2 ligands is at least partially driven by mutant KRAS and NF-κB signaling, which are two of the most commonly dysregulated pathways in PDAC. CyTOF and flow cytometry analyses revealed that myeloid cells are the dominant immune cell population in PDAC tumors, with MDSCs expressing high levels of CXCR2. Moreover, we observed that myeloid cells readily migrated toward conditioned media (CM) derived from PDAC cell cultures using Boyden chamber transwell assays. To therapeutically target immunosuppressive myeloid cells, we designed CXCR2 ligand-Fc fusion proteins. Unexpectedly, these fusion proteins were superior to native chemokines in binding and activation of CXCR2 on myeloid cells. These “superkines” were potent inhibitors of PDAC CM-induced myeloid cell migration and were superior to CXCR2 small-molecule inhibitors and neutralizing antibodies. Finally, we demonstrate that CXCL1-Fc can serve as a modular platform for delivering therapeutic payloads to CXCR2+ cells and may have applications beyond cancer, such as in wound healing. Together, these findings provide mechanistic insight into myeloid dysregulation in PDAC and introduce a promising class of immunotherapeutic agents capable of altering the myeloid landscape to improve treatment outcomes.

Rights

Copyright is held by the author. All rights reserved.

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