Estrogen receptor beta expression in human prostate tissue

Estrogen receptor expression is modulated in human and mouse prostate epithelial cells during cancer progression

Substantial data posit estrogen receptors (ERs) as promising targets for prostate cancer (PCa) therapeutics. However, the trials on assessing the chemo-preventive or therapeutic potential of ER targeting drugs or selective estrogen receptor modulators (SERMs) have not yet established their clinical benefits. This could be ascribed to a possible modulation in the ER expression during PCa progression. Further it is warranted to test various ER targeting drugs in appropriate preclinical models that simulate human ER expression pattern during PCa progression. The study was undertaken to revisit the existing data on the epithelial ER expression pattern in human cancerous prostates and experimentally determine whether these patterns are replicated in TRAMP (Transgenic Adenocarcinoma of Mouse Prostate) mice, a model for human PCa. Estradiol (E2) binding to the plasma membrane of the epithelial cells and its modulation during the PCa progression in TRAMP were also investigated. A reassessment of the existing data revealed a trend towards downregulation in the epithelial expression of wild-type ESR1 transcripts in high-grade PCa, compared to non-cancerous prostate in humans. Next, epithelial cell-enriched populations from TRAMP prostates (TP) displaying low-grade prostatic intraepithelial neoplasia (LGPIN), high-grade PIN (HGPIN), HGPIN with well-differentiated carcinoma (PIN + WDC), WDC (equivalent to grade 2/3 human PCa), and poorly-differentiated carcinoma (PDC-equivalent to grade 4/5 human PCa) revealed significantly higher Esr1 and Esr2 levels in HGPIN and significantly reduced levels in WDC, compared to respective age-matched control prostates. These patterns for the nuclear ERs were similar to the trend shown by E2 binding to the plasma membrane of the epithelial cells during PCa progression in TRAMP. E2 binding to epithelial cells (EpCAM+), though significantly higher in TPs displaying LGPIN, decreased significantly as the disease progressed to WDC. The study highlights a reduction in the epithelial ESR level with the PCa progression and this pattern was evident in both humans and TRAMP. These observations may have major implications in refining PCa therapeutics targeting ER.

Estrogen Receptor ß in Cancer: To ß(e) or not to ß(e)?

Estrogen receptors (ERs) are known to play an important role in the proper development of estrogen-sensitive organs, as well as in the development and progression of various types of cancer. ERα, the first ER to be discovered, has been the focus of most cancer research, especially in the context of breast cancer. However, ERβ expression also plays a significant role in cancer pathophysiology, notably its seemingly protective nature and loss of expression with oncogenesis and progression. Although ERβ exhibits antitumor activity in breast, ovarian, and prostate cancer, its expression is associated with disease progression and worse prognosis in lung cancer. The function of ERβ is complicated by the presence of multiple isoforms and single nucleotide polymorphisms, in addition to tissue-specific functions. This mini-review explores current literature on ERβ and its mechanism of action and clinical implications in breast, ovarian, prostate, and lung cancer.

Association between estrogen receptor β polymorphisms and prostate cancer in a Slovak population

Sex steroid hormones have important roles in the function of the prostate; however, they may also serve as factors in the initiation and progression of carcinogenesis. Estrogens, acting through estrogen receptors, may significantly affect prostate cancer development and progression. The main aim of the present study was to analyze the association between the rs3020449, rs4986938 and rs1256049 polymorphisms in the promoter region of the estrogen receptor β (ESR2) gene and prostate cancer risk in the Slovak population. A total of 510 patients with prostate cancer and 184 healthy men were included in the present study. No association between the rs4986938 and rs1256049 polymorphisms and prostate cancer development and progression was revealed; however, there was a statistically significant association between the rs3020449 GG genotype [odds ratio (OR), 2.35; P=0.002] and the G allele (OR, 1.42; P=0.005) and a higher risk of prostate cancer development. The rs3020449 GG genotype was significantly associated with a higher risk of development of carcinoma with a Gleason score >7 (OR, 2.66; P=0.005), as well as with the development of carcinoma with pT3/pT4 (OR, 2.28; P=0.02). According to the results from the present study, the rs3020449 polymorphism, in the promoter region of ESR2, may be considered to have a role in the development and progression of prostate cancer in the Slovak population.

Expression of estrogen receptor beta isoforms in pancreatic adenocarcinoma

Limited studies have shown that some patients with pancreatic adenocarcinoma (PAC) may benefit from treatment with tamoxifen. PAC has been shown to be largely negative for estrogen receptor alpha (ER-alpha). The aim of this pilot study was to investigate ER-beta expression in human PAC. Sections of tissue microarray with 18 evaluable cases of human PAC were stained by immunohistochemistry (IHC) for ER-beta1, ER-beta2, ER-beta5, and Cyclin A. The levels of ER-beta isoform expression and the S-phase fraction (SPF) were determined using quantitative digital image analysis. Higher mean and median ER-beta2 levels correlated with male sex (p = 0.057 and p = 0.035, respectively), older age (p = 0.005 and p = 0.006, respectively), and lower pT stage (p = 0.008 and p = 0.009). Mean and median ER-beta5 levels correlated negatively with SPF (p = 0.021 and p = 0.047, respectively). Mean ER-beta1 expression did not correlate with any of the above mentioned clinicopathologic factors. The findings in this pilot study, although should be considered preliminary, suggest that some ER-beta isoforms may play a role in the biology of PAC. Additional larger studies are needed to confirm our findings, and to determine whether ER-beta may be considered for future targeted therapy.

In Vivo Study of the Effects of ERβ on Apoptosis and Proliferation of Hormone-Independent Prostate Cancer Cell Lines PC-3M

OBJECTIVE

To evaluate the in vivo therapeutic effects of attenuated Salmonella carrying PCDNA3.1-ERβ plasmid in hormone-independent prostatic cancer in nude mice and to clarify the mechanism by which estrogen receptor β (ERβ) induces apoptosis and proliferation in prostatic cancer cells in mice.

METHODS

The orthotopic prostatic cancer models of mice were randomly divided as follows: MOCK group, treated with PBS, PQ group, treated with attenuated Salmonella alone, PQ-PCDNA3.1 group, treated with attenuated Salmonella carrying PCDNA3.1 plasmid, and PQ-PCDNA3.1-ERβ group, treated with the attenuated Salmonella carrying PCDNA3.1-ERβ plasmid. Then, 10 μl of the plasmid-containing solution, comprising 1 × 107 cfu of the bacteria, was administered via intranasal delivery to each group except the MOCK group. The experimental methods included flow cytometry and terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling (TUNEL) assay, immunohistochemistry, and western blotting.

RESULTS

Compared with the MOCK, PQ, and PQ-PCDNA3.1 groups, the weights of tumors in the PQ-PCDNA3.1-ERβ group were significantly reduced. The results of flow cytometry and TUNEL assay revealed that the number of apoptotic cells in the PQ-PCDNA3.1-ERβ group significantly increased. Compared with PQ-PCDNA3.1 group, the protein expression levels of ERβ, Bad, p-caspase 9, p-caspase 3, and cleaved PARP in the PQ-PCDNA3.1-ERβ group were significantly increased, while the expression levels of Akt, p-Akt, and Bcl-xl were decreased (P < 0.05).

CONCLUSION

The attenuated Salmonella carrying PCDNA3.1-ERβ plasmid could inhibit the growth of orthotopic prostatic cancer in mice by increasing the expression of ERβ.

Testosterone metabolites inhibit proliferation of castration- and therapy-resistant prostate cancer

Novel treatments for castration-resistant prostate cancer (CRPC) such as abiraterone acetate (AA) or enzalutamide effectively target the androgen pathway to arrest aberrant signalling and cell proliferation. Testosterone is able to inhibit tumour cell growth in CRPC. Estrogen receptor-beta (ERβ) binds the testosterone-metabolites 3β-androstanediol and 3α-androstanediol in parallel to the canonical estradiol. In the prostate it is widely accepted that ERβ regulates estrogen signalling, mediating anti-proliferative effects. We used the prostate cancer cell lines LNCaP, PC-3, VCaP, and the non-neoplastic BPH-1. VCaP cells were treated with 1 nmol/L testosterone over 20 passages, yielding the cell line VCaPrev, sensitive to hormone therapies. In contrast, LNCaP cells were grown for more than 100 passages yielding a high passage therapy resistant cell line (hiPLNCaP). VCaP and hiPLNCaP cell lines were treated with 5 μmol/L AA for more than 20 passages, respectively, generating the AA-tolerant-subtypes VCaPAA and hiPLNCaPAA. Cell lines were treated with testosterone, dihydrotestosterone (DHT), R1881, and the androgen-metabolites 3β-androstanediol and 3α-androstanediol. 3β-androstanediol or 3α-androstanediol significantly reduced proliferation in all cell lines except the BPH-1 and androgen receptor-negative PC-3 and markedly downregulated AR and estrogen receptor alpha (ERα). Whereas ERβ expression was increased in all cell lines except BPH-1 or PC-3. In summary, 3β-adiol or 3α-adiol, as well as DHT and R1881, significantly reduced tumour cell growth in CRPC cells. Thus, these compounds represent novel potential therapeutic approaches to overcome drug-resistance in CRPC, especially with regard to AR-V7 function in therapy resistance. Furthermore, these data confirm the tumour suppressor properties of ERβ in CRPC.

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.

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.

Prostate cancer stem cells: the role of androgen and estrogen receptors

Prostate cancer is one of the most commonly diagnosed cancers in men, and androgen deprivation therapy still represents the primary treatment for prostate cancer patients. This approach, however, frequently fails and patients develop castration-resistant prostate cancer, which is almost untreatable.

Cancer cells are characterized by a hierarchical organization, and stem/progenitor cells are endowed with tumor-initiating activity. Accumulating evidence indicates that prostate cancer stem cells lack the androgen receptor and are, indeed, resistant to androgen deprivation therapy. In contrast, these cells express classical (α and/or β) and novel (GPR30) estrogen receptors, which may represent new putative targets in prostate cancer treatment.

In the present review, we discuss the still-debated mechanisms, both genomic and non-genomic, by which androgen and estradiol receptors (classical and novel) mediate the hormonal control of prostate cell stemness, transformation, and the continued growth of prostate cancer. Recent preclinical and clinical findings obtained using new androgen receptor antagonists, anti-estrogens, or compounds such as enhancers of androgen receptor degradation and peptides inhibiting non-genomic androgen functions are also presented. These new drugs will likely lead to significant advances in prostate cancer therapy.

Changes in Estrogen Receptor ERβ (ESR2) Expression without Changes in the Estradiol Levels in the Prostate of Aging Rats

Although the prostate is androgen-dependent, it is also influenced by estrogens, which act via the estrogen receptors ERα and ERβ. In the prostate, ERβ is highly expressed in the epithelium and appears to participate in the regulation of cell proliferation, apoptosis and differentiation. Evidence shows that ERβ is decreased in malignant prostate, suggesting that it plays an important role in protecting this tissue. Despite the relationship between reductions in ERβ and abnormal growth of the gland, little is known about the age-dependent variation of this receptor. Therefore, we aimed to investigate ERβ expression in the prostatic lobes of aging Wistar rats (3 to 24 months). Histopathological alterations, including hyperplasia, intraluminal concretions, nuclear atypia and prostate intraepithelial neoplasias (PIN), were observed in the prostates of aging rats. Epithelial proliferation led to cribriform architecture in some acini, especially in the ventral prostate (VP). In the VP, areas of epithelial atrophy were also observed. Furthermore, in the lateral prostate, there was frequent prostatitis. Immunohistochemistry revealed that the expression of ERβ is reduced in specific areas related to PIN, atrophic abnormalities and cellular atypia in the prostate epithelium of senile rats. Corroborating the involvement of the receptor with proliferative activity, the punctual reduction in ERβ paralleled the increase in cell proliferation especially in areas of PIN and nuclear atypies. The decrease in ERβ reactivity occurred in a hormonal milieu characterized by a constant concentration of estradiol and decreased plasmatic and tissue DHT. This paper is a pioneering study that reveals focal ERβ reduction in the prostate of aging rats and indicates a potential disorder in the ERβ pathway. These data corroborate previous data from humans and dogs that silencing of this receptor may be associated with premalignant or malignant conditions in the prostate.

Clinical significance of estrogen receptor β in breast and prostate cancer from biological aspects

Breast and prostate cancers are among the most common of all cancers. They are referred to as hormone-dependent cancers, because estrogen and androgen are involved in their development and growth. The effects of these hormones are mediated by their respective receptors, estrogen receptor (ER) α and androgen receptor. Around 18 years ago, a second ER, ERβ, which has a very similar structure to ERα, was discovered. Its function has been investigated using a variety of methods and biological systems, leading to our present understanding that ERβ can interact with or inhibit ERα and androgen receptor function directly and/or indirectly, suppress cell growth, and influence responsiveness to endocrine therapy. In order to apply the “inhibition of cell growth” function to cancer treatment, several specific ERβ agonists have been synthesized and are being tested for effectiveness in cancer treatment. We need to keep our eyes on ERβ.

Immunohistochemical expression of hormone receptors in melanoma of pregnant women, nonpregnant women, and men

The survival advantage of women over men with cutaneous melanoma and the reports of accelerated progression of melanoma during pregnancy have led to studies of the effect of hormones and hormone receptors on the development and progression of melanoma. However, the results are inconclusive. We therefore evaluated the expression of estrogen receptor α, estrogen receptor β, and androgen receptor in melanomas of stage- and age-matched pregnant women, nonpregnant women, and men by immunohistochemical analysis of formalin-fixed, paraffin-embedded archival tissues. In addition, we also assessed the mitotic rate using the antiphosphohistone H3 antibody by immunohistochemistry. Our data showed a trend of more frequent expression of estrogen receptor β in the melanomas of pregnant patients than in the melanomas of male patients, without a significant difference observed between pregnant and nonpregnant women. However, no association between the expression of estrogen receptor β and survival was observed. The small cohort may have limited the statistical power of the study, and large-scale studies are needed to elucidate the potential role of estrogen receptor β as a prognostic marker of melanoma.

Deficiency of ERβ and prostate tumorigenesis in FGF8b transgenic mice

Estrogens contribute to the development and growth of the prostate and are implicated in prostate tumorigenesis. In their target tissues, estrogens mediate their effects via estrogen receptor α (ERα (ESR1)) and β (ERβ (ESR2)). Hyperplasia and decreased differentiation of epithelial cells in the prostate have been reported in ERβ knockout (BERKO) mice. Herein, we studied the effect of ERβ deficiency on prostate tumorigenesis by crossing BERKOFVB mice with prostate-targeted human fibroblast growth factor 8b transgenic (FGF8b-Tg) mice. Consistent with results described in our previous report, the prostates of 1-year-old FGF8b-Tg mice displayed stromal aberrations, prostatic intraepithelial neoplasia (mPIN) lesions, inflammation, and occasionally cancer. The prostates of BERKOFVB mice exhibited mild epithelial hypercellularity and inflammation. The prostate phenotypes of FGF8b-Tg-BERKOFVB mice closely resembled those of FGF8b-Tg mice. However, mucinous metaplasia, indicated by Goblet-like cells in the epithelium, was significantly more frequent in the prostates of FGF8b-Tg-BERKOFVB mice when compared with FGF8b-Tg mice. Furthermore, compared with FGF8b-Tg mice, there was a tendency for increased frequency of inflammation but milder hyperplasias in the prostate stroma of FGF8b-Tg-BERKOFVB mice. The expression levels of mRNAs for FGF8b-regulated genes including osteopontin (Spp1), connective tissue growth factor (Ctgf), fibroblast growth factor receptors (Fgfrs), and steroid hormone receptors and cytokines were similar in the prostates of FGF8b-Tg and FGF8b-Tg-BERKOFVB mice. Our results indicate that ERβ plays a role in the differentiation of the prostatic epithelium and, potentially, in the defensive mechanism required for protection against inflammation but do not support a direct tumor-suppressive function of ERβ in the prostate of FGF8b-Tg mice.

Differential expression of estrogen receptor beta isoforms in prostate cancer through interplay between transcriptional and translational regulation

Estrogen receptor β (ERβ) and its isoforms have different putative functions and expression patterns in prostate cancer. Current studies on 5'-most exons, 0K and 0N, show that their respective promoters are actively involved in transcription. These data, however, do not explain why ERβ isoforms are differentially expressed in normal and cancerous tissues, since 0K and 0N transcripts are detectable in clinical specimens. Various combinations of 5' untranslated exons, termed exon 0Xs, associate with promoter 0K only and exon 0Xs accommodate upstream open reading frames (uORFs) reducing protein expression. Moreover, ERβ1, 2, and 5 are transcriptionally linked to promoter 0K; exon 0Xs are spliced only into ERβ2 and ERβ5 transcripts, suggesting that their expressions are regulated post-transcriptionally by exon 0Xs. This study reveals that expression of ERβ1 is regulated primarily at the transcriptional level, whereas that of ERβ2 and ERβ5 is controlled by the interplay between transcriptional and post-transcriptional regulation.

Synergistic effects of histone deacetylase inhibitor in combination with mTOR inhibitor in the treatment of prostate carcinoma

The aim of this study was to elucidate whether the treatment of a prostate carcinoma cell line (LNCaP) and LNCaP-derived tumors with the histone deacetylase (HDAC) inhibitor valproate in combination with the mammalian target of rapamycin (mTOR) inhibitor temsirolimus resulted in synergistic effects on cell proliferation and tumor growth. LNCaP cells were treated with valproate, temsirolimus or a combination of both. The proliferation rates and the expression of key markers of tumorigenesis were evaluated. In in vivo experiments, LNCaP cells were implanted into immune-suppressed male nude mice. Mice were treated with valproate (per os), temsirolimus (intravenously) or with a combination of both. Tumor volumes were calculated and mRNA expression was quantified. The incubation of LNCaP cells with the combination of valproate and temsirolimus resulted in a decrease of cell proliferation with an additive effect of both drugs in comparison to the single treatment. In particular, the combined application of valproate and temsirolimus led to a significant upregulation of insulin-like growth factor-binding protein-3 (IGFBP-3), which mediates apoptosis and inhibits tumor cell proliferation. In the mouse model, we found no significant differences in tumor growth between the different treatment arms but immunohistological analyses showed that tumors treated with a combination of valproate and temsirolimus, but not with the single drugs alone, exhibited a significant lower proliferation capacity.

The role of estrogen-metabolizing enzymes and estrogen receptors in human epidermis

Local estrogen metabolism and its sensitivities in the skin have been also suggested to contribute to skin homeostasis in addition to age- and/or gender-dependent circulating estrogen, even though their local mechanisms have been largely unknown. To characterize their potential correlations, age- and gender-dependencies were evaluated focusing on 5 pivotal estrogen-metabolizing enzymes including aromatase, estrogen sulfotransferase, steroid sulfatase, and 17β-hydroxysteroid dehydrogenases and estrogen receptors (ERα and ERβ) using immunohistochemistry of 100 human skin specimens. When their epidermal expression levels were compared among 7 age groups, ranging from the teens to the seventies, the highest expression in the teens group and the lowest expression in the seventies group were found in the expression of aromatase and ERβ, respectively, while no significant differences between the male and the female groups were found in the immunoreactivities of our interested proteins. Our results suggest that age-related differences in aromatase and ERβ expressions impact epidermal homeostasis.

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.

Androgens and estrogens in benign prostatic hyperplasia: past, present and future

Benign prostatic hyperplasia (BPH) and associated lower urinary tract symptoms (LUTS) are common clinical problems in urology. While the precise molecular etiology remains unclear, sex steroids have been implicated in the development and maintenance of BPH. Sufficient data exists linking androgens and androgen receptor pathways to BPH and use of androgen reducing compounds, such as 5α-reductase inhibitors which block the conversion of testosterone into dihydrotestosterone, are a component of the standard of care for men with LUTS attributed to an enlarged prostate. However, BPH is a multifactorial disease and not all men respond well to currently available treatments, suggesting factors other than androgens are involved. Testosterone, the primary circulating androgen in men, can also be metabolized via CYP19/aromatase into the potent estrogen, estradiol-17β. The prostate is an estrogen target tissue and estrogens directly and indirectly affect growth and differentiation of prostate. The precise role of endogenous and exogenous estrogens in directly affecting prostate growth and differentiation in the context of BPH is an understudied area. Estrogens and selective estrogen receptor modulators (SERMs) have been shown to promote or inhibit prostate proliferation signifying potential roles in BPH. Recent research has demonstrated that estrogen receptor signaling pathways may be important in the development and maintenance of BPH and LUTS; however, new models are needed to genetically dissect estrogen regulated molecular mechanisms involved in BPH. More work is needed to identify estrogens and associated signaling pathways in BPH in order to target BPH with dietary and therapeutic SERMs.

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.

Estrogen receptor β induces antiinflammatory and antitumorigenic networks in colon cancer cells

Several studies suggest estrogen to be protective against the development of colon cancer. Estrogen receptor β (ERβ) is the predominant estrogen receptor expressed in colorectal epithelium and is the main candidate to mediate the protective effects. We have previously shown that expression of ERβ reduces growth of colorectal cancer in xenografts. Little is known of the actions of ERβ and its effect on gene transcription in colon cancers. To dissect the processes that ERβ mediates and to investigate cell-specific mechanisms, we reexpressed ERβ in three colorectal cancer cell lines (SW480, HT29, and HCT-116) and conducted genome-wide expression studies in combination with gene-pathway analyses and cross-correlation to ERβ-chromatin-binding sites. Although induced gene regulation was cell specific, overrepresentation analysis of functional classes indicated that the same biological themes, including apoptosis, cell differentiation, and regulation of the cell cycle, were affected in all three cell lines. Novel findings include a strong ERβ-mediated down-regulation of IL-6 and downstream networks with significant implications for inflammatory mechanisms involved in colon carcinogenesis. We also discovered cross talk between the suggested nuclear receptor coregulator PROX1 and ERβ, demonstrating that ERβ both regulates and shares target genes with PROX1. The influence of ERβ on apoptosis was further explored using functional studies, which suggested an increased DNA-repair capacity. We conclude that reexpression of ERβ induces transcriptome changes that, through several parallel pathways, converge into antitumorigenic capabilities in all three cell lines. We propose that enhancing ERβ action has potential as a novel therapeutic approach for prevention and/or treatment of colon cancer.

Raloxifene induces cell death and inhibits proliferation through multiple signaling pathways in prostate cancer cells expressing different levels of estrogen receptor α and β

Raloxifene (RAL), a selective estrogen receptor (ER) modulator (SERM) seems to induce apoptosis in both androgen-dependent and -independent prostate cell (PC) lines via activation of ERβ and an antagonistic effect on ERα. In this study, we evaluated the effects of RAL on epithelial PC growth using the two following in vitro models: the androgen-dependent cell line EPN which expressed both ERs; and a stabilized epithelial cell line derived from a prostate cancer specimen (CPEC), which expressed low levels of ERβ and lacked ERα. In EPN cells, there was an increase in the pre-G1 apoptotic peak and a reduction in the S phase of the cell cycle with G0/G1 arrest after E2 or RAL treatment; bcl-2 mRNA and Bcl-2 protein levels were significantly reduced, while activated caspase-3 and Par-4 levels increased significantly after either E2 or RAL treatment; in addition, c-myc transcript was inhibited after 10(-6)  M RAL treatment. A dose-dependent increase of metallothionein II gene RNA level was also induced by RAL in EPN. In CPEC, there was only a weak apoptotic peak associated with caspase-3 activation and Par-4 increase after either E2 or RAL treatment; while c-myc transcript level increased. RAL induced a rapid but transient phosphorylation of ERK 1/2 in EPN cells but generated a sustained effect in CPEC. These findings suggest that RAL effects on PC growth control in vitro are cell-specific, depending on ERβ or ERβ/ERα relative expression levels. Moreover, this study demonstrated that RAL affected both transcriptional regulation and non-genomic signals, which resulted in the modulation of multiple signaling pathways of apoptosis and of cell cycle progression.

Estrogen receptor β

CONTEXT

A new class of estrogen receptors was discovered in 1996 and named estrogen receptor β (ER-B); the traditional estrogen receptor, which until a little more than 10 years ago was thought of as the only estrogen receptor in existence, is now called estrogen receptor α. Estrogen receptor β has at least 5 isoforms, which may have different functions and have different tissue distribution. The significance of ER-B expression in tumors was first demonstrated in breast cancer, with several studies demonstrating that women with ER-B-positive breast cancers treated with adjuvant tamoxifen have better survival, independent of estrogen receptor α expression. Pathologists need to be more aware of this increasingly important protein, as it will soon find its way into routine clinical practice.

OBJECTIVE

To provide pathologists with a concise review of ER-B, with special emphasis on current and potential clinical relevance.

DATA SOURCES

A search of the English literature in PubMed (National Library of Medicine, Bethesda, Maryland) for articles with titles including "estrogen receptor beta," with emphasis on "immunohistochemistry." Abstracts were reviewed, and selected articles were used as the basis for writing this review, mostly based on their relevance to pathology.

CONCLUSIONS

Estrogen receptor β and its isoforms have wider tissue distribution, including the gastrointestinal tract, lung, and brain, than the traditional estrogen receptor, now called estrogen receptor α. Estrogen receptor β expression in breast cancer is associated with favorable outcome in women treated with adjuvant tamoxifen, even in tumors negative for estrogen receptor α. The clinical significance of ER-B expression in tumors other than breast is currently under investigation.

Aromatase and regulating the estrogen:androgen ratio in the prostate gland

Although androgens and estrogens both play significant roles in the prostate, it is their combined action--and specifically their balance--that is critically important in maintaining prostate health and tissue homeostasis in adulthood. In men, serum testosterone levels drop by about 35% between the ages of 21 and 85 while estradiol levels remain constant or increase. This changing androgen:estrogen (T:E) ratio has been implicated in the development of benign and malignant prostate disease. The production of estrogens from androgens is mediated by the aromatase enzyme, the aberrant expression of which plays a critical role in the development of malignancy in a number of tissues. The normal prostate expresses aromatase within the stroma, while there is an induction of epithelial expression in malignancy with altered promoter utilisation. This may ultimately lead to an altered T:E ratio that is associated with the development of disease. The role of estrogen and the T:E balance in the prostate is further complicated by the differential actions of both estrogen receptors, alpha and beta. Stimulation of ERalpha leads to aberrant proliferation, inflammation and pre-malignant pathology; whereas activation of ERbeta appears to have beneficial effects regarding cellular proliferation and a putative protective role against carcinogenesis. Overall, these data reveal that homeostasis in the normal prostate involves a finely tuned balance between androgens and estrogens. This has identified estrogen, in addition to androgens, as integral to maintaining normal prostate health, but also as an important mediator of prostate disease.

The multiple roles of estrogens and the enzyme aromatase

Aromatase is the enzyme that catalyzes the last step of estrogen biosynthesis. It is expressed in many tissues such as the gonads, brain and adipose tissue. The regulation of the level and activity of aromatase determines the levels of estrogens that have endocrine, paracrine and autocrine effects on tissues. Estrogens play many roles in the body, regulating reproduction, metabolism and behavior. In the brain, cell survival and the activity of neurons are affected by estrogens and hence aromatase.

Expression of RIZ1 protein (Retinoblastoma-interacting zinc-finger protein 1) in prostate cancer epithelial cells changes with cancer grade progression and is modulated in vitro by DHT and E2

The nuclear protein methyl-transferase Retinoblastoma-interacting zinc-finger protein 1 (RIZ1) is considered to be a downstream effector of estrogen action in target tissues. Silencing of RIZ1 expression is common in many tumors. We analyzed RIZ1 expression in normal and malignant prostate tissue and evaluated whether estradiol (E2) or dihydrotestosterone (DHT) treatment modulated RIZ1 in cultured prostate epithelial cells (PEC). Moreover, we studied the possible involvement of RIZ1 in estrogen action on the EPN prostate cell line, constitutively expressing both estrogen receptor (ER)-alpha and beta. RIZ1 protein, found in the nucleus of normal PECs by immunohistochemistry, was progressively lost in cancer tissues as the Gleason score increased and was only detected in the cytoplasmic compartment. RIZ1 transcript levels, as assayed by semi-quantitative RT-PCR in primary PEC cultures, were significantly reduced in cancer cells (P < 0.05). In EPN DHT treatment significantly increased RIZ1 transcript and protein levels (P < 0.05); E2 induced a reduction of S phase without significant changes of RIZ1 expression. In E2-treated EPN cell extracts RIZ co-immunoprecipitated with ERbeta and ERalpha. Our data demonstrate that RIZ1 is expressed in normal PECs and down-regulated in cancer cells, with a switch of its sub-cellular localization from the nucleus to the cytoplasm upon cancer grade progression. RIZ1 expression levels in the PECs were modulated by DHT or E2 treatment in vitro. Furthermore, the E2 effects on ER-expressing prostate cells involve RIZ1, which confirms a possible role for ER-mediated pathways in a non-classic E(2)-target tissue.

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.

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.

Expression of steroidogenic enzymes and sex-steroid receptors in human prostate

Identification of the cell types expressing the steroidogenic enzymes and sex steroid receptors in the human prostate has recently been performed using immunocytochemistry and in-situ hybridization. The enzymes 3beta-hydroxysteroid dehydrogenase (3beta-HSD), which converts dehydroepiandrosterone (DHEA) into androstenedione, and type 5 17beta-HSD, which catalyzes the reduction of androstenedione to testosterone, have been localized in basal cells of alveoli as well as in stromal cells and endothelial cells of blood vessels. On the other hand, type-2 5alpha-reductase, which converts testosterone into the most potent androgen dihydrotestosterone (DHT), has been mostly observed in the luminal cells in alveoli. Aromatase, which converts testosterone into estradiol, has also been found to be expressed in the luminal cells of the alveoli as well as in stromal cells. Androgen receptor (AR) has been localized in luminal cell nuclei of alveoli and a large number of stromal cells, while estrogen receptor beta has been detected in both basal and luminal cells in alveoli and also in stromal cells.

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.

The relevance of estrogen receptor- expression to the antiproliferative effects observed with histone deacetylase inhibitors and phytoestrogens in prostate cancer treatment

In the prostate, estrogen receptor beta (ERbeta), the preferred receptor for phytoestrogens, has features of a tumor suppressor. To investigate the mechanisms underlying the beneficial effects on prostate cancer of histone deacetylase inhibitor valproic acid (VPA) and phytoestrogen tectorigenin, we analyzed the expression of ERbeta after tectorigenin or VPA treatment. For further functional analysis, we knocked down ERbeta expression by RNA interference. LNCaP prostate cancer cells were treated with 5 mmol/L VPA or 100 micromol/L tectorigenin and transfected with small interfering RNA (siRNA) against ERbeta. Control transfections were done with luciferase (LUC) siRNA. Expression of ERbeta was assessed by Western blot. mRNA expression was quantitated by real-time reverse transcription-PCR. Expression of ERbeta mRNA and protein markedly increased after VPA or tectorigenin treatment. When ERbeta was knocked down by siRNA, the expression of prostate-derived Ets factor, prostate-specific antigen, prostate cancer-specific indicator gene DD3(PCA3), insulin-like growth factor-1 receptor, the catalytic subunit of the telomerase, and ERalpha was up-regulated and the tectorigenin effects were abrogated. ERbeta levels were diminished in prostate cancer and loss of ERbeta was associated with proliferation. Here, we show that siRNA-mediated knockdown of ERbeta increases the expression of genes highly relevant to tumor cell proliferation. In addition, we show that one prominent result of treatment with VPA or tectorigenin is the up-regulation of ERbeta resulting in antiproliferative effects. Thus, these drugs, by restoring the regulatory function of ERbeta in tumor cells, could become useful in the intervention of prostate cancer.

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.

Evaluation of AIbZIP and Cdc47 as markers for human prostatic diseases

OBJECTIVES

Benign prostatic hyperplasia and prostate cancer are important public health issues. However, histologic markers for these diseases are limited.

METHODS

Immunocytochemistry was used to analyze the cellular localization of AIbZIP, Cdc47, androgen receptor and estrogen receptor-beta markers. AIbZIP is a protein recently found to be more abundant in prostate cancer than in benign prostatic tissue, and Cdc47 is a cell proliferation-associated protein. The localization and modulation of androgen receptor and estrogen receptor-beta through the carcinogenesis process have been examined in several studies but controversial results were obtained. These four proteins were evaluated as potential markers of prostatic diseases in 210 needle core biopsies, including normal prostate, benign prostatic hyperplasia, low-grade and high-grade prostatic intraepithelial neoplasia, and different Gleason grades of prostatic adenocarcinoma.

RESULTS

Androgen receptor and estrogen receptor-beta do not discriminate between benign and malignant specimens, while AIbZIP was able to distinguish between them. Cdc47, in contrast, discriminated not only between malignant and benign prostatic tissue, but also between benign prostatic hyperplasia and normal prostatic tissue.

CONCLUSIONS

Cdc47 appears to be a sensitive marker of prostatic diseases since its expression gradually increased in parallel with the severity of the lesion. AIbZIP discriminated between benign tissue and cancer. AIbZIP and Cdc47 thus appear to be useful markers with diagnostic and prognostic values.

Inhibition of androgen-independent prostate cancer by estrogenic compounds is associated with increased expression of immune-related genes

The clinical utility of estrogens for treating prostate cancer (CaP) was established in the 1940s by Huggins. The classic model of the anti-CaP activity of estrogens postulates an indirect mechanism involving the suppression of androgen production. However, clinical and preclinical studies have shown that estrogens exert growth-inhibitory effects on CaP under low-androgen conditions, suggesting additional modes whereby estrogens affect CaP cells and/or the microenvironment. Here we have investigated the activity of 17beta estradiol (E2) against androgen-independent CaP and identified molecular alterations in tumors exposed to E2. E2 treatment inhibited the growth of all four androgen-independent CaP xenografts studied (LuCaP 35V, LuCaP 23.1AI, LuCaP 49, and LuCaP 58) in castrated male mice. The molecular basis of growth suppression was studied by cDNA microarray analysis, which indicated that multiple pathways are altered by E2 treatment. Of particular interest are changes in transcripts encoding proteins that mediate immune responses and regulate androgen receptor signaling. In conclusion, our data show that estrogens have powerful inhibitory effects on CaP in vivo in androgen-depleted environments and suggest novel mechanisms of estrogen-mediated antitumor activity. These results indicate that incorporating estrogens into CaP treatment protocols could enhance therapeutic efficacy even in cases of advanced disease.

The reinforcement of invasion in epithelial ovarian cancer cells by 17β-Estradiol is associated with up-regulation of Snail

OBJECTIVE

The transcription factor Snail, which is implicated in the triggering of epithelial-mesenchymal transitions (EMT), plays an important role in adhesion, invasion and metastasis of tumor cells. In the present study, we assessed 17beta-Estradiol (E2)'s effect on Snail, E-cadherin and MMP-2 expression of epithelial ovarian cancer cell line ES-2 and SKOV3. Then we induced Snail gene silencing by RNA interference to explore the effect of E2 on E-cadherin and MMP-2 expression when Snail gene expression was blocked.

METHODS

Treated by 10(-8) M E2, Snail, E-cadherin and MMP-2 mRNA expression of the cells was measured by RT-PCR; Snail, MMP-2 protein expression was detected by IHC; and MMP-2 activity was determined by Zymography. E-cadherin protein level was measured by Western blot. We constructed the small interfering dsRNA expression vector (pRNAT-U6.1/Neo-Snail) targeting Snail gene, as well as a negative control vector (pRNAT-U6.1/Neo-Neg). Then the cells were transiently transfected with the vectors. Western blot and zymography were conducted to determine E-cadherin protein level and matrix metalloproteinase activity of the cells transfected with pRNAT-U6.1/Neo-Snail or pRNAT-U6.1/Neo-Neg after treated with E2 for 24 h.

RESULTS

The expression of ER alpha mRNA and protein was negative in ES-2 cells and positive in SKOV3 cells, and ER beta expression was positive in both cell lines. 10(-8) mol/l E2 elevated expression of Snail and MMP-2 mRNA and protein in both ES-2 and SKOV3 cells, and reduced expression of E-cadherin mRNA and protein in SKOV3 cells. While in the RNAi group transfected with the small interfering dsRNA expression vector (pRNAT-U6.1/Neo-Snail) targeting Snail gene, E2 treatment did not have a significant effect on MMP-2 activity or E-cadherin protein in ES-2 and SKOV3 cells.

CONCLUSIONS

17beta-Estradiol increased Snail expression in both ER alpha-negative ES-2 cells and ER alpha-positive SKOV3 cells independent of the existence of ER alpha. The increase of MMP-2 expression in ES-2 and SKOV3 cells and decrease of E-cadherin expression in SKOV3 cells induced by E2 were associated with up-regulation of Snail.

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.

Expression of androgen, oestrogen alpha and beta, and progesterone receptors in the canine prostate: differences between normal, inflamed, hyperplastic and neoplastic glands

The expression of receptor for androgen (AR), oestrogen alpha and beta (ERalpha and ERbeta) and progesterone (PR) was examined immunohistochemically in canine prostate specimens (normal, hyperplastic, inflamed [prostatitis] or neoplastic). AR immunolabelling was seen in 100% of epithelial cells of normal and hyperplastic tissue, the corresponding figures for inflamed and carcinomatous tissue being 74% and 65%, respectively. ERalpha labelling was seen in 85% of epithelial cells in normal prostate glands, the corresponding figures for hyperplastic, inflamed and neoplastic glands being 35%, 22% and 12%, respectively. ERbeta labelling was seen in 85% of epithelial cells of normal glands and in about 70% of such cells in glands showing pathological changes. On the other hand, PR expression (weak) in normal glands was observed in fewer epithelial cells (44%) than in hyperplastic (70%), inflamed (62%) or neoplastic (64%) glands.

The distribution of oestrogen receptors in normal, hyperplastic and neoplastic canine prostate, as demonstrated immunohistochemically

The role of oestrogens and their receptors (ERs) in prostatic growth and differentiation and in the progression of prostatic carcinoma has been well investigated in human medicine. In dogs, however, available reports on the expression of ERs in normal, hyperplastic or neoplastic prostates are few and controversial, or completely lacking. Three normal, three hyperplastic and nine neoplastic canine prostates were examined histologically, and immunohistochemically with a polyclonal antibody directed against human ERs. Evaluation of the percentage of immunolabelled cells was performed by digital image analysis. The study showed that ERs were expressed in the nuclei of epithelial and stromal cells in normal, hyperplastic and neoplastic prostates. All nuclei in normal and hyperplastic prostates were strongly and homogeneously immunolabelled by the antibody used. However, the percentages of immunolabelled nuclei in the nine prostatic carcinomas were greatly reduced, ranging from 36.34% to 66.73%. The severe loss of ER expression in canine prostatic carcinomas may account for the relative lack of differentiation of these tumours in the dog.

Expression of enzymes involved in estrogen metabolism in human prostate

There is evidence that estrogens can directly modulate human prostate cell activity. It has also been shown that cultured human prostate cancer LNCaP can synthesize the active estrogen estradiol (E2). To elucidate the metabolism of estrogens in the human prostate, we have studied the expression of enzymes involved in the formation and inactivation of estrogens at the cellular level. 17beta-Hydroxysteroid dehydrogenase (17beta-HSD) types 1, 2, 4, 7, and 12, as well as aromatase mRNA and protein expressions, were studied in benign prostatic hyperplasia (BPH) specimens using in situ hybridization and immunohistochemistry. For 17beta-HSD type 4, only in situ hybridization studies were performed. Identical results were obtained with in situ hybridization and immunohistochemistry. All the enzymes studied were shown to be expressed in both epithelial and stromal cells, with the exception of 17beta-HSD types 4 and 7, which were detected only in the epithelial cells. On the basis of our previous results, showing that 3beta-HSD and 17beta-HSD type 5 are expressed in human prostate, and of the present data, it can be concluded that the human prostate expresses all the enzymes involved in the conversion of circulating dehydroepiandrosterone (DHEA) to E2. The local biosynthesis of E2 might be involved in the development and/or progression of prostate pathology such as BPH and prostate cancer through modulation of estrogen receptors, which are also expressed in epithelial and stromal cells.

Metastases of prostate cancer express estrogen receptor-beta

OBJECTIVES

To examine estrogen receptor-beta (ERbeta) expression in prostate cancer (CaP) metastases, thereby providing a basis for conducting estrogen therapy studies in patients with metastatic CaP. Advanced androgen-independent CaP is a serious health problem with no effective treatment at present. Estrogens have been reported to inhibit the growth of CaP cells in androgen-free environments. Recent reports have shown that the prostatic epithelium and primary CaP cells express ERbeta, with decreased expression of ERbeta accompanying CaP progression. It has been proposed that ERbeta may play a role in the growth regulation of prostate cells. The targeting of ERs by selective ER modulators might be an effective method of treating advanced CaP.

METHODS

The anti-ERbeta antibody GC17 was used in immunohistochemistry to characterize the expression of ERbeta in CaP metastasis specimens (n = 60) obtained from 20 patients who had died of CaP. Statistical analyses were performed to evaluate the association of ERbeta expression with clinical parameters, including prostate-specific antigen levels, radiotherapy, and estrogen exposure.

RESULTS

Nuclear ERbeta staining was detected in all bone CaP metastases (33 of 33) and nonosseous CaP metastases (27 of 27). However, a large variability in the percentage of immunoreactive cells (5% to 100%) was found among patients, as well as among individual patient samples. A statistically significant negative association between nuclear ERbeta staining and estrogen exposure (P = 0.05) was detected.

CONCLUSIONS

Our data have shown that ERbeta is expressed in CaP metastases, validating the initiation of studies to evaluate selective ER modulators for treatment of advanced CaP.

Frequent loss of estrogen and progesterone receptors in human prostatic tumors determined by quantitative real-time PCR

Relative gene expression of the estrogen receptors (ER)-alpha (NR3A1) and ER-beta (NR3A2) along with progesterone receptors PR-A and PR-B (NR3C3) was determined by quantitative real-time PCR in a previously characterized panel of paired human prostate tumor and surrounding unaffected tissue (Prostate 54:275). In approximately half of these cases, a 10-fold or greater reduction in the relative mRNA levels of ER-beta but not ER-alpha was found in the cancer as compared to normal tissue, which was also observed with unpaired samples. Immunohistochemical staining for ER-beta and ER-alpha closely paralleled mRNA expression patterns for both receptors in paired samples. Reduced relative expressions of PR-B and total PR-A and PR-B isoforms were also observed in prostate tumor as compared to unaffected tissue, implying a potential role of PR in prostate tissue. The relative decrease in ER-beta is greater than that observed in prior studies, suggesting that paired samples more accurately reflect differences within individual cases. These findings favor the concept that ER-beta mediates anti-proliferative signals and its loss in prostatic tumor promotes proliferation of these cells.

Hormonal, cellular, and molecular regulation of normal and neoplastic prostatic development

This review on normal and neoplastic growth of the prostate emphasizes the importance of epithelial-mesenchymal/stromal interactions. Accordingly, during prostatic development urogenital sinus mesenchyme (a) specifies prostatic epithelial identity, (b) induces epithelial bud formation, (c) elicits prostatic bud growth and regulates ductal branching, (d) promotes differentiation of a secretory epithelium, and (e) specifies the types of secretory proteins expressed. In reciprocal fashion, prostatic epithelium induces smooth muscle differentiation in the mesenchyme. Epithelial-mesenchymal interactions during development continue postnatally into adulthood as stromal-epithelial interactions which play a homeostatic role and in so doing reciprocally maintain epithelial and stromal differentiation and growth-quiescence. Prostatic carcinogenesis involves perturbation of these reciprocal homeostatic cell-cell interactions. The central role of mesenchyme in prostatic epithelial development has been firmly established through analysis of tissue recombinants composed of androgen-receptor-positive wild-type mesenchyme and androgen-receptor-negative epithelium. These studies revealed that at the very least ductal morphogenesis, epithelial cytodifferentiation, epithelial apoptosis and epithelial proliferation are regulated by stromal and not epithelial androgen receptors. Likewise, progression from non-tumorigenesis to tumorigenesis elicited by testosterone plus estradiol proceeds via paracrine mechanisms. Thus, stromal-epithelial interactions play critical roles in the hormonal, cellular, and molecular regulation of normal and neoplastic prostatic development.

Loss of ERbeta expression as a common step in estrogen-dependent tumor progression

The characterization of estrogen receptor beta (ERbeta) brought new insight into the mechanisms underlying estrogen signaling. Estrogen induction of cell proliferation is a crucial step in carcinogenesis of gynecologic target tissues, and the mitogenic effects of estrogen in these tissues (such as breast, endometrium and ovary) are well documented both in vitro and in vivo. There is also an emerging body of evidence that colon and prostate cancer growth is influenced by estrogens. In all of these tissues, most studies have shown decreased ERbeta expression in cancer as compared with benign tumors or normal tissues, whereas ERalpha expression persists. The loss of ERbeta expression in cancer cells could reflect tumor cell dedifferentiation but may also represent a critical stage in estrogen-dependent tumor progression. Modulation of the expression of ERalpha target genes by ERbeta or ERbeta-specific gene induction could explain that ERbeta has a differential effect on proliferation as compared with ERalpha. ERbeta may exert a protective effect and thus constitute a new target for hormone therapy, such as ligand specific activation. The potential distinct roles of ERalpha and ERbeta expression in carcinogenesis, as suggested by experimental and clinical data, are discussed in this review.

Estrogens and epithelial ovarian cancer

OBJECTIVE

Molecular mechanisms involved in ovarian carcinogenesis are still unclear, but there is growing evidence that estrogens promote tumor progression in an epithelial ovarian cancer (EOC) subgroup.

METHODS

We reviewed current knowledge on the effects of estrogens in ovarian carcinogenesis and new potential research focuses concerning hormonal therapy of EOC.

RESULTS

Experimentally, estrogen stimulates the growth of ovarian tumor cell lines expressing estrogen receptors (ER). We and other authors have demonstrated differential expression of ERalpha or beta during ovarian carcinogenesis, with overexpression of ERalpha as compared to ERbeta in cancer. This differential expression in ER suggests that estrogen-induced proteins may act as ovarian tumor-promoting agents. Among these proteins, c-myc, fibulin-1, cathepsin-D, or several kallikreins may play a role, since high expression levels have been found in EOC. Consistently, recent prospective epidemiological studies have indicated that estrogen replacement therapy in postmenopausal women may increase ovarian cancer incidence and mortality.

CONCLUSION

Questions on the estrogen-sensitivity and potential benefits of new hormone therapies in an EOC subgroup should be readdressed in the light of recent experimental and clinical data.

Estrogens and anti-estrogens: Key mediators of prostate carcinogenesis and new therapeutic candidates

Despite the historical use of estrogens in the treatment of prostate cancer (PCa) little is known about their direct biological effects on the prostate, their role in carcinogenesis, and what mechanisms mediate their therapeutic effects on PCa. It is now known that estrogens alone, or in synergism with an androgen, are potent inducers of aberrant growth and neoplastic transformation in the prostate. The mechanisms of estrogen carcinogenicity could be mediated via induction of unscheduled cell proliferation or through metabolic activation of estrogens to genotoxic metabolites. Age-related changes and race-/ethnic-based differences in circulating or locally formed estrogens may explain differential PCa risk among different populations. Loss of expression of estrogen receptor (ER)-beta expression during prostate carcinogenesis and prevention of estrogen-mediated oxidative damage could be exploited in future PCa prevention strategies. Re-expression of ER-beta in metastatic PCa cells raises the possibility of using ER-beta-specific ligands in triggering cell death in these malignant cells. A variety of new estrogenic/anti-estrogenic/selective estrogen receptor modulator (SERM)-like compounds, including 2-methoxyestradiol, genistein, resveratrol, licochalcone, Raloxifene, ICI 182,780, and estramustine are being evaluated for their potential in the next generation of PCa therapies. Increasing numbers of patients self-medicate with herbal formulations such as PC-SPES. Some of these compounds are selective ER-beta ligands, while most of them have minimal interaction with ER-alpha. Although many may inhibit testosterone production by blockade of the hypothalamal-pituitary-testis axis, the most effective agents also exhibit direct cytostatic, cytotoxic, or apoptotic action on PCa cells. Some of them are potent in interfering with tubulin polymerization, blocking angiogenesis and cell motility, suppressing DNA synthesis, and inhibiting specific kinase activities. Further discovery of other compounds with potent apoptotic activities but minimal estrogen action should promote development of a new generation of effective PCa preventive or treatment regimens with few or no side-effects due to estrogenicity. Further advancement of our knowledge of the role of estrogens in prostate carcinogenesis through metabolic activation of estrogens and/or ER-mediated pathways will certainly result in better preventive or therapeutic modalities for PCa.

EBAG9/RCAS1 expression and its prognostic significance in prostatic cancer

Estrogen receptor-binding fragment-associated gene 9 (EBAG9) has been identified as a primary estrogen-responsive gene from MCF-7 human breast cancer cells (Watanabe T, et al., Mol Cell Biol 1998;18:442-9). EBAG9 is identical with RCAS1 (receptor-binding cancer antigen expressed on SiSo cells), which has been reported as a cancer cell surface antigen implicated in immune escape (Nakashima M, et al., Nat Med 1999;5:938-42). In our present study, we examined EBAG9 expression in human prostatic tissues and investigated its prognostic significance in patients with prostatic cancer. EBAG9 expression in normal prostatic epithelial cells and PC-3, DU145 and LNCaP cancer cells was determined by Western blot analysis. Immunohistochemic analysis was performed in 21 benign and 81 malignant prostatic specimens, and patients' charts were reviewed for clinical, pathologic and survival data. EBAG9 was abundantly expressed in the prostate cancer cells compared to the normal epithelial cells. Strong and diffuse immunostaining in the cytoplasm of EBAG9 was found in 44 of 81 (54%) cancerous tissue samples. EBAG9 expression significantly correlated with advanced pathologic stages and high Gleason score (p = 0.0305 and < 0.0001, respectively). EBAG9 was more frequently expressed at sites of capsular penetration (79%) and lymph node metastasis (100%) compared to intracapsular primary tumors (54%) (p = 0.0264 and 0.0048, respectively). Positive EBAG9 immunoreactivity significantly correlated with poor PSA failure-free survival (p = 0.0059). EBAG9/RCAS1 may play a significant role in cancer progression via an immune escape system. Immunodetection of EBAG9/RCAS1 expression can be a negative prognostic indicator for patients with prostatic cancer.

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.

Gene expression profiling of mouse bladder inflammatory responses to LPS, substance P, and antigen-stimulation

Inflammatory bladder disorders such as interstitial cystitis (IC) deserve attention since a major problem of the disease is diagnosis. IC affects millions of women and is characterized by severe pain, increased frequency of micturition, and chronic inflammation. Characterizing the molecular fingerprint (gene profile) of IC will help elucidate the mechanisms involved and suggest further approaches for therapeutic intervention. Therefore, in the present study we used established animal models of cystitis to determine the time course of bladder inflammatory responses to antigen, Escherichia coli lipopolysaccharide (LPS), and substance P (SP) by morphological analysis and cDNA microarrays. The specific aim of the present study was to compare bladder inflammatory responses to antigen, LPS, and SP by morphological analysis and cDNA microarray profiling to determine whether bladder responses to inflammation elicit a specific universal gene expression response regardless of the stimulating agent. During acute bladder inflammation, there was a predominant infiltrate of polymorphonuclear neutrophils into the bladder. Time-course studies identified early, intermediate, and late genes that were commonly up-regulated by all three stimuli. These genes included: phosphodiesterase 1C, cAMP-dependent protein kinase, iNOS, beta-NGF, proenkephalin B and orphanin, corticotrophin-releasing factor (CRF) R, estrogen R, PAI2, and protease inhibitor 17, NFkB p105, c-fos, fos-B, basic transcription factors, and cytoskeleton and motility proteins. Another cluster indicated genes that were commonly down-regulated by all three stimuli and included HSF2, NF-kappa B p65, ICE, IGF-II and FGF-7, MMP2, MMP14, and presenilin 2. Furthermore, we determined gene profiles that identify the transition between acute and chronic inflammation. During chronic inflammation, the urinary bladder presented a predominance of monocyte/macrophage infiltrate and a concomitant increase in the expression of the following genes: 5-HT 1c, 5-HTR7, beta 2 adrenergic receptor, c-Fgr, collagen 10 alpha 1, mast cell factor, melanocyte-specific gene 2, neural cell adhesion molecule 2, potassium inwardly-rectifying channel, prostaglandin F receptor, and RXR-beta cis-11-retinoic acid receptor. We conclude that microarray analysis of genes expressed in the bladder during experimental inflammation may be predictive of outcome. Further characterization of the inflammation-induced gene expression profiles obtained here may identify novel biomarkers and shed light into the etiology of cystitis.

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

BACKGROUND

Although androgens have long been implicated in the development, regulation, and pathophysiology of the prostate, evidence suggests that estrogens may also affect these processes. Specifically, estrogens have been shown to influence the development of the fetal and neonatal rodent prostate and to induce a pathognomonic change, termed squamous metaplasia, in the developing and adult prostate. Studies have been inconclusive, however, as to whether estrogens enhance or restrain the growth of the gland. Although the fetal rodent prostate has been reported to contain both estrogen receptor alpha (ER-alpha) and beta (ER-beta), there have been no reports as to whether either of the ER subtypes is expressed in the developing human prostate.

METHODS

In the present study, we used a novel antibody, directed against a unique sequence in the F domain of ER-beta, and laser capture microdissection/reverse transcriptase-polymerase chain reaction to study the expression of the receptor in the fetal, neonatal, and prepubertal human prostate. Results were compared with the expression of ER-alpha, androgen receptor (AR), prostatic acid phosphatase (PAP), prostate specific antigen (PSA), high molecular weight cytokeratin (HMCK), and the proliferative marker Ki67.

RESULTS

For the first time, we report that ER-beta is the only estrogen receptor detected at the protein level in the morphologically normal developing human fetal prostate. By midgestation, strong immunostaining for ER-beta was detected in the nuclei of nearly 100% of epithelial and in the majority of stromal cells. This pattern of expression was evident in the fetal, neonatal, and early prepubertal prostate. However, by 11 years postnatal, staining for the receptor became restricted primarily to the basal epithelial and stromal compartments, a pattern analogous to that observed in the normal adult gland. ER-alpha mRNA was present in microdissected stroma of the fetal gland. Although ER-alpha was not immunodetected in any morphologically normal fetal epithelial or stromal cells, weak staining for the receptor, however, was found in some examples of squamous metaplasia, suggesting the role of alpha-subtype in this lesion. ER-alpha was clearly visualized immunohistochemically at 1 month of postnatal development where it was then localized exclusively in periacinar stromal nuclei, which suggests that it may exert paracrine influences on further prostatic glandular development. Interestingly, the expression of ER-beta early in prostatic development occurred coincident with both the increasing rate of epithelial cell proliferation, observed in the first half of gestation, and the reported high levels of estrogen in the gland from midgestation until term. Paradoxically, however, staining for the receptor remained intense, despite the dramatic decrease in Ki67 labeling observed in the second half of gestation.

CONCLUSION

Our results indicate that the effects of estrogens on the growth of the human fetal prostate are mediated primarily by ER-beta but that ER-alpha contributes to postnatal glandular development. Furthermore, these results suggest that ER-beta, possibly in concert with androgens, may mediate diverse effects on prostate epithelial proliferation by first promoting cell expansion early in gestation, and then acting to limit growth later in prostatic development.