Stromal-epithelial interactions--I. Induction of prostatic phenotype in urothelium of testicular feminized (Tfm/y) mice

Interactions between androgen and IGF1 axes in prostate tumorigenesis

Androgen signalling through the androgen receptor (AR) is essential for prostate tumorigenesis. However, androgen signalling pathways also interact with other growth factor-mediated signalling pathways to regulate the prostatic cell cycle, differentiation, apoptosis and proliferation in the initiation and progression of prostate cancer. Insulin-like growth factor 1 (IGF1) is one of the most prominent growth factors in prostate tumorigenesis. Clinical and experimental evidence has demonstrated that IGF1 signalling supports both androgen-dependent and androgen-independent prostate tumorigenesis, suggesting that improved understanding of the interactions between the IGF1 and androgen axes might aid the development of new therapeutic strategies. Available data have shown a dynamic role of androgen-AR signalling in the activation of IGF1-signalling pathways by augmenting transcription of the IGF1 receptor in prostatic basal epithelial cells and by increasing IGF1 secretion through the suppression of IGF-binding protein 3 expression in prostatic stromal cells. In turn, IGF1 stimulates Wnt-β-catenin signalling in prostatic basal progenitors to promote prostatic oncogenic transformation and prostate cancer development. These findings highlight the cooperative, autocrine and paracrine interactions that underlie the oncogenic effects of androgens and IGF1 and open up new opportunities for therapeutic targeting.

Stromal androgen signaling governs essential niches in supporting prostate development and tumorigenesis

Androgens and androgen receptor (AR) mediated signaling pathways are essential for prostate development, morphogenesis, growth, and regeneration. Early tissue recombination experiments showed that AR-deficient urogenital sinus mesenchyme combined with intact urogenital sinus epithelium failed to develop into a prostate, demonstrating a stem cell niche for mesenchymal AR in prostatic development. Androgen signaling remains critical for prostate maturation and growth during postnatal stages. Importantly, most primary prostate cancer (PCa) cells express the AR, and aberrant activation of AR directly promotes PCa development, growth, and progression. Therefore, androgen deprivation therapy (ADT) targeting the AR in PCa cells is the main treatment for advanced PCa. However, it eventually fails, leading to the development of castration-resistant PCa, an incurable disease. Given these clinical challenges, the oncogenic AR action needs to be reevaluated for developing new and effective therapies. Recently, an essential niche role of stromal AR was identified in regulating prostate development and tumorigenesis. Here, we summarize the latest discoveries of stromal AR niches and their interactions with prostatic epithelia. In combination with emerging clinical and experimental evidence, we specifically discuss several important and long-term unanswered questions regarding tumor niche roles of stromal AR and highlight future therapeutic strategies by co-targeting epithelial and stromal AR for treating advanced PCa.

MicroRNA signature of stromal-epithelial interactions in prostate and breast cancers

Stromal-epithelial communication is an absolute necessity when it comes to the morphogenesis and pathogenesis of solid tissues, including the prostate and breast. So far, signalling pathways of several growth factors have been investigated. Besides such chemical factors, non-coding RNAs such as miRNAs have recently gained much interest because of their variety and complexity of action. Prostate and breast tissues being highly responsive to steroid hormones such as androgen and estrogen, respectively, it is not surprising that a huge set of available literature critically investigated the interplay between such hormones and miRNAs, especially in carcinogenesis. This review showcases our effort to highlight hormonally-related miRNAs that also somehow perturb the regular stromal-epithelial interactions during carcinogenesis in the prostate and breast. In future, we look forward to exploring how hormonal changes in the tissue microenvironment bring about miRNA-mediated changes in stromal-epithelial interactome in carcinogenesis and cancer progression.

Integrated single-cell analysis defines the epigenetic basis of castration-resistant prostate luminal cells

Understanding prostate response to castration and androgen receptor signaling inhibitors (ARSI) is critical to improving long-term prostate cancer (PCa) patient survival. Here, we use a multi-omics approach on 229,794 single cells to create a mouse single-cell reference atlas for interpreting mouse prostate biology and castration response. Our reference atlas refines single-cell annotations and provides a chromatin context, which, when coupled with mouse lineage tracing, demonstrates that castration-resistant luminal cells are distinct from the pre-existent urethra-proximal stem/progenitor cells. Molecular pathway analysis and therapeutic studies further implicate AP1 (JUN/FOS), WNT/β-catenin, FOXQ1, NF-κB, and JAK/STAT pathways as major drivers of castration-resistant luminal populations with relevance to human PCa. Our datasets, which can be explored through an interactive portal (https://visportal.roswellpark.org/data/tang/), can aid in developing combination treatments with ARSI for advanced PCa patients.

YAP is required for prostate development, regeneration, and prostate stem cell function

Prostate development and regeneration depend on prostate stem cell function, the delicate balance of stem cell self-renewal and differentiation. However, mechanisms modulating prostate stem cell function remain poorly identified. Here, we explored the roles of Yes-associated protein 1 (YAP) in prostate stem cells, prostate development and regeneration. Using YAPfl/fl, CD133-CreER mice, we found that stem cell-specific YAP-deficient mice had compromised branching morphogenesis and epithelial differentiation, resulting in damaged prostate development. YAP inhibition also significantly affected the regeneration process of mice prostate, leading to impaired regenerated prostate. Furthermore, YAP ablation in prostate stem cells significantly reduced its self-renewal activity in vitro, and attenuated prostate regeneration of prostate grafts in vivo. Further analysis revealed a decrease in Notch and Hedgehog pathways expression in YAP inhibition cells, and treatment with exogenous Shh partially restored the self-renewal ability of prostate sphere cells. Taken together, our results revealed the roles of YAP in prostate stem cell function and prostate development and regeneration through regulation of the Notch and Hedgehog signaling pathways.

The testosterone paradox of advanced prostate cancer: mechanistic insights and clinical implications

The discovery of the benefits of castration for prostate cancer treatment in 1941 led to androgen deprivation therapy, which remains a mainstay of the treatment of men with advanced prostate cancer. However, as early as this original publication, the inevitable development of castration-resistant prostate cancer was recognized. Resistance first manifests as a sustained rise in the androgen-responsive gene, PSA, consistent with reactivation of the androgen receptor axis. Evaluation of clinical specimens demonstrates that castration-resistant prostate cancer cells remain addicted to androgen signalling and adapt to chronic low-testosterone states. Paradoxically, results of several studies have suggested that treatment with supraphysiological levels of testosterone can retard prostate cancer growth. Insights from these studies have been used to investigate administration of supraphysiological testosterone to patients with prostate cancer for clinical benefits, a strategy that is termed bipolar androgen therapy (BAT). BAT involves rapid cycling from supraphysiological back to near-castration testosterone levels over a 4-week cycle. Understanding how BAT works at the molecular and cellular levels might help to rationalize combining BAT with other agents to achieve increased efficacy and tumour responses.

Stromal androgen signaling acts as tumor niches to drive prostatic basal epithelial progenitor-initiated oncogenesis

The androgen receptor (AR)-signaling pathways are essential for prostate tumorigenesis. Although significant effort has been devoted to directly targeting AR-expressing tumor cells, these therapies failed in most prostate cancer patients. Here, we demonstrate that loss of AR in stromal sonic-hedgehog Gli1-lineage cells diminishes prostate epithelial oncogenesis and tumor development using in vivo assays and mouse models. Single-cell RNA sequencing and other analyses identified a robust increase of insulin-like growth factor (IGF) binding protein 3 expression in AR-deficient stroma through attenuation of AR suppression on Sp1-regulated transcription, which further inhibits IGF1-induced Wnt/β-catenin activation in adjacent basal epithelial cells and represses their oncogenic growth and tumor development. Epithelial organoids from stromal AR-deficient mice can regain IGF1-induced oncogenic growth. Loss of human prostate tumor basal cell signatures reveals in basal cells of stromal AR-deficient mice. These data demonstrate a distinct mechanism for prostate tumorigenesis and implicate co-targeting stromal and epithelial AR-signaling for prostate cancer.

Cellular specificity of androgen receptor, coregulators, and pioneer factors in prostate cancer

Androgen signalling, through the transcription factor androgen receptor (AR), is vital to all stages of prostate development and most prostate cancer progression. AR signalling controls differentiation, morphogenesis, and function of the prostate. It also drives proliferation and survival in prostate cancer cells as the tumour progresses; given this importance, it is the main therapeutic target for disseminated disease. AR is also essential in the surrounding stroma, for the embryonic development of the prostate and controlling epithelial glandular development. Stromal AR is also important in cancer initiation, regulating paracrine factors that excite cancer cell proliferation, but lower stromal AR expression correlates with shorter time to progression/worse outcomes. The profile of AR target genes is different between benign and cancerous epithelial cells, between castrate-resistant prostate cancer cells and treatment-naïve cancer cells, between metastatic and primary cancer cells, and between epithelial cells and fibroblasts. This is also true of AR DNA-binding profiles. Potentially regulating the cellular specificity of AR binding and action are pioneer factors and coregulators, which control and influence the ability of AR to bind to chromatin and regulate gene expression. The expression of these factors differs between benign and cancerous cells, as well as throughout disease progression. The expression profile is also different between fibroblast and mesenchymal cell types. The functional importance of coregulators and pioneer factors in androgen signalling makes them attractive therapeutic targets, but given the contextual expression of these factors, it is essential to understand their roles in different cancerous and cell-lineage states.

Stromal androgen and hedgehog signaling regulates stem cell niches in pubertal prostate development

Stromal androgen-receptor (AR) action is essential for prostate development, morphogenesis and regeneration. However, mechanisms underlying how stromal AR maintains the cell niche in support of pubertal prostatic epithelial growth are unknown. Here, using advanced mouse genetic tools, we demonstrate that selective deletion of stromal AR expression in prepubescent Shh-responsive Gli1-expressing cells significantly impedes pubertal prostate epithelial growth and development. Single-cell transcriptomic analyses showed that AR loss in these prepubescent Gli1-expressing cells dysregulates androgen signaling-initiated stromal-epithelial paracrine interactions, leading to growth retardation of pubertal prostate epithelia and significant development defects. Specifically, AR loss elevates Shh-signaling activation in both prostatic stromal and adjacent epithelial cells, directly inhibiting prostatic epithelial growth. Single-cell trajectory analyses further identified aberrant differentiation fates of prostatic epithelial cells directly altered by stromal AR deletion. In vivo recombination of AR-deficient stromal Gli1-lineage cells with wild-type prostatic epithelial cells failed to develop normal prostatic epithelia. These data demonstrate previously unidentified mechanisms underlying how stromal AR-signaling facilitates Shh-mediated cell niches in pubertal prostatic epithelial growth and development.

Correlation Between Testosterone Replacement Treatment and Lower Urinary Tract Symptoms

Lower urinary tract symptoms (LUTS) are a cluster of voiding symptoms, such as weak stream, hesitancy, intermittency, urinary frequency, urgency, and nocturia. LUTS are frequent in elderly men and it considered the ultimate clinical symptoms of benign prostatic hyperplasia. With aging, male hypogonadism is increased which is defined as decreased ability of the testes to produce sperm and sex steroids because of a pituitary/hypothalamic, or testicular deficiency. In academic andrology associations, the term "male hypogonadism" is commonly used to categorize testosterone deficiency. Testosterone deficiency syndrome (TDS) is defined as a decrease in serum testosterone accompanied by symptoms such as libido decrease, depressive disorder, erectile dysfunction, and fatigue. Although the mechanism about testosterone-replacement therapy (TRT) effects on men with hypogonadism is not yet identified, TRT has been shown to effectively relieve the symptoms of TDS as well as LUTS by several studies. Although the present review demonstrates the effectiveness and safety of TRT in men with TDS by prior studies, future large scale of clinical trials should be conducted to present more high-quality evidence to clinicians and patients.

Androgen action in cell fate and communication during prostate development at single-cell resolution

Androgens/androgen receptor (AR)-mediated signaling pathways are essential for prostate development, morphogenesis and regeneration. Specifically, stromal AR signaling has been shown to be essential for prostatic initiation. However, the molecular mechanisms underlying AR-initiated mesenchymal-epithelial interactions in prostate development remain unclear. Here, using a newly generated mouse model, we have directly addressed the fate and role of genetically marked AR-expressing cells during embryonic prostate development. Androgen signaling-initiated signaling pathways were identified in mesenchymal niche populations at single-cell transcriptomic resolution. The dynamic cell-signaling networks regulated by stromal AR were additionally characterized in relation to prostatic epithelial bud formation. Pseudotime analyses further revealed the differentiation trajectory and fate of AR-expressing cells in both prostatic mesenchymal and epithelial cell populations. Specifically, the cellular properties of Zeb1-expressing progenitors were assessed. Selective deletion of AR signaling in a subpopulation of mesenchymal rather than epithelial cells dysregulated the expression of the master regulators and significantly impaired prostatic bud formation. These data provide novel, high-resolution evidence demonstrating the important role of mesenchymal androgen signaling in the cellular niche controlling prostate early development by initiating dynamic mesenchyme-epithelia cell interactions.

Current experimental human tissue-derived models for prostate cancer research

Scientists engaged in prostate cancer research have been conducting experiments using two-dimensional cultures of prostate cancer cell lines for decades. However, these experiments fail to reproduce and reflect the clinical course of individual patients with prostate cancer, or the molecular and genetic characteristics of prostate cancer, the basic requirement for most of the preclinical studies on prostate cancer. The use of human prostate cancer tissues in experiments has enabled the collection and verification of clinically relevant data, including chemical reactions, changes in proteins, and specific gene expression. Tissue recombination models have been employed for studying prostate development, the initiation and progression of prostate cancer, and the tumor microenvironment. Notably, the epithelial-stromal interaction, which might play a critical role in prostate cancer pathogenesis, can be reproduced in this model. Patient-derived xenograft models have been developed as powerful avatars comprising patient-derived prostate cancer tissues implanted in immunocompromised mice and could serve as a precision medicine approach for each prostate cancer patient. Spheroid and organoid assays, representative of modern three-dimensional cultures, can replicate the conditions in human prostate tumors and the prostate organ itself as a miniature model. Although an intact immune system against the tumor is missing from the models aimed at investigating immuno-oncological reagents in various malignancies, all these experimental models can help researchers in developing new drugs and selecting appropriate treatment strategies for prostate cancer patients.

Tumor Microenvironment-Derived NRG1 Promotes Antiandrogen Resistance in Prostate Cancer

Despite the development of second-generation antiandrogens, acquired resistance to hormone therapy remains a major challenge in treating advanced prostate cancer. We find that cancer-associated fibroblasts (CAFs) can promote antiandrogen resistance in mouse models and in prostate organoid cultures. We identify neuregulin 1 (NRG1) in CAF supernatant, which promotes resistance in tumor cells through activation of HER3. Pharmacological blockade of the NRG1/HER3 axis using clinical-grade blocking antibodies re-sensitizes tumors to hormone deprivation in vitro and in vivo. Furthermore, patients with castration-resistant prostate cancer with increased tumor NRG1 activity have an inferior response to second-generation antiandrogen therapy. This work reveals a paracrine mechanism of antiandrogen resistance in prostate cancer amenable to clinical testing using available targeted therapies.

The role of the androgen receptor in prostate development and benign prostatic hyperplasia: A review

Benign prostatic hyperplasia (BPH) is a benign enlargement of the prostate in which incidence increases linearly with age, beginning at about 50 years old. BPH is a significant source of morbidity in aging men by causing lower urinary tract symptoms and acute urinary retention. Unfortunately, the etiology of BPH incidence and progression is not clear. This review highlights the role of the androgen receptor (AR) in prostate development and the evidence for its involvement in BPH. The AR is essential for normal prostate development, and individuals with defective AR signaling, such as after castration, do not experience prostate enlargement with age. Furthermore, decreasing dihydrotestosterone availability through therapeutic targeting with 5α-reductase inhibitors diminishes AR activity and results in reduced prostate size and symptoms in some BPH patients. While there is some evidence that AR expression is elevated in certain cellular compartments, how exactly AR is involved in BPH progression has yet to be elucidated. It is possible that AR signaling within stromal cells alters intercellular signaling and a "reawakening" of the embryonic mesenchyme, loss of epithelial AR leads to changes in paracrine signaling interactions, and/or chronic inflammation aids in stromal or epithelial proliferation evident in BPH. Unfortunately, a subset of patients fails to respond to current medical approaches, forcing surgical treatment even though age or associated co-morbidities make surgery less attractive. Fundamentally, new therapeutic approaches to treat BPH are not currently forthcoming, so a more complete molecular understanding of BPH etiology is necessary to identify new treatment options.

Loss of androgen signaling in mesenchymal sonic hedgehog responsive cells diminishes prostate development, growth, and regeneration

Prostate embryonic development, pubertal and adult growth, maintenance, and regeneration are regulated through androgen signaling-mediated mesenchymal-epithelial interactions. Specifically, the essential role of mesenchymal androgen signaling in the development of prostate epithelium has been observed for over 30 years. However, the identity of the mesenchymal cells responsible for this paracrine regulation and related mechanisms are still unknown. Here, we provide the first demonstration of an indispensable role of the androgen receptor (AR) in sonic hedgehog (SHH) responsive Gli1-expressing cells, in regulating prostate development, growth, and regeneration. Selective deletion of AR expression in Gli1-expressing cells during embryogenesis disrupts prostatic budding and impairs prostate development and formation. Tissue recombination assays showed that urogenital mesenchyme (UGM) containing AR-deficient mesenchymal Gli1-expressing cells combined with wildtype urogenital epithelium (UGE) failed to develop normal prostate tissue in the presence of androgens, revealing the decisive role of AR in mesenchymal SHH responsive cells in prostate development. Prepubescent deletion of AR expression in Gli1-expressing cells resulted in severe impairment of androgen-induced prostate growth and regeneration. RNA-sequencing analysis showed significant alterations in signaling pathways related to prostate development, stem cells, and organ morphogenesis in AR-deficient Gli1-expressing cells. Among these altered pathways, the transforming growth factor β1 (TGFβ1) pathway was up-regulated in AR-deficient Gli1-expressing cells. We further demonstrated the activation of TGFβ1 signaling in AR-deleted prostatic Gli1-expressing cells, which inhibits prostate epithelium growth through paracrine regulation. These data demonstrate a novel role of the AR in the Gli1-expressing cellular niche for regulating prostatic cell fate, morphogenesis, and renewal, and elucidate the mechanism by which mesenchymal androgen-signaling through SHH-responsive cells elicits the growth and regeneration of prostate epithelium.

Prostate formation, growth, and regeneration, as well as tumorigenesis, depend on androgens and androgen receptor (AR)-mediated signaling pathways. Tissue recombination assays done more than 30 years ago demonstrated a decisive role for stromal androgen signaling in prostatic epithelium development. However, in the intervening time, the identity of the mesenchymal cells in the urogenital sinus mesenchyme that convey androgen signaling and control prostate epithelium development, morphogenesis, and regeneration has not been determined. In this study, using mouse genetic tools, we demonstrate for the first time that selective deletion of AR in mesenchymal Gli1-expressing cells abolishes early development of prostate tissue and normal prostate formation, and diminishes prostate pubertal growth and regeneration. In addition, using tissue recombination assays, we directly determined an essential requirement for AR expression in mesenchymal Gli1-expressing cells during prostate epithelium development. Our results not only resolve a 30-year-old scientific puzzle by identifying the mesenchymal cell properties of androgen-responsive cells that elicit development of the embryonic prostate epithelium, but also explore a new regulatory mechanism for androgen and Shh signaling-mediated cellular niches in regulating prostatic cell fate, growth, and renewal through paracrine regulation. Given the importance of sex hormone and hedgehog signaling pathways in human development and tumorigenesis, this study extends beyond the field of prostate biology, raising new questions underlying sex hormone and SHH signaling in development and tumorigenesis.

Genome-wide analysis of androgen receptor binding and transcriptomic analysis in mesenchymal subsets during prostate development

Prostate development is controlled by androgens, the androgen receptor (AR) and mesenchymal–epithelial signalling. We used chromatin immunoprecipitation sequencing (ChIP-seq) to define AR genomic binding in the male and female mesenchyme. Tissue- and single-cell-based transcriptional profiling was used to define mesenchymal AR target genes. We observed significant AR genomic binding in females and a strong enrichment at proximal promoters in both sexes. In males, there was greater AR binding to introns and intergenic regions as well as to classical AR binding motifs. In females, there was increased proximal promoter binding and involvement of cofactors. Comparison of AR-bound genes with transcriptomic data enabled the identification of novel sexually dimorphic AR target genes. We validated the dimorphic expression of AR target genes using published datasets and confirmed regulation by androgens using ex vivo organ cultures. AR targets showed variable expression in patients with androgen insensitivity syndrome. We examined AR function at single-cell resolution using single-cell RNA sequencing (scRNA-seq) in male and female mesenchyme. Surprisingly, both AR and target genes were distributed throughout cell subsets, with few positive cells within each subset. AR binding was weakly correlated with target gene expression.

Summary: A study of how androgens lead to sexually dimorphic development of the prostate using transcription factor genome binding and transcriptome analysis in mesenchymal subsets.

ZBTB46, SPDEF, and ETV6: Novel Potential Biomarkers and Therapeutic Targets in Castration-Resistant Prostate Cancer

Prostate cancer (PCa) is the second most common killer among men in Western countries. Targeting androgen receptor (AR) signaling by androgen deprivation therapy (ADT) is the current therapeutic regime for patients newly diagnosed with metastatic PCa. However, most patients relapse and become resistant to ADT, leading to metastatic castration-resistant PCa (CRPC) and eventually death. Several proposed mechanisms have been proposed for CRPC; however, the exact mechanism through which CRPC develops is still unclear. One possible pathway is that the AR remains active in CRPC cases. Therefore, understanding AR signaling networks as primary PCa changes into metastatic CRPC is key to developing future biomarkers and therapeutic strategies for PCa and CRPC. In the current review, we focused on three novel biomarkers (ZBTB46, SPDEF, and ETV6) that were demonstrated to play critical roles in CRPC progression, epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) drug resistance, and the epithelial-to-mesenchymal transition (EMT) for patients treated with ADT or AR inhibition. In addition, we summarize how these potential biomarkers can be used in the clinic for diagnosis and as therapeutic targets of PCa.

Testosterone and Benign Prostatic Hyperplasia

INTRODUCTION

Benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS) are frequent in aging. Nonetheless, their pathogenesis is largely unknown. The androgen dependence of the first phases of prostate development have inspired the historical view that higher testosterone (T) may be involved in BPH occurrence; however, recent evidence suggests a different scenario.

AIM

To review the available knowledge on the pathogenesis of BPH particularly concerning the role of T and the possible connections with metabolic impairments.

METHODS

Relevant records were retrieved by an extensive search in Medline, including the following keywords ("testosterone"[MeSH Terms] OR "testosterone"[All Fields]) AND ("prostatic hyperplasia"[MeSH Terms] OR ("prostatic"[All Fields] AND "hyperplasia"[All Fields]) OR "prostatic hyperplasia"[All Fields] OR ("benign"[All Fields] AND "prostatic"[All Fields] AND "hyperplasia"[All Fields]) OR "benign prostatic hyperplasia"[All Fields]). There were no limitations in terms of publication date or study design.

MAIN OUTCOME MEASURES

Preclinical and clinical studies have been reported, with special emphasis on our contribution and interpretation.

RESULTS

Inflammation is a key aspect of BPH development. Along with infectious agents, prostate inflammation can be triggered by metabolic stimuli, such as dyslipidemia, an important component of metabolic syndrome (MetS). Low T and hyperestrogenism frequently occur in MetS. Mounting evidence shows that low, rather than high, T and hyperestrogenism may favor prostate inflammation. Considering these data as a whole, we postulate that BPH is the result of the action of multiple factors, which reinforce their mutual detrimental effects.

CONCLUSION

T is not detrimental for the prostate, and treating hypogonadism could even produce relief from LUTS and limit prostatic inflammation, which generates and maintains the process leading to BPH. Rastrelli G, Vignozzi L, Corona G, et al. Testosterone and Benign Prostatic Hyperplasia. Sex Med Rev 2019;7:259-271.

Prostate Stroma Increases the Viability and Maintains the Branching Phenotype of Human Prostate Organoids

The fibromuscular stroma of the prostate regulates normal epithelial differentiation and contributes to carcinogenesis in vivo. We developed and characterized a human 3D prostate organoid co-culture model that incorporates prostate stroma. Primary prostate stromal cells increased organoid formation and directed organoid morphology into a branched acini structure similar to what is observed in vivo. Organoid branching occurred distal to physical contact with stromal cells, demonstrating non-random branching. Stroma-induced phenotypes were similar in all patients examined, yet they maintained inter-patient heterogeneity in the degree of response. Stromal cells expressed growth factors involved in epithelial differentiation, which was not observed in non-prostatic fibroblasts. Organoids derived from areas of prostate cancer maintained differential expression of alpha-methylacyl-CoA racemase and showed increased viability and passaging when co-cultured with stroma. The addition of stroma to epithelial cells in vitro improves the ability of organoids to recapitulate features of the tissue and enhances the viability of organoids.

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Co-culture with human primary prostate stroma improves epithelial organoid viability

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Stromal cell contact in co-culture directs epithelial organoid branching

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Prostate stromal cells express morphogenic factors unique from non-prostate fibroblasts

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Co-culture with stroma maintains AMACR and increases survival of cancer derived-organoids

Genome-wide analysis of AR binding and comparison with transcript expression in primary human fetal prostate fibroblasts and cancer associated fibroblasts

The androgen receptor (AR) is a transcription factor, and key regulator of prostate development and cancer, which has discrete functions in stromal versus epithelial cells. AR expressed in mesenchyme is necessary and sufficient for prostate development while loss of stromal AR is predictive of prostate cancer progression. Many studies have characterized genome-wide binding of AR in prostate tumour cells but none have used primary mesenchyme or stroma. We applied ChIPseq to identify genomic AR binding sites in primary human fetal prostate fibroblasts and patient derived cancer associated fibroblasts, as well as the WPMY1 cell line overexpressing AR. We identified AR binding sites that were specific to fetal prostate fibroblasts (7534), cancer fibroblasts (629), WPMY1-AR (2561) as well as those common among all (783). Primary fibroblasts had a distinct AR binding profile versus prostate cancer cell lines and tissue, and showed a localisation to gene promoter binding sites 1 kb upstream of the transcriptional start site, as well as non-classical AR binding sequence motifs. We used RNAseq to define transcribed genes associated with AR binding sites and derived cistromes for embryonic and cancer fibroblasts as well as a cistrome common to both. These were compared to several in vivo ChIPseq and transcript expression datasets; which identified subsets of AR targets that were expressed in vivo and regulated by androgens. This analysis enabled us to deconvolute stromal AR targets active in stroma within tumour samples. Taken together, our data suggest that the AR shows significantly different genomic binding site locations in primary prostate fibroblasts compared to that observed in tumour cells. Validation of our AR binding site data with transcript expression in vitro and in vivo suggests that the AR target genes we have identified in primary fibroblasts may contribute to clinically significant and biologically important AR-regulated changes in prostate tissue.

Stromal Gli signaling regulates the activity and differentiation of prostate stem and progenitor cells

Interactions between cells in the stroma and epithelium facilitate prostate stem cell activity and tissue regeneration capacity. Numerous molecular signal transduction pathways, including the induction of sonic hedgehog (Shh) to activate the Gli transcription factors, are known to mediate the cross-talk of these two cellular compartments. However, the details of how these signaling pathways regulate prostate stem and progenitor cell activity remain elusive. Here we demonstrate that, although cell-autonomous epithelial Shh-Gli signaling is essential to determine the expression levels of basal cell markers and the renewal potential of epithelial stem and progenitor cells, stromal Gli signaling regulates prostate stem and progenitor cell activity by increasing the number and size of prostate spheroids in vitro Blockade of stromal Gli signaling also inhibited prostate tissue regeneration in vivo The inhibition of stromal Gli signaling suppressed the differentiation of basal and progenitor cells to luminal cells and limited prostate tubule secretory capability. Additionally, stromal cells were able to compensate for the deficiency of epithelial Shh signaling in prostate tissue regeneration. Mechanistically, suppression of Gli signaling increased the signaling factor transforming growth factor β (TGFβ) in stromal cells. Elevation of exogenous TGFβ1 levels inhibited prostate spheroid formation, suggesting that a stromal Gli-TGFβ signaling axis regulates the activity of epithelial progenitor cells. Our study illustrates that Gli signaling regulates epithelial stem cell activity and renewal potential in both epithelial and stromal compartments.

An Indispensable Role of Androgen Receptor in Wnt Responsive Cells During Prostate Development, Maturation, and Regeneration

Androgen signaling is essential for prostate development, morphogenesis, and regeneration. Emerging evidence indicates that Wnt/β-catenin signaling also contributes to prostate development specifically through regulation of cell fate determination. Prostatic Axin2-expressing cells are able to respond to Wnt signals and possess the progenitor properties to regenerate prostatic epithelium. Despite critical roles of both signaling pathways, the biological significance of androgen receptor (AR) in Axin2-expressing/Wnt-responsive cells remains largely unexplored. In this study, we investigated this important question using a series of newly generated mouse models. Deletion of Ar in embryonic Axin2-expressing cells impaired early prostate development in both ex vivo and tissue implantation experiments. When Ar expression was deleted in prostatic Axin2-expressing cells at pre-puberty stages, it results in smaller and underdeveloped prostates. A subpopulation of Axin2 expressing cells in prostate epithelium is resistant to castration and, following androgen supplementation, is capable to expand to prostatic luminal cells. Deletion of Ar in these Axin2-expressing cells reduces their regenerative ability. These lines of evidence demonstrate an indispensable role for the Ar in Wnt-responsive cells during the course of prostate development, morphogenesis, and regeneration, which also imply an underlying interaction between the androgen and Wnt signaling pathways in the mouse prostate. Stem Cells 2018;36:891-902.

Interaction of prostate carcinoma-associated fibroblasts with human epithelial cell lines in vivo

Stromal-epithelial interactions play a crucial and poorly understood role in carcinogenesis and tumor progression. Mesenchymal-epithelial interactions have a long history of research in relation to the development of organs. Models designed to study development are often also applicable to studies of benign and malignant disease. Tumor stroma is a complex mixture of cells that includes a fibroblastic component often referred to as cancer-associated fibroblasts (CAF), desmoplasia or "reactive" stroma. Here we discuss the history of, and approaches to, understanding these interactions with particular reference to prostate cancer and to in vivo modeling using human cells and tissues. A series of studies have revealed a complex mixture of signaling molecules acting both within the stromal tissue and between the stromal and epithelial tissues. We are starting to understand the interactions of some of these pathways, however the work is still ongoing. This area of research provide a basis for new medical approaches aimed at stabilizing early stage cancers rendering them chronic rather than acute problems. Such work is especially relevant to slow growing tumors found in older patients, a class that would include many prostate cancers.

RET-mediated glial cell line-derived neurotrophic factor signaling inhibits mouse prostate development

In humans and rodents, the prostate gland develops from the embryonic urogenital sinus (UGS). The androgen receptor (AR) is thought to control the expression of morphogenetic genes in inductive UGS mesenchyme, which promotes proliferation and cytodifferentiation of the prostatic epithelium. However, the nature of the AR-regulated morphogenetic genes and the mechanisms whereby AR controls prostate development are not understood. Glial cell line-derived neurotrophic factor (GDNF) binds GDNF family receptor α1 (GFRα1) and signals through activation of RET tyrosine kinase. Gene disruption studies in mice have revealed essential roles for GDNF signaling in development; however, its role in prostate development is unexplored. Here, we establish novel roles of GDNF signaling in mouse prostate development. Using an organ culture system for prostate development and Ret mutant mice, we demonstrate that RET-mediated GDNF signaling in UGS increases proliferation of mesenchyme cells and suppresses androgen-induced proliferation and differentiation of prostate epithelial cells, inhibiting prostate development. We also identify Ar as a GDNF-repressed gene and Gdnf and Gfrα1 as androgen-repressed genes in UGS, thus establishing reciprocal regulatory crosstalk between AR and GDNF signaling in prostate development.

Dissecting cell-type-specific roles of androgen receptor in prostate homeostasis and regeneration through lineage tracing

Androgen signals through androgen receptor (AR) to influence prostate development and cancer. How stromal and epithelial AR regulate prostate homeostasis remains unclear. Using genetic lineage tracing, we systematically investigated the role of cell-autonomous AR in different prostate epithelial cell types. Here we show that AR is dispensable for basal cell maintenance, but is cell-autonomously required for the luminal differentiation of rare basal stem cells. In contrast, AR deletion in luminal cells alters cell morphology and induces transient over-proliferation, without affecting androgen-mediated luminal cell survival or regeneration. However, AR is selectively required for the maintenance of daughter cells produced by castration-resistant Nkx3.1-expressing luminal stem cells (CARNs). Notably, Pten loss can override AR-loss effects in both basal and luminal compartments to initiate tumours. Our data reveal distinct cell-type-specific roles of epithelial AR in orchestrating prostate homeostasis, and question the notion that epithelial AR serves as a tumour suppressor in early cancer initiation.

Androgen receptor is an important regulator of prostate development and cancer. In this study, the authors use genetic lineage tracing in mice to clarify the role of AR in different prostate epithelial cells.

Stromal Androgen Receptor in Prostate Cancer Development and Progression

Prostate cancer development and progression is the result of complex interactions between epithelia cells and fibroblasts/myofibroblasts, in a series of dynamic process amenable to regulation by hormones. Whilst androgen action through the androgen receptor (AR) is a well-established component of prostate cancer biology, it has been becoming increasingly apparent that changes in AR signalling in the surrounding stroma can dramatically influence tumour cell behavior. This is reflected in the consistent finding of a strong association between stromal AR expression and patient outcomes. In this review, we explore the relationship between AR signalling in fibroblasts/myofibroblasts and prostate cancer cells in the primary site, and detail the known functions, actions, and mechanisms of fibroblast AR signaling. We conclude with an evidence-based summary of how androgen action in stroma dramatically influences disease progression.

WOMEN IN CANCER THEMATIC REVIEW: New roles for nuclear receptors in prostate cancer

Prostate cancer has, for decades, been treated by inhibiting androgen signalling. This is effective in the majority of patients, but inevitably resistance develops and patients progress to life-threatening metastatic disease - hence the quest for new effective therapies for 'castrate-resistant' prostate cancer (CRPC). Studies into what pathways can drive tumour recurrence under these conditions has identified several other nuclear receptor signalling pathways as potential drivers or modulators of CRPC.The nuclear receptors constitute a large (48 members) superfamily of transcription factors sharing a common modular functional structure. Many of them are activated by the binding of small lipophilic molecules, making them potentially druggable. Even those for which no ligand exists or has yet been identified may be tractable to activity modulation by small molecules. Moreover, genomic studies have shown that in models of CRPC, other nuclear receptors can potentially drive similar transcriptional responses to the androgen receptor, while analysis of expression and sequencing databases shows disproportionately high mutation and copy number variation rates among the superfamily. Hence, the nuclear receptor superfamily is of intense interest in the drive to understand how prostate cancer recurs and how we may best treat such recurrent disease. This review aims to provide a snapshot of the current knowledge of the roles of different nuclear receptors in prostate cancer - a rapidly evolving field of research.

Contribution of Caudal Müllerian Duct Mesenchyme to Prostate Development

A fundamental understanding of prostate development and tissue homeostasis has the high potential to reveal mechanisms for prostate disease initiation and identify novel therapeutic approaches for disease prevention and treatment. Our current understanding of prostate lineage specification stems from the use of developmental model systems that rely upon the embryonic preprostatic urogenital sinus mesenchyme to induce the formation of mature prostate epithelial cells. It is unclear, however, how the urogenital sinus epithelium can derive both adult urethral glands and prostate epithelia. Furthermore, the vast disparity in disease initiation between these two glands highlights key developmental factors that predispose prostate epithelia to hyperplasia and cancer. In this study we demonstrate that the caudal Müllerian duct mesenchyme (CMDM) drives prostate epithelial differentiation and is a key determinant in cell lineage specification between urethral glands and prostate epithelia. Utilizing both human embryonic stem cells and mouse embryonic tissues, we document that the CMDM is capable of inducing the specification of androgen receptor, prostate-specific antigen, NKX3.1, and Hoxb13-positive prostate epithelial cells. These results help to explain key developmental differences between prostate and urethral gland differentiation, and implicate factors secreted by the caudal Müllerian duct as novel targets for prostate disease prevention and treatment.

New transcription factors involved with postnatal ventral prostate gland development in male Wistar rats during the first week

AIMS

The high incidence in men of prostatic diseases, including benign and malignant tumors, makes the understanding of prostate development and biology very important. Understanding the organogenesis of the prostate gland has been a substantial challenge as "prostatic code" is not well defined at the present time. The novelty of this work lies in unveiling new transcription factors (TFs) during neonatal ventral prostate (VP) gland development in male Wistar rats.

MAIN METHODS

The techniques of qRT-PCR and immunohistochemistry have been employed to perform this work while the VP gland was obtained from neonatal rats at day zero (the day of birth) day 3 and 6.

KEY FINDINGS

16 TFs were studied and we found an increased expression of Eya2, Lhrh and Znf142, invariable levels of Znf703 and Dbp, and decreased expression of 11 others at postnatal development day 3 and 6 as compared to day zero. ZNF703 was found by immunohistochemistry in epithelial cells at days 0, 3 and 6. qRT-PCR for Eya2 and Dmrt2 showed the highest and lowest fold change for them respectively, and immunohistochemistry showed that the former is being expressed at the three selected time points while the latter appears to be diminishing with very few cells expressing it until day 6.

SIGNIFICANCE

Results from this work is reporting the role of these TFs for the first time and will significantly contribute to the current understanding of the development and branching morphogenesis of the neonatal VP gland during the first week of postnatal development.

Stromal androgen receptor roles in the development of normal prostate, benign prostate hyperplasia, and prostate cancer

The prostate is an androgen-sensitive organ that needs proper androgen/androgen receptor (AR) signals for normal development. The progression of prostate diseases, including benign prostate hyperplasia (BPH) and prostate cancer (PCa), also needs proper androgen/AR signals. Tissue recombination studies report that stromal, but not epithelial, AR plays more critical roles via the mesenchymal-epithelial interactions to influence the early process of prostate development. However, in BPH and PCa, much more attention has been focused on epithelial AR roles. However, accumulating evidence indicates that stromal AR is also irreplaceable and plays critical roles in prostate disease progression. Herein, we summarize the roles of stromal AR in the development of normal prostate, BPH, and PCa, with evidence from the recent results of in vitro cell line studies, tissue recombination experiments, and AR knockout animal models. Current evidence suggests that stromal AR may play positive roles to promote BPH and PCa progression, and targeting stromal AR selectively with AR degradation enhancer, ASC-J9, may allow development of better therapies with fewer adverse effects to battle BPH and PCa.

Glial cell line-derived neurotrophic factor induces cell proliferation in the mouse urogenital sinus

Glial cell line-derived neurotrophic factor (GDNF) is a TGFβ family member, and GDNF signals through a glycosyl-phosphatidylinositol-linked cell surface receptor (GFRα1) and RET receptor tyrosine kinase. GDNF signaling plays crucial roles in urogenital processes, ranging from cell fate decisions in germline progenitors to ureteric bud outgrowth and renal branching morphogenesis. Gene ablation studies in mice have revealed essential roles for GDNF signaling in urogenital development, although its role in prostate development is unclear. We investigated the functional role of GDNF signaling in the urogenital sinus (UGS) and the developing prostate of mice. GDNF, GFRα1, and RET show time-specific and cell-specific expression during prostate development in vivo. In the UGS, GDNF and GFRα1 are expressed in the urethral mesenchyme (UrM) and epithelium (UrE), whereas RET is restricted to the UrM. In each lobe of the developing prostate, GDNF and GFRα1 expression declines in the epithelium and becomes restricted to the stroma. Using a well-established organ culture system, we determined that exogenous GDNF increases proliferation of UrM and UrE cells, altering UGS morphology. With regard to mechanism, GDNF signaling in the UrM increased RET expression and phosphorylation of ERK1/2. Furthermore, inhibition of RET kinase activity or ERK kinases suppressed GDNF-induced proliferation of UrM cells but not UrE cells. We therefore propose that GDNF signaling in the UGS increases proliferation of UrM and UrE cells by different mechanisms, which are distinguished by the role of RET receptor tyrosine kinase and ERK kinase signaling, thus implicating GDNF signaling in prostate development and growth.

Stromal androgen receptor in prostate development and cancer

The androgen receptor (AR) in stromal cells contributes significantly to the development and growth of prostate during fetal stages as well as during prostate carcinogenesis and cancer progression. During prostate development, stromal AR induces and promotes epithelial cell growth, as observed from tissue recombinant and mouse knockout studies. During prostate carcinogenesis and progression, the stromal cells begin to lose AR expression as early as at the stage of high-grade prostatic intraepithelial neoplasia. The extent of loss of stromal AR is directly proportional to the degree of differentiation (Gleason grade) and progression of prostate cancer (PCa). Co-culture studies suggested that stromal AR inhibits the growth of malignant epithelial cells, possibly through expression of certain paracrine factors in the presence of androgens. This functional reversal of stromal AR, from growth promotion during fetal prostate development to mediating certain growth-inhibiting effects in cancer, explains to some extent the reason that loss of AR expression in stromal cells may be crucial for development of resistance to androgen ablation therapy for PCa. From a translational perspective, it generates the need to re-examine the current therapeutic options and opens a fundamental new direction for therapeutic interventions, especially in advanced PCa.

Influence of stromal-epithelial interactions on androgen action

Androgen receptor (AR) signaling is vital to the development and function of the prostate and is a key pathway in prostate cancer. AR is differentially expressed in the stroma and epithelium, with both paracrine and autocrine control throughout the prostate. Stromal-epithelial interactions within the prostate are commonly dependent on AR signaling and expression. Alterations in these pathways can promote tumorigenesis. AR is also expressed in normal and malignant mammary tissues. Emerging data indicate a role for AR in certain subtypes of breast cancer that has the potential to be exploited therapeutically. The aim of this review is to highlight the importance of these interactions in normal development and tumorigenesis, with a focus on the prostate and breast.

Budding process during the organogenesis of the ventral prostatic lobe in Mongolian gerbil

The prostate is a mammalian gland that shows a complex process of organogenesis. Here, a morphological study to characterize the organogenesis of the ventral prostate lobe in male gerbils was conducted. The urogenital sinus (UGS) was dissected out and processed for paraffin embedding. Histological sections were subjected to cytochemical, immunofluorescence, immunohistochemical, and three-dimensional reconstruction techniques. We found that the first ventral buds emerged from the ventral urethral epithelium between the days 20 and 21 of prenatal life, reaching the ventral mesenchymal pad and initiating the branching process on the first day of postnatal life. The buds presented a V-shaped elongation, suggesting that the smooth muscle layer (SML) plays an important role during budding events. Indeed, whereas the androgen receptor (AR) was preferentially found in the UGS mesenchyme (UGM), estrogen receptor alpha (ERα) was localized in both the UGM and in the emerging buds. This study characterized the morphological aspects of the budding process in a different rodent from rat and mice, serving as a new model for future studies on developmental biology of the prostate.

Benign prostatic hyperplasia: a new metabolic disease of the aging male and its correlation with sexual dysfunctions

Metabolic syndrome (MetS) is a well-recognized cluster of cardiovascular (CV) risk factors including obesity, hypertension, dyslipidemia, and hyperglycaemia, closely associated with an increased risk of forthcoming cardiovascular disease and type 2 diabetes mellitus. Emerging evidence indicates that benign prostate hyperplasia (BPH) and its related lower urinary tract symptoms (LUTS) represent other clinical conditions frequently observed in subjects with MetS. Several modifiable factors involved in MetS determinism, such as inadequate diet, lack of physical exercise, and smoking and drinking behaviours are emerging as main contributors to the development of BPH. The pathogenetic mechanisms underlying the connection between MetS and BPH have not been completely clarified. MetS and its components, hypogonadism, and prostate inflammation probably play an important role in inducing BPH/LUTS. Although historically considered as a "normal" consequence of the aging process, BPH/LUTS should now be faced proactively, as a preventable disorder of the elderly. Type of diet and level of physical activity are now considered important factors affecting prostate health in the aging male. However, whether physical exercise, weight loss, and modifications of dietary habit can really alter the natural history of BPH/LUTS remains to be determined. Further research is advisable to better clarify these points.

Formation of human prostate epithelium using tissue recombination of rodent urogenital sinus mesenchyme and human stem cells

Progress in prostate cancer research is severely limited by the availability of human-derived and hormone-naïve model systems, which limit our ability to understand genetic and molecular events underlying prostate disease initiation. Toward developing better model systems for studying human prostate carcinogenesis, we and others have taken advantage of the unique pro-prostatic inductive potential of embryonic rodent prostate stroma, termed urogenital sinus mesenchyme (UGSM). When recombined with certain pluripotent cell populations such as embryonic stem cells, UGSM induces the formation of normal human prostate epithelia in a testosterone-dependent manner. Such a human model system can be used to investigate and experimentally test the ability of candidate prostate cancer susceptibility genes at an accelerated pace compared to typical rodent transgenic studies. Since Human embryonic stem cells (hESCs) can be genetically modified in culture using inducible gene expression or siRNA knock-down vectors prior to tissue recombination, such a model facilitates testing the functional consequences of genes, or combinations of genes, which are thought to promote or prevent carcinogenesis. The technique of isolating pure populations of UGSM cells, however, is challenging and learning often requires someone with previous expertise to personally teach. Moreover, inoculation of cell mixtures under the renal capsule of an immunocompromised host can be technically challenging. Here we outline and illustrate proper isolation of UGSM from rodent embryos and renal capsule implantation of tissue mixtures to form human prostate epithelium. Such an approach, at its current stage, requires in vivo xenografting of embryonic stem cells; future applications could potentially include in vitro gland formation or the use of induced pluripotent stem cell populations (iPSCs).

TCDD inhibition of canonical Wnt signaling disrupts prostatic bud formation in mouse urogenital sinus

In mice, in utero exposure to 2,3,7,8-tetrachlorodibenzo-p- dioxin (TCDD) reduces the number of dorsolateral prostatic buds resulting in a smaller dorsolateral prostate and prevents formation of ventral buds culminating in ventral prostate agenesis. The genes and signaling pathways affected by TCDD that are responsible for disrupting prostate development are largely unknown. Here we show that treatment of urogenital sinus (UGS) organ cultures with known inhibitors of canonical Wnt signaling also inhibits prostatic bud formation. In support of the hypothesis that TCDD decreases canonical Wnt signaling, we identify inhibitory effects of TCDD on multiple components of the canonical Wnt signaling pathway in the UGS that temporally coincide with the inhibitory effect of TCDD on prostatic bud formation: (1) expression of R-spondins (Rspo2 and Rspo3) that promote canonical Wnt signaling is reduced; (2) expression of Lef1, Tcf1, and Wif1, established canonical Wnt target genes, is decreased; (3) expression of Lgr5, a RSPO receptor that activates canonical Wnt signaling, is reduced; and (4) expression of Dickkopfs (Dkks), inhibitors of canonical Wnt signaling, is not increased by TCDD. Thus, the TCDD-induced reduction in canonical Wnt signaling is associated with a decrease in activators (Rspo2 and Rspo3) rather than an increase in inhibitors (Dkk1 and Dkk2) of the pathway. This study focuses on determining whether treatment of TCDD-exposed UGS organ cultures with RSPO2 and/or RSPO3 is capable of rescuing the inhibitory effects of TCDD on canonical Wnt signaling and prostatic bud formation. We discovered that each RSPO alone or in combination partially rescues TCDD inhibition of both canonical Wnt signaling and prostatic bud formation.

Prostate epithelial AR inactivation leads to increased intraprostatic androgen synthesis

BACKGROUND

Regulation of steroid synthesis within the prostate is not well understood. In this study, we examined androgen synthesis and metabolism in the mouse prostate.

METHODS

Using LC-MSMS steroid assays, immunohistochemistry and real-time PCR we examined the role of prostate epithelial AR in regulating 5αR expression and subsequent androgen metabolism by analyzing natural differences in epithelial AR expression between lobes as well as in the prostate epithelial AR knockout (PEARKO) mouse model. Subsequently, the role of intraprostatic androgen metabolism and epithelial AR in the generation and progression of prostate epithelial pathology was examined using long-term exogenous testosterone (T) + estradiol (E2) exposure.

RESULTS

Epithelial AR and 5αR2 expression as well as intraprostatic DHT followed the same lobe-specific pattern being lower in anterior than the other lobes (n = 6-8, P < 0.05). Lobe-specific 5αR2 expression was similar in PEARKO and wild-type (WT) prostate. However, PEARKO prostate had higher intraprostatic DHT content with significantly increased 5αR2 expression localized in abnormal epithelium. T + E2 treatment induced epithelial pathology was more common in PEARKO prostate compared to WT (20% vs. 2%), and was associated with increased 5αR2 expression (n = 6, P < 0.001).

CONCLUSIONS

We suggest that androgen synthesis via 5αR2 expression is driven by its own product (DHT) acting on adjacent stromal cells in a paracrine loop leading to increased in situ androgen levels in the PEARKO prostate. This may form part of a feed-forward loop that promotes the development of epithelial pathology.

The mouse as a model to investigate sex steroid metabolism in the normal and pathological prostate

Metabolism of sex steroids within the prostate is an important factor affecting its growth and pathology. Mouse models with genetic gain- and especially loss-of-function have characterised different steroid metabolic pathways and their contribution to prostate pathology. With reference to the human prostate, this review aims to summarize the steroidogenic pathways in the mouse prostate as the basis for using the mouse as a model for intraprostatic steroid signalling. In this review we summarize the current information for three main components of the steroid signalling pathway in the mouse prostate: circulating steroids, steroid receptors and steroidogenic enzymes with regard to signalling via androgen, estrogen, progesterone and glucocorticoid pathways. This review reveals many opportunities for characterisation steroid metabolism in various mouse models. The knowledge of steroid metabolism within prostate tissue and in a lobe (rodent)/region (human) specific manner, will give valuable information for future, novel hypotheses of intraprostatic control of steroid actions. This review summarizes knowledge of steroid metabolism in the mouse prostate and its relevance to the human.

Lxrα regulates the androgen response in prostate epithelium

Benign prostatic hyperplasia is a nonmalignant enlargement of the prostate that commonly occurs in older men. We show that liver X receptor (Lxr)-α knockout mice (lxrα(-/-)) develop ventral prostate hypertrophy, correlating with an overaccumulation of secreted proteins in prostatic ducts and an alteration of vesicular trafficking in epithelial cells. In the fluid of the lxrα(-/-) prostates, spermine binding protein is highly accumulated and shows a 3000-fold increase of its mRNA. This overexpression is mediated by androgen hypersensitivity in lxrα(-/-) mice, restricted to the ventral prostate. Generation of chimeric recombinant prostates demonstrates that Lxrα is involved in the establishment of the epithelial-mesenchymal interactions in the mouse prostate. Altogether these results point out the crucial role of Lxrα in the homeostasis of the ventral prostate and suggest lxrα(-/-) mice may be a good model to investigate the molecular mechanisms of benign prostatic hyperplasia.

Altered prostate epithelial development in mice lacking the androgen receptor in stromal fibroblasts

BACKGROUND

Androgens and the androgen receptor (AR) play important roles in the development of male urogenital organs. We previously found that mice with total AR knockout (ARKO) and epithelial ARKO failed to develop normal prostate with loss of differentiation. We have recently knocked out AR gene in smooth muscle cells and found the reduced luminal infolding and IGF-1 production in the mouse prostate. However, AR roles of stromal fibroblasts in prostate development remain unclear.

METHODS

To further probe the stromal fibroblast AR roles in prostate development, we generated tissue-selective knockout mice with the AR gene deleted in stromal fibroblasts (FSP-ARKO). We also used primary culture stromal cells to confirm the in vivo data and investigate mechanisms related to prostate development.

RESULTS

The results showed cellular alterations in the FSP-ARKO mouse prostate with decreased epithelial proliferation, increased apoptosis, and decreased collagen composition. Further mechanistic studies demonstrated that FSP-ARKO mice have defects in the expression of prostate stromal growth factors. To further confirm these in vivo findings, we prepared primary cultured mouse prostate stromal cells and found knocking down the stromal AR could result in growth retardation of prostate stromal cells and co-cultured prostate epithelial cells, as well as decrease of some stromal growth factors.

CONCLUSIONS

Our FSP-ARKO mice not only provide the first in vivo evidence in Cre-loxP knockout system for the requirement of stromal fibroblast AR to maintain the normal development of the prostate, but may also suggest the selective knockdown of stromal AR might become a potential therapeutic approach to battle prostate hyperplasia and cancer.

Suppressed prostate epithelial development with impaired branching morphogenesis in mice lacking stromal fibromuscular androgen receptor

Using the cre-loxP system, we generated a new mouse model [double stromal androgen receptor knockout (dARKO)] with selectively deleted androgen receptor (AR) in both stromal fibroblasts and smooth muscle cells, and found the size of the anterior prostate (AP) lobes was significantly reduced as compared with those from wild-type littermate controls. The reduction in prostate size of the dARKO mouse was accompanied by impaired branching morphogenesis and partial loss of the infolding glandular structure. Further dissection found decreased proliferation and increased apoptosis of the prostate epithelium in the dARKO mouse AP. These phenotype changes were further confirmed with newly established immortalized prostate stromal cells (PrSC) from wild-type and dARKO mice. Mechanistically, IGF-1, placental growth factor, and secreted phosphoprotein-1 controlled by stromal AR were differentially expressed in PrSC-wt and PrSC-ARKO. Moreover, the conditioned media (CM) from PrSC-wt promoted prostate epithelium growth significantly as compared with CM from PrSC-dARKO. Finally, adding IGF-1/placental growth factor recombinant proteins into PrSC-dARKO CM was able to partially rescue epithelium growth. Together, our data concluded that stromal fibromuscular AR could modulate epithelium growth and maintain cellular homeostasis through identified growth factors.

The calcium sensor STIM1 is regulated by androgens in prostate stromal cells

BACKGROUND

Prostate development and maintenance in the adult results from an interaction of stromal and glandular components. Androgens can drive this process by direct action on the stroma. We investigated whether there was a direct link between androgens and another key regulator of stromal cells, intracellular Ca2+ ([Ca2+ ]i ).

METHODS

Prostate stromal cells were freshly obtained and cultures derived from patients with benign prostatic hyperplasia. Gene expression in dihydrotestosterone treated and untreated cells was compared using Affymetrix gene expression arrays and Ca2+ regulated features were identified by Gene Ontology (GO). Changes in [Ca2+]i were determined in Fluo-4 loaded cells. Androgen regulation was confirmed by chromatin immunoprecipitaion.

RESULTS

Stromal cell cultures were sorted for expression of integrin α1 β1 , which enriched for cells expressing the androgen receptor (AR). We identified key functional categories, within the androgen-induced gene expression signature, focusing on genes involved in calcium signaling. From this analysis, stromal interaction molecule-1 (STIM1) was identified as a significantly differentially expressed gene with four relevant associated GO terms. DNA sequence analysis showed that the promoter region of STIM1 contained putative androgen response element sequences in which AR binding ability of STIM1 was confirmed. Androgens directly regulated STIM1 expression and STIM1 effects on store-operated calcium entry were inhibited by STIM1 knock-down. Reduced STIM1 expression in prostate stromal cells led to a reduction in basal Ca2+ levels, the amount of Ca2+ released by thapsigargin and a reduction in store filling following TG-induced store depletion.

CONCLUSIONS

These results indicate that androgens modulate [Ca2+]i through the direct regulation of the STIM1 gene by AR binding to the STIM1 promoter.

A high-resolution molecular atlas of the fetal mouse lower urogenital tract

Epithelial-stromal interactions in the lower urogenital tract (LUT) are integral to prostatic and seminal vesicle development in males, vaginal and uterine development in females, and urethral development in both sexes. Gene expression profiling of isolated LUT stroma and epithelium has unraveled mechanisms of LUT development, but such studies are confounded by heterogeneous and ill-defined cell sub-populations contained within each tissue compartment. We used in situ hybridization to synthesize a high-resolution molecular atlas of 17-day post-coitus fetal mouse LUT. We identified mRNAs that mark selective cell populations of the seminal vesicle, ejaculatory duct, prostate, urethra, and vagina, subdividing these tissues into 16 stromal and 8 epithelial sub-compartments. These results provide a powerful tool for mapping LUT gene expression patterns and also reveal previously uncharacterized sub-compartments that may play mechanistic roles in LUT development of which we were previously unaware.

A high throughput in situ hybridization method to characterize mRNA expression patterns in the fetal mouse lower urogenital tract

Development of the lower urogenital tract (LUT) is an intricate process. This complexity is evidenced during formation of the prostate from the fetal male urethra, which relies on androgenic signals and epithelial-mesenchymal interactions(1,2). Understanding the molecular mechanisms responsible for prostate development may reveal growth mechanisms that are inappropriately reawakened later in life to give rise to prostate diseases such as benign prostatic hyperplasia and prostate cancer. The developing LUT is anatomically complex. By the time prostatic budding begins on 16.5 days post conception (dpc), numerous cell types are present. Vasculature, nerves and smooth muscle reside within the mesenchymal stroma(3). This stroma surrounds a multilayered epithelium and gives rise to the fetal prostate through androgen receptor-dependent paracrine signals(4). The identity of the stromal androgen receptor-responsive genes required for prostate development and the mechanism by which prostate ductal epithelium forms in response to these genes is not fully understood. The ability to precisely identify cell types and localize expression of specific factors within them is imperative to further understand prostate development. In situ hybridization (ISH) allows for localization of mRNAs within a tissue. Thus, this method can be used to identify pattern and timing of expression of signaling molecules and their receptors, thereby elucidating potential prostate developmental regulators. Here, we describe a high throughput ISH technique to identify mRNA expression patterns in the fetal mouse LUT using vibrating microtome-cut sections. This method offers several advantages over other ISH protocols. Performing ISH on thin sections adhered to a slide is technically difficult; cryosections frequently have poor structural quality while both cryosections and paraffin sections often result in weak signal resolution. Performing ISH on whole mount tissues can result in probe trapping. In contrast, our high throughput technique utilizes thick-cut sections that reveal detailed tissue architecture. Modified microfuge tubes allow easy handling of sections during the ISH procedure. A maximum of 4 mRNA transcripts can be screened from a single 17.5dpc LUT with up to 24 mRNA transcripts detected in a single run, thereby reducing cost and maximizing efficiency. This method allows multiple treatment groups to be processed identically and as a single unit, thereby removing any bias for interpreting data. Most pertinently for prostate researchers, this method provides a spatial and temporal location of low and high abundance mRNA transcripts in the fetal mouse urethra that gives rise to the prostate ductal network.

Increased CK5/CK8-positive intermediate cells with stromal smooth muscle cell atrophy in the mice lacking prostate epithelial androgen receptor

Results from tissue recombination experiments documented well that stromal androgen receptor (AR) plays essential roles in prostate development, but epithelial AR has little roles in prostate development. Using cell specific knockout AR strategy, we generated pes-ARKO mouse with knock out of AR only in the prostate epithelial cells and demonstrated that epithelial AR might also play important roles in the development of prostate gland. We found mice lacking the prostate epithelial AR have increased apoptosis in epithelial CK8-positive luminal cells and increased proliferation in epithelial CK5-positive basal cells. The consequences of these two contrasting results could then lead to the expansion of CK5/CK8-positive intermediate cells, accompanied by stromal atrophy and impaired ductal morphogenesis. Molecular mechanism dissection found AR target gene, TGF-β₁, might play important roles in this epithelial AR-to-stromal morphogenesis modulation. Collectively, these results provided novel information relevant to epithelial AR functions in epithelial-stromal interactions during the development of normal prostate, and suggested AR could also function as suppressor in selective cells within prostate.

Cell autonomous role of PTEN in regulating castration-resistant prostate cancer growth

Alteration of the PTEN/PI3K pathway is associated with late-stage and castrate-resistant prostate cancer (CRPC). However, how PTEN loss is involved in CRPC development is not clear. Here, we show that castration-resistant growth is an intrinsic property of Pten null prostate cancer (CaP) cells, independent of cancer development stage. PTEN loss suppresses androgen-responsive gene expressions by modulating androgen receptor (AR) transcription factor activity. Conditional deletion of Ar in the epithelium promotes the proliferation of Pten null cancer cells, at least in part, by downregulating the androgen-responsive gene Fkbp5 and preventing PHLPP-mediated AKT inhibition. Our findings identify PI3K and AR pathway crosstalk as a mechanism of CRPC development, with potentially important implications for CaP etiology and therapy.

PPARγ: a molecular link between systemic metabolic disease and benign prostate hyperplasia

The emergent epidemic of metabolic syndrome and its complex list of sequelae mandate a more thorough understanding of benign prostatic hyperplasia and lower urinary tract symptoms (BPH/LUTS) in the context of systemic metabolic disease. Here we discuss the nature and origins of BPH, examine its role as a component of LUTS and review retrospective clinical studies that have drawn associations between BPH/LUTS and type II diabetes, inflammation and dyslipidemia. PPARγ signaling, which sits at the nexus of systemic metabolic disease and BPH/LUTS through its regulation of inflammation and insulin resistance, is proposed as a candidate for molecular manipulation in regard to BPH/LUTS. Finally, we introduce new cell and animal models that are being used to study the consequences of obesity, diabetes and inflammation on benign prostatic growth.