Expression of estrogen receptor in diseased human prostate assessed by non-radioactive in situ hybridization and immunohistochemistry

Selective estrogen receptor modulators contribute to prostate cancer treatment by regulating the tumor immune microenvironment

Prostate cancer (PC) has previously been established as a cold tumor and develops in an inert immunosuppressive environment. Current research focuses on altering the immune microenvironment of PC from cold to hot; thus, in the present review, the diverse roles of estrogen and estrogen receptor (ER) signaling was examined in the tumor cell and tumor immune microenvironment (TIM). We hypothesized that ERα promotes PC progression and ERβ impedes epithelial-mesenchymal transition in PC cells, while in the TIM, ERβ mediates the immunosuppressive environment, and low levels of ERα is associated with disease development. Selective estrogen receptor modulators (SERMs) or selective ER degraders play diverse roles in the regulation of ER isoforms. Patients with PC may benefit from the use of SERMs, including raloxifene, in combination with anti-PD1/PD-L1 checkpoint immunotherapy, or TGF-β or Wnt antagonists. The present review demonstrated that immunotherapy-based strategies combined with SERMs may be an option for the future of PC-targeting therapy.

Partial Epithelial-Mesenchymal Transition Was Observed Under p63 Expression in Acquired Middle Ear Cholesteatoma and Congenital Cholesteatoma

INTRODUCTION

Partial epithelial-mesenchymal transition (p-EMT) is a process by which epithelial cells partially lose their intercellular adhesion and change to obtain migration ability. The transcription factor p63 regulates the expression of cadherin family and induces epithelial cell proliferation. In this study, we hypothesized that p-EMT under p63 expression may be a key factor in epithelial cell growth in middle ear cholesteatoma.

METHODS

Specimens were surgically excised from patients with congenital cholesteatoma (CC) (n = 48), acquired middle ear cholesteatoma (AC) (n = 120), and normal skin tissue (n = 34). We analyzed immunohistochemically for the EMT marker (N-cadherin), adherence junction marker (E-cadherin), and tight junction marker (claudin-1, claudin-4, occludin). We also examined the labeling index (LI) of p63 and Proliferating cell nuclear antigen (PCNA) (late S phase marker), and Snail expression as a mobility marker.

RESULTS

The expression of p63 (CC 51.0 ± 7.4%, AC 50.0 ± 5.9%) was significantly higher in the thickened epithelium of CC and AC compared with normal skin tissue (p < 0.0001). The loss of E-cadherin was observed (CC 50.0%, AC 55.8%) but the expression patterns in the tight junction were almost normal. N-cadherin was partially detected in the basal and upper layer of epithelium in CC and AC. In contrast to that of normal skin tissue, the LI of PCNA was significantly higher in AC (p < 0.0001). The positive rate of Snail was significantly higher in CC (p < 0.0001).

CONCLUSION

This study indicates that p-EMT via the p63 signaling pathway might plays an essential role in epithelial growth in AC and CC formation, although tight junction formation and terminal differentiation were not affected in those processes.

Estrogen and Androgen Blockade for Advanced Prostate Cancer in the Era of Precision Medicine

Androgen deprivation therapy (ADT) has been widely prescribed for patients with advanced prostate cancer (PC) to control key signaling pathways via androgen receptor (AR) and AR-collaborative transcriptional factors; however, PC gradually acquires a lethal phenotype and results in castration-resistant PC (CRPC) during ADT. Therefore, new therapeutic strategies are required in clinical practice. In addition, ARs; estrogen receptors (ERs; ERα and ERβ); and estrogen-related receptors (ERRs; ERRα, ERRβ, and ERRγ) have been reported to be involved in the development or regulation of PC. Recent investigations have revealed the role of associated molecules, such as KLF5, FOXO1, PDGFA, VEGF-A, WNT5A, TGFβ1, and micro-RNA 135a of PC, via ERs and ERRs. Selective ER modulators (SERMs) have been developed. Recently, estrogen and androgen blockade (EAB) using a combination of toremifene and ADT has been demonstrated to improve biochemical recurrence rate in treatment-naïve bone metastatic PC. In the future, the suitability of ADT alone or EAB for individuals may be evaluated by making clinical decisions on the basis of information obtained from RT-PCR, gene-panel, or liquid biopsy to create a “personalized medicine” or “precision medicine”. In this review, we summarize ER and ERR signaling pathways, molecular diagnosis, and SERMs as candidates for advanced PC treatment.

Specific deletion of LKB1/Stk11 in the Müllerian duct mesenchyme drives hyperplasia of the periurethral stroma and tumorigenesis in male mice

Nearly all older men will experience lower urinary tract symptoms associated with benign prostatic hyperplasia (BPH), the etiology of which is not well understood. We have generated Stk11^CKO mice by conditional deletion of the liver kinase B1 (LKB1) tumor suppressor gene, Stk11 (serine threonine kinase 11), in the fetal Müllerian duct mesenchyme (MDM), the caudal remnant of which is thought to be assimilated by the urogenital sinus primordial mesenchyme in males during fetal development. We show that MDM cells contribute to the postnatal stromal cells at the dorsal aspect of the prostatic urethra by lineage tracing. The Stk11^CKO mice develop prostatic hyperplasia with bladder outlet obstruction, most likely because of stromal expansion. The stromal areas from prostates of Stk11^CKO mice, with or without significant expansion, were estrogen receptor positive, which is consistent with both MD mesenchyme-derived cells and the purported importance of estrogen receptors in BPH development and/or progression. In some cases, stromal hyperplasia was admixed with epithelial metaplasia, sometimes with keratin pearls, consistent with squamous cell carcinomas. Mice with conditional deletion of both Stk11 and Pten developed similar features as the Stk11^CKO mice, but at a highly accelerated rate, often within the first few months after birth. Western blot analyses showed that the loss of LKB1 and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) induces activation of the phospho-5' adenosine monophosphate-activated protein kinase and phospho-AKT serine/threonine kinase 1 signaling pathways, as well as increased total and active β-catenin. These results suggest that activation of these signaling pathways can induce hyperplasia of the MD stroma, which could play a significant role in the etiology of human BPH.

Immunohistochemical analysis of estrogen receptors in prostate and clinical correlation in men with benign prostatic hyperplasia

Purpose

Estrogens act through interaction with 2 receptor subtypes, ER alpha (ERα) and ER beta (ERβ), in human prostate. The aim of the present study was to semiquantitatively assess the differential expression of ER subtypes in human benign prostatic hyperplasia (BPH) by use of immunocytochemistry (IHC) methods and to explore their relationship with various measures of BPH.

Materials and Methods

A total of 45 patients with BPH undergoing transurethral resection of the prostate and 22 patients with bladder cancer with normal prostate undergoing surveillance cystoscopy were studied as cases and controls, respectively. Quantitative immunolabeling of ER subtypes was scored by use of a semiquantitative scale. Also, correlations were assessed between ER levels in prostate and various measures of BPH.

Results

Overall, we found strong immunostaining for ERα in stroma and for ERβ in epithelium, respectively. The IHC score for ERα differed significantly between BPH patients and controls in both stroma (p≤0.001) and epithelium (p=0.008), respectively. The ERβ IHC score was also significantly higher in the epithelium of BPH patients (p=0.01). Also, we found a significant correlation between prostatic ER levels and various clinical measures of BPH.

Conclusions

ERs may play an important role in the pathogenesis of BPH.

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.

Associations between estrogen receptor genetic polymorphisms, smoking status, and prostate cancer risk: a case-control study in Japanese men

OBJECTIVE

Prostate cancer (PCa) is one of the major causes of death among men. Our study investigated the association of ESR1 and ESR2 genotypes with susceptibility to PCa in relation to smoking status in Japanese.

METHOD

A case-control study was performed with 750 Japanese prostate cancer patients and 870 healthy controls. After age-matching in case-controls, 352 controls and 352 cases were enrolled in this study. By using logistic regression analysis, the different genotypes from ESR1 and ESR2 were analyzed according to case/control status.

RESULT

ESR2 rs4986938 AG and AG + AA genotypes were associated with significantly decreased risk of PCa (AG: OR = 0.68, 95 % CI 0.47-0.97, P < 0.05 and AG + AA: OR = 0.67, 95 % CI 0.47-0.94, P < 0.05). However, there was no significant association between ESR1 rs2234693 and PCa risk. When patients were grouped according to smoking status, the ESR2 rs1256049 AA genotype (OR = 0.48, 95 % CI 0.25-0.95, P < 0.05) and ESR2 rs4986938 AG + AA genotype (OR = 0.64, 95 % CI 0.41-1.00, P < 0.05) showed significantly decreased PCa risk in the ever-smoker group.

CONCLUSION

Our results suggest that the estrogen receptor ESR2 has a very important function to predict PCa and that different SNPs have different predictive values. Smoking may influence estrogenic activity and may influence PCa together with the estrogen receptor.

Sex steroid receptor expression and localization in benign prostatic hyperplasia varies with tissue compartment

Androgens and estrogens, acting via their respective receptors, are important in benign prostatic hyperplasia (BPH). The goals of this study were to quantitatively characterize the tissue distribution and staining intensity of androgen receptor (AR) and estrogen receptor-alpha (ERα), and assess cells expressing both AR and ERα, in human BPH compared to normal prostate. A tissue microarray composed of normal prostate and BPH tissue was used and multiplexed immunohistochemistry was performed to detect AR and ERα. We used a multispectral imaging platform for automated scanning, tissue and cell segmentation and marker quantification. BPH specimens had an increased number of epithelial and stromal cells and increased percentage of epithelium. In both stroma and epithelium, the mean nuclear area was decreased in BPH relative to normal prostate. AR expression and staining intensity in epithelial and stromal cells was significantly increased in BPH compared to normal prostate. ERα expression was increased in BPH epithelium. However, stromal ERα expression and staining intensity was decreased in BPH compared to normal prostate. Double positive (AR and ERα) epithelial cells were more prevalent in BPH, and fewer double negative (AR and ERα) stromal and epithelial negative cells were observed in BPH. These data underscore the importance of tissue layer localization and expression of steroid hormone receptors in the prostate. Understanding the tissue-specific hormone action of androgens and estrogens will lead to a better understanding of mechanisms of pathogenesis in the prostate and may lead to better treatment for BPH.

Estrogen receptors alpha (rs2234693 and rs9340799), and beta (rs4986938 and rs1256049) genes polymorphism in prostate cancer: evidence for association with risk and histopathological tumor characteristics in Iranian men

We evaluated the effect of estrogen receptor (ER)-α and ER-β genes polymorphisms on development of prostate cancer (PCa) and its correlation with serum reproductive hormones and with clinicopathological characteristics in a sample of Iranian men. One hundred sixty-two men with PCa (mean age 63.7 ± 3.4 years) and 324 age-matched healthy controls (mean age 63.1 ± 3.2 years) were recruited in this study. Genotypes for ER-α and ER-β genes polymorphisms were identified by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. Serum levels of reproductive hormones were also measured. Of PCa patients, 38.3%, and 61.7% had localized and advanced tumor, and 45.7%, and 54.3%, had low grade and high-grade cancer, respectively. There was a significant difference in genotype frequency distribution of ER-α gene polymorphism (P = 0.002), and ER-β gene polymorphism (P = 0.003) between cancer patients and controls. The ER-α Pvull C allele carriers (TC or CC) had a significantly increased risk of PCa compared with the TT homozygotes [odds ratio (OR) 3.12; 95% confidence interval (CI) 1.87-5.84, and OR = 4.73, 95% CI:2.44-7.33, respectively]. It was also found that the ER-α XbaI AG (OR = 4.36; 95% CI:2.47-6.68; P = 0.001) and ER-β AluI AG (OR = 2.66, 95% CI:1.61-4.16; P = 0.004) genotypes were significantly associated with increased risk of PCa. The ER-β RsaI genotype was not associated with PCa. Baseline serum free E2 levels tended to be lower in men with PCa (0.35 ± 0.04 pg/ml) compared to healthy men (0.48 ± 0.05 pg/ml). Genotypes which confer susceptibility for developing PCa, accompanied with lowest serum levels of free E2. In the Iranian population, genetic polymorphisms of the ER-α and ER-β genes may be involved in the etiology of PCa.

Expression of keratinocyte growth factor (KGF) and its receptor in a middle-ear cavity problem

OBJECTIVES

To investigate the pathogenesis of one of the most troublesome conditions following ear surgery, a middle-ear cavity problem.

METHODS

Keratinocyte growth factor (KGF) and its receptor (KGFR), the ratio of proliferating epithelial cells using Ki-67, and the extent of infiltration of B cells and T cells were examined immunohistochemically in 10 ears with a cavity problem, 70 ears with cholesteatoma and 8 ears with normal skin at the retroauricular incision.

RESULTS

KGF was positive in 40% of cavity problem specimens, 37.5% of normal skin specimens, and was positive in 88% of cholesteatoma specimens (cavity problem vs. cholesteatoma, p=0.0004). The positive rate of KGFR in the cavity problem group (33.3%) was between those in cholesteatoma (60%) and normal skin (0%). In contrast to the cholesteatoma specimens, a significantly smaller number of Ki-67 labeling index (LI) was detected in the cavity problem specimens. B cell LI was significantly higher but T cell LI was significantly lower in the cavity problem specimens than in the cholesteatoma group.

CONCLUSIONS

Our present study indicated that the discordance of paracrine action between stromal KGF and epithelial KGFR with a large number of infiltrating B cells may play an important role in the pathogenesis of a cavity problem.

Estrogen and androgen signaling in the pathogenesis of BPH

Estrogens and androgens have both been implicated as causes of benign prostatic hyperplasia (BPH). Although epidemiological data on an association between serum androgen concentrations and BPH are inconsistent, it is generally accepted that androgens play a permissive role in BPH pathogenesis. In clinical practice, inhibitors of 5α-reductase (which converts testosterone to the more potent androgen dihydrotestosterone) have proven effective in the management of BPH, confirming an essential role for androgens in BPH pathophysiology. To date, multiple lines of evidence support a role for estrogens in BPH pathogenesis. Studies of the two estrogen receptor (ER) subtypes have shed light on their differential functions in the human prostate; ERα and ERβ have proliferative and antiproliferative effects on prostate cells, respectively. Effects of estrogens on the prostate are associated with multiple mechanisms including apoptosis, aromatase expression and paracrine regulation via prostaglandin E2. Selective estrogen receptor modulators or other agents that can influence intraprostatic estrogen levels might conceivably be potential therapeutic targets for the treatment of BPH.

Differential expression of estrogen-related receptors beta and gamma (ERRbeta and ERRgamma) and their clinical significance in human prostate cancer

Estrogen-related receptor (ERR) is a nuclear receptor that modulates the estrogen-signaling pathway. Here, we investigated the expression of both ERRbeta and ERRgamma in human prostate tissues. Using original rabbit polyclonal anti-ERRbeta and anti-ERRgamma antibodies, the expression of ERRbeta and ERRgamma was evaluated by immunohistochemical analysis of cancerous lesions (n = 107) and benign foci (n = 92), obtained by radical prostatectomy. Stained slides were evaluated for the proportion of immunoreactive cells and their staining intensity. Total immunoreactivity scores (IR scores; range, 0-8) were calculated as the sum of the proportion and intensity scores. The relationship between the clinicopathological characteristics of the patients and the expression of the three ERRs (ERRalpha, ERR beta, and ERR gamma) was evaluated. IR scores for ERRbeta and ERRgamma were significantly lower in cancerous lesions than that in benign foci (P < 0.0001, for both). Clinicopathological analyses revealed that the patients with low ERRgamma IR scores ( Collapse

Key Words Collapse

MESH Headings

• Aged
• Humans
• Immunohistochemistry
• Male
• Middle Aged
• Prognosis
• Prostatic Neoplasms/chemistry
• Prostatic Neoplasms/mortality
• Receptors, Estrogen/analysis

Collapse

Grants Collapse

Affiliation(s)

Tetsuya Fujimura Department of Urology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
Satoru Takahashi
Tomohiko Urano
Nobuhiro Ijichi
Kazuhiro Ikeda
Jinpei Kumagai
Taro Murata
Kenichi Takayama
Kuniko Horie-Inoue
Yasuyoshi Ouchi
Masami Muramatsu
Yukio Homma
Satoshi Inoue

Collapse

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.

ERAP75 functions as a coactivator to enhance estrogen receptor alpha transactivation in prostate stromal cells

BACKGROUND

Estrogen receptor alpha (ER alpha) has been reported to be expressed and function in the prostate stromal cells, and numerous evidences indicated that the stromal ER alpha signal pathway plays critical roles in prostate development and cancer. ER alpha requires distinct coregulators for efficient transcriptional regulation. The goal of this study is to examine physical and functional interaction between ER alpha and ERAP75 in the context of prostate stromal cells.

METHOD

Yeast two-hybrid assays were used to screen novel ER alpha interaction proteins. The interaction between ER alpha and ERAP75 was confirmed by mammalian two-hybrid, GST pull-down, and co-immunoprecipitation methods. The interaction motif was examined by site-directed mutagenesis. The effect of ERAP75 on ER alpha transactivation and the expression of ER alpha target genes were determined by luciferase assay and real-time PCR, respectively.

RESULT

ER alpha can interact with the C terminus of ERAP75 via its ligand binding domain both in vivo and in vitro. The conserved LXXLL motif within the C terminus of ERAP75 is required for the interaction between ER alpha and ERAP75. ERAP75 can enhance ER alpha transactivation in a dose-dependent manner and up-regulate the expression of the endogenous ER alpha target gene, stromal-derived factor-1 (SDF-1), in the prostate stromal cells.

CONCLUSION

ERAP75 functions as a novel coactivator that can modulate ER alpha function in the prostate stromal cells. The understanding of the mechanism of ER alpha transactivation in prostate stromal cells could possibly help in the development of new strategies to control or treat prostate cancer by targeting its transactivation protein complex.

Increased expression of estrogen-related receptor alpha (ERRalpha) is a negative prognostic predictor in human prostate cancer

The nuclear receptor ERRalpha (estrogen-related receptor alpha) is known to modulate the estrogen-signaling pathway, but the biological significance of ERRalpha in the prostate remains unclear. We investigated the expression of ERRalpha in human prostate tissues and cancer cell lines to evaluate the potential roles of the receptor in prostate cancer (PC). Western blot analysis of ERRalpha was performed in three cell lines of human PC (LNCaP, DU145 and PC-3). The expressions of ERRalpha in cancerous lesions (n = 106) and benign foci (n = 99) of 106 surgically obtained prostate specimens were evaluated by immunohistochemistry. The relationships between the ERRalpha expression and clinicopathological features were evaluated. Western blot analysis using the polyclonal anti-ERRalpha antibody detected a 52 kD band in all three PC cell lines. Positive immunostaining of ERRalpha in the nuclei was found in 73 (69%) cancerous and 47 (47.5%) benign epithelium, whereas the stromal tissues were negative for ERRalpha. The mean immunoreactivity score (IR score) of the cancerous lesions (3.5 +/- 2.6) was significantly higher than that of the benign foci (1.8 +/- 2.1) (p < 0.0001). The IR score of the cancerous lesions significantly correlated with the Gleason score (p = 0.0135). Univariate and multivariate hazard analyses revealed significant correlations between elevated ERRalpha expression and poor cancer-specific survival (p = 0.0141 and 0.0367, respectively). The enhanced expression of ERRalpha might play a role in the development of human PC and serve as a significant prognostic factor for the disease.

Toremifene for the prevention of prostate cancer in men with high grade prostatic intraepithelial neoplasia: results of a double-blind, placebo controlled, phase IIB clinical trial

PURPOSE

A randomized, double-blind, dose finding, placebo controlled, parallel group clinical study was done to determine the incidence of prostate cancer in men with high grade prostatic intraepithelial neoplasia treated with toremifene.

MATERIALS AND METHODS

A total of 514 patients with high grade prostatic intraepithelial neoplasia and no evidence of prostate cancer on screening biopsy were randomized to 20, 40 or 60 mg toremifene, or placebo daily for 12 months. Patients underwent re-biopsy at 6 and 12 months.

RESULTS

The number of evaluable patients, that is those with 1 on study biopsy who were compliant, was 447. The cumulative risk of prostate cancer was decreased in patients on 20 mg toremifene compared with placebo (24.4% vs 31.2%, p <0.05). The annualized rate of prevention was 6.8 cancers per 100 men treated. In patients with no biopsy evidence of cancer at baseline and 6 months, the 12-month incidence of prostate cancer was decreased by 48.2% with 20 mg toremifene compared with placebo (9.1% vs 17.4%, p <0.05). The 20 mg dose was most effective but cumulative and 12-month incidences of prostate cancer were lower for each toremifene dose vs placebo with a cumulative risk of 29.2% and 28.1%, and a 12-month incidence of 14.3% and 13.0% for 40 and 60 mg, respectively. Gleason scores were similar across treatments. The overall incidence of drug related and serious adverse events did not differ between any of the toremifene groups and the placebo group.

CONCLUSIONS

Toremifene decreased the incidence of prostate cancer by 1 year and had a tolerability profile comparable to that of placebo in a high risk population.

Diethylstilbestrol increases the density of prolactin cells in male mouse pituitary by inducing proliferation of prolactin cells and transdifferentiation of gonadotropic cells

Diethylstilbestrol (DES) has been implicated in mammalian abnormalities. We examined the effects of DES on follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL) cells in the pituitaries of male mice treated with various doses of DES for 20 days. DES reduced the density of FSH and LH cells in a dose-dependent manner, but increased that of PRL cells. When the expression of estrogen receptor (ER) alpha and beta was assessed, an induction of ERbeta by DES was found predominantly in PRL cells. However, since these effects were abolished in ERalpha knockout mice, DES appears to act primarily through ERalpha. When the expression of Ki-67 and Pit-1 in PRL cells was examined at various time-points after DES treatment, some PRL cells became Ki-67 positive at 10-15 days, and Pit-1-positive cells were increased at 5-15 days. Furthermore, some FSH and LH cells became Pit-1 positive, and co-localized with PRL at 5-10 days. Our results indicate that DES increases PRL cells by inducing proliferation of PRL cells and transdifferentiation of FSH/LH cells to PRL cells.

Identification and localization of estrogen receptor alpha- and beta-positive cells in adult male and female mouse intestine at various estrogen levels

Although estrogen is implicated in the regulation of mammalian intestinal function, the presence and the distribution of estrogen receptor (ER)-positive cells in the intestine are still controversial. The present study was designed to localize ERalpha- and ERbeta-expressing cells in female and male mouse intestines immunohistochemically under various estrogen conditions, especially in female mice, ovariectomized as well at various phases of the estrous cycle. Western blot analysis detected both ERalpha (66-kDa band) and ERbeta (56-kDa band). Immunohistochemical staining of paraffin-embedded sections after antigen-retrieval treatment with autoclaving revealed staining for ERalpha in submucosal interstitial cells, and double staining identified these cells as a subtype of intestinal macrophages. The number of these cells varied according to the estrous cycle phase. Administration of 17beta-estradiol to ovariectomized mice resulted in a significant increase in the number of ERalpha-positive macrophages. On the other hand, the nuclei of nerve cells in Auerbach and Meissner plexuses were positive for both ERalpha and ERbeta, but the number of positive nerve cells was not affected by estrogen. Our results indicate that estrogen and estrogenic compounds may exert their actions on the intestine in two ways; one is through interstitial macrophages and the other is through intestinal neurons.

Relationship between upregulated oestrogen receptors and expression of growth factors in cultured, human, prostatic stromal cells exposed to estradiol or dihydrotestosterone

This study investigated the hypothesis that, in benign prostatic hyperplasia (BPH), upregulated oestrogen receptors (ER) and the action of androgens differentially regulate expression of stromal growth factors. Eight human prostatic stromal cell strains were subjected to a procedure to upregulate their ER by exposing them to 1 micromol 17beta-estradiol for 10 days followed by passage and growth in the absence of steroids. Four of the cell strains instead received 100 nmol dihydrotestosterone for 48 h. Immunoexpression of ERalpha, AR and six growth factors was quantified by flow cytometry in each case. Expression of ERalpha was significantly increased in six of eight cell strains. Expressions of six growth factors (FGF-2, FGF-7, IGF-1, TGF-beta1 NGF and e NOS) were elevated but only for FGF-7 was it significant. There was a significant positive correlation between the change in ERalpha and the change in FGF-2 and FGF-7, but not the other growth factors. Exposure to dihydrotestosterone reduced expression of ERalpha and all six growth factors, compared with oestrogen-treated cells but not significantly. It is concluded that upregulated ERalpha in prostatic stroma may have a greater modulating influence on synthesis of certain growth factors than the direct action of androgens and, by enhancing synthesis of FGF-2 and FGF-7, could play a significant role in the development of BPH.

Association Study of Polymorphisms in the Human Estrogen Receptor Alpha Gene and Prostate Cancer Risk

OBJECTIVES

Prostate cancer is a very common hormone-related malignancy in Western countries. It is initially dependent on androgen stimulation but in vitro growth of prostate cancer cells are also dependent on estrogen. Our goal was to elucidate if some polymorphisms of estrogen receptor alpha gene might be associated with the risk of prostate cancer.

METHODS

Using DHPLC techniques, each coding exon of the estrogen receptor alpha gene was screened for new polymorphisms in germline DNA from 96 healthy controls and 96 sporadic prostate cancer cases. Identified polymorphisms were then genotyped and their distribution compared between the two populations.

RESULTS

Thirteen polymorphisms were identified. A difference was found in the distribution of one newly identified polymorphism, namely a GGGA repeat located in the first intron of the gene. The common wild type genotype consisted of two alleles with five GGGA repetitions (5/5 genotype). Indeed this 5/5 genotype was found in 294/296 controls (99.3%) and 285/294 patients (96.9%; OR, 4.6; 95% CI, 0.99-21.67). Among the nine patients with a different genotype, one was 4/5, seven were 5/6 and one was 6/6.

CONCLUSION

These results suggest that variants of the GGGA polymorphism from the estrogen receptor alpha gene may be associated with an increased risk of developing prostate cancer.

Regulation of estrogen receptor alpha and beta expression by testosterone in the rat prostate gland

Although ER beta is known to be expressed at high levels in the rat prostate gland, its regulation is not well understood. Here we examined ER mRNA expression and the effects of testosterone administration in male rats at 1, 4 and 9 weeks of age who were castrated and/or treated with testosterone for a week, and then sacrificed. ER alpha was the major type of ER expressed in 2 week-old animals while dominant expression of ER beta mRNA was apparent in older age groups. Interestingly while ER beta expression was diminished and ER alpha mRNA increased in the castrated group, testosterone administration reversed this effect. A time-course study indicated that induction of ER beta mRNA increased within 9 hr and ER alpha decreased in 2 days after an injection (i.p.) of testosterone. Our results suggested that 1) testosterone up-regulates ER beta mRNA expression while ER alpha is down-regulated; and that 2) great changes in ER alpha and beta expression in the prostate gland during development from the newborn to adult may be due to the influence of testosterone.

Antiestrogens and selective estrogen receptor modulators reduce prostate cancer risk

The development of chemoprevention strategies against prostate cancer would have the greatest overall impact both medically and economically against prostate cancer. Estrogens are required for prostate carcinogenesis. Estrogenic stimulation through estrogen receptor alpha in a milieu of decreasing androgens contributes significantly to the genesis of benign prostatic hyperplasia, prostate dysplasia, and prostate cancer. The ability of antiestrogens and selective estrogen receptor modulators (SERMs) to delay and to suppress prostate carcinogenesis is supported by preclinical, clinical, and epidemiological studies. SERMs have many features that make them attractive candidates for prostate cancer chemoprevention including their favorable safety profile and efficacy in preclinical prostate cancer models. The true clinical benefits of SERMs for chemoprevention to prevent prostate cancer, however, should continue to be investigated through human clinical trials. A phase IIb/III human clinical trial is currently evaluating safety and efficacy of toremifene, a SERM, in men who have high-grade prostatic intraepithelial neoplasia.

Upregulation of estrogen and androgen receptors modulate expression of FGF-2 and FGF-7 in human, cultured, prostatic stromal cells exposed to high concentrations of estradiol

This study was performed to develop an experimental model in which expression of estrogen receptors (ER) by human prostatic stromal cells could be reproducibly enhanced relative to similar cells with low ER expression. The second aim was to characterise changes in expression of ER, androgen receptor (AR), FGF-2 and FGF-7 in stromal cells exposed to high and low concentrations of estradiol and testosterone mimicking the different sex hormone levels between young and elderly men. Five strains of human prostatic stromal cells, isolated from BPH resections, were grown in steroid-free medium plus 1 micromol 17beta-estradiol. After 10 days, cells were passaged and grown in the same medium without estradiol until confluent. In a second study four cell strains were exposed to high and low concentrations of 17beta-estradiol and testosterone for 10 days. Cells were labelled with fluorescent antibodies to ERalpha, AR, FGF-2 and FGF-7 and the fluorescence intensity measured by flow cytometry. Following exposure to 1 micromol estradiol, stromal cells showed reduced expression of AR and ERalpha but after passage without estradiol they showed a 25% increase in both receptors over controls. Different combinations of sex hormones induced inconsistent changes with respect to expression of ER, AR and FGFs in the various cell-strains. However, there was a highly significant correlation between AR, ER and FGF-2 and FGF-7, which was cell strain-specific. Thus, changes in sex hormone balance per se may not be solely responsible for the observed increases in prostatic ER levels in BPH. Since expression of ER is correlated with synthesis of FGF-2 and FGF-7, it is likely that increases in stromal ER may mediate the synthesis of stromally-derived growth factors which contribute to the aetiopathogenesis of benign prostatic hyperplasia.

Zone-dependent expression of estrogen receptors alpha and beta in human benign prostatic hyperplasia

Estrogen, which acts through estrogen receptors (ERs) alpha and beta, has been implicated in the pathogenesis of benign and malignant human prostatic tumors, i.e. benign prostatic hyperplasia and prostate cancer, thought to originate from different zones of the prostate [the transition zone (TZ) and peripheral zone (PZ), respectively]. Here, we examined the cellular distribution of ERalpha and ERbeta in human normal and hyperplastic prostate tissues, using in situ hybridization and immunohistochemistry. ERalpha expression was restricted to stromal cells of PZ. In contrast, ERbeta was expressed in the stromal cells of PZ as well as TZ. ERbeta-positive epithelial cells were evenly distributed in PZ and TZ of the prostate. Our results suggest that estrogen may play a crucial role in the pathogenesis of benign prostatic hyperplasia through ERbeta.

Possible involvement of keratinocyte growth factor and its receptor in enhanced epithelial-cell proliferation and acquired recurrence of middle-ear cholesteatoma

Middle-ear cholesteatoma is characterized by enhanced proliferation of epithelial cells and granular tissue formation. However, the molecular mechanism underlying these pathological changes is largely unknown. Keratinocyte growth factor (KGF) is a mesenchymal cell-derived paracrine growth factor that specifically stimulates epithelial cell proliferation. In the present study, we investigated the possible involvement of KGF and its receptor, KGFR, in the pathogenesis of cholesteatoma using in situ hybridization and immunohistochemistry, respectively. We examined 56 cholesteatoma specimens, and 8 normal skin areas as control. KGF and KGFR expression was examined by immunohistochemistry using rabbit anti-human KGF and anti-human KGFR polyclonal antisera raised in our laboratories against synthetic peptides corresponding to parts of human KGF and KGFR, respectively. KGF protein and mRNA were detected exclusively in stromal fibroblasts and infiltrating T lymphocytes in 80% of cholesteatoma cases, whereas KGFR protein and mRNA were localized in the epithelium in 72% of cases. Assessment of the proliferative activity of cholesteatoma using the labeling index for Ki-67 showed a significantly higher Ki-67 labeling index (66%) in KGF+/KGFR+ cases than other cases. There was a significant correlation between KGF+/KGFR+ expression and recurrence. Our results indicate the possible involvement of both KGF and KGFR in enhanced epithelial cell proliferative activity and recurrence of cholesteatoma.

Direct response of the murine prostate gland and seminal vesicles to estradiol

In the prostate, testosterone action depends on conversion to bioactive metabolites dihydrotestosterone and 17beta-estradiol (E2) via the 5alpha-reductase and aromatase enzymes, respectively. Exogenous estrogen inhibits prostate growth by indirect effects caused by suppression of pituitary gonadotropins and testicular testosterone output, but direct effects are less well known. Direct effects of estrogens were evaluated using the hypogonadal (hpg) mouse model, which has postnatal deficiency in gonadotropins and testosterone but remains hormone sensitive. Mature hpg mice were implanted sc with implants filled with E2. After 6 wk, prostate lobe [anterior prostate (AP) and ventral prostate (VP)] and seminal vesicle (SV) organ volumes were significantly increased (P < 0.05) but remained smaller than wild-type mice. Analysis of the relative volumes (the proportional composition) of each tissue compartment in these organs showed significant increases in cellular and luminal volumes (P < 0.05) in AP (but not VP) and in SVs. Stromal fibroblasts proliferated, whereas smooth muscle cells were reduced in the AP and SVs. In the epithelia, basal cells proliferated and became metaplastic in the AP and VP. In the AP, luminal debris accumulated, together with an inflammatory response, but there was no evidence of malignant changes. The current study unequivocally demonstrates direct proliferative responses to E2 in the hpg mouse AP and VP lobes and SVs, characterized by discrete lobe-specific changes, including smooth-muscle regression, fibroblast proliferation, inflammation, and basal epithelial cell proliferation and metaplasia.

Prostate carcinoma expression of estrogen receptor-beta as detected by PPG5/10 antibody has positive association with primary Gleason grade and Gleason score

The objective of this study was to study the expression of estrogen receptor-beta (ER-beta) in prostatic adenocarcinoma and correlate it with Gleason grade and clinical outcome. Immunohistochemical evaluation was performed on prostate needle biopsies from 53 patients (T1-T3pN0M0). ER-beta and ER-alpha transcripts were also studied by semiquantitative reverse transcriptase polymerase chain reaction in PC-3 and LNCaP prostate carcinoma cell lines. ERbeta was expressed in 93% of adenocarcinomas and was positively associated with primary Gleason grade (P = 0.028 for percentage of positive cells and P = 0.046 using a semiquantitative scale) and Gleason score (P = 0.010 for percentage of positive cells and P = 0.014 using a semiquantitative scale). ER-beta expression in the benign epithelium of prostates with adenocarcinoma was detected in 92% of cases and in the stroma in 47% of cases. A trend for longer time to treatment failure was noted for cases with low ER-beta expression after curatively intended radiotherapy (P = 0.082). PC-3, an aggressive prostate cancer cell line with invasive properties in nude mice, expressed higher levels of ER-beta than LNCaP, a nonmetastasizing cell line, whereas no difference for ER-alpha transcripts could be observed. Our findings suggest that ER-beta, as detected by PPG5/10 antibody, may have a role in the process of dedifferentiation of prostate adenocarcinomas, with higher levels present in less differentiated tumors.

Effect of fatty acids on estradiol and testosterone binding to whole DU-145 prostate cells

Cancer of the prostate is one of the leading causes of cancer related deaths in men. An important role in the development of prostate cancer is played by androgens and androgen ablation is therefore currently used in cancer treatment. In the past, estrogens were widely used in treatment of prostate cancer, but there are indications that estrogens could also be involved in carcinogenesis. Lately, much research has been done on the modulation of the binding of steroid hormones to their receptors by polyunsaturated fatty acids (PUFAs), which could interfere with the steroid hormone's message. Therefore, the aim of this study was to determine in whole DU-145 human prostate cells the effect of EFAs and their metabolites on the binding and affinity of the estrogen receptor (ER) and androgen receptor (AR) to estradiol (E(2)) and testosterone (T), respectively. Fatty acids were dissolved in ethanol and added to the cell culture in a final ethanol concentration of 0.2% on the fourth day of incubation. The results showed that the PUFAs under investigation inhibited the AR's capacity, in contrast to the ER's capacity which was stimulated. However, the dissociation constants (K(d)) of the AR and ER complexes in the presence of the PUFAs, were as follows. Except for eicosapentaenoic acid (EPA) which decreased the AR dissociation constant and EPA and alpha-linolenic acid (ALA) which increased the ER dissociation constant, the remaining FAs had no significant effect on the K(d) values of both the AR and ER complexes. According to these priliminary results it is postulated that men should benefit with a diet rich in certain essential polyunsaturated fatty acids although its function remains to be clarified.

Differential expression of estrogen receptor beta (ERbeta) and its C-terminal truncated splice variant ERbetacx as prognostic predictors in human prostatic cancer

Estrogens have been widely used for the treatment of advanced prostatic adenocarcinoma. However, their direct effect to prostatic cancer cells via estrogen receptors remains unclear. We investigated expression of ERalpha, wild-type ERbeta (wtERbeta), and a C-terminal truncated splice variant of ERbeta (ERbetacx) in 50 benign and 100 malignant human prostatic tissue samples by immunohistochemistry. While strong immunostaining of ERalpha was consistently identified in the stromal compartment, wtERbeta was expressed in epithelial cells in both the benign and malignant foci. However, wtERbeta expression was significantly lower in the cancers than in the benign epithelium and inversely correlated with Gleason tumor grade (P < 0.0001 and P = 0.0099, respectively). In contrast, ERbetacx was significantly more expressed in the high-grade cancers (83%) compared with the low-grade tumors (22%) and the benign sites (11%) (P < 0.0001, both). Cancer-specific survival of patients with lower wtERbeta expression was significantly worse than those with higher expression of wtERbeta (P = 0.0018). Conversely, higher ERbetacx expression significantly correlated with poor cancer-specific survival (P = 0.0058). These results suggest that differential expressions of wtERbeta and ERbetacx may be prognostic predictors for prostatic cancer.

Comparative studies of the estrogen receptors beta and alpha and the androgen receptor in normal human prostate glands, dysplasia, and in primary and metastatic carcinoma

An antibody, GC-17, thoroughly characterized for its specificity for estrogen receptor-beta (ER-beta), was used to immunolocalize the receptor in histologically normal prostate, prostatic intraepithelial neoplasia, primary carcinomas, and in metastases to lymph nodes and bone. Comparisons were made between ER-beta, estrogen receptor-alpha (ER-alpha), and androgen receptor (AR) immunostaining in these tissues. Concurrently, transcript expression of the three steroid hormone receptors was studied by reverse transcriptase-polymerase chain reaction analysis on laser capture-microdissected samples of normal prostatic acini, dysplasias, and carcinomas. In Western blot analyses, GC-17 selectively identified a 63-kd protein expressed in normal and malignant prostatic epithelial cells as well as in normal testicular and prostatic tissues. This protein likely represents a posttranslationally modified form of the long-form ER-beta, which has a predicted size of 59 kd based on polypeptide length. In normal prostate, ER-beta immunostaining was predominately localized in the nuclei of basal cells and to a lesser extent stromal cells. ER-alpha staining was only present in stromal cell nuclei. AR immunostaining was variable in basal cells but strongly expressed in nuclei of secretory and stromal cells. Overall, prostatic carcinogenesis was characterized by a loss of ER-beta expression at the protein and transcript levels in high-grade dysplasias, its reappearance in grade 3 cancers, and its diminution/absence in grade 4/5 neoplasms. In contrast, AR was strongly expressed in all grades of dysplasia and carcinoma. Because ER-beta is thought to function as an inhibitor of prostatic growth, androgen action, presumably mediated by functional AR and unopposed by the beta receptor, may have provided a strong stimulus for aberrant cell growth. With the exception of a small subset of dysplasias in the central zone and a few carcinomas, ER-alpha-stained cells were not found in these lesions. The majority of bone and lymph node metastases contained cells that were immunostained for ER-beta. Expression of ER-beta in metastases may have been influenced by the local microenvironment in these tissues. In contrast, ER-alpha-stained cells were absent in bone metastases and rare in lymph nodes metastases. Irrespective of the site, AR-positive cells were found in all metastases. Based on our recent finding of anti-estrogen/ER-beta-mediated growth inhibition of prostate cancer cells in vitro, the presence of ER-beta in metastatic cells may have important implications for the treatment of late-stage disease.

Estrogen receptor beta expression in human prostate tissue

Estrogen receptor subtype beta (ERbeta) is highly expressed in rat prostate epithelium, but its presence in human prostate needs to be confirmed. Here we investigated the expression of ERbeta in five benign (normal and/or hyperplastic) and 10 malignant (Gleasons' score 2-7) prostate tissue specimens using immunohistochemistry. Immunohistochemistry was performed on formalin-fixed, paraffin-embedded tissue sections, using a commercially available ERbeta polyclonal antibody developed against the C-terminal amino acid residue. Nuclear ERbeta expression was found in the nuclei of glandular epithelium of benign prostate tissue specimens; faint nuclear ERbeta positivity was also present in a few stromal cells around normal epithelium. Nuclear ERbeta specific immunostaining was undetectable in all prostate cancer sections.

Selective estrogen receptor modulators for the chemoprevention of prostate cancer

The ability to interfere with prostate carcinogenesis, and as a consequence, prevent prostate cancer with drugs is the basis for chemoprevention. The prostate contains estrogen receptors in both the stroma and epithelium. Both animal models and human epidemiologic studies have implicated estrogens as an initiator of prostate cancer. In the aging male, prostate cancer occurs in an environment of rising estrogen and decreasing androgen levels. Selective estrogen receptor modulators (SERMs) have shown the ability to prevent (GTx-006 [acapodene]) and treat (GTx-006 and arzoxifene) prostate cancer, suggesting that they may be used in prostate cancer chemoprevention. A phase 2 clinical trial using GTx-006 for prostate cancer chemoprevention is currently being conducted.

Cultured stromal cells: an in vitro model of prostatic mesenchymal biology

BACKGROUND

Initial efforts to develop in vitro models to study prostatic biology focused on the culture and characterization of epithelial cells. Recently, attention has turned towards inclusion of stromal cells in experimental systems.

METHODS

Improved methods to isolate and culture stromal cells have been developed. An array of markers are employed to characterize subtypes of stromal cells, with particular interest in smooth muscle differentiation.

RESULTS

Defined, serum-free media are available for certain experimental applications. Conditions that promote smooth muscle differentiation have been identified. Investigators have characterized hormonal and peptide factors that regulate the growth of prostatic stromal cells, and have also described paracrine factors produced by stromal cells that influence epithelial biology.

CONCLUSIONS

Prostatic stromal-cell cultures are now widely employed by a large number of investigators for a diverse array of experimental purposes. While further refinement is required to obtain model systems that fully mimic in vivo processes, the availability of stromal- and epithelial-cell cultures provides a valuable resource for studying normal prostatic biology as well as benign prostatic hyperplasia (BPH) and cancer.

Modulating effect of estrogen and testosterone on prostatic stromal cell phenotype differentiation induced by noradrenaline and doxazosin

BACKGROUND

Noradrenaline (NA) has been shown to enhance expression of the contractile phenotype of human prostatic stromal cells in tissue culture. This study examined the possibility that changing levels of sex hormones in elderly men with BPH may modulate the differentiating effect of NA and hence the efficacy of alpha(1)-adrenoceptor-blocking drugs.

METHODS

Confluent, quiescent stromal cell cultures from 6 different patients were treated with combinations of 20 microM NA, 1 microM doxazosin, 0.1 microM beta-estradiol, and 0.1 microM testosterone, over a period of 10 days. Harvested cells were labelled with fluorescein-conjugated antisera to alpha-smooth muscle actin and myosin to identify cells of contractile phenotype which were thereafter analyzed flow-cytometrically.

RESULTS

NA increased mean immunoexpression of both actin and myosin. Enhancement of myosin expression was highly significant (P </= 0.02). This effect was incompletely opposed by doxazosin. Neither estradiol nor testosterone influenced mean expression of contractile filaments and did not significantly enhance or inhibit the effects of NA or doxazosin. However, both sex hormones exhibited a differentially powerful effect on cell lines from individual patients. The expression of myosin increased by NA was further elevated by addition of estradiol in four of the cell lines and by testosterone in three.

CONCLUSIONS

The data suggest that levels of estrogens and androgens, either alone or in combination, are unlikely to predict the development of obstructive symptoms in patients with BPH or their response to doxazosin. Nevertheless, prostatic stromal cells from individual patients may be exceptionally sensitive to both sex hormones, with enhanced modulation towards a contractile phenotype. Since alpha- and beta-subtypes of the estrogen receptor are differentially expressed between the stroma and epithelium of the early fetal prostate, it is likely that interaction between sex hormones and noradrenaline is an important factor in determining the phenotypic composition of prostatic stroma at this early stage of development, and possibly predisposition to BPH during later adult life.

Induction of apoptosis by mifepristone and tamoxifen in human LNCaP prostate cancer cells in culture

BACKGROUND

Published data indicate that antiprogestins and antiestrogens could inhibit prostate cancer cell growth in vitro and in vivo. The main objective of the present studies was to explore the role of bcl(2) and TGFbeta(1) for induction of apoptosis in LNCaP prostate cancer cells growing in culture as a treatment response to the antiprogestin, mifepristone, and the antiestrogen, 4-hydroxytamoxifen.

METHODS

In vitro cell viability (cytotoxicity), DNA fragmentation, and changes in the expression of bcl(2) and TGFbeta(1) proteins were assessed using the sulforhodamine B protein dye-binding assay, specific ELISA, and competitive inhibition assays.

RESULTS

Both steroid antagonists induced a significant time- and dose-dependent cell growth inhibition (cytotoxicity). This inhibition of viable cells was associated with a significant increase in DNA fragmentation (apoptosis), downregulation of bcl(2), and induction of TGFbeta(1) protein. Abrogation of the mifepristone- and 4-hydroxytamoxifen-induced cytotoxicity by TGFbeta(1)-neutralizing antibody and by the addition of mannose-6-phosphate confirmed the correlation between induction of active TGFbeta(1) and subsequent prostate cancer cell death. The effect of mifepristone was not significantly reduced or prevented by occupying the progesterone or glucocorticoid receptors by their corresponding high-affinity native ligands. On the contrary, the effect of a combination of mifepristone with progesterone or hydrocortisone on the increase in DNA fragmentation, bcl(2) downregulation, and induction of TGFbeta(1) protein was additive and significantly different (P < 0.05) from the effect of mifepristone monotherapy.

CONCLUSIONS

Our data suggest that mifepristone and tamoxifen are effective inducers of apoptosis and may represent nonandrogen-ablation, novel therapeutic approaches to overcome a potential intrinsic apoptosis resistance of androgen-independent prostate cancer cells.

Antitumor activity of mifepristone in the human LNCaP, LNCaP-C4, and LNCaP-C4-2 prostate cancer models in nude mice

BACKGROUND

Antiprogestins are a promising new class of mammary tumor inhibitors with a unique mechanism of action. Previously published results also suggest a tumor-inhibitory effect of antiprogestins in prostate cancer models. The objective of the present studies was to determine whether androgen-sensitive and androgen-insensitive variants of the well-characterized LNCaP human prostate cancer cell line exhibit stable differences in their sensitivity to in vivo antitumor activity of the antiprogestin, mifepristone.

METHODS

Exponentially growing LNCaP, LNCaP-C4, and LNCaP-C4-2 prostate cancer cells in culture were mixed with Matrigel and injected subcutaneously (s.c.) into the flank of 6-8-week-old male nude mice. The tumors were permitted to grow until they reached a volume of 270-300 mm(3). The animals were then randomly assigned to two groups. One group received mifepristone (50 mg/kg/day s.c.). Control animals were treated with vehicle. Tumor volume was determined every 4 days. After 28 days of treatment, the tumors were harvested and wet weights were determined.

RESULTS

The inoculated tumor cells produced progressively growing tumors in male nude mice. However, the androgen-insensitive LNCaP-C4-2 cells showed the most aggressive and most rapid growth rate and shortest time to tumor progression. The tumors derived from the LNCaP-C4 cells exhibited a higher rate of tumor growth as compared with those derived from the parental androgen-sensitive LNCaP cells. In all three models, mifepristone treatment caused a significant retardation of tumor progression: after 28 days of treatment, about 50% inhibition of tumor weight was observed in the mifepristone treatment groups (P < 0.05) compared with the corresponding control groups.

CONCLUSIONS

This is the first report demonstrating significant antitumor activity of mifepristone in both androgen-sensitive and androgen-insensitive variants of the LNCaP human prostate cancer model in nude mice. These results suggest a potential clinical benefit of the use of antiprogestins as a novel nonandrogen ablation therapeutic approach in the management of prostate cancer.

Estrogen receptors in the human male prostatic urethra and prostate in prostatic cancer and benign prostatic hyperplasia

Estrogen receptors (ERs) in the prostate and prostatic urethra were examined in 33 men with benign prostatic hyperplasia (BPH) and in 11 with prostate cancer (PC). The Abbot monoclonal ER-ICA assay was used for immunohistochemical investigation. In the BPH group, ERs were revealed in the prostatic stroma in eight cases and in the glandular epithelium in one. In four cases ERs were seen in the prostatic stroma and in the glandular epithelium. In the prostatic urethra, ERs were found in 19 cases located in the urothelium, lamina propria and/or periurethral glands. In the PC group, ERs were demonstrated in the prostatic stroma and/or prostatic urethra in 6 out of 11 cases. In both BPH and PC patients, immunoreactivity was weak and confined to few cells, indicating low ER content in the prostate as well as in the prostatic urethra. Dextran-coated charcoal (DCC) analysis was used for detection and quanticization of cytosolic and nuclear ERs. In the BPH group, ERs were detected once in the prostate and prostatic urethra in the nuclear and cytosol, and additionally in the prostatic urethra in the cytosol fraction in three cases. In all cases, ER content was low, ranging from 10-15 fmol/mg protein. In the PC group, ERs were detected in the prostatic urethra and/or prostate in the cytosol fraction from two patients. The contents were low, ranging from 10-13 fmol/mg protein. We conclude that in human BPH and PC, ERs can be present in the prostate and prostatic urethra. In the prostate, ERs are mainly located in the stroma, but in BPH specimens they can also be found in the glandular epithelium. Biochemically, the use of the DCC analysis is of limited value, since ER content in the human prostate and prostatic urethra is at the limit of detection with this method.

Estrogen receptor expression in prostate cancer and premalignant prostatic lesions

Estrogens have been implicated in prostatic cancerogenesis and tumor progression. The mechanisms underlying estrogen signaling in human prostate tissue, however, remain poorly understood. Using immunohistochemical and in situ hybridization (ISH) techniques, the present study demonstrates the classical estrogen receptor (ERalpha) in premalignant lesions and prostatic adenocarcinoma through the various stages of the disease. Conversely, the novel characterized ERbeta subtype was undetectable in human prostate tissue. High-grade prostatic intraepithelial neoplasia revealed ERalpha mRNA and protein expression in 28% and 11% of cases evaluated. Focal ER immunoreactivity was detected in a minority of low- to intermediate-grade adenocarcinoma. High-grade (primary Gleason grade 4 and 5) tumors revealed ER protein expression in 43% (62% respectively) of cases. The most significant ERalpha gene expression on mRNA and protein levels was observed in hormone refractory tumors and metastatic lesions, including lymph node and bone metastases. Results of the current study suggest that estrogens can affect prostatic cancerogenesis and neoplastic progression through an ER-mediated process in human prostate tissue.

Prostate stroma: physiology

BACKGROUND

The separate structural and functional activities of the prostatic stroma were only recently discovered and are still poorly understood.

METHODS

This review summarizes recent literature on the structure, and on the angiogenic, contractile, proliferative, and secretory activities mediated by the prostatic stroma and its agents.

RESULTS

The stroma undergirds the acinar epithelium through its fibromuscular substance. Neovascularization of its hypoxic cells, a process driven by cytokines, especially vascular endothelial growth factor, provides fuel for glycolytic empowerment of smooth muscle contraction, growth, and secretion. Signals from the stromal complement of cholinergic and adrenergic fibers, modulated by also-elaborated nitric oxide, provide tight regulation of uroflow. Apparently, autonomic control is independent of that of the powerful endothelin, secreted by the epithelium. Superimposed on these intrinsic elements of prostatic stromal control are the effects of steroid hormones and their effectors.

CONCLUSIONS

The illumination of the stroma's role in prostatic physiology, coupled with advances in knowledge of its pharmacology, should aid in our understanding, management, and prevention of prostatic disease.

Changes in structure and functions of prostate by long-term administration of an androgen, testosterone enanthate, in rhesus monkey (Macaca mulatta)

The increasing use of androgens in clinical trials for developing a safe, effective, and reversible male contraceptive has necessitated a critical evaluation of the effects of their long-term use on the structure and functions of the prostate gland, which is androgen dependent. Combination regimens using progestogens, gonadotropin-releasing hormone antagonists, or antiandrogens along with androgens are undergoing clinical evaluation as antispermatogenic agents. The majority of these regimens have used testosterone enanthate (TE) as the androgen of choice, but very limited information is available on the side effects of long-term androgen use. The present study is the first report that critically evaluates the effects of long-term use of TE on prostate structure and functions. Adult male rhesus monkeys received intramuscular injections of 50 mg of TE once in 14 days for 33 months. The cranial and caudal lobes of the prostate, which were removed under ketamine anesthesia, were processed for the preparation of semithin sections to evaluate histological changes. The DNA distribution in the cells was studied in single cell suspensions of cranial and caudal lobes of the prostate by using flow cytometry. Changes in the levels of testosterone, estradiol, prostate-specific acid phosphatase (PAP), and prostate-specific antigen (PSA) in samples collected during the pretreatment period and at the time of removal of the prostate were estimated by using conventional procedures. Control samples were processed simultaneously. The administration of TE for 33 months caused the following changes: 1) significant increase in the weight of both lobes of the prostate, 2) cellular hypertrophy and increase in secretory material in the cells and in the lumen of the acini in the central and peripheral zones of the two lobes of the prostate, 3) cellular hyperplasia indicated by flow cytometric analysis of DNA content, 4) significant increase in the secretion of PAP and levels of estradiol, and 5) a marked increase in fibromuscular stroma in the central and peripheral zones of both the lobes of the prostate. The present study is the first report to provide evidence that long-term androgen treatment has caused hypertrophy of the prostatic epithelial cells, which showed increased secretory activity. The hyperplastic changes indicate a need for the development of new androgens with a better pharmacokinetic profile for use in male contraceptive regimens.

Metastatic lesions from prostate cancer do not express oestrogen and progesterone receptors

Oestrogen receptors (ER) and progesterone receptors (PR) have been reported by several authors in the stromal cells of the human prostate. Controversial results exist on the expression of ER and PR in epithelial cells of the prostate. Some recent publications, in contrast to previous findings, have suggested that these receptors are also present in human prostate cancer cell lines derived from metastatic lesions. The expression of ER and PR in these cell lines has been re-examined to determine their presence in lymph node metastases from patients who did not receive any kind of endocrine therapy and in distant metastases obtained from patients who failed endocrine treatment. ER and PR expression in LNCaP, PC-3, and DU-145 cells was assessed by means of the reverse transcriptase-polymerase chain reaction, ligand binding assays, and immunohistochemistry. With all the techniques applied, the three cell lines were found to be negative for both ER and PR. Immunohistochemical analyses were performed in four lymph node metastases obtained at radical prostatectomy from patients who did not receive endocrine therapy and in 17 distant metastases obtained at palliative surgery from patients who failed endocrine therapy. All 21 metastases were negative for ER and PR on immunohistochemistry. These results do not support the recently developed concept that receptors for oestrogenic and progestagenic steroids are present in metastases from human prostate cancer.

Estradiol activates p60src, p53/56lyn and renatured p50/55 protein tyrosine kinases in the dog prostate

Protein tyrosine kinases (PTKs) are key enzymes implicated in signal transduction pathways regulated by growth factors (GFs). We have previously shown by immunohistochemistry that the level of phosphotyrosine (pY) proteins is increased in prostatic basal epithelial cells following estrogen treatment in castrated dogs. In this study, we investigated if this treatment increases the level and distribution of prostatic PTK activity, and more specifically, if it alters the expression and/or activity of the Src family members p60src and p53/56lyn. Prostates from normal and hyperplastic dog prostates, as well as those from castrated dogs treated with androgens, were also examined. Only the glands obtained from estrogen-treated dogs had a significantly increased total and specific PTK activity, observed uniquely in the particulate extract, as compared to the other types of prostates studied. In addition, this increased activity was correlated upon gel filtration chromatography with the presence of an additional peak of activity with an apparent molecular weight of 130 kDa, which was absent in other prostate fractions presenting only 50 kDa peaks. Using antibodies, we demonstrate that active p60src and pp53/56lyn kinases accounted for 81% of the activity in this 130 kDa peak. On the other hand, in situ renaturation also revealed the presence of still uncharacterized 50/55 kDa PTKs in the 130 kDa peak. Altogether, these findings raise the possibility that these PTKs contribute to the transmission of mitogenic signals originating directly or indirectly from estrogen stimulation of the basal cell layer of the prostate.