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The Impacts of Inflammation on Adult Prostate Stem Cells
Adult prostate stem cells (PSC) are a rare epithelial progenitor population in the prostate. While essential for normal homeostasis, they have also been implicated in hyperplasia and cancer initiation. While studies have shown that inflammatory growth factors and cytokines can fuel stem cell expansion, the impact of inflammation on PSC is not well understood. To study the impact of inflammation on the prostate, the Ratliff laboratory developed the Prostate Ovalbumin Expressing Transgenic 3 (POET3), an inducible mouse model of abacterial T cell mediated prostate inflammation, which functions as a model for human autoimmune prostatitis. Previous studies using the POET3 demonstrated that inflammation increased proliferation and differentiation of PSC enrichments. Based on these findings, it was speculated that inflammation impacts prostate stem cells to enhance mechanisms of survival, possibly as a means of tissue protection.
Since androgen receptor (AR) signaling is the major driver of cellular differentiation and survival in the prostate, it was further hypothesized that inflammation promotes AR signaling in the PSC. To address this hypothesis, PSC and their resulting organoids from inflamed and non-inflamed (naïve) POET3 mice as well as human patient samples were assessed for AR and its signaling components.
These data were expanded by single cell mRNA sequencing using Fluidigm’s C1 platform, which revealed changes in stem cell populations, differential expression of interleukin 1 alpha (IL-1⍺) and its signaling components, and upregulation of various genes associated with immune regulation. Thus, experiments described herein probed the impacts of inflammation on AR, IL-1⍺, and T cell regulatory abilities in the PSC.The results of these studies indicate that indeed, inflammation increases PSC survival. Inhibition of IL-1⍺ via inflammation-mediated up-regulation of IL-1 receptor antagonist (IL-1RA) promotes AR signaling, resulting in proliferation, differentiation, and AR target gene expression which can be modulated by Enzalutamide (a clinical AR inhibitor). Furthermore, PSC from inflamed mice are able to suppress cytotoxic T cell function in ex vivo assays. These studies set the foundation for new ways to treat proliferative diseases of the prostate by targeting IL-1⍺, AR, and immune regulation in the PSC.