Investigating luminal plasticity in prostate tumorigenesis

PROJECT SUMMARY The most common prostate disorders, benign prostate enlargement and prostate cancer (PCa), are associated with aging and attributed to hormonal imbalances and loss of glandular homeostasis. Given the major impact prostate pathologies have on men’s health and their significant burden on healthcare systems, it is important to elucidate the cellular and molecular mechanisms underlying prostate hyperproliferations in aging and cancer. To date, most studies focused on elucidating the identity of various stem cell prostate populations and on validating their stem cell potential in culture assays and tissue regeneration. Recent single cell transcriptomics highlighted the previously underappreciated prostate epithelial heterogeneity and the importance of lineage plasticity in generating intratumor cellular heterogeneity. To date, little is known about the functional cell types that maintain epithelial homeostasis and what specific dysregulations enable their uncontrolled proliferation in aging and cancer. In preliminary studies, we found that p63 and increased Wnt signaling mark a previously uncharacterized prostate “luminal intermediate” (LumI) population that contributes to normal homeostatic clonal growth. These cells and Wnt signaling appear to significantly increase in aged mouse and human prostate samples and constitute a large proportion of PCa cells. Based on these data, we hypothesize that LumI cells and their Wnt- p63 signaling are required for maintenance of clonal expansions in luminal layer in intact prostate, that this “hybrid transcriptional state” expands with age and creates a pool of cells more susceptible to transformation. Moreover, during growth of early tumor clones, the malignant cells hijack this program for rapid proliferation. In this application, we will investigate the role of LumI cells and their specific Wnt-p63 signaling in luminal clonal expansions in aging and cancer with the ultimate goal of finding new targetable mechanisms that would halt cancer progression. We will pursue this goal through three Specific Aims: 1) Functional analyses of Wnt signaling in prostate luminal intermediate cells in aging and cancer in vivo and in vitro in prostate organoids, 2) Investigate the role of p63 in luminal plasticity in prostate cancer through loss- and gain-of-function studies coupled with gene circuits approaches for fine tuning of p63 protein levels and lineage diversification, and 3) Elucidate the gene regulatory network and co-factors controlled by p63 in the LumI state by transcriptomics, epigenomics and mechanistic validation of top target genes and co-factors. Taken together, our studies will provide a comprehensive understanding of luminal lineage plasticity and its effects on clonal expansions in normal, aging and malignant conditions. The proposed studies will offer insights into novel markers for detection of progressive cancer lesions and new venues for cell-targeted cancer therapies focused on Wnt-p63 signaling.