Androgen receptor expression of proliferating basal and luminal cells in adult murine ventral prostate

Androgens suppress the sialyltransferases ST3GAL1 and ST3GAL4 and modulate mucin 10 glycosylation in the submandibular gland, related to sex differences in commensal microbiota composition in mice

Sex differences exist in the commensal microbiota that impact on multiple physiological processes in the host. Here, we examined the mechanism by which the sex differences are formed. In addition to the epithelial ductal cell, the acinar cell mass in the submandibular gland was associated with androgen-androgen receptor (AR) signaling. Sex differences in the formation of submandibular mucin 10 (MUC10) were identified using SDS-PAGE. Neuraminidase treatment, which hydrolyzes terminal sialic acid, influenced the mobility shift of MUC10. Androgen-AR signaling negatively regulated ST3 β-galactoside α-2,3-sialyltransferase 1 (St3gal1) and St3gal4 in the submandibular gland. There was a trend and significant sex differences in α-diversity (Shannon, P = .09) and β-diversity (unweighted UniFrac) in oral microbiota composition, respectively. Some female-preferring bacteria including Akkermansia muciniphila can assimilate mucin by degrading terminal sialic acids. Our results indicate that androgen-AR signaling suppresses ST3GAL1 and ST3GAL4, which can influence sex differences in commensal microbiota composition.

The Role of Epigenetic Change in Therapy-Induced Neuroendocrine Prostate Cancer Lineage Plasticity

The androgen receptor (AR) signaling pathway is critical for growth and differentiation of prostate cancer cells. For that reason, androgen deprivation therapy with medical or surgical castration is the principal treatment for metastatic prostate cancer. More recently, new potent AR signaling inhibitors (ARSIs) have been developed. These drugs improve survival for men with metastatic castration-resistant prostate cancer (CRPC), the lethal form of the disease. However, ARSI resistance is nearly universal. One recently appreciated resistance mechanism is lineage plasticity or switch from an AR-driven, luminal differentiation program to an alternate differentiation program. Importantly, lineage plasticity appears to be increasing in incidence in the era of new ARSIs, strongly implicating AR suppression in this process. Lineage plasticity and shift from AR-driven tumors occur on a continuum, ranging from AR-expressing tumors with low AR activity to AR-null tumors that have activation of alternate differentiation programs versus the canonical luminal program found in AR-driven tumors. In many cases, AR loss coincides with the activation of a neuronal program, most commonly exemplified as therapy-induced neuroendocrine prostate cancer (t-NEPC). While genetic events clearly contribute to prostate cancer lineage plasticity, it is also clear that epigenetic events-including chromatin modifications and DNA methylation-play a major role. Many epigenetic factors are now targetable with drugs, establishing the importance of clarifying critical epigenetic factors that promote lineage plasticity. Furthermore, epigenetic marks are readily measurable, demonstrating the importance of clarifying which measurements will help to identify tumors that have undergone or are at risk of undergoing lineage plasticity. In this review, we discuss the role of AR pathway loss and activation of a neuronal differentiation program as key contributors to t-NEPC lineage plasticity. We also discuss new epigenetic therapeutic strategies to reverse lineage plasticity, including those that have recently entered clinical trials.

MALAT1 Fusions and Basal Cells Contribute to Primary Resistance against Androgen Receptor Inhibition in TRAMP Mice

Simple Summary

We deeply characterized a frequently used mouse model of prostate cancer and found cellular and molecular regulators of resistance against antihormonal treatment, such as basal cell function and MALAT1 gene fusions. As these mechanisms also occur in human disease, our findings highlight the importance of this model for human cancer and may be helpful for future research focusing on overcoming antihormonal treatment resistance.

Abstract

Targeting testosterone signaling through androgen deprivation therapy (ADT) or antiandrogen treatment is the standard of care for advanced prostate cancer (PCa). Although the large majority of patients initially respond to ADT and/or androgen receptor (AR) blockade, most patients suffering from advanced PCa will experience disease progression. We sought to investigate drivers of primary resistance against antiandrogen treatment in the TRAMP mouse model, an SV-40 t-antigen driven model exhibiting aggressive variants of prostate cancer, castration resistance, and neuroendocrine differentiation upon antihormonal treatment. We isolated primary tumor cell suspensions from adult male TRAMP mice and subjected them to organoid culture. Basal and non-basal cell populations were characterized by RNA sequencing, Western blotting, and quantitative real-time PCR. Furthermore, effects of androgen withdrawal and enzalutamide treatment were studied. Basal and luminal TRAMP cells exhibited distinct molecular signatures and gave rise to organoids with distinct phenotypes. TRAMP cells exhibited primary resistance against antiandrogen treatment. This was more pronounced in basal cell-derived TRAMP organoids when compared to luminal cell-derived organoids. Furthermore, we found MALAT1 gene fusions to be drivers of antiandrogen resistance in TRAMP mice through regulation of AR. Summarizing, TRAMP tumor cells exhibited primary resistance towards androgen inhibition enhanced through basal cell function and MALAT1 gene fusions.

TDP2 suppresses genomic instability induced by androgens in the epithelial cells of prostate glands

Androgens stimulate the proliferation of epithelial cells in the prostate by activating topoisomerase 2 (TOP2) and regulating the transcription of target genes. TOP2 resolves the entanglement of genomic DNA by transiently generating double‐strand breaks (DSBs), where TOP2 homodimers covalently bind to 5′ DSB ends, called TOP2‐DNA cleavage complexes (TOP2ccs). When TOP2 fails to rejoin TOP2ccs generating stalled TOP2ccs, tyrosyl DNA phosphodiesterase‐2 (TDP2) removes 5′ TOP2 adducts from stalled TOP2ccs prior to the ligation of the DSBs by nonhomologous end joining (NHEJ), the dominant DSB repair pathway in G₀/G₁ phases. We previously showed that estrogens frequently generate stalled TOP2ccs in G₀/G₁ phases. Here, we show that physiological concentrations of androgens induce several DSBs in individual human prostate cancer cells during G₁ phase, and loss of TDP2 causes a five times higher number of androgen‐induced chromosome breaks in mitotic chromosome spreads. Intraperitoneally injected androgens induce several DSBs in individual epithelial cells of the prostate in TDP2‐deficient mice, even at 20 hr postinjection. In conclusion, physiological concentrations of androgens have very strong genotoxicity, most likely by generating stalled TOP2ccs.

New Insights in Prostate Cancer Development and Tumor Therapy: Modulation of Nuclear Receptors and the Specific Role of Liver X Receptors

Prostate cancer (PCa) incidence has been dramatically increasing these last years in westernized countries. Though localized PCa is usually treated by radical prostatectomy, androgen deprivation therapy is preferred in locally advanced disease in combination with chemotherapy. Unfortunately, PCa goes into a castration-resistant state in the vast majority of the cases, leading to questions about the molecular mechanisms involving the steroids and their respective nuclear receptors in this relapse. Interestingly, liver X receptors (LXRα/NR1H3 and LXRβ/NR1H2) have emerged as new actors in prostate physiology, beyond their historical roles of cholesterol sensors. More importantly LXRs have been proposed to be good pharmacological targets in PCa. This rational has been based on numerous experiments performed in PCa cell lines and genetic animal models pointing out that using selective liver X receptor modulators (SLiMs) could actually be a good complementary therapy in patients with a castration resistant PCa. Hence, this review is focused on the interaction among the androgen receptors (AR/NR3C4), estrogen receptors (ERα/NR3A1 and ERβ/NR3A2), and LXRs in prostate homeostasis and their putative pharmacological modulations in parallel to the patients' support.

Impaired serotonin communication during juvenile development in rats diminishes adult sperm quality

Spermatogenesis and steroidogenesis are testicular functions regulated by gonadotrophins as well as other factors, including serotonin. Testicular serotonin acts as an autocrine regulator of testosterone secretion, but studies on its role in spermatogenesis and sperm quality are scarce. Here, we analyzed the effects of intratesticular inhibition of serotonin synthesis on gonadotrophins, testosterone, and sperm quality. Both testicles of 30-day-old rats were injected once with saline solution (SS) or distinct concentrations of p-chloroamphetamine (PCA) (0.03, 0.06, or 0.12 mg). At 65 days of age, rats were euthanized and sperm density, motility, membrane integrity, mitochondrial function, and abnormalities were evaluated in gametes from the vas deferens. Inhibition of synthesis of intratesticular serotonin by PCA diminished the concentrations of testosterone and follicle-stimulating hormone (FSH) but luteinizing hormone (LH) levels were unaltered. Sperm density was not modified in animals injected with the different concentrations of PCA. In contrast, the percentage of sperm with abnormalities increased and the sperm membrane integrity decreased in animals injected at higher PCA concentrations. The functionality of sperm mitochondria in PCA-injected animals decreased only at the highest PCA dose. Our results indicate that testicular serotonin plays a role in testosterone synthesis and in the normal development of sperm, and blocking its effects disrupts the hormonal communication between the testis and hypophysis.

ABBREVIATIONS

SS: saline solution; PCA: p-chloroamphetamine; FSH: follicle-stimulating hormone; LH: luteinizing hormone; TPH: tryptophan hydroxylase; MAO: monoamine oxidase; AC: absolute control group; PI: propidium iodide; FLICA: fluorescence inhibitor of caspase; 3β-HSD: 3β-hydroxysteroid dehydrogenase; 17-KSR: 17-ketosteroid reductase; DHT: 5-dihydrotestosterone.

Role of Stromal Paracrine Signals in Proliferative Diseases of the Aging Human Prostate

Androgens are essential for the development, differentiation, growth, and function of the prostate through epithelial–stromal interactions. However, androgen concentrations in the hypertrophic human prostate decrease significantly with age, suggesting an inverse correlation between androgen levels and proliferative diseases of the aging prostate. In elderly males, age- and/or androgen-related stromal remodeling is spontaneously induced, i.e., increased fibroblast and myofibroblast numbers, but decreased smooth muscle cell numbers in the prostatic stroma. These fibroblasts produce not only growth factors, cytokines, and extracellular matrix proteins, but also microRNAs as stromal paracrine signals that stimulate prostate epithelial cell proliferation. Surgical or chemical castration is the standard systemic therapy for patients with advanced prostate cancer. Androgen deprivation therapy induces temporary remission, but the majority of patients eventually progress to castration-resistant prostate cancer, which is associated with a high mortality rate. Androgen deprivation therapy-induced stromal remodeling may be involved in the development and progression of castration-resistant prostate cancer. In the tumor microenvironment, activated fibroblasts stimulating prostate cancer cell proliferation are called carcinoma-associated fibroblasts. In this review, we summarize the role of stromal paracrine signals in proliferative diseases of the aging human prostate and discuss the potential clinical applications of carcinoma-associated fibroblast-derived exosomal microRNAs as promising biomarkers.

Differential requirements of androgen receptor in luminal progenitors during prostate regeneration and tumor initiation

Master regulatory genes of tissue specification play key roles in stem/progenitor cells and are often important in cancer. In the prostate, androgen receptor (AR) is a master regulator essential for development and tumorigenesis, but its specific functions in prostate stem/progenitor cells have not been elucidated. We have investigated AR function in CARNs (CAstration-Resistant Nkx3.1-expressing cells), a luminal stem/progenitor cell that functions in prostate regeneration. Using genetically--engineered mouse models and novel prostate epithelial cell lines, we find that progenitor properties of CARNs are largely unaffected by AR deletion, apart from decreased proliferation in vivo. Furthermore, AR loss suppresses tumor formation after deletion of the Pten tumor suppressor in CARNs; however, combined Pten deletion and activation of oncogenic Kras in AR-deleted CARNs result in tumors with focal neuroendocrine differentiation. Our findings show that AR modulates specific progenitor properties of CARNs, including their ability to serve as a cell of origin for prostate cancer.

Prostate organogenesis: tissue induction, hormonal regulation and cell type specification

Prostate organogenesis is a complex process that is primarily mediated by the presence of androgens and subsequent mesenchyme-epithelial interactions. The investigation of prostate development is partly driven by its potential relevance to prostate cancer, in particular the apparent re-awakening of key developmental programs that occur during tumorigenesis. However, our current knowledge of the mechanisms that drive prostate organogenesis is far from complete. Here, we provide a comprehensive overview of prostate development, focusing on recent findings regarding sexual dimorphism, bud induction, branching morphogenesis and cellular differentiation.

The Notch-1 receptor in prostate tumorigenesis

The Notch signalling pathway plays a fundamental role in tissue development due to its involvement in cell fate determination and postnatal tissue differentiation. Its capacity to regulate cell growth and development has been linked to the occurrence of several cancers including that of the prostate. The transmembrane receptor Notch-1 of this pathway has been linked to the oncogenic role of Notch signalling in prostate adenocarcinoma. Other studies have suggested a tumour suppressive function for Notch-1. This review focuses on the role of Notch-1 in prostate cancer development and maintenance and relates this to the fundamental role of Notch in normal prostate development. The current understanding of the aberrant Notch signalling characteristic of prostate cancer is discussed, and recent therapeutic advances in this field are presented.

Nfib Regulates Transcriptional Networks That Control the Development of Prostatic Hyperplasia

A functional complex consisting of androgen receptor (AR) and forkhead box A1 (FOXA1) proteins supports prostatic development, differentiation, and disease. In addition, the interaction of FOXA1 with cofactors such as nuclear factor I (NFI) family members modulates AR target gene expression. However, the global role of specific NFI family members has yet to be described in the prostate. In these studies, chromatin immunoprecipitation followed by DNA sequencing in androgen-dependent LNCaP prostate cancer cells demonstrated that 64.3% of NFIB binding sites are associated with AR and FOXA1 binding sites. Interrogation of published data revealed that genes associated with NFIB binding sites are predominantly induced after dihydrotestosterone treatment of LNCaP cells, whereas NFIB knockdown studies demonstrated that loss of NFIB drives increased AR expression and superinduction of a subset of AR target genes. Notably, genes bound by NFIB only are associated with cell division and cell cycle. To define the role of NFIB in vivo, mouse Nfib knockout prostatic tissue was rescued via renal capsule engraftment. Loss of Nfib expression resulted in prostatic hyperplasia, which did not resolve in response to castration, and an expansion of an intermediate cell population in a small subset of grafts. In human benign prostatic hyperplasia, luminal NFIB loss correlated with more severe disease. Finally, some areas of intermediate cell expansion were also associated with NFIB loss. Taken together, these results show a fundamental role for NFIB as a coregulator of AR action in the prostate and in controlling prostatic hyperplasia.

Androgen Receptor-Mediated Growth Suppression of HPr-1AR and PC3-Lenti-AR Prostate Epithelial Cells

The androgen receptor (AR) mediates the developmental, physiologic, and pathologic effects of androgens including 5α-dihydrotestosterone (DHT). However, the mechanisms whereby AR regulates growth suppression and differentiation of luminal epithelial cells in the prostate gland and proliferation of malignant versions of these cells are not well understood, though they are central to prostate development, homeostasis, and neoplasia. Here, we identify androgen-responsive genes that restrain cell cycle progression and proliferation of human prostate epithelial cell lines (HPr-1AR and PC3-Lenti-AR), and we investigate the mechanisms through which AR regulates their expression. DHT inhibited proliferation of HPr-1AR and PC3-Lenti-AR, and cell cycle analysis revealed a prolonged G₁ interval. In the cell cycle, the G₁/S-phase transition is initiated by the activity of cyclin D and cyclin-dependent kinase (CDK) complexes, which relieve growth suppression. In HPr-1AR, cyclin D1/2 and CDK4/6 mRNAs were androgen-repressed, whereas CDK inhibitor, CDKN1A, mRNA was androgen-induced. The regulation of these transcripts was AR-dependent, and involved multiple mechanisms. Similar AR-mediated down-regulation of CDK4/6 mRNAs and up-regulation of CDKN1A mRNA occurred in PC3-Lenti-AR. Further, CDK4/6 overexpression suppressed DHT-inhibited cell cycle progression and proliferation of HPr-1AR and PC3-Lenti-AR, whereas CDKN1A overexpression induced cell cycle arrest. We therefore propose that AR-mediated growth suppression of HPr-1AR involves cyclin D1 mRNA decay, transcriptional repression of cyclin D2 and CDK4/6, and transcriptional activation of CDKN1A, which serve to decrease CDK4/6 activity. AR-mediated inhibition of PC3-Lenti-AR proliferation occurs through a similar mechanism, albeit without down-regulation of cyclin D. Our findings provide insight into AR-mediated regulation of prostate epithelial cell proliferation.

Cell kinetic studies fail to identify sequentially proliferating progenitors as the major source of epithelial renewal in the adult murine prostate

There is evidence that stem cells and their progeny play a role in the development of the prostate. Although stem cells are also considered to give rise to differentiated progeny in the adult prostate epithelium ex vivo, the cohort of adult prostate stem cells in vivo as well as the mechanisms by which the adult prostate epithelium is maintained and regenerated remain highly controversial. We have attempted to resolve this conundrum by performing in vivo tracing of serially replicating cells after the sequential administration of two thymidine analogues to mice. Our results show that, during normal prostate homeostasis, sequentially proliferating cells are detected at a rate that is consistent with a stochastic process. These findings indicate that in vivo, under steady-state conditions, most adult prostate epithelial cells do not represent the progeny of a small number of specialized progenitors that generate sequentially replicating transit-amplifying (TA) cells but are formed by stochastic cell division. Similarly, no rapidly cycling TA cells were detected during regeneration following one cycle of androgen-mediated involution/regeneration of the prostate epithelium. These findings greatly enhance our understanding of the mechanisms regulating prostate epithelial cell renewal and may have significant implications in defining the cell of origin of proliferative prostatic diseases.

Androgens and androgen receptor signaling in prostate tumorigenesis

Androgens and androgen receptor (AR) signaling are necessary for prostate development and homeostasis. AR signaling also drives the growth of nearly all prostate cancer cells. The role of androgens and AR signaling has been well characterized in metastatic prostate cancer, where it has been shown that prostate cancer cells are exquisitely adept at maintaining functional AR signaling to drive cancer growth. As androgens and AR signaling are so intimately involved in prostate development and the proliferation of advanced prostate cancer, it stands to reason that androgens and AR are also involved in prostate cancer initiation and the early stages of cancer growth, yet little is known of this process. In this review, we summarize the current state of knowledge concerning the role of androgens and AR signaling in prostate tissue, from development to metastatic, castration-resistant prostate cancer, and use that information to suggest potential roles for androgens and AR in prostate cancer initiation.

Transcription factors involved in prostate gland adaptation to androgen deprivation

Androgens regulate prostate physiology, and exert their effects through the androgen receptor. We hypothesized that androgen deprivation needs additional transcription factors to orchestrate the changes taking place in the gland after castration and for the adaptation of the epithelial cells to the androgen-deprived environment, ultimately contributing to the origin of castration-resistant prostate cancer. This study was undertaken to identify transcription factors that regulate gene expression after androgen deprivation by castration (Cas). For the sake of comparison, we extended the analysis to the effects of administration of a high dose of 17β-estradiol (E2) and a combination of both (Cas+E2). We approached this by (i) identifying gene expression profiles and enrichment terms, and by searching for transcription factors in the derived regulatory pathways; and (ii) by determining the density of putative transcription factor binding sites in the proximal promoter of the 10 most up- or down-regulated genes in each experimental group in comparison to the controls Gapdh and Tbp7. Filtering and validation confirmed the expression and localized EVI1 (Mecom), NFY, ELK1, GATA2, MYBL1, MYBL2, and NFkB family members (NFkB1, NFkB2, REL, RELA and RELB) in the epithelial and/or stromal cells. These transcription factors represent major regulators of epithelial cell survival and immaturity as well as an adaptation of the gland as an immune barrier in the absence of functional stimulation by androgens. Elk1 was expressed in smooth muscle cells and was up-regulated after day 4. Evi1 and Nfy genes are expressed in both epithelium and stroma, but were apparently not affected by androgen deprivation.

Prostate progenitor cells proliferate in response to castration

Androgen-deprivation is a mainstay of therapy for advanced prostate cancer but tumor regression is usually incomplete and temporary because of androgen-independent cells in the tumor. It has been speculated that these tumor cells resemble the stem/progenitor cells of the normal prostate. The purpose of this study was to examine the response of slow-cycling progenitor cells in the adult mouse prostate to castration. Proliferating cells in the E16 urogenital sinus were pulse labeled by BrdU administration or by doxycycline-controlled labeling of the histone-H2B GFP mouse. A small population of labeled epithelial cells in the adult prostate localized at the junction of the prostatic ducts and urethra. Fluorescence-activated cell sorting (FACS) showed that GFP label-retaining cells were enriched for cells co-expressing stem cell markers Sca-1, CD133, CD44 and CD117 (4- marker cells; 60-fold enrichment). FACS showed, additionally, that 4-marker cells were androgen receptor positive. Castration induced proliferation and dispersal of E16 labeled cells into more distal ductal segments. When naïve adult mice were administered BrdU daily for 2 weeks after castration, 16% of 4-marker cells exhibited BrdU label in contrast to only 6% of all epithelial cells (P<0.01). In sham-castrated controls less than 4% of 4-marker cells were BrdU labeled (P<0.01). The unexpected and admittedly counter-intuitive finding that castration induced progenitor cell proliferation suggests that androgen deprivation therapy in men with advanced prostate cancer could not only exert pleiotrophic effects on tumor sub-populations but may induce inadvertent expansion of tumor stem cells.

Activation of FGF2-FGFR signaling in the castrated mouse prostate stimulates the proliferation of basal epithelial cells

The prostate gland is unique in that it undergoes rapid regression following castration but regenerates completely once androgens are replaced. Residual ductal components play an important role in the regeneration of a fully functional prostate. In this study, to examine how androgen status affects prostate structure and components, we conducted histopathological studies of the involuted and regenerated mouse dorsolateral prostate (DLP). In the castrated mouse DLP, the number of luminal epithelial cells decreased in a time-dependent manner. On Day 14 postandrogen replacement, the number of luminal epithelial cells was completely restored to the baseline level. In contrast, the number of basal epithelial cells gradually increased in the castrated mouse prostate. The Ki67-labeling index of prostate basal epithelial cells was significantly increased after castration. The number of basal epithelial cells decreased to baseline after androgen replacement. After castration, mRNA expression levels of specific growth factors, such as Fgf2, Fgf7, Hgf, Tgfa, and Tgfb, were relatively abundant in whole mouse DLPs. In organ culture experiments, basal epithelial proliferation was recapitulated in the absence of dihydrotestosterone (DHT). The proliferation of basal epithelial cells in the absence of DHT was suppressed by treatment with an FGF receptor inhibitor (PD173074). Moreover, FGF2 treatment directly stimulated the proliferation of basal epithelial cells. Taken together, these data indicated that the FGF2-FGF receptor signal cascade in the prostate gland may be one of the pathways stimulating the proliferation of basal epithelial cells in the absence of androgens.

Androgen receptor (AR) differential roles in hormone-related tumors including prostate, bladder, kidney, lung, breast and liver

The androgen receptor (AR) is expressed in many cell types and the androgen/AR signaling has been found to have important roles in modulating tumorigenesis and metastasis in several cancers including prostate, bladder, kidney, lung, breast and liver. However, whether AR has differential roles in the individual cells within these tumors that contain a variety of cell types remains unclear. Generation of AR knockout (ARKO) mouse models with deletion of AR in selective cells within tumors indeed have uncovered many unique AR roles in the individual cell types during cancer development and progression. This review will discuss the results obtained from various ARKO mice and different human cell lines with special attention to the cell type- and tissue-specific ARKO models. The understanding of various results showing the AR indeed has distinct and contrasting roles in each cell type within many hormone-related tumors (as stimulator in bladder, kidney and lung metastases vs as suppressor in prostate and liver metastases) may eventually help us to develop better therapeutic approaches by targeting the AR or its downstream signaling in individual cell types to better battle these hormone-related tumors in different stages.

Androgen receptors in hormone-dependent and castration-resistant prostate cancer

In the United States, prostate cancer (PCa) is the most commonly diagnosed non-cutaneous cancer in males and the second leading cause of cancer-related death for men. The prostate is an androgen-dependent organ and PCa is an androgen-dependent disease. Androgen action is mediated by the androgen receptor (AR), a hormone activated transcription factor. The primary treatment for metastatic PCa is androgen deprivation therapy (ADT). For the most part, tumors respond to ADT, but most become resistant to therapy within two years. There is persuasive evidence that castration resistant (also termed castration recurrent) PCa (CRPC) remains AR dependent. Recent studies have shown that there are numerous factors that contribute to AR reactivation despite castrate serum levels of androgens. These include changes in AR expression and structure through gene amplification, mutation, and alternative splicing. Changes in steroid metabolism, cell signaling, and coregulator proteins are also important contributors to AR reactivation in CRPC. Most AR targeted therapies have been directed at the hormone binding domain. The finding that constitutively active AR splice variants that lack the hormone binding domain are frequently expressed in CRPC highlights the need to develop therapies that target other portions of AR. In this review, the role of AR in normal prostate, in PCa, and particularly the mechanisms for its reactivation subsequent to ADT are summarized. In addition, recent clinical trials and novel approaches to target AR are discussed.

Testosterone deficiency induces markedly decreased serum triglycerides, increased small dense LDL, and hepatic steatosis mediated by dysregulation of lipid assembly and secretion in mice fed a high-fat diet

OBJECTIVE

Although low serum testosterone (T) is associated with metabolic disorders, the mechanism of this association is unclear. The objective of the present study was to investigate the combined effects of T deficiency and a high-fat diet (HFD) on hepatic lipid homeostasis in mice.

MATERIALS/METHODS

Orchiectomized (ORX) mice and sham-operated (SHAM) mice were randomly divided into five groups: SHAM mice fed a standard diet (SD), SHAM mice fed HFD, ORX mice fed SD, ORX mice fed HFD, and ORX mice fed HFD with T supplementation. After 4weeks of treatment, we investigated the synthesis and secretion of lipids in the liver and detailed serum lipoprotein profiles in each group.

RESULTS

ORX mice fed HFD showed increased hepatic steatosis, markedly decreased serum triglyceride (TG) and TG-VLDL content, and increased serum very small-LDL content. Gene expression analysis revealed that ORX mice fed HFD showed significantly decreased expression of microsomal triglyceride transfer protein, lipin-1, peroxisome proliferator-activated receptor (PPAR)-α and PPAR-γ coactivator 1-α, and significantly increased sterol regulatory element-binding protein-1, diacylglycerol acyltransferase-2 and fatty acid synthase. Reduction of hepatic AMPK phosphorylation was observed in ORX mice fed HFD. These perturbations in ORX mice fed HFD were normalized to the levels of SHAM mice fed HFD by T supplementation.

CONCLUSION

T deficiency is associated with failure of lipid homeostasis mediated by altered expression of genes involved in hepatic assembly and secretion of lipids.

Identification and Characterization of an Antigen Recognized by Monoclonal Antibody TRA 54 in Mouse Epididymis and Vas Deferens

Spermatozoa in testicular fluid are known to have weak forward motility and cannot fertilize eggs. The epididymis is known to participate in sperm maturation leading fertilization, but little is known about the specific epididymal molecules involved in the modification of sperm. In this study, we characterized the new pattern of expression of an antigen previously identified in testicular germ cells by monoclonal antibody (mAb) TRA 54. This antigen is expressed in epididymal and vas deferens epithelial cells in mice older than 24 days but not during younger developmental stages. Evaluation by immunohistochemistry shows that antigen expression is limited to the cytoplasm of a specific cell population of epithelia along the epididymal regions and vas deferens of adult mice. The molecules synthesized and released by epididymal and vas deferens epithelia into their lumen seem to bind on spermatozoa moving down through the ducts. Immunoblot analysis showed that the molecules recognized by mAb TRA 54 in testis and epididymis were similar and share a common epitope involving carbohydrate domains. Interestingly, the antigens identified in epididymal and vas deferens epithelial cells were expressed independently of testicular germ cells and are produced in an androgen-dependent manner. Finally, the molecules recognized by mAb TRA 54 seem to play an important role in spermatogenesis, as well as in epididymal function related to spermatozoa maturation and ability to fertilize.

Testosterone effect on the expression of genes that mediate testosterone metabolism and genes that mediate the effect of those metabolites on the prostate

AIMS

The aim of this study was to investigate the effect of testosterone treatment on the proliferation index and the mRNA expression levels of 5α-reductase, CYP7B1, androgen receptor (AR), and estrogen receptor β (ΕRβ) in the canine prostate.

MAIN METHODS

Immature dogs were treated with testosterone for one month, after which prostate gland growth was assessed by comparing the proliferation index in prostates from testosterone-treated dogs with that of untreated control dogs. The relative mRNA expression levels of the aforementioned genes in the prostate glands of testosterone-treated and untreated dogs were determined by real time PCR.

KEY FINDINGS

Testosterone treatment induced a highly significant reduction in proliferation index in prostate gland. This inhibition of prostate gland growth was associated with differential mRNA expression of 5α-reductase, CYP7B1, AR, and ΕRβ by the prostate gland of testosterone-treated dogs, as compared to that of untreated dogs. While the expression levels of 5α-reductase and CYP7B1 mRNA were significantly down-regulated by testosterone treatment, the expression level of ER-β mRNA was highly up-regulated. In contrast, AR mRNA expression was not significantly altered.

SIGNIFICANCE

Prostate gland proliferation appeared to be associated with the expression levels of genes that encode proteins that control intra-prostatic levels of testosterone metabolites and their respective receptors. Testosterone treatment may regulate gene expression in the prostate to generate a phenotype that suppresses growth-promoting signaling through AR and enhances anti-proliferative signaling through ERβ. Therefore, targeting disturbances of this genetic machinery in benign prostate hyperplasia and prostate cancer is of a therapeutic potential.

Altered differentiation and proliferation of prostate epithelium in mice lacking the androgen receptor cofactor p44/WDR77

Although it has been observed that various cofactors modulate activity of the androgen receptor (AR), the specific relationship between AR cofactors and prostate development and functions has not been well studied. To determine whether AR cofactor p44/WDR77 is important in prostate growth and development, we examined prostate architecture in p44/WDR77-null mice and wild-type (WT) littermates. Prostate glands from p44/WDR77-deficient animals were not only smaller than those from WT mice but also had fewer branches and terminal duct tips and were deficient in production of secretory proteins. The p44/WDR77-null prostate tissue was less differentiated and hyperproliferative relative to WT littermates. In addition, the altered expression of androgen-regulated genes was observed in the p44/WDR77-null prostate. Thus, these results suggest that the AR cofactor p44/WDR77 plays important roles in prostate growth and differentiation by modulating AR-target gene expression.

Differential androgen receptor signals in different cells explain why androgen-deprivation therapy of prostate cancer fails

Prostate cancer is one of the major causes of cancer-related death in the western world. Androgen-deprivation therapy (ADT) for the suppression of androgens binding to the androgen receptor (AR) has been the norm of prostate cancer treatment. Despite early success to suppress prostate tumor growth, ADT eventually fails leading to recurrent tumor growth in a hormone-refractory manner, even though AR remains to function in hormone-refractory prostate cancer. Interestingly, some prostate cancer survivors who received androgen replacement therapy had improved quality of life without adverse effect on their cancer progression. These contrasting clinical data suggest that differential androgen/AR signals in individual cells of prostate tumors can exist in the same or different patients, and may be used to explain why ADT of prostate cancer fails. Such a hypothesis is supported by the results obtained from transgenic mice with selective knockout of AR in prostatic stromal vs epithelial cells and orthotopic transplants of various human prostate cancer cell lines with AR over-expression or knockout. These studies concluded that AR functions as a stimulator for prostate cancer proliferation and metastasis in stromal cells, as a survival factor of prostatic cancer epithelial luminal cells, and as a suppressor for prostate cancer basal intermediate cell growth and metastasis. These dual yet opposite functions of the stromal and epithelial AR may challenge the current ADT to battle prostate cancer and should be taken into consideration when developing new AR-targeting therapies in selective prostate cancer cells.

E-cadherin-mediated survival of androgen-receptor-expressing secretory prostate epithelial cells derived from a stratified in vitro differentiation model

The androgen receptor (AR) is expressed in differentiated secretory prostate epithelial cells in vivo. However, in the human prostate, it is unclear whether androgens directly promote the survival of secretory cells, or whether secretory cells survive through androgen-dependent signals from the prostate stroma. Biochemical and mechanistic studies have been hampered by inadequate cell-culture models. In particular, large-scale differentiation of prostate epithelial cells in culture has been difficult to achieve. Here, we describe the development of a differentiation system that is amenable to functional and biochemical analysis and its application to deciphering the survival pathways in differentiated AR-expressing epithelial cells. Confluent prostate epithelial cell cultures were treated with keratinocyte growth factor (KGF) and dihydrotestosterone. After 2 weeks, a suprabasal cell layer was formed in which cells no longer expressed alpha2, alpha3, alpha6, alphav, beta1 or beta4 integrins or p63, K5, K14, EGFR, FGFR2IIIb or Bcl-2, but instead expressed AR and androgen-induced differentiation markers, including K18, K19, TMPRSS2, Nkx3.1, PMSA, KLK2 and secreted prostate-specific antigen (PSA). Differentiated prostate cell survival depended on E-cadherin and PI3K, but not KGF, androgen, AR or MAPK. Thus survival of differentiated prostate epithelial cells is mediated by cell-cell adhesion, and not through androgen activity or prostate stroma-derived KGF.

Basal epithelial stem cells are efficient targets for prostate cancer initiation

Prevailing theories suggest that luminal cells are the origin of prostate cancer because it is histologically defined by basal cell loss and malignant luminal cell expansion. We introduced a series of genetic alterations into prospectively identified populations of murine basal/stem and luminal cells in an in vivo prostate regeneration assay. Stromal induction of FGF signaling, increased expression of the ETS family transcription factor ERG1, and constitutive activation of PI3K signaling were evaluated. Combination of activated PI3K signaling and heightened androgen receptor signaling, which is associated with disease progression to androgen independence, was also performed. Even though luminal cells fail to respond, basal/stem cells demonstrate efficient capacity for cancer initiation and can produce luminal-like disease characteristic of human prostate cancer in multiple models. This finding provides evidence in support of basal epithelial stem cells as one target cell for prostate cancer initiation and demonstrates the propensity of primitive cells for tumorigenesis.

The SWI/SNF ATPase Brm is a gatekeeper of proliferative control in prostate cancer

Factors that drive prostate cancer progression remain poorly defined, thus hindering the development of new therapeutic strategies. Disseminated tumors are treated through regimens that ablate androgen signaling, as prostate cancer cells require androgen for growth and survival. However, recurrent, incurable tumors that have bypassed the androgen requirement ultimately arise. This study reveals that the Brm ATPase, a component of selected SWI/SNF complexes, has significant antiproliferative functions in the prostate that protect against these transitions. First, we show that targeted ablation of Brm is causative for the development of prostatic hyperplasia in mice. Second, in vivo challenge revealed that Brm-/- epithelia acquire the capacity for lobe-specific, castration-resistant cellular proliferation. Third, investigation of human specimens revealed that Brm mRNA and protein levels are attenuated in prostate cancer. Fourth, Brm down-regulation was associated with an increased proliferative index, consistent with the mouse model. Lastly, gene expression profiling showed that Brm loss alters factors upstream of E2F1; this was confirmed in murine models, wherein Brm loss induced E2F1 deregulation in a tissue-specific manner. Combined, these data identify Brm as a major effector of serum androgen-induced proliferation in the prostate that is disrupted in human disease, and indicate that loss of Brm confers a proliferative advantage in prostate cancer.

Cancer stem cell markers in common cancers - therapeutic implications

Rapid advances in the cancer stem cell (CSC) field have provided cause for optimism for the development of more reliable cancer therapies in the future. Strategies aimed at efficient targeting of CSCs are becoming important for monitoring the progress of cancer therapy and for evaluating new therapeutic approaches. Here, we characterize and compare the specific markers that have been found to be present on stem cells, cancer cells and CSCs in selected tissues (colon, breast, liver, pancreas and prostate). We then discuss future directions of this intriguing new research field in the context of new diagnostic and therapeutic opportunities.

Testosterone decreased urinary-frequency in nNOS-deficient mice

To observe the effect of testosterone on the frequency of urination in mice lacking neuronal nitric oxide synthase (nNOS(-/-)), we compared the urination patterns between unanaesthetized male wild-type (n = 27) and nNOS(-/-) mice (n = 50) with or without testosterone treatment. Compared with wild-type mice, nNOS(-/-) mice showed a greater frequency of urination during a 24-h observation period (3.0 vs. 5.4 times/day, p < 0.0001) without any significant difference in the total voided volume or the functional voiding capacity. While testosterone treatment did not affect the urination patterns in wild-type, it decreased the daytime frequency of urination (5.4 vs. 3.7 times, p = 0.0198) and the nighttime urination (4.4 vs. 2.9 times, p = 0.039) in nNOS(-/-) mice. The nNOS(-/-) mice can be a useful animal model for urinary frequency. Testosterone improved the functional abnormalities in the voiding of nNOS(-/-) mice.

The role of androgen in determining differentiation and regulation of androgen receptor expression in the human prostatic epithelium transient amplifying population

Abnormal differentiation in epithelial stem cells or their immediate proliferative progeny, the transiently amplifying population (TAP), may explain malignant pathogenesis in the human prostate. These models are of particular importance as differing sensitivities to androgen among epithelial cell subpopulations during differentiation are recognised and may account for progression to androgen independent prostate cancer. Androgens are crucial in driving terminal differentiation and their indirect effects via growth factors from adjacent androgen responsive stroma are becoming better characterised. However, direct effects of androgen on immature cells in the context of a prostate stem cell model have not been investigated in detail and are studied in this work. In alpha2beta1hi stem cell enriched basal cells, androgen analogue R1881 directly promoted differentiation by the induction of differentiation-specific markers CK18, androgen receptor (AR), PSA and PAP. Furthermore, treatment with androgen down-regulated alpha2beta1 integrin expression, which is implicated in the maintenance of the immature basal cell phenotype. The alpha2beta1hi cells were previously demonstrated to lack AR expression and the direct effects of androgen were confirmed by inhibition using the anti-androgen bicalutamide. AR protein expression in alpha2beta1hi cells became detectable when its degradation was repressed by the proteosomal inhibitor MG132. Stratifying the alpha2beta1hi cells into stem (CD133(+)) and transient amplifying population (TAP) (CD133(-)) subpopulations, AR mRNA expression was found to be restricted to the CD133(-) (TAP) cells. The presence of a functional AR in the TAP, an androgen independent subpopulation for survival, may have particular clinical significance in hormone resistant prostate cancer, where both the selection of immature cells and functioning AR regulated pathways are involved.

Increased prostate cell proliferation and loss of cell differentiation in mice lacking prostate epithelial androgen receptor

Developmental studies of the prostate have established that ductal morphogenesis, epithelial cytodifferentiation, and proliferation/apoptosis are regulated by androgens acting through stromal androgen receptor (AR). Here, we found mice lacking epithelial AR within the mature prostate (pes-ARKO) developed prostate tissue that was less differentiated and hyperproliferative relative to WT littermates. Epithelial AR protein was significantly decreased in 6-week-old mice and was nearly absent by >/=24 weeks of age. Circulating levels of testosterone, external genitalia, or fertility were not altered in pes-ARKO mice. A significant (P < 0.05) increase in bromo-deoxyuridine-positive epithelia was observed in ventral and dorsal-lateral prostates of pes-ARKO mice at 24 weeks of age. Less differentiation was observed as indicated by decreased epithelial height and glandular infolding through 24 weeks of age, differentiation markers probasin, PSP-94, and Nkx3.1 were sig nificantly decreased, and epithelial sloughing and luminal cell apoptosis increased from 6 to 32 weeks of age in pes-ARKO mice. Gain of function occurred by crossing pes-ARKO to the T857A transgenic mice containing constitutively activated AR. In T857A-pes-ARKO mice prostates were of normal size, contained glandular infoldings, and maintained high secretory epithelium, and the appropriate prostatic epithelial proliferation was restored. Collectively, these results suggest that prostatic epithelial AR plays an important role in the homeostasis of the prostate gland. These data support the hypothesis that epithelial AR controls prostate growth by suppressing epithelial proliferation in the mature gland.

Interaction of testosterone with inhibin alpha and betaA subunits to regulate prostate gland growth

Testosterone regulation of prostate gland growth has been shown to involve reciprocal interaction with inhibin and activin. This study was therefore conducted to correlate the effect of testosterone on prostate gland proliferation and differentiation with the level of expression of inhibin alpha and betaA subunits. Immature dogs were treated with testosterone for 0, 3, 7, and 14 days and prostate gland growth was assessed by morphological and immunohistological localization of differentiation and proliferation markers. The results showed that testosterone treatment resulted in an initial significant increase in PCNA proliferation index by days 3 and 7, followed by a significant decrease by day 14 post-treatment. Interestingly, the decrease of cell proliferation was associated with structural and biochemical changes characteristic of glandular and stromal differentiation of the prostate gland. These changes include progressive glandular ductal canalization and inter-ductal stroma differentiation which were apparent from a gradual shift from vimentin expression to vimentin and alpha-actin expression. Testosterone also had a differential effect on inhibin alpha and beta subunits. Although testosterone treatment resulted in significant and constant inhibition of alpha subunit mRNA expression, it resulted in a significant increase of betaA mRNA expression by day 3, followed by a decrease by days 7 and 14. These results indicated that testosterone acts first to drive proliferation of undifferentiated prostatic cells and then to maintain a low proliferation turnover of differentiated cells. Because it has been shown that activin is an antagonistic regulator of androgens, the attenuated stimulatory effect of testosterone on cell proliferation by day 14 might be mediated, at least in part, by interplay between testosterone and activin.

Testosterone effect on immature prostate gland development associated with suppression of transforming growth factor-β

The aim of this study was to evaluate the effect of testosterone treatment on the pattern of prostate cell proliferation and differentiation and their correlation with the expression of transforming growth factor-beta (TGF-beta). Prostate gland development was compared in intact immature dogs with one-month testosterone-treated immature dogs. Testosterone treatment resulted in a tenfold increase in prostate gland weight compared to untreated dogs, with a typical organization of the gland into a structure similar to that observed in mature dogs. The narrow acini which contain flat basal cells in immature glands were transformed into tubuloacinar structures containing columnar secretory cells and basal cells. The stromal compartments showed an increase in the muscular component as evidenced by the high reactivity to alpha-actin with no remarkable changes in the vimentin expression. In addition, testosterone treatment induced a significant reduction in the proliferation capacity of stromal cells but with no noticeable changes in the proliferation pattern of epithelial cells. These changes in the prostate are associated with a twofold decrease in TGF-beta mRNA expression as assessed by Real-Time PCR. However, the immunolocalization of TGF-beta was shifted slightly from the epithelial cells in untreated animals to the stromal cells of treated animals. Based on these results it appears that testosterone acts to coordinate prostatic cell proliferation and differentiation and direct their organization into a structure resembling that of the mature gland. The testosterone regulation of the prostate gland appears to involve the regulation of TGF-beta gene expression.

Expression and role of Foxa proteins in prostate cancer

The molecular mechanism(s) for prostate cancer progression to androgen independence are poorly understood. We have recently shown that Foxa1 and Foxa2 proteins are differentially expressed in epithelial cells during murine prostate development, growth, and adult function. Currently, the role of Foxa proteins in prostate cancer development and progression is unknown. Foxa protein expression was investigated in the LPB-Tag LADY mouse prostate cancer models, in human prostate cancer specimens, and various prostate cancer cell lines using Western blot and immunostaining analysis. In vitro transient transfection, studies were performed to investigate Foxa/prostate-specific gene regulation. Foxa1 was strongly expressed in areas of prostatic intraepithelial neoplasia (PIN) in both the androgen dependent 12T-7f and in the metastatic, androgen independent 12T-10 LADY models. Prominent Foxa1 and Foxa2 expression was observed in 12T-10 invasive undifferentiated neuroendocrine carcinomas, in the hormone independent and metastasizing 12T-10 derived, NE-10 allograft tumors, and in all metastatic lesions isolated from 12T-10 mice. Foxa1 protein expression was always observed in human prostate carcinomas, regardless of Gleason grade score, while Foxa2 was only detected in neuroendocrine small cell carcinomas and in some high Gleason score adenocarcinomas. Foxa proteins were also differentially expressed in three prostate cancer cell lines. Importantly, in vitro functional assays demonstrated that Foxa2 could activate androgen-dependent prostate-specific genes in an androgen receptor and ligand-independent manner. These results suggest that Foxa proteins are important in prostate carcinogenesis. In particular, Foxa2 may be involved in progression of prostate cancer to androgen independence. As such, Foxa proteins may represent novel targets for therapeutic intervention.

Stem/progenitor and intermediate cell types and the origin of human prostate cancer

Theories of cell lineage in human prostatic epithelium, based on protein expression, propose that basal and luminal cells: 1) are either independently capable of self-renewal or 2) arise from stem cells expressing a full spectrum of proteins (p63, cytokeratins CK5/14, CK8/18, and glutathione-S-transferase-pi [GST-pi]) similar to cells of the embryonic urogenital sinus (UGS). Such embryonic-like stem cells are thought to give rise to mature basal cells and secretory luminal cells. By single cell cloning of an immortalized, normal human prostate-derived, non-tumorigenic RWPE-1 cell line, we isolated and characterized two epithelial cell types, WPE-stem and WPE-int. WPE-stem cells show: i) strong, sixfold greater nuclear expression of p63; ii) nearly twofold greater expression of CK14; iii) threefold less CK18, and iv) low androgen receptor (AR) expression as compared with WPE-int cells. WPE-stem cells are androgen-independent for growth and survival. WPE-int cells express very low p63 and CK5/14, and high CK18. WPE-int cells are androgen-independent for growth and survival but are highly responsive as shown by androgen induction of AR and prostate specific antigen (PSA). Compared with WPE-int cells, WPE-stem cells are smaller and show more rapid growth. WPE-stem cells can grow in an anchorage-independent manner in agar with 4.5-fold greater cloning efficiency and as free floating "prostaspheres" in liquid medium; and express over 40-fold higher matrix metalloproteinase-2 activity. These results indicate that WPE-stem cells express several features characteristic of stem/progenitor cells present in the UGS and in adult prostatic epithelium. In contrast, WPE-int cells have an intermediate, committed phenotype on the pathway to luminal cell differentiation. We propose that in normal prostatic epithelium, cells exist at many stages in a continuum of differentiation progressing from stem cells to definitive basal and luminal cells. Establishment and characterization of clones of human prostatic epithelial cells provide novel models for determining cell lineages, the origin of prostate cancer, and for developing new strategies for tumor prevention and treatment.

Castration induced changes in dog prostate gland associated with diminished activin and activin receptor expression

This study was conducted to evaluate the effect of androgen ablation on dog prostate gland structure and the proliferation capacity of the prostatic cells and their association with the expression of Activin A and Activin RIIA receptor. The effect of androgen on the prostate gland was compared in intact and castrated dogs after one and two weeks. Specific primary antibodies were used to immunolocalize activin-A, activin receptor type II A and the proliferation marker (PCNA). The results showed that the glandular acini of the prostate gland of intact dogs are lined by tall columnar secretory cells and less abundant flattened basal cells and surrounded by a thin fibromuscular tissue. The cytoplasm of the glandular cells exhibited an intense immunoreaction for activin A and activin RIIA receptor while basal cells expressed PCNA. Castration induced a remarkable atrophy of the prostatic acini associated with a progressive loss of secretory epithelial cells, which showed a dramatic decrease to complete disappearance of Activin A and Activin RIIA receptor immunoreactions. The remaining cells of the atrophied acini continue to express PCNA and the inter-acinar fibromuscular tissue showed a remarkable increase in its mass and are induced to express PCNA. These results indicated that androgen is required for the survival of epithelial cells and to maintain growth-quiescent fibromuscular cells, while basal cell proliferation is androgen independent. The changes in the Activin A and Activin RIIA receptor localization and their association with the dynamic pattern of prostate gland regression after castration suggested that Activin A and Activin RIIA receptor expression are androgen dependent.

Expression of Foxa transcription factors in the developing and adult murine prostate

BACKGROUND

The Foxa family (a1, a2, and a3) of proteins are transcription factors that are central to endodermal development. Recently, Foxa1 has been shown to regulate the transcription of several murine and human prostate specific genes involved in differentiated function by interacting with DNA promoter sequences and androgen receptors. Currently, the developmental expression pattern of Foxa proteins in the murine prostate is unknown.

METHODS

Male CD-1 mice (embryonic, prepubertal, pubertal, and adult) were used for immunohistochemical analysis of Foxa1, a2, and a3. Immunofluorescence was also performed for androgen receptor and cytokeratin 14 expression. Prostate tissue from pre-pubertal, pubertal, and adult mice were analyzed by Western blot and RT-PCR analysis for Foxa1, a2, and a3 expression.

RESULTS

Strong Foxa1 immunoreactivity was observed in epithelial cells throughout prostate development, growth, and adult differentiation. Prominent Foxa2 protein expression was only observed in the early stages of prostate development and was exclusively localized to epithelial cells of the forming buds. RT-PCR analysis identified low Foxa2 mRNA expression levels in the ventral and dorsolateral lobes of the adult prostate, with Foxa2 epithelial cell expression being localized to periurethral regions of the murine adult prostatic complex. Foxa3 expression was not observed in the murine prostate.

CONCLUSIONS

Foxa proteins represent epithelial cell markers in the murine prostate gland. The early expression of Foxa1 and a2 proteins in prostate formation suggests that these proteins play an important role in normal prostate development, in addition to differentiated secretory function.

Effect of androgen ablation on prostatic cell differentiation in dogs

This study was conducted to gain further insight into the role of androgen in maintaining a balanced prostate gland growth in dogs. Effects of castration on prostatic cell were assessed by comparing the expression level of high molecular weight cytokeratin (HMW), alpha-actin, and vimentin in intact and castrated dogs. Mature dogs were castrated while they were under general anesthesia and were killed after 1 month. Mature prostate gland structures from intact dogs are characterized by the presence of differentiated columnar secretary epithelial cells and progenitor basal cells that are located within acini and ducts embedded in a thin fibromuscular tissue. Basal cells were distinguished from secretory epithelial cells by HMW cytokeratin immunostaining, which is expressed specifically by basal cells but not by epithelial cells. Castration-induced secretory epithelial cell death, leave the basal cells intact to form a continuous layer lining the atrophied acini. However, the survived basal cells lost their capacity to differentiate to secretory epithelial cells. In addition, androgen ablation induced remarkable reorganization of the cellular components of the fibromuscular compartment. In intact dogs, this compartment of prostate gland is composed mainly of differentiated smooth muscles and scattered mesenchymal muscles as reflected by the high and low actin and vimentin expressions, respectively. Castration for 1 month induced a progressive shift toward mesenchymal cells, which appeared to occupy most of the fibromuscular compartment. Based on these findings, it appears that androgen acts to maintain a steady state of prostate gland by driving the differentiation of prostatic cells and by maintaining its fully differentiated state.

Selective capture of prostatic basal cells and secretory epithelial cells for proteomic and genomic analysis☆

Basal cells play an undefined role in signaling the growth and differentiation of normal secretory epithelial cells in the human prostate. Because basal cells disappear during malignant transformation, we hypothesize that loss of basal cell function may have a permissive role in progression of prostate intraepithelial neoplasia into invasive carcinoma. We describe an immuno-laser capture microdissection approach to selectively capture basal cells. Using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry, we identified several protein candidates selectively expressed in microdissected basal cells. We also demonstrate that the RNA derived form this technique is an excellent source for gene-array studies. Thus, we provide evidence that proteomic and microgenomic techniques can be successfully applied to investigate the expression profiles of basal and secretory cells after immuno-capture.

Expression study of three secretory proteins (prostatic secretory protein of 94 amino acids, probasin, and seminal vesicle secretion II) in dysplastic and neoplastic rat prostates

BACKGROUND

Prostatic secretory protein of 94 amino acids (PSP94), probasin, and seminal vesicle secretion II (SVSII) are the three major proteins secreted by the lateral lobe of the rat prostate gland. Among these proteins, rodent PSP94 but not probasin and SVSII has a human homologue and it is also a major secretory protein of the human prostate, in addition to prostatic acid phosphatase and prostate-specific antigen.

METHODS

In this study, we examined and compared the mRNA expression of these three secretory markers in three rat models of prostate cancer including the sex steroid-induced dysplasia (prostatic intraepithelial neoplasia or PIN) in Noble (Nb) rat model, an androgen-independent Nb rat prostatic tumor (AIT) and Dunning rat prostatic adenocarcinomas (both androgen-dependent and -independent) by in situ hybridization (ISH), reverse transcriptase-polymerase chain reaction (RT-PCR), and immunohistochemistry.

RESULTS

The transcripts for the three markers were highly expressed in the secretory epithelium of normal lateral prostate (LP). Their hybridization signals became reduced in the epithelial cells in the low-grade PINs and significantly weakened or lost in the high-grade PINs induced in the LP. Interestingly, we observed that some dysplastic cells located at the basal compartment of the PIN lesions, and nests of outpouching epithelial cells in the vicinity of PINs, expressed positive hybridization signals of three markers. In the adenocarcinoma, signals of probasin but not PSP94 and SVSII were detected. No hybridization signals were detected in both Dunning and AIT tumors. By RT-PCR, transcripts for these proteins were still detected but significantly reduced in the Dunning tumors, whereas in the AIT tumor, only SVSII transcripts were detected. Immunohistochemistry of PSP94 also showed a reduced staining in the PIN lesions, but no immunoreactivity was seen in the rat prostatic tumors.

CONCLUSIONS

The mRNA expression of the three prostatic secretory markers were decreased in the hormone-induced PINs and in two rat prostatic tumors, indicating that the androgen-regulated secretory differentiation was impaired during the development of the premalignant lesion and further reduced in advanced tumors. The abnormal expression pattern of these secretory markers and androgen receptor (AR) in the basal compartment of the PIN lesions suggests that there is a population of cell types with secretory phenotype appearing in the basal cell layer during the early malignant transformation of the prostatic epithelium.

Hoxb13 is required for normal differentiation and secretory function of the ventral prostate

The murine prostate is a structure that is made up of four distinct lobes; the dorsal and lateral prostates (often grouped together as the dorsolateral prostate), the anterior (coagulating gland) and the ventral prostate. Previous work has implicated Hox genes in the development of these structures, but how each lobe acquires unique identities for specific functions has not been addressed. In this study, the ventral prostate-specific function of Hoxb13 is described. Mice lacking Hoxb13 function show normal numbers of duct tips, but mice mutant for both Hoxb13 and Hoxd13 exhibit severe hypoplasia of the duct tips, revealing a role for Hoxb13 in ventral prostate morphogenesis. Additionally, a ventral lobe-specific defect was identified in Hoxb13 mutants wherein the epithelium is composed of simple cuboidal cells rather than of tall columnar cells. Ventral prostate ducts appear devoid of contents and do not express the ventral prostate-specific secretory proteins p12, a kazal-type protease inhibitor and p25, a spermine binding protein. These defects are not due to reduction of Nkx3.1 expression or to a global effect on androgen receptor signaling. These results suggest a specific role for Hoxb13 in a differentiation pathway that gives the ventral prostate epithelium a unique identity, as well as a more general role in ventral prostate morphogenesis that is redundant with other Hox13 paralogs.

Establishment of an androgen-responsive prostatic cell line "PEA5" from a p53-deficient mouse

BACKGROUND

We demonstrated that p53-deficiency is sufficient for the establishment of clonal cell lines from the uterus and prostate. In the present study, we improved cloning methods to establish androgen-responsive cell lines.

METHODS

In our previous study, a prostatic cell line was established from the ventral prostate of a p53-deficient mouse and was maintained in a medium containing heat-inactivated fetal calf serum at 10% supplemented with insulin (10 microg/ml), transferrin (10 microg/ml), cholera toxin (10 ng/ml) and selenium (10(-8) M). In the present study, 5alpha-dihydrotestosterone (10(-8) M) was added to the medium from the beginning of cloning procedures.

RESULTS

We succeeded in the establishment of an androgen receptor positive prostatic cell line, designated PEA5. PEA5 cells exhibited a typical epithelial morphology in culture and growth was stimulated by androgens in a dose-dependent manner. In addition, they grew and formed three-dimensional structures in collagen gel, in which growth was also stimulated by androgen.

CONCLUSIONS

Although PEA5 lacks p53 gene, it still retains androgen sensitivity. In collagen gel culture, PEA5 cells can grow and form three-dimensional structures similar to those of the primary cultures reported previously. Furthermore, prostates of p53-deficient mice are shown to be useful sources for obtaining androgen-responsive cells lines.