Markers of prostate region-specific epithelial identity define anatomical locations in the mouse prostate that are molecularly similar to human prostate cancers

In vitro induction of prostate buds from murine urogenital epithelium in the absence of mesenchymal cells

The prostate is a male reproductive gland which secretes prostatic fluid that enhances male fertility. During development and instigated by fetal testosterone, prostate cells arise caudal to the bladder at the urogenital sinus (UGS), when the urogenital mesenchyme (UGM) secretes signals to the urogenital epithelium (UGE). These initial mesenchymal signals induce prostate-specific gene expression in the UGE, after which epithelial progenitor cells form prostatic buds. Although many important factors for prostate development have been described using UGS organ cultures, those necessary and sufficient for prostate budding have not been clearly identified. This has been in part due to the difficulty to dissect the intricate signaling and feedback between epithelial and mesenchymal UGS cells. In this study, we separated the UGM from the UGE and tested candidate growth factors to show that when FGF10 is present, testosterone is not required for initiating prostate budding from the UGE. Moreover, in the presence of low levels of FGF10, canonical WNT signaling enhances the expression of several prostate progenitor markers in the UGE before budding of the prostate occurs. At the later budding stage, higher levels of FGF10 are required to increase budding and retinoic acid is indispensable for the upregulation of prostate-specific genes. Lastly, we show that under optimized conditions, female UGE can be instructed towards a prostatic fate, and in vitro generated prostate buds from male UGE can differentiate into a mature prostate epithelium after in vivo transplantation. Taken together, our results clarify the signals that can induce fetal prostate buds in the urogenital epithelium in the absence of the surrounding, instructive mesenchyme.

Male Lower Urinary Tract Dysfunction: An Underrepresented Endpoint in Toxicology Research

Lower urinary tract dysfunction (LUTD) is nearly ubiquitous in men of advancing age and exerts substantial physical, mental, social, and financial costs to society. While a large body of research is focused on the molecular, genetic, and epigenetic underpinnings of the disease, little research has been dedicated to the influence of environmental chemicals on disease initiation, progression, or severity. Despite a few recent studies indicating a potential developmental origin of male LUTD linked to chemical exposures in the womb, it remains a grossly understudied endpoint in toxicology research. Therefore, we direct this review to toxicologists who are considering male LUTD as a new aspect of chemical toxicity studies. We focus on the LUTD disease process in men, as well as in the male mouse as a leading research model. To introduce the disease process, we describe the physiology of the male lower urinary tract and the cellular composition of lower urinary tract tissues. We discuss known and suspected mechanisms of male LUTD and examples of environmental chemicals acting through these mechanisms to contribute to LUTD. We also describe mouse models of LUTD and endpoints to diagnose, characterize, and quantify LUTD in men and mice.

Urethral luminal epithelia are castration-insensitive cells of the proximal prostate

BACKGROUND

Castration-insensitive epithelial progenitors capable of regenerating the prostate have been proposed to be concentrated in the proximal region based on facultative assays. Functional characterization of prostate epithelial populations isolated with individual cell surface markers has failed to provide a consensus on the anatomical and transcriptional identity of proximal prostate progenitors.

METHODS

Here, we use single-cell RNA sequencing to obtain a complete transcriptomic profile of all epithelial cells in the mouse prostate and urethra to objectively identify cellular subtypes. Pan-transcriptomic comparison to human prostate cell types identified a mouse equivalent of human urethral luminal cells, which highly expressed putative prostate progenitor markers. Validation of the urethral luminal cell cluster was performed using immunostaining and flow cytometry.

RESULTS

Our data reveal that previously identified facultative progenitors marked by Trop2, Sca-1, KRT4, and PSCA are actually luminal epithelial cells of the urethra that extend into the proximal region of the prostate, and are resistant to castration-induced androgen deprivation. Mouse urethral luminal cells were identified to be the equivalent of previously identified human club and hillock cells that similarly extend into proximal prostate ducts. Benign prostatic hyperplasia (BPH) has long been considered an "embryonic reawakening," but the cellular origin of the hyperplastic growth concentrated in the periurethral region is unclear. We demonstrate an increase in urethral luminal cells within glandular nodules from BPH patients. Urethral luminal cells are further increased in patients treated with a 5-α reductase inhibitor.

CONCLUSIONS

Our data demonstrate that cells of the proximal prostate that express putative progenitor markers, and are enriched by castration in the proximal prostate, are urethral luminal cells and that these cells may play an important role in the etiology of human BPH.

Search for Novel Diagnostic Biomarkers of Prostate Inflammation-Related Disorders: Role of Transglutaminase Isoforms as Potential Candidates

Investigations on prostate inflammation-related disorders, including acute and chronic prostatitis, chronic pelvic pain syndrome, benign prostate hyperplasia (BPH), and prostate cancer (PCa), are still ongoing to find new, accurate, and noninvasive biomarkers for a differential diagnosis of those pathological conditions sharing some common macroscopic features. Moreover, an ideal biomarker should be useful for risk assessment of prostate inflammation progression to more severe disorders, like BPH or PCa, as well as for monitoring of treatment response and prognosis establishment in carcinoma cases. Recent literature evidence highlighted that changes in the expression of transglutaminases, enzymes that catalyze transamidation reactions leading to posttranslational modifications of soluble proteins, occur in prostate inflammation-related disorders. This review focuses on the role specifically played by transglutaminases 4 (TG4) and 2 (TG2) and suggests that both isoenzymes hold a potential to be included in the list of candidates as novel diagnostic biomarkers for the above-cited prostate pathological conditions.

An immunohistochemical identification key for cell types in adult mouse prostatic and urethral tissue sections

Though many methods can be used to identify cell types contained in complex tissues, most require cell disaggregation and destroy information about where cells reside in relation to their microenvironment. Here, we describe a polytomous key for cell type identification in intact sections of adult mouse prostate and prostatic urethra. The key is organized as a decision tree and initiates with one round of immunostaining for nerve, epithelial, fibromuscular/hematolymphoid, or vascular associated cells. Cell identities are recursively eliminated by subsequent staining events until the remaining pool of potential cell types can be distinguished by direct comparison to other cells. We validated our identification key using wild type adult mouse prostate and urethra tissue sections and it currently resolves sixteen distinct cell populations which include three nerve fiber types as well as four epithelial, five fibromuscular/hematolymphoid, one nerve-associated, and three vascular-associated cell types. We demonstrate two uses of this novel identification methodology. We first used the identification key to characterize prostate stromal cell type changes in response to constitutive phosphatidylinositide-3-kinase activation in prostate epithelium. We then used the key to map cell lineages in a new reporter mouse strain driven by Wnt10aem1(cre/ERT2)Amc. The identification key facilitates rigorous and reproducible cell identification in prostate tissue sections and can be expanded to resolve additional cell types as new antibodies and other resources become available.

Changes in mitotic reorientation and Wnt/AR signaling in rat prostate epithelial cells exposed to subchronic testosterone

The aim of the present study was to investigate the changes in mitotic reorientation and relative differential gene expression in rat prostate epithelial cells following long-term exposure to testosterone propionate (TP). Sprague-Dawley rats were randomly divided into two groups as follows: TP group, which received 3.7 mg/kg/day TP for 30 days (n=10); and control group, in which rats were injected with olive oil (n=10). Microscopic analysis of the prostate tissue was performed by immunohistochemical analysis and hematoxylin and eosin staining. Differential gene expression analysis was performed via gene microarray, and a total of five genes (Dkk3, Ran, Fas, Tgm4 and Wnt2) were selected and their expression levels were verified using reverse transcription-polymerase chain reaction. For rats treated with TP, mitosis was significantly reoriented, becoming parallel to the basement membrane. By contrast, in the control group cells mitotic orientation remained perpendicular to the basement membrane. Genes such as Ran and Tgm4 in the androgen receptor (AR) signaling pathway and Wnt2 in the Wnt signaling pathway, were upregulated following treatment with TP. Conversely, the Dkk3 and Fas genes were downregulated following treatment with TP. In conclusion, mitotic orientation of prostate epithelial cells was altered following long-term administration of TP. Wnt and AR signaling pathways influenced cell proliferation and may have participated in the mitotic orientation change.

Characterization of Heterogeneous Prostate Tumors in Targeted Pten Knockout Mice

Previously, we generated a preclinical mouse prostate tumor model based on PSA-Cre driven inactivation of Pten. In this model homogeneous hyperplastic prostates (4-5m) developed at older age (>10m) into tumors. Here, we describe the molecular and histological characterization of the tumors in order to better understand the processes that are associated with prostate tumorigenesis in this targeted mouse Pten knockout model. The morphologies of the tumors that developed were very heterogeneous. Different histopathological growth patterns could be identified, including intraductal carcinoma (IDC), adenocarcinoma and undifferentiated carcinoma, all strongly positive for the epithelial cell marker Cytokeratin (CK), and carcinosarcomas, which were negative for CK. IDC pattern was already detected in prostates of 7-8 month old mice, indicating that it could be a precursor stage. At more than 10 months IDC and carcinosarcoma were most frequently observed. Gene expression profiling discriminated essentially two molecular subtypes, denoted tumor class 1 (TC1) and tumor class 2 (TC2). TC1 tumors were characterized by high expression of epithelial markers like Cytokeratin 8 and E-Cadherin whereas TC2 tumors showed high expression of mesenchyme/stroma markers such as Snail and Fibronectin. These molecular subtypes corresponded with histological growth patterns: where TC1 tumors mainly represented adenocarcinoma/intraductal carcinoma, in TC2 tumors carcinosarcoma was the dominant growth pattern. Further molecular characterization of the prostate tumors revealed an increased expression of genes associated with the inflammatory response. Moreover, functional markers for senescence, proliferation, angiogenesis and apoptosis were higher expressed in tumors compared to hyperplasia. The highest expression of proliferation and angiogenesis markers was detected in TC2 tumors. Our data clearly showed that in the genetically well-defined PSA-Cre;Pten-loxP/loxP prostate tumor model, histopathological, molecular and biological heterogeneity occurred during later stages of tumor development.

Transglutaminase 4 as a prostate autoantigen in male subfertility

Autoimmune polyendocrine syndrome type 1 (APS1), a monogenic disorder caused by AIRE gene mutations, features multiple autoimmune disease components. Infertility is common in both males and females with APS1. Although female infertility can be explained by autoimmune ovarian failure, the mechanisms underlying male infertility have remained poorly understood. We performed a proteome-wide autoantibody screen in APS1 patient sera to assess the autoimmune response against the male reproductive organs. By screening human protein arrays with male and female patient sera and by selecting for gender-imbalanced autoantibody signals, we identified transglutaminase 4 (TGM4) as a male-specific autoantigen. Notably, TGM4 is a prostatic secretory molecule with critical role in male reproduction. TGM4 autoantibodies were detected in most of the adult male APS1 patients but were absent in all the young males. Consecutive serum samples further revealed that TGM4 autoantibodies first presented during pubertal age and subsequent to prostate maturation. We assessed the animal model for APS1, the Aire-deficient mouse, and found spontaneous development of TGM4 autoantibodies specifically in males. Aire-deficient mice failed to present TGM4 in the thymus, consistent with a defect in central tolerance for TGM4. In the mouse, we further link TGM4 immunity with a destructive prostatitis and compromised secretion of TGM4. Collectively, our findings in APS1 patients and Aire-deficient mice reveal prostate autoimmunity as a major manifestation of APS1 with potential role in male subfertility.

βIII-tubulin overexpression is an independent predictor of prostate cancer progression tightly linked to ERG fusion status and PTEN deletion

Evidence suggests that class III β-tubulin (βIII-tubulin) may represent a prognostic and predictive molecular marker in prostate cancer. βIII-Tubulin expression was determined by IHC in 8179 prostate cancer specimens in a TMA format. Results were compared with tumor phenotype, biochemical recurrence, v-ets avian erythroblastosis virus E26 oncogene homolog (ERG) status, and deletions on PTEN, 3p13, 5q21, and 6q15. βIII-Tubulin expression was detectable in 25.6% of 8179 interpretable cancers. High βIII-tubulin expression was strongly associated with both TMPRSS2:ERG rearrangement and ERG expression (P < 0.0001 each). High βIII-tubulin expression was tightly linked to high Gleason grade, advanced pT stage, and early prostate-specific antigen (PSA) recurrence in all cancers (P < 0.0001 each), but also in the subgroups of ERG-negative and ERG-positive cancers. When all tumors were analyzed, the prognostic role of βIII-tubulin expression was independent of Gleason grade, pT stage, pN stage, surgical margin status, and preoperative PSA. Independent prognostic value became even more evident if the analysis was limited to preoperatively available features, such as biopsy specimen Gleason grade, preoperative PSA, cT stage, and βIII-tubulin expression (P < 0.0001 each). βIII-Tubulin expression was associated with PTEN (P < 0.0001) when all tumors were analyzed, but also in the subgroups of ERG-negative and ERG-positive cancers. βIII-Tubulin expression is an independent prognostic parameter. The significant associations with key genomic alterations of prostate cancer, such as TMPRSS2:ERG fusions and PTEN deletions, suggest interactions with several pivotal pathways involved in prostate cancer.

Changes in proteomic profiles in different prostate lobes of male rats throughout growth and development and aging stages of the life span

BACKGROUND

Aging-related changes in important cellular pathways in the prostate may promote a permissive environment for an increased risk for prostatic disease development such as prostate cancer. Our objectives were to examine for such changes, by systematically determining the effects of growth and development and aging on proteomic profiles in different lobes of the rat prostate.

METHODS

Prostate lobes (dorsolateral lobe, DL and ventral lobe, VL) were obtained from male Fisher rats of various ages representing young (4 months), mature (12 months), old (18 months), and very old (24 months). Differentially expressed proteins between age groups in each lobe were identified using a proteomic approach, isobaric Tags for Relative and Absolute Quantitation (iTRAQ). Select changes in the DL and VL were verified by immunoblot analysis.

RESULTS

iTRAQ identified 317 proteins with high confidence. iTRAQ discovered 12 and 6 proteins significantly modulated in response to growth and development in the DL and VL, respectively, and 42 and 29 proteins significantly modulated in response to aging in the DL and VL, respectively. Proteins modulated during growth and development in the DL and VL are involved in a variety of biological processes including cell communication and development, whereas proteins modulated during aging were predominantly related to antioxidant activity and immunity. Immunoblot analysis verified age-related changes for α-1 antitrypsin, annexin A1, hypoxia up-regulated protein 1, and 78 kDa glucose-regulated protein.

CONCLUSIONS

Aging results in changes in numerous prostatic proteins and pathways which are mainly linked to inflammation and may lead to prostatic disease development.

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.

The role of Pax2 in mouse prostate development

BACKGROUND

Loss-of-function of Pax2 results in severe defects of the male reproductive system, and Pax2 expression is detected in mouse prostate lobes and human prostatic cancers. However, the role for Pax2 in prostate development remains poorly understood.

METHODS

The expression of Pax2 was examined by in situ hybridization at various developmental stages. Urogenital sinuses were dissected out at E18.5 from mouse Pax2 mutants and controls, cultured in vitro or grafted under the renal capsule of CD1 nude mice. The expression of prostate developmental regulatory factors was analyzed by semi-quantitative real-time PCR or immuohistochemistry.

RESULTS

Pax2 is expressed in the epithelial cells of prostate buds. Loss-of-function of Pax2 does not affect the initiation of prostatic buds, but in vitro culture assays show that the prostates of Pax2 mutants are hypomorphic and branching is severely disrupted compared to controls. RT-PCR data from Pax2 mutant prostates demonstrate increased expression levels of dorsolateral prostate marker MSMB and ventral prostate marker SBP and dramatically reduced expression levels of anterior prostate marker TGM4.

CONCLUSIONS

Pax2 is essential for mouse prostate development and regulates prostatic ductal growth, branching, and lobe-specific identity. These findings are important for understanding the molecular regulatory mechanisms in prostate development.

Multivariate gene expression analysis reveals functional connectivity changes between normal/tumoral prostates

BACKGROUND

Prostate cancer is a leading cause of death in the male population, therefore, a comprehensive study about the genes and the molecular networks involved in the tumoral prostate process becomes necessary. In order to understand the biological process behind potential biomarkers, we have analyzed a set of 57 cDNA microarrays containing approximately 25,000 genes.

RESULTS

Principal Component Analysis (PCA) combined with the Maximum-entropy Linear Discriminant Analysis (MLDA) were applied in order to identify genes with the most discriminative information between normal and tumoral prostatic tissues. Data analysis was carried out using three different approaches, namely: (i) differences in gene expression levels between normal and tumoral conditions from an univariate point of view; (ii) in a multivariate fashion using MLDA; and (iii) with a dependence network approach. Our results show that malignant transformation in the prostatic tissue is more related to functional connectivity changes in their dependence networks than to differential gene expression. The MYLK, KLK2, KLK3, HAN11, LTF, CSRP1 and TGM4 genes presented significant changes in their functional connectivity between normal and tumoral conditions and were also classified as the top seven most informative genes for the prostate cancer genesis process by our discriminant analysis. Moreover, among the identified genes we found classically known biomarkers and genes which are closely related to tumoral prostate, such as KLK3 and KLK2 and several other potential ones.

CONCLUSION

We have demonstrated that changes in functional connectivity may be implicit in the biological process which renders some genes more informative to discriminate between normal and tumoral conditions. Using the proposed method, namely, MLDA, in order to analyze the multivariate characteristic of genes, it was possible to capture the changes in dependence networks which are related to cell transformation.

Participation of caudal müllerian mesenchyma in prostate development

PURPOSE

The human prostate is a heterogeneous tissue. The cause remains unknown. This riddle has become a major problem to modern medicine because it hinders the understanding of human prostatic diseases. I examined the progress recently made in research on urogenital tract development and pathology.

MATERIALS AND METHODS

A comprehensive review of all relevant literature was performed.

RESULTS

During müllerian duct regression in males the epithelial cells undergo epithelial-mesenchymal transition and enter the mesenchymal compartment. The caudal müllerian mesenchyma participates in the development of the rodent and human prostate under the induction of androgen receptor. It retains responsiveness to estrogenic stimulation. Heterogeneous distributions of different mesenchymas cause heterogeneity. This confirms the hypothesis of Price of homologies between rodent and human prostates.

CONCLUSIONS

Like the gonad gland, the caudal müllerian duct has a sexual dimorphism of differentiation. It would develop into the vagina in females or the prostate in males, which is controlled by androgen receptor. The features of prostatic müllerian mesenchyma might shed light on the etiology of prostatic carcinogenesis.

WNT5A selectively inhibits mouse ventral prostate development

The establishment of prostatic budding patterns occurs early in prostate development but mechanisms responsible for this event are poorly understood. We investigated the role of WNT5A in patterning prostatic buds as they emerge from the fetal mouse urogenital sinus (UGS). Wnt5a mRNA was expressed in UGS mesenchyme during budding and was focally up-regulated as buds emerged from the anterior, dorsolateral, and ventral UGS regions. We observed abnormal UGS morphology and prostatic bud patterns in Wnt5a null male fetuses, demonstrated that prostatic bud number was decreased by recombinant mouse WNT5A protein during wild type UGS morphogenesis in vitro, and showed that ventral prostate development was selectively impaired when these WNT5A-treated UGSs were grafted under under kidney capsules of immunodeficient mice and grown for 28 d. Moreover, a WNT5A inhibitory antibody, added to UGS organ culture media, rescued prostatic budding from inhibition by a ventral prostatic bud inhibitor, 2,3,8,7-tetrachlorodibenzo-p-dioxin, and restored ventral prostate morphogenesis when these tissues were grafted under immunodeficient mouse kidney capsules and grown for 28 d. These results suggest that WNT5A participates in prostatic bud patterning by restricting mouse ventral prostate development.

Secreted frizzled related protein 1 is a paracrine modulator of epithelial branching morphogenesis, proliferation, and secretory gene expression in the prostate

Previous in vitro studies identified secreted frizzled related protein 1 (SFRP1) as a candidate pro-proliferative signal during prostatic development and cancer progression. This study determined the in vivo roles of SFRP1 in the prostate using expression studies in mice and by creating loss- and gain-of-function mouse genetic models. Expression studies using an Sfrp1(lacZ) knock-in allele showed that Sfrp1 is expressed in the developing mesenchyme/stroma of the prostate. Nevertheless, Sfrp1 null prostates exhibited multiple prostatic developmental defects in the epithelium including reduced branching morphogenesis, delayed proliferation, and increased expression of genes encoding prostate-specific secretory proteins. Interestingly, over-expression of SFRP1 in the adult prostates of transgenic mice yielded opposite effects including prolonged epithelial proliferation and decreased expression of genes encoding secretory proteins. These data demonstrated a previously unrecognized role for Sfrp1 as a stromal-to-epithelial paracrine modulator of epithelial growth, branching morphogenesis, and epithelial gene expression. To clarify the mechanism of SFRP1 action in the prostate, the response of WNT signaling pathways to SFRP1 was examined. Forced expression of SFRP1 in prostatic epithelial cells did not alter canonical WNT/beta-catenin signaling or the activation of CamKII. However, forced expression of SFRP1 led to sustained activation of JNK, and inhibition of JNK activity blocked the SFRP1-induced proliferation of prostatic epithelial cells, suggesting that SFRP1 acts through the non-canonical WNT/JNK pathway in the prostate.

Noggin is required for normal lobe patterning and ductal budding in the mouse prostate

Mesenchymal expression of the BMP antagonist NOGGIN during prostate development plays a critical role in pre-natal ventral prostate development and opposes BMP4-mediated inhibition of cell proliferation during postnatal ductal development. Morphologic examination of newborn Noggin-/- male fetuses revealed genitourinary anomalies including cryptorchidism, incomplete separation of the hindgut from the urogenital sinus (UGS), absence of the ventral mesenchymal pad, and a complete loss of ventral prostate (VP) budding. Examination of lobe-specific marker expression in the E14 Noggin-/- UGS rescued by transplantation under the renal capsule of a male nude mouse confirmed a complete loss of VP determination. More modest effects were observed in the other lobes, including decreased number of ductal buds in the dorsal and lateral prostates of newborn Noggin-/- males. BMP4 and BMP7 have been shown to inhibit ductal budding and outgrowth by negatively regulating epithelial cell proliferation. We show here that NOGGIN can neutralize budding inhibition by BMP4 and rescues branching morphogenesis of BMP4-exposed UGS in organ culture and show that the effects of BMP4 and NOGGIN activities converge on P63+ epithelial cells located at nascent duct tips. Together, these studies show that the BMP-NOGGIN axis regulates patterning of the ventral prostate, regulates ductal budding, and controls proliferation of P63+ epithelial cells in the nascent ducts of developing mouse prostate.