Expression of estrogen receptor beta in the fetal, neonatal, and prepubertal human prostate

A Review of Prostate Organogenesis and a Role for iPSC-Derived Prostate Organoids to Study Prostate Development and Disease

The prostate is vulnerable to two major age-associated diseases, cancer and benign enlargement, which account for significant morbidity and mortality for men across the globe. Prostate cancer is the most common cancer reported in men, with over 1.2 million new cases diagnosed and 350,000 deaths recorded annually worldwide. Benign prostatic hyperplasia (BPH), characterised by the continuous enlargement of the adult prostate, symptomatically afflicts around 50% of men worldwide. A better understanding of the biological processes underpinning these diseases is needed to generate new treatment approaches. Developmental studies of the prostate have shed some light on the processes essential for prostate organogenesis, with many of these up- or downregulated genes expressions also observed in prostate cancer and/or BPH progression. These insights into human disease have been inferred through comparative biological studies relying primarily on rodent models. However, directly observing mechanisms of human prostate development has been more challenging due to limitations in accessing human foetal material. Induced pluripotent stem cells (iPSCs) could provide a suitable alternative as they can mimic embryonic cells, and iPSC-derived prostate organoids present a significant opportunity to study early human prostate developmental processes. In this review, we discuss the current understanding of prostate development and its relevance to prostate-associated diseases. Additionally, we detail the potential of iPSC-derived prostate organoids for studying human prostate development and disease.

Combined Effects of Different Endocrine-Disrupting Chemicals (EDCs) on Prostate Gland

Endocrine-disrupting chemicals (EDCs) belong to a heterogeneous class of environmental pollutants widely diffused in different aquatic and terrestrial habitats. This implies that humans and animals are continuously exposed to EDCs from different matrices and sources. Moreover, pollution derived from anthropic and industrial activities leads to combined exposure to substances with multiple mechanisms of action on the endocrine system and correlated cell and tissue targets. For this reason, specific organs, such as the prostate gland, which physiologically are under the control of hormones like androgens and estrogens, are particularly sensitive to EDC stimulation. It is now well known that an imbalance in hormonal regulation can cause the onset of various prostate diseases, from benign prostate hyperplasia to prostate cancer. In this review, starting with the description of normal prostate gland anatomy and embryology, we summarize recent studies reporting on how the multiple and simultaneous exposure to estrogenic and anti-androgenic compounds belonging to EDCs are responsible for an increase in prostate disease incidence in the human population.

Developmental estrogenization: Prostate gland reprogramming leads to increased disease risk with aging

While estrogens are involved in normal prostate morphogenesis and function, inappropriate early-life estrogenic exposures, either in type, dose or timing, can reprogram the prostate gland and lead to increased disease risk with aging. This process is referred to as estrogen imprinting or developmental estrogenization of the prostate gland. The present review discusses published and new evidence for prostatic developmental estrogenization that includes extensive research in rodent models combined with epidemiology findings that together have helped to uncover the architectural and molecular underpinnings that promote this phenotype. Complex interactions between steroid receptors, developmental morphoregulatory factors, epigenetic machinery and stem-progenitor cell targets coalesce to hard wire structural, cellular and epigenomic reorganization of the tissue which retains a life-long memory of early-life estrogens, ultimately predisposing the gland to prostatitis, hyperplasia and carcinogenesis with aging.

Ontogeny of estrogen receptors in human male and female fetal reproductive tracts

This paper reviews and provides new observations on the ontogeny of estrogen receptor alpha (ESR1) and estrogen receptor beta (ESR2) in developing human male and female internal and external genitalia. Included in this study are observations on the human fetal uterine tube, the uterotubal junction, uterus, cervix, vagina, penis and clitoris. We also summarize and report on the ontogeny of estrogen receptors in the human fetal prostate, prostatic urethra and epididymis. The ontogeny of ESR1 and ESR2, which spans from 8 to 21 weeks correlates well with the known "window of susceptibility" (7-15 weeks) for diethylstilbestrol (DES)-induced malformations of the human female reproductive tract as determined through examination of DES daughters exposed in utero to this potent estrogen. Our fairly complete mapping of the ontogeny of ESR1 and ESR2 in developing human male and female internal and external genitalia provides a mechanistic framework for further investigation of the role of estrogen in normal development and of abnormalities elicited by exogenous estrogens.

The FGF/FGFR system in the physiopathology of the prostate gland

Fibroblast growth factors (FGFs) are a family of proteins possessing paracrine, autocrine, or endocrine functions in a variety of biological processes, including embryonic development, angiogenesis, tissue homeostasis, wound repair, and cancer. Canonical FGFs bind and activate tyrosine kinase FGF receptors (FGFRs), triggering intracellular signaling cascades that mediate their biological activity. Experimental evidence indicates that FGFs play a complex role in the physiopathology of the prostate gland that ranges from essential functions during embryonic development to modulation of neoplastic transformation. The use of ligand- and receptor-deleted mouse models has highlighted the requirement for FGF signaling in the normal development of the prostate gland. In adult prostate, the maintenance of a functional FGF/FGFR signaling axis is critical for organ homeostasis and function, as its disruption leads to prostate hyperplasia and may contribute to cancer progression and metastatic dissemination. Dissection of the molecular landscape modulated by the FGF family will facilitate ongoing translational efforts directed toward prostate cancer therapy.

Development of the human prostate

This paper provides a detailed compilation of human prostatic development that includes human fetal prostatic gross anatomy, histology, and ontogeny of selected epithelial and mesenchymal differentiation markers and signaling molecules throughout the stages of human prostatic development: (a) pre-bud urogenital sinus (UGS), (b) emergence of solid prostatic epithelial buds from urogenital sinus epithelium (UGE), (c) bud elongation and branching, (d) canalization of the solid epithelial cords, (e) differentiation of luminal and basal epithelial cells, and (f) secretory cytodifferentiation. Additionally, we describe the use of xenografts to assess the actions of androgens and estrogens on human fetal prostatic development. In this regard, we report a new model of de novo DHT-induction of prostatic development from xenografts of human fetal female urethras, which emphasizes the utility of the xenograft approach for investigation of initiation of human prostatic development. These studies raise the possibility of molecular mechanistic studies on human prostatic development through the use of tissue recombinants composed of mutant mouse UGM combined with human fetal prostatic epithelium. Our compilation of human prostatic developmental processes is likely to advance our understanding of the pathogenesis of benign prostatic hyperplasia and prostate cancer as the neoformation of ductal-acinar architecture during normal development is shared during the pathogenesis of benign prostatic hyperplasia and prostate cancer.

Immunohistochemical expression analysis of the human fetal lower urogenital tract

We have studied the ontogeny of the developing human male and female urogenital tracts from 9 weeks (indifferent stage) to 16 weeks (advanced sex differentiation) of gestation by immunohistochemistry on mid-sagittal sections. Sixteen human fetal pelvises were serial sectioned in the sagittal plane and stained with antibodies to epithelial, muscle, nerve, proliferation and hormone receptor markers. Key findings are: (1) The corpus cavernosum in males and females extends into the glans penis and clitoris, respectively, during the ambisexual stage (9 weeks) and thus appears to be an androgen-independent event. (2) The entire human male (and female) urethra is endodermal in origin based on the presence of FOXA1, KRT 7, uroplakin, and the absence of KRT10 staining. The endoderm of the urethra interfaces with ectodermal epidermis at the site of the urethral meatus. (3) The surface epithelium of the verumontanum is endodermal in origin (FOXA1-positive) with a possible contribution of Pax2-positive epithelial cells implying additional input from the Wolffian duct epithelium. (4) Prostatic ducts arise from the endodermal (FOXA1-positive) urogenital sinus epithelium near the verumontanum. (5) Immunohistochemical staining of mid-sagittal and para-sagittal sections revealed the external anal sphincter, levator ani, bulbospongiosus muscle and the anatomic relationships between these developing skeletal muscles and organs of the male and female reproductive tracts. Future studies of normal human developmental anatomy will lay the foundation for understanding congenital anomalies of the lower urogenital tract.

Carcinogenic risk and Bisphenol A exposure: A focus on molecular aspects in endoderm derived glands

Epidemiological and experimental evidence associates the exposure to Bisphenol A with the increase of cancer risk in several organs, including prostate. BPA targets different pathways involved in carcinogenicity including the Nuclear Receptors (i.e. estrogen and androgen receptors), stress regulated proteins and, finally, epigenetic changes. Here, we analyse BPA-dependent carcinogenesis in endoderm-derived glands, thyroid, liver, pancreas and prostate focusing on cell signalling, DNA damage repair pathways and epigenetic modifications. Mainly, we gather molecular data evidencing harmful effects at doses relevant for human risk (low-doses). Since few molecular data are available, above all for the pancreas, we analysed transcriptomic data generated in our laboratory to suggest possible mechanisms of BPA carcinogenicity in endoderm-derived glands, discussing the role of nuclear receptors and stress/NF-kB pathways. We evidence that an in vitro toxicogenomic approach might suggest mechanisms of toxicity applicable to cells having the same developmental origin. Although we cannot draw firm conclusions, published data summarized in this review suggest that exposure to BPA, primarily during the developmental stages, represents a risk for carcinogenesis of endoderm-derived glands.

Estrogens in Male Physiology

Estrogens have historically been associated with female reproduction, but work over the last two decades established that estrogens and their main nuclear receptors (ESR1 and ESR2) and G protein-coupled estrogen receptor (GPER) also regulate male reproductive and nonreproductive organs. 17β-Estradiol (E2) is measureable in blood of men and males of other species, but in rete testis fluids, E2 reaches concentrations normally found only in females and in some species nanomolar concentrations of estrone sulfate are found in semen. Aromatase, which converts androgens to estrogens, is expressed in Leydig cells, seminiferous epithelium, and other male organs. Early studies showed E2 binding in numerous male tissues, and ESR1 and ESR2 each show unique distributions and actions in males. Exogenous estrogen treatment produced male reproductive pathologies in laboratory animals and men, especially during development, and studies with transgenic mice with compromised estrogen signaling demonstrated an E2 role in normal male physiology. Efferent ductules and epididymal functions are dependent on estrogen signaling through ESR1, whose loss impaired ion transport and water reabsorption, resulting in abnormal sperm. Loss of ESR1 or aromatase also produces effects on nonreproductive targets such as brain, adipose, skeletal muscle, bone, cardiovascular, and immune tissues. Expression of GPER is extensive in male tracts, suggesting a possible role for E2 signaling through this receptor in male reproduction. Recent evidence also indicates that membrane ESR1 has critical roles in male reproduction. Thus estrogens are important physiological regulators in males, and future studies may reveal additional roles for estrogen signaling in various target tissues.

Effects of low dose of bisphenol A on the proliferation and mechanism of primary cultured prostate epithelial cells in rodents

Bisphenol A (BPA) is a well-known endocrine disruptor compound (EDC) that aggravates testosterone-induced benign prostate hyperplasia by increasing the relative weight of the ventral and dorsolateral prostate in rats. This phenomenon is primarily attributed to the exogenous estrogen effect of BPA. However, the direct effect of BPA on prostate cells has not been characterized. The present study investigated the proliferative effect and possible mechanisms of action of BPA on the prostatic epithelium of rats. The ventral prostate epithelial cells were cultured in vitro and the proliferation effects of BPA on cells were studied. The cells were identified as prostatic epithelial cells, and cell viability, cell apoptosis and the expressions of androgen receptors (AR) and estrogen receptors (ER), were detected. It was observed that 0.01–1 nM BPA promoted cell growth, with 1 nM BPA inducing the greatest increase in the rate of cell growth. However, BPA-treated cells exhibited no marked morphological changes compared with the control group. The cell apoptosis rate in each BPA-treated group was lower compared with the control group. The expression levels of ERα and ERβ increased, but the expression of AR decreased. The present study demonstrated that environmental exposure to BPA directly promoted the proliferation of prostate cells in rats through increasing the expression of estrogen receptors, reducing the expression of androgen receptors of the cells and decreasing apoptosis-induced cell death.

Correlation between the germline methylation status in ERβ promoter and the risk in prostate cancer: a prospective study

Familial aggregation of cancer may reflect an overall contribution of inherited genes or a shared mechanism for the manipulation of gene function. DNA methylation in the promoter regions is considered to be a mechanism through which tumor suppressor genes are inhibited, which will lead to tumorigenesis and tumor progression. To evaluate the association between the methylation status in the promoter of estrogen receptor (ER) β,possibly a tumor suppressor gene specific for prostate cancer, and the risk in prostate cancer in a Chinese population, a case-control study that included 56 sporadic prostate cancer cases and 60 healthy controls was conducted. Genomic DNA was extracted from peripheral blood of all the subjects for analyzing the methylation status of the ERβ promoter by methylation-specific PCR, which was verified by bisulfite genomic sequencing PCR. A significant difference was observed in the methylation frequencies of the ERβ promoter between cancer patients (12/56, 21.4%) and healthy controls (5/60, 8.3%). Prostate cancer (PC-3 and DU-145) and prostatic epithelial (RWPE-1) cell lines were treated with various concentrations of the methyltransferase inhibitor 5-Aza-2'-dC. Expression of ERβ was detected at both transcriptional and translational levels. As a result, both mRNA and protein of ERβ were elevated following treatment with increasing concentrations of the demethylating agent. Taken together, our results support the conclusion that abnormal methylation of the ERβ promoter may increase genetic susceptibility to prostate cancer.

Importance of Estrogenic Signaling and Its Mediated Receptors in Prostate Cancer

Prostate cancer (PCa) treatment was first established by Huggins and Hodges in 1941, primarily described as androgen deprivation via interference of testicular androgen production. The disease remains incurable with relapse of hormone-refractory cancer after treatments. Epidemiological and clinical studies disclosed the importance of estrogens in PCa. Discovery of estrogen receptor ERβ prompted direct estrogenic actions, in conjunction with ERα, on PCa cells. Mechanistically, ERs upon ligand binding transactivate target genes at consensus genomic sites via interactions with various transcriptional co-regulators to mold estrogenic signaling. With animal models, Noble revealed estrogen dependencies of PCa, providing insight into potential uses of antiestrogens in the treatment. Subsequently, various clinical trials were conducted and molecular and functional consequences of antiestrogen treatment in PCa were delineated. Besides, estrogens can also trigger rapid non-genomic signaling responses initiated at the plasma membrane, at least partially via an orphan G-protein-coupled receptor GPR30. Activation of GPR30 significantly inhibited in vitro and in vivo PCa cell growth and the underlying mechanism was elucidated. Currently, molecular networks of estrogenic and antiestrogenic signaling via ERα, ERβ and GPR30 in PCa have not been fully deciphered. This crucial information could be beneficial to further developments of effective estrogen- and antiestrogen-based therapy for PCa patients.

Stem Cells as Hormone Targets That Lead to Increased Cancer Susceptibility

Major advances during the past decade have permitted a clearer understanding of processes that regulate stem cell self-renewal and lineage commitment toward differentiated progeny that populate all tissues. Considerable evidence has also accumulated to indicate that aberrations in the stem and progenitor cell populations can lead to increased cancer risk in specific organs systems. It is long recognized that environmental factors play a major role in cancer etiology, and emerging data suggest that endocrine-disrupting chemicals (EDCs) may contribute to an increased cancer risk. Using the prostate gland as a model system, the present review highlights recent data that find that estrogens and EDCs can reprogram prostate stem and progenitor cell populations, leading to increased cancer susceptibility. We propose that stem cell programming during early development in hormone-regulated tissues may lead to heightened sensitivity to early-life EDC exposures and that aberrant stem cell reprogramming by EDCs may contribute to the developmental basis of adult cancer risk.

The role of estrogen receptor β in prostate cancer

Although androgen receptor (AR) signaling is the main molecular tool regulating growth and function of the prostate gland, estrogen receptor β (ERβ) is involved in the differentiation of prostatic epithelial cells and numerous antiproliferative actions on prostate cancer cells. However, ERβ splice variants have been associated with prostate cancer initiation and progression mechanisms. ERβ is promising as an anticancer therapy and in the prevention of prostate cancer. Herein, we review the recent experimental findings of ERβ signaling in the prostate.

A tortuous proximal urethra in urorectal septum malformation sequence?

We observed a newborn boy with urorectal septum malformation sequence. Anomalies of the genitalia and rectum were present. He expired on the first day of life, due to severe lung hypoplasia. Autopsy showed a colon that ended in a blind sac, an enlarged bladder with no grossly visible urethra, and dysplastic kidneys. A cone-shaped tissue at the usual site of the bladder outlet contained tortuous and slit-like lumina, suggesting an undeveloped proximal urethra. The urethral structure was lined by transitional epithelium with squamous metaplasia. Many small buds-lined with columnar epithelium-branched from the urethral structure. These ductal buds lined with columnar epithelium stained for prostatic acid phosphatase. Basal cells surrounding the ductal buds stained for p63 and high molecular weight cytokeratin-supporting an interpretation that the buds were early prostatic ducts with normal histology. To our knowledge, these are the first histological images of an undeveloped, obstructed urethra associated with the urorectal septum malformation sequence.

Bisphenol A promotes human prostate stem-progenitor cell self-renewal and increases in vivo carcinogenesis in human prostate epithelium

Previous studies in rodent models have shown that early-life exposure to bisphenol A (BPA) reprograms the prostate and enhances its susceptibility to hormonal carcinogenesis with aging. To determine whether the human prostate is similarly sensitive to BPA, the current study used human prostate epithelial stem-like cells cultured from prostates of young, disease-free donors. Similar to estradiol-17β (E2), BPA increased stem-progenitor cell self-renewal and expression of stem-related genes in a dose-dependent manner. Further, 10 nM BPA and E2 possessed equimolar membrane-initiated signaling with robust induction of p-Akt and p-Erk at 15 minutes. To assess in vivo carcinogenicity, human prostate stem-progenitor cells combined with rat mesenchyme were grown as renal grafts in nude mice, forming normal human prostate epithelium at 1 month. Developmental BPA exposure was achieved through oral administration of 100 or 250 μg BPA/kg body weight to hosts for 2 weeks after grafting, producing free BPA levels of 0.39 and 1.35 ng/mL serum, respectively. Carcinogenesis was driven by testosterone plus E2 treatment for 2 to 4 months to model rising E2 levels in aging men. The incidence of high-grade prostate intraepithelial neoplasia and adenocarcinoma markedly increased from 13% in oil-fed controls to 33% to 36% in grafts exposed in vivo to BPA (P < .05). Continuous developmental BPA exposure through in vitro (200 nM) plus in vivo (250 μg/kg body weight) treatments increased high-grade prostate intraepithelial neoplasia/cancer incidence to 45% (P < .01). Together, the present findings demonstrate that human prostate stem-progenitor cells are direct BPA targets and that developmental exposure to BPA at low doses increases hormone-dependent cancer risk in the human prostate epithelium.

Maturation of the developing human fetal prostate in a rodent xenograft model

BACKGROUND

Prostate cancer is the most commonly diagnosed nonskin cancer in men. The etiology of prostate cancer is unknown, although both animal and epidemiologic data suggest that early life exposures to various toxicants, may impact DNA methylation status during development, playing an important role.

METHODS

We have developed a xenograft model to characterize the growth and differentiation of human fetal prostate implants (gestational age 12-24 weeks) that can provide new data on the potential role of early life stressors on prostate cancer. The expression of key immunohistochemical markers responsible for prostate maturation was evaluated, including p63, cytokeratin 18, α-smooth muscle actin, vimentin, caldesmon, Ki-67, prostate-specific antigen, estrogen receptor-α, and androgen receptor. Xenografts were separated into epithelial and stromal compartments using laser capture microdissection (LCM), and the DNA methylation status was assessed in >480,000 CpG sites throughout the genome.

RESULTS

Xenografts demonstrated growth and maturation throughout the 200 days of post-implantation evaluation. DNA methylation profiles of laser capture microdissected tissue demonstrated tissue-specific markers clustered by their location in either the epithelium or stroma of human prostate tissue. Differential methylated promoter region CpG-associated gene analysis revealed significantly more stromal than epithelial DNA methylation in the 30- and 90-day xenografts. Functional classification analysis identified CpG-related gene clusters in methylated epithelial and stromal human xenografts.

CONCLUSION

This study of human fetal prostate tissue establishes a xenograft model that demonstrates dynamic growth and maturation, allowing for future mechanistic studies of the developmental origins of later life proliferative prostate disease.

High circulating estrogens and selective expression of ERβ in prostate tumors of Americans: implications for racial disparity of prostate cancer

Although estrogen receptor beta (ERβ) has been implicated in prostate cancer (PCa) progression, its potential role in health disparity of PCa remains elusive. The objective of this study was to examine serum estrogens and prostate tumor ERβ expression and examine their correlation with clinical and pathological parameters in African American (AA) versus Caucasian American (CA) men. The circulating 17β-estradiol (E2) was measured by enzyme immunoassay in blood procured from racially stratified normal subjects and PCa patients. Differential expression profile analysis of ERβ was analyzed by quantitative immunohistochemistry using ethnicity-based tissue microarray encompassing 300 PCa tissue cores. In situ ERβ expression was validated by quantitative reverse transcription-PCR in matched microdissected normal prostate epithelium and tumor cells and datasets extracted from independent cohorts. In comparison with normal age-matched subjects, circulating E2 levels were significantly elevated in all PCa patients. Further analysis demonstrates an increase in blood E2 levels in AA men in both normal and PCa in comparison with age- and stage-matched counterparts of CA decent. Histochemical score analysis reveals intense nuclear immunoreactivity for ERβ in tumor cores of AA men than in CA men. Gene expression analysis in microdissected tumors corroborated the biracial differences in ERβ expression. Gene expression analysis from independent cohort datasets revealed correlation between ERβ expression and PCa progression. However, unlike in CA men, adjusted multivariate analysis showed that ERβ expression correlates with age at diagnosis and low prostate-specific antigen recurrence-free survival in AA men. Taken together, our results suggest that E2-ERβ axis may have potential clinical utility in PCa diagnosis and clinical outcome among AA men.

Male reprotoxicity and endocrine disruption

Mammalian reproductive tract development is a tightly regulated process that can be disrupted following exposure to drugs, toxicants, endocrine-disrupting chemicals (EDCs), or other compounds via alterations to gene and protein expression or epigenetic regulation. Indeed, the impacts of developmental exposure to certain toxicants may not be fully realized until puberty or adulthood when the reproductive tract becomes sexually mature and altered functionality is manifested. Exposures that occur later in life, once development is complete, can also disrupt the intricate hormonal and paracrine interactions responsible for adult functions, such as spermatogenesis. In this chapter, the biology and toxicology of the male reproductive tract is explored, proceeding through the various life stages including in utero development, puberty, adulthood, and senescence. Special attention is given to the discussion of EDCs, chemical mixtures, low-dose effects, transgenerational effects, and potential exposure-related causes of male reproductive tract cancers.

Estrogenic environmental chemicals and drugs: mechanisms for effects on the developing male urogenital system

Development and differentiation of the prostate from the fetal urogenital sinus (UGS) is dependent on androgen action via androgen receptors (AR) in the UGS mesenchyme. Estrogens are not required for prostate differentiation but do act to modulate androgen action. In mice exposure to exogenous estrogen during development results in permanent effects on adult prostate size and function, which is mediated through mesenchymal estrogen receptor (ER) alpha. For many years estrogens were thought to inhibit prostate growth because estrogenic drugs studied were administered at very high concentrations that interfered with normal prostate development. There is now extensive evidence that exposure to estrogen at very low concentrations during the early stages of prostate differentiation can stimulate fetal/neonatal prostate growth and lead to prostate disease in adulthood. Bisphenol A (BPA) is an environmental endocrine disrupting chemical that binds to both ER receptor subtypes as well as to AR. Interest in BPA has increased because of its prevalence in the environment and its detection in over 90% of people in the USA. In tissue culture of fetal mouse UGS mesenchymal cells, BPA and estradiol stimulated changes in the expression of several genes. We discuss here the potential involvement of estrogen in regulating signaling pathways affecting cellular functions relevant to steroid hormone signaling and metabolism and to inter- and intra-cellular communications that promote cell growth. The findings presented here provide additional evidence that BPA and the estrogenic drug ethinylestradiol disrupt prostate development in male mice at administered doses relevant to human exposures.

Estrogens and prostate cancer: etiology, mediators, prevention, and management

The mainstay targets for hormonal prostate cancer (PCa) therapies are based on negating androgen action. Recent epidemiologic and experimental data have pinpointed the key roles of estrogens in PCa development and progression. Racial and geographic differences, as well as age-associated changes, in estrogen synthesis and metabolism contribute significantly to the etiology. This article summarizes how different estrogens/antiestrogens/estrogen mimics contribute to prostate carcinogenesis, the roles of the different mediators of estrogen in the process, and the potentials of new estrogenic/antiestrogenic compounds for prevention and treatment of PCa.

The human female prostate-immunohistochemical study with prostate-specific antigen, prostate-specific alkaline phosphatase, and androgen receptor and 3-D remodeling

INTRODUCTION

The constitution of glands surrounding the human female urethra has been under debate; especially regarding as to what extent they equal the male prostate. Defining their composition may help to understand the development of neoplasms arising from this tissue.

AIMS

The aim of this study was to define the existence, structure, and arrangement of a possible human female prostate.

METHODS

Urethras of 25 women were investigated by immunohistochemistry and stained with specific monoclonal antibodies against prostate-specific antigen (PSA, mono- and polyclonal antibody), prostate specific alkaline phosphatase (PSAP), and androgen receptor (AR). From two urethras, which underwent a totally serial work up with PSA-staining, a three-dimensional model of the urethra and the prostatic glands was created to enable 3D-perception of the results.

MAIN OUTCOME MEASURE

The main outcome measures used in this study were identifying glandular structures in hematoxylin-eosin-staining, positive staining with the respective antibodies, and 3-D orientation of described glands.

RESULTS

Fourteen of 25 patients had glandular structures encircling the urethra. Twelve of 14 showed positive staining for PSA, PSAP, and AR in gland acini, while the excretory ducts, the urethra, and the surrounding stroma did not express those proteins. The strongest PSA and PSAP expression was found in apical cytoplasm of the glandular cells, and AR was confined to cell nuclei. Prostatic glands were located laterally to the distal half of the urethra.

CONCLUSION

A female prostate was found in every second woman in this study and can be discriminated from other urethral caverns and immature paraurethral ducts. Possible neoplasms of this source tissue expressing the prostate-specific markers may therefore be denominated as female prostate tumors.

Estrogen action and prostate cancer

Early work on the hormonal basis of prostate cancer focused on the role of androgens, but more recently estrogens have been implicated as potential agents in the development and progression of prostate cancer. In this article, we review the epidemiological, laboratory and clinical evidence that estrogen may play a causative role in human prostate cancer, as well as rodent and grafted in vivo models. We then review recent literature highlighting potential mechanisms by which estrogen may contribute to prostate cancer, including estrogenic imprinting and epigenetic modifications, direct genotoxicity, hyperprolactinemia, inflammation and immunologic changes, and receptor-mediated actions. We discuss the work performed so far separating the actions of the different known estrogen receptors (ERs), ERα and ERβ, as well as G-protein-coupled receptor 30 and their specific roles in prostate disease. Finally, we predict that future work in this field will involve more investigations into epigenetic changes, experiments using new models of hormonal dysregulation in developing human prostate tissue, and continued delineation of the roles of the different ER subtypes, as well as their downstream signaling pathways that may serve as therapeutic targets.

Oestrogen receptors in the developing rat prostate

This study aimed to illustrate the histological picture of the developing rat prostate and to localise the oestrogen receptors (ERs) distribution. Fifty male albino rats were divided into five equal subgroups: subgroup 1, rats aged 2 days (before morphogenesis of prostate from urogenital sinus); subgroup 2, rats aged 1 week (after early morphogenesis); subgroup 3, rats aged 2 weeks (early pubertal stage); subgroup 4, rats aged 4 weeks (late pubertal stage) and subgroup 5 rats aged 6 weeks (maturation stage). After the rats had been killed, the prostates were dissected and specimens were obtained from the anterior lobe. Paraffin sections of these specimens were subjected to haematoxylin and eosin stain, immunohistochemistry and quantitative immunohistochemistry for ERs distribution and the area of strong positive cytoplasmic immunoreactivity. The results demonstrated that ERs protein decreased gradually with increased age and that it decreased markedly with the onset of puberty. It is concluded that the prostate despite being an androgen dependent gland, depends greatly on oestrogen in its development in the prepubertal period.

Estrogen receptor beta2 and beta5 are associated with poor prognosis in prostate cancer, and promote cancer cell migration and invasion

Estrogens play a pivotal role in the development and progression of prostate cancer (PCa). Their actions are mediated by estrogen receptors (ERs), particularly ERbeta in the prostate epithelium. With the discovery of ERbeta isoforms, data from previous studies that focused principally on the wild-type ERbeta (ERbeta1) may not be adequate in explaining the still controversial role of ERbeta(s) in prostate carcinogenesis. In this study, using newly generated isoform-specific antibodies, immunohistochemistry (IHC) was performed on a tumor microarray comprised of 144 specimens. IHC results were correlated with pathological and clinical follow-up data to delineate the distinct roles of ERbeta1, ERbeta2, and ERbeta5 in PCa. ERbeta2 was commonly found in the cytoplasm and was the most abundant isoform followed by ERbeta1 localized predominantly in the nucleus, and ERbeta5 was primarily located in the cytoplasm. Logistic regression analyses demonstrated that nuclear ERbeta2 (nERbeta2) is an independent prognostic marker for prostate specific antigen (PSA) failure and postoperative metastasis (POM). In a Kaplan-Meier analysis, the combined expression of both nERbeta2 and cytoplasmic ERbeta5 identified a group of patients with the shortest POM-free survival. Cox proportional hazard models revealed that nERbeta2 predicted shorter time to POM. In concordance with IHC data, stable, ectopic expression of ERbeta2 or ERbeta5 enhanced PCa cell invasiveness but only PCa cells expressing ERbeta5 exhibited augmented cell migration. This is the first study to uncover a metastasis-promoting role of ERbeta2 and ERbeta5 in PCa, and show that the two isoforms, singularly and conjointly, have prognostic values for PCa progression. These findings may aid future clinical management of PCa.

46,XY disorders of sex development--the undermasculinised male with disorders of androgen action

Insensitivity to the action of androgens is a common cause of undermasculinisation in 46,XY individuals. These disorders are a result of the failure of major androgens to act via the intracellular androgen receptor and, thus, the genomic effects of androgen signalling are disrupted. The phenotype of affected individuals can vary considerably, depending on the dysfunction of the receptor. In childhood, the diagnosis is often complicated due to the lack of sensitive biochemical determinants, whilst during adolescence and in adults, the diagnosis can be readily made because of the striking clinical feminisation and a conclusive laboratory analysis. A variety of mutations in the androgen receptor have been analysed, providing insight into the complex pathways of intracellular processing and signal transduction via the androgen receptor. Endocrine therapy in androgen-insensitivity syndrome is controversial, because till date the special hormonal profiles in androgen insensitivity have not been acknowledged in replacement strategies.

Characterization of the oestrogenic activity of non-aromatic steroids: are there male-specific endogenous oestrogen receptor modulators?

BACKGROUND AND PURPOSE

The endogenous oestrogens have important biological functions in men as well as in women. Because 17beta-oestradiol and oestrone are also formed in the male body, these aromatic oestrogens are generally thought to be responsible for exerting the required oestrogenic functions in the male. In the present study, we tested the hypothesis that some of the non-aromatic steroids that are androgen precursors or metabolites with hydroxyl groups at C-3 and/or C-17 positions may also be able to serve as ligands for the oestrogen receptors (ER) in the male.

EXPERIMENTAL APPROACH

A total of sixty non-aromatic steroids (selected from families of androstens, androstans, androstadiens, oestrens and oestrans) were analysed for their ability to bind and activate the human ERalpha and ERbetain vitro and in cultured cells.

KEY RESULTS

Six of the non-aromatic steroids, that is, 5-androsten-3beta,17beta-diol, 5alpha-androstan-3beta,17beta-diol, 5(10)-oestren-3alpha,17beta-diol, 5(10)-oestren-3beta,17beta-diol, 4-oestren-3beta,17beta-diol and 5alpha-oestran-3beta,17beta-diol, were found to have physiologically relevant high binding affinity ( approximately 50% of that of oestrone) for human ERalpha and ERbeta. These non-aromatic steroids also activated the transcriptional activity of human ERs and elicited biological responses (such as growth stimulation) in two representative ER-positive human cancer cell lines (MCF-7 and LNCaP) with physiologically relevant potency and efficacy. Molecular docking analysis of these six active compounds showed that they could bind to ERalpha and ERbeta in a manner similar to that of 17beta-oestradiol.

CONCLUSIONS AND IMPLICATIONS

These results provide evidence for the possibility that some of the endogenous androgen precursors or metabolites could serve as male-specific ER ligands.

Quantitative RT-PCR analysis of estrogen receptor gene expression in laser microdissected prostate cancer tissue

BACKGROUND

Real-time quantitative RT-PCR analysis of laser microdissected tissue is considered the most accurate technique for determining tissue gene expression. The discovery of estrogen receptor beta (ERbeta) has focussed renewed interest on the role of estrogen receptors in prostate cancer, yet few studies have utilized the technique to analyze estrogen receptor gene expression in prostate cancer.

METHODS

Fresh tissue was obtained from 11 radical prostatectomy specimens and from 6 patients with benign prostate hyperplasia. Pure populations of benign and malignant prostate epithelium were laser microdissected, followed by RNA isolation and electrophoresis. Quantitative RT-PCR was performed using primers for androgen receptor (AR), estrogen receptor beta (ERbeta), estrogen receptor alpha (ERalpha), progesterone receptor (PGR) and prostate specific antigen (PSA), with normalization to two housekeeping genes. Differences in gene expression were analyzed using the Mann-Whitney U-test. Correlation coefficients were analyzed using Spearman's test.

RESULTS

Significant positive correlations were seen when AR and AR-dependent PSA, and ERalpha and ERalpha-dependent PGR were compared, indicating a representative population of RNA transcripts. ERbeta gene expression was significantly over-expressed in the cancer group compared with benign controls (P < 0.01). In contrast, PGR expression was significantly down-regulated in the cancer group (P < 0.05). There were no significant differences in AR, ERalpha or PSA expression between the groups. This study represents the first to show an upregulation of ERbeta gene expression in laser microdissected prostate cancer specimens.

CONCLUSIONS

In concert with recent studies the findings suggest differential production of ERbeta splice variants, which may play important roles in the genesis of prostate cancer.

Endothelial NOS, estrogen receptor beta, and HIFs cooperate in the activation of a prognostic transcriptional pattern in aggressive human prostate cancer

The identification of biomarkers that distinguish between aggressive and indolent forms of prostate cancer (PCa) is crucial for diagnosis and treatment. In this study, we used cultured cells derived from prostate tissue from patients with PCa to define a molecular mechanism underlying the most aggressive form of PCa that involves the functional activation of eNOS and HIFs in association with estrogen receptor beta (ERbeta). Cells from patients with poor prognosis exhibited a constitutively hypoxic phenotype and increased NO production. Upon estrogen treatment, formation of ERbeta/eNOS, ERbeta/HIF-1alpha, or ERbeta/HIF-2alpha combinatorial complexes led to chromatin remodeling and transcriptional induction of prognostic genes. Tissue microarray analysis, using an independent cohort of patients, established a hierarchical predictive power for these proteins, with expression of eNOS plus ERbeta and nuclear eNOS plus HIF-2alpha being the most relevant indicators of adverse clinical outcome. Genetic or pharmacologic modulation of eNOS expression and activity resulted in reciprocal conversion of the transcriptional signature in cells from patients with bad or good outcome, respectively, highlighting the relevance of eNOS in PCa progression. Our work has considerable clinical relevance, since it may enable the earlier diagnosis of aggressive PCa through routine biopsy assessment of eNOS, ERbeta, and HIF-2alpha expression. Furthermore, proposing eNOS as a therapeutic target fosters innovative therapies for PCa with NO inhibitors, which are employed in preclinical trials in non-oncological diseases.

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.

Estrogen receptor-alpha signaling in growth of the ventral prostate: comparison of neonatal growth and postcastration regrowth

A role for estrogen receptor (ER)-alpha in branching morphogenesis in the ventral prostate (VP) has previously been demonstrated; in the VP of ERalpha(-/-) mice, there are fewer side branches than in wild-type littermates. In the present study, we show that in the postnatal VP, fibroblast growth factor 10 (FGF10) is expressed in wild-type mice but not in ERalpha(-/-) mice, and because branching involves proliferation pathways also used in malignant growth, we investigated whether branching during regrowth of the VP after castration involves ERalpha and FGF10. ERalpha was not detectable in the prostates of sham-operated or castrated mice but was expressed in the prostatic epithelium between d 3 and 5 after testosterone replacement. Blocking either ERalpha or ERbeta with ICI 182,780 had no detectable effects on epithelial cell proliferation during regrowth by testosterone. The ERalpha agonist, propylpyrazoletriol, did not induce regrowth by itself, but exposure to propylpyrazoletriol on d 3-5 of testosterone replacement resulted in cyclin D1-positive cells in the ductal epithelium, invasion of FGF10-positive immune cells in the regrowing prostate, and budding 14 d later. Testosterone replacement alone did not induce cyclin D1, FGF10, or bud formation. These results indicate that stimulation of ERalpha is essential for ductal branching during postnatal prostate growth. During regrowth after castration, there is a window in time when selective stimulation of ERalpha can also induce ductal branching. The FGF10 for this growth comes from the immune system, not from the prostatic mesenchyme.

Estrogen-regulated development and differentiation of the prostate

Both androgens and estrogens play a significant role in the prostate and are critical for normal prostate growth and development, as well as the maintenance of adult prostatic homeostasis throughout life. It is the balance of these two hormones, rather than each individually, that is important for prostatic development and differentiation. Estrogen action is mediated by the estrogen receptors, ERalpha and ERbeta. ERalpha is expressed throughout the prostatic tissue during fetal and early neonatal life, and if activated inappropriately, produces late-life disease, including inflammation and emergence of pre-malignant pathologies. In contrast, ERbeta expression is initiated after ERalpha, is localized primarily to the epithelium, and appears to be important during later periods of development such as puberty and adulthood, acting to regulate cellular proliferation and differentiation in the adult tissue. Therefore, there is also a spatial and temporal balance between ERalpha and ERbeta that is critical for development. Together with the shifting balance between androgens and estrogens themselves, the subtle, yet critical, balance between the activity of ERalpha and ERbeta is what ultimately determines the response of the prostate to estrogen, and is crucial for prostate health.

SOX9 is expressed in human fetal prostate epithelium and enhances prostate cancer invasion

SOX9 is a transcription factor that plays a critical role in the development of multiple tissues. We previously reported that SOX9 in normal human adult prostate was restricted to basal epithelium. SOX9 was also expressed in a subset of prostate cancer (PCa) cells and was increased in relapsed hormone-refractory PCa. Moreover, SOX9 expression in PCa cell lines enhanced tumor cell proliferation and was beta-catenin regulated. Here we report additional in vivo results showing that SOX9 is highly expressed during fetal prostate development by epithelial cells expanding into the mesenchyme, suggesting it may contribute to invasive growth in PCa. Indeed, SOX9 overexpression in LNCaP PCa xenografts enhanced growth, angiogenesis, and invasion. Conversely, short hairpin RNA-mediated SOX9 suppression inhibited the growth of CWR22Rv1 PCa xenografts. These results support important functions of SOX9 in both the development and maintenance of normal prostate, and indicate that these functions contribute to PCa tumor growth and invasion.

The role of estrogens and estrogen receptors in normal prostate growth and disease

Estrogens have significant direct and indirect effects on prostate gland development and homeostasis and have been long suspected in playing a role in the etiology of prostatic diseases. Direct effects are mediated through prostatic estrogen receptors alpha (ERalpha) and beta (ERbeta) with expression levels changing over time and with disease progression. The present review examines the evidence for a role of estrogens and specific estrogen receptors in prostate growth, differentiation and disease states including prostatitis, benign prostatic hyperplasia (BPH) and cancer and discusses potential therapeutic strategies for growth regulation via these pathways.

Estrogen receptor beta: an overview and update

The discovery of a second estrogen receptor (ER), designated ERbeta (NR3A2), has redefined our knowledge about the mechanisms underlying cellular signaling by estrogens and has broad implications for our understanding of regulation of estrogen-responsive tissues. Highly variable and even contrasting effects of estrogens in different tissues seem to be at least partially explained by different estrogen signaling pathways, involving ERalpha (NR3A1) and/or ERbeta. To date, two key conclusions can be drawn from the significant body of work carried out on the specific roles of the two receptor subtypes in diverse estrogen target tissues. First, ERalpha and ERbeta have different biological functions, as indicated by their specific expression patterns and the distinct phenotypes observed in ERalpha and ERbeta knockout (alphaERKO and betaERKO) mice. Second, ERalpha and ERbeta appear to have overlapping but also unique sets of downstream target genes, as judged from a set of microarray experiments. Thus, ERalpha and ERbeta have different transcriptional activities in certain ligand, cell-type, and promoter contexts, which may help to explain some of the major differences in their tissue-specific biological actions. The phenotypes observed for betaERKO mice have suggested certain therapeutic areas to be further explored. The development of ERbeta-selective ligands active in animal disease models indicates new avenues for clinical exploration. ERbeta agonists are being explored and validated as drugs for a growing number of indications. Hopefully, some ERbeta targeted drugs will prove to be efficient in enhancing human health.

Androgen receptors are expressed in a variety of human fetal extragenital tissues: an immunohistochemical study

AIM

To investigate the expression of androgen receptors in the extragenital tissues of developing human embryo.

METHODS

Using immunohistochemistry, we investigated the distribution of androgen receptor (AR) in the extragenital tissues of paraffin-embedded tissue sections of first trimester (8-12 weeks gestation) human embryos. Gender was determined by polymerized chain reaction.

RESULTS

There were no differences in the expression and distribution of AR in male and female embryos at any stage of gestation. AR expression was seen in the thymus gland. The bronchial epithelium of the lungs showed intense positive staining with surrounding stroma negative. Furthermore, positive staining for androgen receptor was exhibited in the spinal cord with a few positive cells in the surrounding tissues. Cardiac valves also showed strong positive staining but with faint reactivity of the surrounding cardiac muscle. There was no staining in kidney, adrenal, liver or bowel.

CONCLUSION

This study demonstrates that immunoreactive AR protein is present in a wide variety of human first trimester fetal tissues and shows the potential for androgen affecting tissues, which are mostly not considered to be androgen dependent. Moreover, it implies that androgen might act as a trophic factor and affect the early development of these organs rather than simply sexual differentiation.

Unique bisphenol A transcriptome in prostate cancer: novel effects on ERbeta expression that correspond to androgen receptor mutation status

BACKGROUND

Prostatic adenocarcinomas are dependent on androgen receptor (AR) activity for growth and progression, and therapy for disseminated disease depends on ablation of AR activity. Recurrent tumors ultimately arise wherein AR has been re-activated. One mechanism of AR restoration is via somatic mutation, wherein cells containing mutant receptors become susceptible to activation by alternative ligands, including bisphenol A (BPA). In tumors with specific AR mutations, BPA promotes therapeutic bypass, suggesting significant negative impact to the clinical management of prostate cancer.

OBJECTIVE

Our goal was to determine the mechanism of BPA action in cancer cells carrying BPA-responsive AR mutants.

METHODS

The molecular signature of BPA activity in prostate cancer cells harboring mutant AR was delineated via genetic microarray analysis. Specificity of BPA action was assessed by comparison with the molecular signature elicited by dihydrotestosterone (DHT).

RESULTS

BPA and DHT elicited distinct transcriptional signatures in prostate cancer cells expressing the BPA-responsive mutant AR-T877A. BPA dramatically attenuated estrogen receptor beta (ERbeta) expression; this finding was specific to prostate tumor cells in which BPA induces cellular proliferation.

CONCLUSIONS

BPA induces a distinct gene expression signature in prostate cancer cells expressing somatic AR mutation, and a major molecular consequence of BPA action is down-regulation of ERbeta. Since ERbeta functions to antagonize AR function and AR-dependent proliferation, these findings reveal a novel mechanism by which BPA likely regulates cellular proliferation. Future investigation directed at dissecting the importance of ERbeta in the proliferative response to BPA will establish the contribution of this event to adverse effects associated with human exposure.

ERRgamma suppresses cell proliferation and tumor growth of androgen-sensitive and androgen-insensitive prostate cancer cells and its implication as a therapeutic target for prostate cancer

Estrogen receptor-related receptors (ERR) are orphan nuclear receptors, which are constitutively activated without estrogen binding. Recent evidence indicates that the ligand-independent ERRs may be involved in similar ER-mediated regulatory pathways and modulate estrogen responsiveness in certain target cells. We recently showed that an ERR subtype, ERRgamma, is coexpressed with ERbeta in normal human prostatic epithelial cells and exhibits reduced expression in many prostate cancer cell lines and clinical neoplastic prostate tissues. Based on this, we hypothesize that ERRgamma may have growth regulatory roles in prostate and prostate cancer. We showed in this study that ERRgamma was expressed in epithelial cell nuclei in fetal and pubertal human prostates, whereas its nuclear expression became reduced in advanced prostate cancer lesions. Stable ERRgamma expression by retroviral transduction suppressed significantly both in vitro cell growth and in vivo tumorigenicity of two prostate cancer cell lines, LNCaP and DU145, as evidenced by a cell-cycle arrest at G(1)-S transition and also induction of two cyclin-dependent kinase inhibitors p21(WAF1/CIP1) and p27(KIP1). We further showed by reporter assay that induction of p21 and p27 by ERRgamma was mediated through direct transactivation of their gene promoters. Moreover, we also showed that a selective ERRgamma-agonist, DY131, could potentiate the ERRgamma-induced growth inhibition in LNCaP-ERRgamma and DU145-ERRgamma cells in a dose-dependent manner compared with respective parental cells. Taken together, our results show that ERRgamma may perform an antiproliferative or tumor-suppressing function in prostate cancer cells. More importantly, our results suggest that ERRgamma could be a novel therapeutic target for prostate cancer treatment.

Estradiol and Bisphenol A stimulate androgen receptor and estrogen receptor gene expression in fetal mouse prostate mesenchyme cells

BACKGROUND

Hormonal alterations during development have lifelong effects on the prostate gland. Endogenous estrogens, including 17beta-estradiol (E(2)), and synthetic estrogenic endocrine disruptors, such as bisphenol A (BPA), have similar effects on prostate development. Increasing exposure to estrogens within the low-dose, physiologic range results in permanent increases in the size and androgen responsiveness of the prostate, whereas exposure within the high-dose, pharmacologic range has the opposite effects.

OBJECTIVES

We tested the hypothesis that the low-dose effects of estrogens on the developing prostate are associated with increased expression of androgen receptor (Ar) and estrogen receptor 1 (alpha) (Esr1) genes in mesenchyme cells.

METHODS

Ar and Esr1 mRNA levels were quantified in primary cultures of fetal mouse prostate mesenchyme cells treated with E(2) and BPA.

DISCUSSION

Ar and Esr1 mRNA expression increased in response to E(2), with thresholds of 0.001 and 0.037 nM, respectively; and in response to BPA, with a threshold of 1 nM for both mRNAs. We did not observe the expected inhibition of Ar mRNA expression by pharmacologic levels of E(2) relative to unexposed cells.

CONCLUSIONS

The observed induction of gene expression occurred at concentrations within the range of free E(2) previously shown to permanently increase prostate size, thus supporting the involvement of direct effects of estrogens on gene expression in prostate mesenchyme. The effects of BPA occurred within the range of concentrations currently measured in human serum, demonstrating the vulnerability of developing tissues to xenoestrogens.

Developmental estrogen exposures predispose to prostate carcinogenesis with aging

Prostate morphogenesis occurs in utero in humans and during the perinatal period in rodents. While largely driven by androgens, there is compelling evidence for a permanent influence of estrogens on prostatic development. If estrogenic exposures are abnormally high during the critical developmental period, permanent alterations in prostate morphology and function are observed, a process referred to as developmental estrogenization. Using the neonatal rodent as an animal model, it has been shown that early exposure to high doses of estradiol results in an increased incidence of prostatic lesions with aging which include hyperplasia, inflammatory cell infiltration and prostatic intraepithelial neoplasia or PIN, believed to be the precursor lesion for prostatic adenocarcinoma. The present review summarizes research performed in our laboratory to characterize developmental estrogenization and identify the molecular pathways involved in mediating this response. Furthermore, recent studies performed with low-dose estradiol exposures during development as well as exposures to environmentally relevant doses of the endocrine disruptor bisphenol A show increased susceptibility to PIN lesions with aging following additional adult exposure to estradiol. Gene methylation analysis revealed a potential epigenetic basis for the estrogen imprinting of the prostate gland. Taken together, our results suggest that a full range of estrogenic exposures during the postnatal critical period - from environmentally relevant bisphenol A exposure to low-dose and pharmacologic estradiol exposures - results in an increased incidence and susceptibility to neoplastic transformation of the prostate gland in the aging male which may provide a fetal basis for this adult disease.

The role of estrogens in normal and abnormal development of the prostate gland

Estrogens play a physiologic role during prostate development with regard to programming stromal cells and directing early morphogenic events. However, if estrogenic exposures are abnormally high during the critical developmental period, permanent alterations in prostate branching morphogenesis and cellular differentiation will result, a process referred to as neonatal imprinting or developmental estrogenization. These perturbations are associated with an increased incidence of prostatic lesions with aging, which include hyperplasia, inflammation, and dysplasia. To understand how early estrogenic exposures can permanently alter the prostate and predispose it to neoplasia, we examined the effects of estrogens on prostatic steroid receptors and key developmental genes. Transient and permanent alterations in prostatic AR, ERalpha, ERbeta, and RARs are observed. We propose that estrogen-induced alterations in these critical transcription factors play a fundamental role in initiating prostatic growth and differentiation defects by shifting the prostate from an androgen-dominated gland to one whose development is regulated by estrogens and retinoids. This in turn leads to specific disruptions in the expression patterns of key prostatic developmental genes that normally dictate morphogenesis and differentiation. Specifically, we find transient reductions in Nkx3.1 and permanent reductions in Hoxb-13, which lead to differentiation defects particularly within the ventral lobe. Prolonged developmental expression of Bmp-4 contributes to hypomorphic growth throughout the prostatic complex. Reduced expression of Fgf10 and Shh and their cognate receptors in the dorsolateral lobes leads to branching defects in those specific regions in response to neonatal estrogens. We hypothesize that these molecular changes initiated early in life predispose the prostate to the neoplastic state upon aging.

Estrogens and Antiestrogens as Etiological Factors and Therapeutics for Prostate Cancer

Mounting evidence supports a key role played by estrogen or estrogen in synergy with an androgen, in the pathogenesis of prostate cancer (PCa). New experimental data suggest that this process could begin as early as prenatal life. During adulthood, estrogen carcinogenicity is believed to be mediated by the combined effects of hormone-induced, unscheduled cell proliferation and bioactivation of estrogens to genotoxic carcinogens. Increased bioavailability of estrogen through age-dependent increases in conversion from androgen could also be a contributing factor. Individual variations and race-/ethnic-based differences in circulating or locally formed estrogens or in tissue estrogen responsiveness may explain differential PCa risk among individuals or different populations. Estrogen receptor (ER)-alpha and ER-beta are the main mediators of estrogen action in the prostate. However, ER-beta is the first ER subtype expressed in the fetal prostate. During cancer development, ER-beta expression is first lost as tumors progress into high grade in the primary site. Yet, its reexpression occurs in all metastatic cases of PCa. A change in cytosine methylation in a regulatory CpG island located in the proximal promoter of ER-beta may constitute an "on/off" switch for reversible regulation of ER-beta expression. A variety of estrogenic/antiestrogenic/selective estrogen receptor modulator (SERM)-like compounds have been shown to use non-ERE pathways, such as tethering of ER-beta to NF-kappaB binding proteins, Sp2, or Ap1 for gene transactivation. These findings open new avenues for drug design that now focuses on developing a new generation of estrogen-based PCa therapies with maximal proapoptotic action but few or no side effects.

Nuclear and cytoplasmic interaction of pRb2/p130 and ER-β in MCF-7 breast cancer cells

Estrogens exhibit important biological functions and influence several pathological processes of hormone-dependent diseases. The biological actions of estrogens require their interaction with two estrogen receptors (ER-alpha and ER-beta), which are ligand-dependent transcription factors. ER-alpha and ER-beta exhibit distinct tissue expression patterns as well as show different patterns of gene regulation. In addition, it has been suggested that ER-beta works as a counter partner of ER-alpha through inhibition of the transactivating functions of ER-alpha. For instance, ER-beta seems to play a different role in breast tumorigenesis than ER-alpha, as ER-beta decreased expression in breast cancer has been correlated with bad prognosis. Biological activities of ER-alpha and ER-beta could be controlled by a number of interacting proteins such as activators/inhibitors, ligand binding and kinases. We have previously reported that pRb2/p130, retinoblastoma related protein, could be involved in the silencing of ER-alpha gene during breast tumorigenesis. Here, we report that ER-beta and pRb2/p130 proteins co-immunoprecipitate in both nucleus and cytoplasm of MCF-7 breast cancer cells. Our hypothesis is that the interaction of pRb2/130 with ER-beta may have a functional significance in regulating ER-beta activity.

Toremifene--a promising therapy for the prevention of prostate cancer and complications of androgen deprivation therapy

Deregulation of the estrogen axis in humans prompts a series of tissue-specific events. In the breast and prostate, alterations in estrogen signalling lead to genotypic and phenotypic molecular alterations that result in dysplastic cellular appearance, deregulated cell growth and carcinoma. In bone, decreased estrogen leads to increased osteoclastogenesis and bone resorption, decreased bone mineral density and a significant fracture risk. Toremifene is a selective estrogen receptor modulator that exerts pharmacological activity in the breast, bone and prostate. An intense interest in developing this agent for prostate cancer chemoprevention is based on the reduction of premalignant and malignant prostate lesions in a transgenic model of prostate cancer. Biological and clinical activity was demonstrated in Phase II trials by the prevention of progression to prostate cancer in men with high-grade prostate intraepithelial neoplasia and through suppression of bone turnover biomarkers and increased bone mineral density in men on androgen deprivation therapy for prostate cancer.

17beta-estradiol induces apoptosis in the developing rodent prostate independently of ERalpha or ERbeta

Estrogens induce both proliferative and antiproliferative responses in the prostate gland. To date, antiproliferative effects of estrogens are generally considered to be due to systemic antiandrogenic actions. However, estrogen action mediated through estrogen receptor (ER) beta was recently suggested as another mechanism of induction of apoptosis in the prostate. This study aimed to explore the hypothesis that the antiproliferative effects of estrogen are directly mediated through ERbeta using a prostate organ culture system. We previously reported effects of 17beta-estradiol (E2) using rat ventral prostate (VP) tissues, and adapted the system for culturing mouse tissues. In both rat and mouse models, estrogen-induced apoptosis was detected that was spatially and regionally localized to the epithelium of the distal tips. Using organ cultures of alphaER knockout (alphaERKO) and betaERKO prostates, we failed to demonstrate that apoptosis induced by E2 was mediated through either receptor subtype. Activation of ER-selective ligands (ERalpha, propyl pyrazole triol, ERbeta, diaryl-proprionitrile, and 5alpha-androstane-3beta,17beta-diol) in organ culture experiments failed to induce apoptosis, as did the membrane impermeable conjugate E2:BSA, discounting the possibility of nongenomic effects. Consequently, E2 regulation of androgen receptor (AR) expression was examined and, in the presence of nanomolar testosterone levels, E2 caused a specific reduction in AR protein expression in wild-type, alphaERKO, and betaERKO mice, particularly in the distal region where apoptosis was detected. This down-regulation of AR protein provides a possible mechanism for the proapoptotic action of E2 that is independent of ERs or nongenomic effects.