Graduation Date

Fall 12-20-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Interdisciplinary Graduate Program in Biomedical Sciences

First Advisor

Leah M. Cook, PhD

Second Advisor

Jennifer D. Black, PhD

Abstract

Bone metastasis continues to be the greatest challenge in treating prostate cancer (PCa) patients, despite ongoing research into the molecular mechanisms of PCa in bone, where tumors are known to hijack normal bone remodeling processes to drive cancer progression. Although PCa regulation of bone remodeling has been studied for decades, current bone-targeted therapies have little impact on patient survival, demonstrating the need for a greater understanding of the complexities of the tumor-bone microenvironment. Many factors contribute to creating a favorable microenvironment for prostate tumors in bone, including cell signaling proteins produced by osteoid cells. This study investigated changes in bone marrow mesenchymal stem cells (MSCs) to better understand how PCa alters pre-osteoblastic cells and how those changes impact PCa tumor progression in bone. Specifically, prior studies indicated an important role for chemokine signaling in promoting PCa progression in the bone microenvironment. Since the pro-inflammatory chemokine CXCL8 is strongly upregulated in MSCs by BM-PCa, we investigated the impact of MSC-derived CXCL8 signaling in the BM-PCa tumor microenvironment. Using murine MSCs with genetic deletion of the murine homolog Cxcl1, we discovered a novel role for CXCL1/8 in regulating MSC osteoblast differentiation. We also observed significant impact of MSC CXCL1 on BM-PCa growth in vitro and in vivo. Bulk RNA sequencing of Cxcl1 KO MSCs revealed significant changes in extracellular matrix factors, especially collagens, which was confirmed via trichrome staining of tumors from our intratibial studies. RNA sequencing also revealed altered immune response pathways, both in Cxcl1 KO MSCs and BM-PCa tumors containing Cxcl1 KO MSCs. These findings highlight the importance of MSC-derived CXCL1/8 in the bone microenvironment and the therapeutic potential of a chemokine-targeted therapy in BM-PCa. In order to translate findings from mouse models to patients, additional models of the tumor bone microenvironment are required. This study also characterized a new human MSC cell line, the first to be derived from a spinal metastasis from a patient with PCa. We discovered that these Rapid Autopsy Program (RAP) MSCs lack osteoblast differentiation potential while retaining adipogenic differentiation potential. Further, we observed differences in chemokine and receptor expression in RAP MSCs compared to healthy control human MSCs, suggesting a re-programming of MSCs in the BM-PCa tumor microenvironment. To aid in the design of studies exploring the crosstalk between BM-PCa and MSCs, we evaluated the impact of cell culture media on MSC gene expression. We found that low glucose medium upregulates expression of bone matrix factor Type 1 Collagen in MSCs. These results emphasize the need to more fully characterize environment-dependent changes in MSC phenotype in order to distinguish tumor-induced changes. Since results from this study and prior research show a complex crosstalk between PCa tumor cells, osteoid cells, and other stromal cells in bone, such as immune cells, a deeper analysis of the immune response in BM-PCa and the exploration of its roles in the tumor microenvironment is needed. This will require additional model systems; therefore, we also characterized a previously established promyelocyte cell line. We validated its ability to differentiate into polymorphonuclear neutrophils (PMNs) and its potential for the study of their role in BM-PCa. Collectively, these findings emphasize the importance of the tumor microenvironment in BM-PCa progression. These results demonstrate both the ability of BM-PCa to impact MSCs and the effect of changes in MSCs on PCa tumor progression in bone.

Comments

2025 Copyright, the authors

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