Antiestrogens and selective estrogen receptor modulators reduce prostate cancer risk

Therapeutic prospects of sex hormone receptor signaling in hormone-responsive cancers

Globally, hormone-responsive cancers afflict millions of people contributing to cancer-related morbidity and mortality. While hormone-responsive cancers overburden patients, their close families, and even health budgets at the local levels, knowledge of these cancers particularly their biology and possible avenues for therapy remains poorly exploited. Herewith, this review highlights the role of sex hormones (estrogens and androgens) in the pathophysiology of hormone-responsive cancers and the exploration of therapeutic targets. Major scientific databases including but not limited to Scopus, PubMed, Science Direct, Web of Science core collections, and Google Scholar were perused using a string of search terms: Hormone-responsive cancers, androgens and cancers, estrogens and cancer, androgen receptor signalling, estrogen receptor signalling, etc.

Novel frontiers in urogenital cancers: from molecular bases to preclinical models to tailor personalized treatments in ovarian and prostate cancer patients

Over the last few decades, the incidence of urogenital cancers has exhibited diverse trends influenced by screening programs and geographical variations. Among women, there has been a consistent or even increased occurrence of endometrial and ovarian cancers; conversely, prostate cancer remains one of the most diagnosed malignancies, with a rise in reported cases, partly due to enhanced and improved screening efforts.Simultaneously, the landscape of cancer therapeutics has undergone a remarkable evolution, encompassing the introduction of targeted therapies and significant advancements in traditional chemotherapy. Modern targeted treatments aim to selectively address the molecular aberrations driving cancer, minimizing adverse effects on normal cells. However, traditional chemotherapy retains its crucial role, offering a broad-spectrum approach that, despite its wider range of side effects, remains indispensable in the treatment of various cancers, often working synergistically with targeted therapies to enhance overall efficacy.For urogenital cancers, especially ovarian and prostate cancers, DNA damage response inhibitors, such as PARP inhibitors, have emerged as promising therapeutic avenues. In BRCA-mutated ovarian cancer, PARP inhibitors like olaparib and niraparib have demonstrated efficacy, leading to their approval for specific indications. Similarly, patients with DNA damage response mutations have shown sensitivity to these agents in prostate cancer, heralding a new frontier in disease management. Furthermore, the progression of ovarian and prostate cancer is intricately linked to hormonal regulation. Ovarian cancer development has also been associated with prolonged exposure to estrogen, while testosterone and its metabolite dihydrotestosterone, can fuel the growth of prostate cancer cells. Thus, understanding the interplay between hormones, DNA damage and repair mechanisms can hold promise for exploring novel targeted therapies for ovarian and prostate tumors.In addition, it is of primary importance the use of preclinical models that mirror as close as possible the biological and genetic features of patients' tumors in order to effectively translate novel therapeutic findings "from the bench to the bedside".In summary, the complex landscape of urogenital cancers underscores the need for innovative approaches. Targeted therapy tailored to DNA repair mechanisms and hormone regulation might offer promising avenues for improving the management and outcomes for patients affected by ovarian and prostate cancers.

Investigation of the potential effects of estrogen receptor modulators on immune checkpoint molecules

Immune checkpoints regulate the immune system response. Recent studies suggest that flavonoids, known as phytoestrogens, may inhibit the PD-1/PD-L1 axis. We explored the potential of estrogens and 17 Selective Estrogen Receptor Modulators (SERMs) as inhibiting ligands for immune checkpoint proteins (CTLA-4, PD-L1, PD-1, and CD80). Our docking studies revealed strong binding energy values for quinestrol, quercetin, and bazedoxifene, indicating their potential to inhibit PD-1 and CTLA-4. Quercetin and bazedoxifene, known to modulate EGFR and IL-6R alongside estrogen receptors, can influence the immune checkpoint functionality. We discuss the impact of SERMs on PD-1 and CTLA-4, suggesting that these SERMs could have therapeutic effects through immune checkpoint inhibition. This study highlights the potential of SERMs as inhibitory ligands for immune checkpoint proteins, emphasizing the importance of considering PD-1 and CTLA-4 inhibition when evaluating SERMs as therapeutic agents. Our findings open new avenues for cancer immunotherapy by exploring the interaction between various SERMs and immune checkpoint pathways.

Comprehensive plasma steroidomics reveals subtle alterations of systemic steroid profile in patients at different stages of prostate cancer disease

The steroid submetabolome, or steroidome, is of particular interest in prostate cancer (PCa) as the dependence of PCa growth on androgens is well known and has been routinely exploited in treatment for decades. Nevertheless, the community is still far from a comprehensive understanding of steroid involvement in PCa both at the tissue and at systemic level. In this study we used liquid chromatography/high resolution mass spectrometry (LC/HRMS) backed by a dynamic retention time database DynaSTI to obtain a readout on circulating steroids in a cohort reflecting a progression of the PCa. Hence, 60 relevant compounds were annotated in the resulting LC/HRMS data, including 22 unknown steroid isomers therein. Principal component analysis revealed only subtle alterations of the systemic steroidome in the study groups. Next, a supervised approach allowed for a differentiation between the healthy state and any of the stages of the disease. Subsequent clustering of steroid metabolites revealed two groups responsible for this outcome: one consisted primarily of the androgens, whereas another contained corticosterone and its metabolites. The androgen data supported the currently established involvement of a hypothalamic-pituitary-gonadal axis in the development of PCa, whereas biological role of corticosterone remained elusive. On top of that, current results suggested a need for improvement in the dynamic range of the analytical methods to better understand the role of low abundant steroids, as the analysis revealed an involvement of estrogen metabolites. In particular, 2-hydroxyestradiol-3-methylether, one of the compounds present in the disease phenotype, was annotated and reported for the first time in men.

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.

Tianma Gouteng Decoction Exerts Pregnancy-Protective Effects Against Preeclampsia via Regulation of Oxidative Stress and NO Signaling

Preeclampsia (PE), a pregnancy-specific syndrome with the major molecular determinants of placenta-borne oxidative stress and consequently impaired nitric oxide (NO) generation, has been considered to be one of the leading causes of maternal morbidity as well as mortality and preterm delivery worldwide. Several medical conditions have been found to be associated with increased PE risk, however, the treatment of PE remains unclear. Here, we report that Tianma Gouteng Decoction (TGD), which is used clinically for hypertension treatment, regulates oxidative stress and NO production in human extravillous trophoblast-derived TEV-1 cells. In human preeclamptic placental explants, reactive oxygen species (ROS) levels were elevated and NO production was inhibited, while TGD treatment at different periods effectively down-regulated the H2O2-induced ROS levels and significantly up-regulated the H2O2-suppressed NO production in human TEV-1 cells. Mechanistically, TGD enhanced the activity of total nitric oxide synthase (TNOS), which catalyze L-arginine oxidation into NO, and simultaneously, TGD promoted the expression of neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS), two isoforms of nitric oxide synthetases (NOS) in human placenta, resulting in the increased NO generation. More importantly, TGD administration not only increased the weight gain during pregnancy and revealed a hypotensive effect, but also improved the placental weight gain and attenuated fetal growth restriction in an NG-nitro-L-arginine methyl ester (L-NAME)-induced mouse PE-like model. Our results thereby provide new insights into the role of TGD as a potentially novel treatment for PE.

Estrogen Receptors in Epithelial-Mesenchymal Transition of Prostate Cancer

Prostate cancer (PC) remains a widespread malignancy in men. Since the androgen/androgen receptor (AR) axis is associated with the pathogenesis of prostate cancer, suppression of AR-dependent signaling by androgen deprivation therapy (ADT) still represents the primary intervention for this disease. Despite the initial response, prostate cancer frequently develops resistance to ADT and progresses. As such, the disease becomes metastatic and few therapeutic options are available at this stage. Although the majority of studies are focused on the role of AR signaling, compelling evidence has shown that estrogens and their receptors control prostate cancer initiation and progression through a still debated mechanism. Epithelial versus mesenchymal transition (EMT) is involved in metastatic spread as well as drug-resistance of human cancers, and many studies on the role of this process in prostate cancer progression have been reported. We discuss here the findings on the role of estrogen/estrogen receptor (ER) axis in epithelial versus mesenchymal transition of prostate cancer cells. The pending questions concerning this issue are presented, together with the impact of the available data in clinical management of prostate cancer patients.

Estrogen and estrogen receptor alpha promotes malignancy and osteoblastic tumorigenesis in prostate cancer

The role of estrogen signaling in regulating prostate tumorigenesis is relatively underexplored. Although, an increasing body of evidence has linked estrogen receptor beta (ERβ) to prostate cancer, the function of estrogen receptor alpha (ERα) in prostate cancer is not very well studied. We have discovered a novel role of ERα in the pathogenesis of prostate tumors. Here, we show that prostate cancer cells express ERα and estrogen induces oncogenic properties in prostate cancer cells through ERα. Importantly, ERα knockdown in the human prostate cancer PacMetUT1 cells as well as pharmacological inhibition of ERα with ICI 182,780 inhibited osteoblastic lesion formation and lung metastasis in vivo. Co-culture of pre-osteoblasts with cancer cells showed a significant induction of osteogenic markers in the pre-osteoblasts, which was attenuated by knockdown of ERα in cancer cells suggesting that estrogen/ERα signaling promotes crosstalk between cancer and osteoblastic progenitors to stimulate osteoblastic tumorigenesis. These results suggest that ERα expression in prostate cancer cells is essential for osteoblastic lesion formation and lung metastasis. Thus, inhibition of ERα signaling in prostate cancer cells may be a novel therapeutic strategy to inhibit the osteoblastic lesion development as well as lung metastasis in patients with advanced prostate cancer.

Oxidative Stress Alters miRNA and Gene Expression Profiles in Villous First Trimester Trophoblasts

The relationship between oxidative stress and miRNA changes in placenta as a potential mechanism involved in preeclampsia (PE) is not fully elucidated. We investigated the impact of oxidative stress on miRNAs and mRNA expression profiles of genes associated with PE in villous 3A first trimester trophoblast cells exposed to H₂O₂ at 12 different concentrations (0-1 mM) for 0.5, 4, 24, and 48 h. Cytotoxicity, determined using the SRB assay, was used to calculate the IC₅₀ of H₂O₂. RNA was extracted after 4 h exposure to H₂O₂ for miRNA and gene expression profiling. H₂O₂ exerted a concentration- and time-dependent cytotoxicity on 3A trophoblast cells. Short-term exposure of 3A cells to low concentration of H₂O₂ (5% of IC₅₀) significantly altered miRNA profile as evidenced by significant changes in 195 out of 595 evaluable miRNAs. Tool for annotations of microRNAs (TAM) analysis indicated that these altered miRNAs fall into 43 clusters and 34 families, with 41 functions identified. Exposure to H₂O₂ altered mRNA expression of 22 out of 84 key genes involved in dysregulation of placental development. In conclusion, short-term exposure of villous first trimester trophoblasts to low concentrations of H₂O₂ significantly alters miRNA profile and expression of genes implicated in placental development.

Ultrasensitive quantification of serum estrogens in postmenopausal women and older men by liquid chromatography-tandem mass spectrometry

An ultrasensitive stable isotope dilution liquid chromatography-tandem mass spectrometry method (LC-MS/MS) was developed and validated for multiplexed quantitative analysis of six unconjugated and conjugated estrogens in human serum. The quantification utilized a new derivatization procedure, which formed analytes as pre-ionized N-methyl pyridinium-3-sulfonyl (NMPS) derivatives. This method required only 0.1mL of human serum, yet was capable of simultaneously quantifying six estrogens within 20min. The lower limit of quantitation (LLOQ) for estradiol (E2), 16α-hydroxy (OH)-E2, 4-methoxy (MeO)-E2 and 2-MeO-E2 was 1fg on column, and was 10fg on column for 4-OH-E2 and 2-OH-E2. All analytes demonstrated a linear response from 0.5 to 200pg/mL (5-2000pg/mL for 4-OH-E2 and 2-OH-E2). Using this validated method, the estrogen levels in human serum samples from 20 female patients and 20 male patients were analyzed and compared. The levels found for unconjugated serum E2 from postmenopausal women (mean 2.7pg/mL) were very similar to those obtained by highly sensitive gas chromatography-mass spectrometry (GC-MS) methodology. However, the level obtained in serum from older men (mean 9.5pg/mL) was lower than has been reported previously by both GC-MS and LC-MS procedures. The total (unconjugated+conjugated) 4-MeO-E2 levels were significantly higher in female samples compared with males (p<0.05). The enhanced sensitivity offered by the present method will allow for a more specific analysis of estrogens and their metabolites. Our observations might suggest that the level of total 4-MeO-E2 could be a potential biomarker for breast cancer cases.

Anti-estrogenic activity of a human resveratrol metabolite

BACKGROUND AND AIMS

Resveratrol, the most investigated dietary compound in studies aimed at linking wine consumption to human health, is an extremely minor component of this beverage and it is generally studied in vitro as the unconjugated aglycone at concentrations largely exceeding those found in the human circulatory system after dietary intake. Moreover, following intestinal absorption, trans-resveratrol and its glucoside, which are naturally present in wine and other food sources, are converted to sulphate and glucuronide metabolites. An estrogenic activity has previously been documented for resveratrol, yet nothing is known about the activity of its blood-circulating metabolic derivatives.

METHODS AND RESULTS

Using a yeast two-hybrid detection system relying on the interaction between the ligand-binding domain of the human oestrogen receptors α and β and the human coactivator Tif2, we have systematically examined the oestrogen agonist and antagonist activities of the two main resveratrol forms present in planta (trans-resveratrol and trans-resveratrol-3-O-glucoside) and of the three main metabolites found in human plasma (trans-resveratrol-3-O-sulphate, trans-resveratrol-3-O-glucuronide and trans-resveratrol-4'-O-glucuronide). Only resveratrol-3-O-sulphate was found to display a fairly strong and oestrogen receptor α-preferential antagonistic activity, which was confirmed in a human breast adenocarcinoma cell line containing a luciferase reporter gene under the control of an oestrogen-responsive promoter.

CONCLUSIONS

We show, for the first time, that resveratrol-3-O-sulphate, but neither of its metabolites, is endowed with anti-estrogenic activity and how human metabolism of phenolic substances plays a pivotal role in modulating their biological effect.

Prostate cancer diagnosis among men with isolated high-grade intraepithelial neoplasia enrolled onto a 3-year prospective phase III clinical trial of oral toremifene

PURPOSE

Prostate cancer (PCa) prevention remains an appealing strategy for the reduction of overtreatment and secondary adverse effects. We evaluated the efficacy of toremifene citrate 20 mg in PCa prevention among men with isolated high-grade prostatic intraepithelial neoplasia (HGPIN) on biopsy.

PATIENTS AND METHODS

One thousand five hundred ninety men with HGPIN, or HGPIN and atypia, and no PCa on prostate biopsy were randomly assigned 1:1 to receive toremifene citrate 20 mg or placebo in a 3-year phase III, double-blind, multicenter trial. Men underwent annual biopsy until cancer detection or study end. Efficacy analysis was performed in 1,467 men who underwent at least one on-study biopsy. Baseline risk factors were evaluated to determine influence on cancer detection.

RESULTS

Cancer was detected in 34.7% and 32.3% of men in the placebo and treatment groups, respectively, with no observed difference (P = .39, log-rank test) in PCa-free survival. The 3-year Kaplan-Meier PCa-free survival estimate was 54.9% (99% CI, 43.3% to 66.5%) in the placebo group and 59.5% (99% CI, 48.1% to 70.9%) in the treatment group. Exploration of baseline risk factors demonstrated no subset in which a risk reduction was observed. In the placebo group, 17.9%, 12.9%, and 13.6% of men at risk at the beginning of years 1, 2, and 3, respectively, were diagnosed with PCa.

CONCLUSION

Although toremifene 20 mg did not lower the PCa detection rate, men with isolated HGPIN have a high likelihood of eventual PCa diagnosis, demonstrating they are ideal candidates for inclusion in chemoprevention trials and require surveillance by periodic prostate biopsy.

Precursors of prostate cancer

High-grade prostatic intraepithelial neoplasia (PIN) is the only accepted precursor of prostatic adenocarcinoma, according to numerous studies of animal models and man; other proposed precursors include atrophy and malignancy-associated changes (with no morphologic changes). PIN is characterized by progressive abnormalities of phenotype and genotype that are intermediate between benign prostatic epithelium and cancer, indicating impairment of cell differentiation and regulatory control with advancing stages of prostatic carcinogenesis. The only method of detection of PIN is biopsy because it does not significantly elevate serum prostate-specific antigen concentration and cannot be detected by ultrasonography. The mean incidence of PIN in biopsies is 9% (range, 4%-16%), representing about 115,000 new cases of isolated PIN diagnosed each year in the United States. The clinical importance of PIN is its high predictive value as a marker for adenocarcinoma, and its identification warrants repeat biopsy for concurrent or subsequent carcinoma, especially when multifocal or observed in association with atypical small acinar proliferation (ASAP). Carcinoma develops in most patients with PIN within 10 years. Androgen deprivation therapy and radiation therapy decrease the prevalence and extent of PIN, suggesting that these forms of treatment may play a role in prevention of subsequent cancer. Multiple clinical trials to date of men with PIN have had modest success in delaying or preventing subsequent cancer.

Epidemiology of prostate cancer and treatment remarks

Prostate cancer is one of the most common types of cancer and one of the leading causes of cancer death among men in the Western countries. The aim of the present analysis is to assess the cancer burden in order to ensure accurate strategies for chemoprevention and treatment, including the major therapeutic approaches for localized high-risk disease - surgery and radiation therapy - and quality of life issues related to each option.

Pharmacokinetic evaluation of toremifene and its clinical implications for the treatment of osteoporosis

INTRODUCTION

Toremifene is a triphenylethylene selective estrogen receptor modulator (SERM) that differs from tamoxifen in a single chloride ion addition on a side chain, resulting in a potentially more favorable toxicity profile.

AREAS COVERED

This article reviews the pharmacokinetics of toremifene and its potential use for the treatment of osteoporosis. This article was based on articles found through a literature search containing the terms 'toremifene' and 'SERMs.'

EXPERT OPINION

Toremifene can be administered orally with an excellent bioavailability. The overall pharmacokinetic profile is remarkably similar to tamoxifen. Toremifene is highly metabolized in the liver and is eliminated primarily in the feces following enterohepatic circulation. Some of its metabolites retain biological activity. This SERM was approved by the FDA for the treatment of estrogen receptor-positive metastatic breast cancer and is under investigation for its potential skeletal benefits in men on androgen deprivation therapy. Despite the positive preclinical and clinical evidences for the prevention of bone loss and fractures, the chemopreventive effect on prostate cancer remains to be confirmed and an increased risk of venous thromboembolism was evidenced in a large Phase III trial. Thus, additional data are required to establish the full clinical profile of this compound and its potential advantages over antiresorptive agents commonly in use for the treatment of osteoporosis.

Local inflammation influences oestrogen metabolism in prostatic tissue

What's known on the subject? and What does the study add? The role of oestrogen in prostatic inflammation has been extensively shown. The catechol oestrogens are known to be more potent oestrogenic moieties that not only aggravate the inflammatory response in situ, but are also believed to have oxidative stress and genotoxic effects. The present study highlights a significant role of inflammation in oestrogen metabolism and, particularly, in generating 'bad' oestrogen metabolites. This finding may pave the way for new therapeutic methods for the treatment and/or prevention of prostate diseases.

OBJECTIVE

• To investigate the impact of experimentally induced inflammation on oestrogen metabolism in rat prostate.

MATERIALS AND METHODS

• Prostatitis was induced in normal and oestrogen-treated male rats by injecting 2% carrageenan solution into the ventral prostate. After 48 h, the rats were killed and the ventral prostate was collected. • Prostatic inflammation and proliferation were confirmed by gross visual evidence, histology and elevated tumour necrosis factor-α, prostaglandin E(2) and cyclin-D(1) . • Expression of oestrogen-metabolizing enzymes was assessed using capillary electrophoresis, and oestrogen metabolites within prostate tissue were assayed using liquid chromatography mass spectrometry.

RESULTS

• Animals exposed to carrageenan insult combined with oestrogen treatment showed the most prominent inflammatory and proliferative response. • Treatment of animals with oestrogen alone induced moderate inflammation and proliferation. • Oestrogen-metabolizing enzymes were overexpressed in animals with experimental prostatitis with sequential accumulation of catechol oestrogens within prostatic tissues. • Oestrogen receptor-α was underexpressed in the prostatitis with oestrogen group, while oestrogen receptor-β was overexpressed.

CONCLUSIONS

• The present work provides experimental evidence that local inflammation enhances oestrogen synthesis and directs oestrogen metabolism to generate catechol oestrogens within prostatic tissues. • This may contribute, at least partly, to enhanced prostatic cell proliferation.

Strategies for prostate cancer prevention: Review of the literature

The goal of primary chemoprevention is to decrease the incidence of a given cancer, simultaneously reducing treatment-related adverse events, cost of treatment of the disease and mortality. Prostate cancer is an attractive and appropriate target for primary prevention because of its high incidence and prevalence, increased disease-related mortality, long latency and molecular pathogenesis and epidemiological data indicating that modifiable environmental factors may decrease risk. Various agents have been suggested to prevent prostate cancer and many clinical trials are currently on. Ultimately the adoption of a preventive strategy hinges on its potential benefits weighed against the potential risks of the specific agents used. This article is aimed to examine the experimental and epidemiological data spanning a period of 1998 to 2007, demonstrating the chemopreventive activity, safety and toxicity of various nutritional elements and other agents that can help prevent prostate cancer and/or slow disease progression.

Estrogen regulates tumor growth through a nonclassical pathway that includes the transcription factors ERβ and KLF5

Clinical evidence suggests that antiestrogens inhibit the development of androgen-insensitive prostate cancer. Here, we show that the estrogen receptor β (ERβ) mediates inhibition by the antiestrogen ICI 182,780 (ICI) and its enhancement by estrogen. ERβ associated with gene promoters through the tumor-suppressing transcription factor KLF5 (Krüppel-like zinc finger transcription factor 5). ICI treatment increased the recruitment of the transcription coactivator CBP [CREB (adenosine 3',5'-monophosphate response element-binding protein)-binding protein] to the promoter of FOXO1 through ERβ and KLF5, which enhanced the transcription of FOXO1. The increase in FOXO1 abundance led to anoikis in prostate cancer cells, thereby suppressing tumor growth. In contrast, estrogen induced the formation of complexes containing ERβ, KLF5, and the ubiquitin ligase WWP1 (WW domain containing E3 ubiquitin protein ligase 1), resulting in the ubiquitination and degradation of KLF5. The combined presence of KLF5 and ERβ positively correlated with longer cancer-specific survival in prostate cancer patients. Our results demonstrate that estrogens and antiestrogens affect prostate tumor growth through ERβ-mediated regulation of KLF5.

Contemporary clinical management of isolated high-grade prostatic intraepithelial neoplasia

High-grade prostatic intraepithelial neoplasia (HGPIN) is a premalignant lesion associated with increased risk of coexistent cancer or delayed progression to carcinoma. Extended biopsy schemes have improved the ability to rule out concurrent cancers, increased the detection of isolated HGPIN and removed the routine necessity for immediate repeat biopsy. As the natural history of HGPIN is poorly defined, and no non-invasive marker allows monitoring of progression to cancer, routine delayed interval biopsy should be considered in all patients. In this article, we present an overview of the existing literature on HGPIN and a proposed strategy for clinical management.

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

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

Phytoestrogens from Belamcanda chinensis regulate the expression of steroid receptors and related cofactors in LNCaP prostate cancer cells

OBJECTIVE

To investigate the changes in expression underlying the marked reduction of tumour growth in vivo, by analysing the effect of Belamcanda chinensis extract (BCE) on LNCaP cells in vitro, as phytoestrogens are chemopreventive in prostate cancer, and in previous studies we examined the effects of the isoflavone tectorigenin isolated from B. chinensis on LNCaP prostate cancer cells, and a BCE consisting of 13 phytoestrogenic compounds on tumour-bearing nude mice.

MATERIALS AND METHODS

LNCaP cells were treated with 100, 400 or 1400 microg/mL BCE; proliferation was assessed with an Alamar Blue assay. We used real-time reverse transcription-polymerase chain reaction to quantify mRNA expression of the androgen receptor (AR), the AR coactivator prostate derived Ets transcription factor (PDEF), NKX3.1, prostate specific antigen (PSA) and oestrogen receptor-beta (ER-beta) compared with the expression of the housekeeping gene porphobilinogen deaminase (PBGD). PSA secretion from LNCaP cells was measured and protein expression of the AR investigated by Western blot analysis.

RESULTS

Concomitant with a marked decrease of tumour cell proliferation BCE down-regulated the expression of the AR, PDEF, NKX3.1 and PSA. In the same experiments, the expression of PBGD was unaltered, whereas ER-beta expression increased. Furthermore, AR protein and PSA secretion were markedly diminished after treatments with the BCE.

CONCLUSION

BCE, comprising 13 different phytoestrogens, decreases the expression of the AR and its co-activator PDEF concomitant with diminished cell proliferation and PSA secretion. NKX3.1 expression was also reduced by BCE. We hypothesise that the positive effects of BCE are initiated by up-regulation of the ER-beta, a putative tumour-suppressor gene.

Assessing intraepithelial neoplasia and drug safety in cancer-preventive drug development

Despite significant interest from the research community and the population in general, drug approvals for cancer prevention and/or cancer risk reduction are few. This is due, in part, to the requirement that new cancer-preventive drugs must first be shown to be efficacious in reducing cancer incidence or mortality. Moreover, such drugs need to have proven safety for long-term administration. This process can be improved by focusing on precancer (intraepithelial neoplasia) to identify subjects at risk and prove efficacy in shorter, smaller trials as well as on detecting early markers of potential toxicities of chronic exposure to cancer-preventive drug regimens.

Phytosterol Pygeum africanum regulates prostate cancer in vitro and in vivo

BACKGROUND

Prostate cancer is an important public health problem. It is an excellent candidate disease for chemoprevention because prostate cancer is typically slow growing and is usually diagnosed in elderly males. Pygeum africanum (Prunus africana or Rosaceae) is an African prune (plum) tree found in tropical Africa. An extract from the bark of Pygeum africanum has been used in Europe as a prevention and treatment of prostate disorders including benign prostatic hypertrophy (BPH). More recently in the USA, the phytotherapeutic preparations of Pygeum africanum and Saw palmetto have been marketed for prostate health including prostate cancer prevention and treatment.

METHODS

The anti-cancer potential of Pygeum africanum has been tested both in vitro (PC-3 and LNCaP cells) and in vivo (TRAMP mouse model).

RESULTS

In tissue culture, ethanolic extracts (30%) of Pygeum africanum inhibited the growth of PC-3 and LNCaP cells; induced apoptosis and altered cell kinetics; down regulated ERalpha and PKC-alpha protein, and demonstrated good binding ability to both mouse uterine estrogen receptors and LNCaP human androgen receptors. TRAMP mice fed Pygeum africanum showed a significant reduction (P = 0.034) in prostate cancer incidence (35%) compared to casein fed mice (62.5%).

CONCLUSION

Pygeum africanum, which is widely used in Europe and USA for treatment of BPH, has a significant role in regulation of prostate cancer both in vitro and in vivo and therefore may be a useful supplement for people at high risk for developing prostate cancer.

Transcript profiling of the androgen signal in normal prostate, benign prostatic hyperplasia, and prostate cancer

Human prostate adenocarcinoma (CaP) and benign prostatic hyperplasia (BPH) have epithelial and stromal cell origins, respectively. To determine whether the androgen signal is processed differently in these cell types the expression of transcripts for enzymes that control ligand access to the androgen receptor (AR) were measured. Transcripts for type 2 5alpha-reductase, ketosteroid reductases [aldo-keto reductase (AKR)1C1-AKR1C4], the major oxidative 3alpha-hydroxysteroid dehydrogenase (HSD) retinol dehydrogenase (RODH)-like 3alpha-HSD (RL-HSD) and nuclear receptors [AR, estrogen receptor (ER)alpha, and ERbeta] were determined in whole human prostate and in cultures of primary epithelial cells (PEC) and primary stromal cells (PSC) from normal prostate, CaP and BPH by real-time RT-PCR. Normal PEC (n=14) had higher levels of AKR1C1 (10-fold, P<0.001), AKR1C2 (115-fold, P<0.001) and AKR1C3 (6-fold, P<0.001) than normal PSC (n=15), suggesting that reductive androgen metabolism occurs. By contrast, normal PSC had higher levels of AR (8-fold, P<0.001) and RL-HSD (21-fold, P<0.001) than normal PEC, suggesting that 3alpha-androstanediol is converted to 5alpha-dihydrotestosterone to activate AR. In CaP PEC (n=14), no significant changes in transcript levels vs. normal PEC were observed. In BPH PSC (n=21) transcripts for AR (2-fold, P<0.001), AKR1C1 (4-fold, P<0.001), AKR1C2 (10-fold P<0.001), AKR1C3 (4-fold, P<0.001) and RL-HSD (3-fold, P<0.003) were elevated to increase androgen response. Differences in the AR:ERbeta transcript ratios (eight in normal PEC vs. 280 in normal PSC) were maintained in PEC and PSC in diseased prostate. These data suggest that CaP may be more responsive to an ERbeta agonist and BPH may be more responsive to androgen ablation.

An update on chemoprevention strategies in prostate cancer for 2006

PURPOSE OF REVIEW

An increasing volume of research has been directed at the prevention of prostate cancer. This review proposes to summarize the large trials, novel approaches and molecular mechanisms of effect published in 2004 and 2005.

RECENT FINDINGS

The impact of the Prostate Cancer Prevention Trial continues and subsequent articles have addressed the increase of high-grade prostate cancers detected in the finasteride arm of the trial, as well as the potential costs and benefits of extrapolating the findings to a public health campaign. Studies of risk have been published warning of excessive vitamin E and cyclooxygenase-2 inhibitor use in chemoprevention. Growing evidence supports the concept of chemopreventative agent combinations and further data on the roles of selenium, lycopene, soy, green tea, anti-inflammatories and statins in prostate-cancer prevention are presented.

SUMMARY

Level one evidence exists for the preventative effects of finasteride in prostate cancer. The evidence for other agents is less conclusive but a number of large-scale, appropriately designed trials will hopefully address some of the relevant issues in prostate-cancer prevention over the next decade.

Platinum(II) complexes interfering with testicular steroid biosynthesis: drugs for the therapy of advanced or recurrent prostate cancers? Preclinical studies

[Meso-1,2-bis(2,6-dihalo-3/4-hydroxyphenyl)ethylenediamine]platinum(II) complexes (meso-1-PtLL': 2,6-F(2),3-OH; meso-2-PtLL': 2,6-F(2),4-OH; meso-3-PtLL': 2,6-Cl(2),3-OH; meso-4-PtLL': 2,6-Cl(2),4-OH; L = OH(2), L' = OSO(3) or L,L' = Cl(2)) were designed with the aim to get drugs comprising both cytotoxic and testosterone level lowering potencies. It is assumed that such compounds are more efficient than the established endocrine therapeutic measures and can affect the development of hormone refractory prostate cancer (PC). With exception of meso-3-PtLL' all Pt-complexes and the comparison compound cisplatin significantly reduced the testosterone level in experiments on male rats. However, in the test on the Dunning R3327 PC of the rat only cisplatin and meso-4-PtLL' showed a significant anti-tumor activity at well-tolerated dose ranges. Meso-4-PtLL' also significantly extended the time to disease progression in comparison with orchiectomy in this tumor model. Interestingly, the relapsed tumor, too, responded to meso-4-PtLL' as demonstrated in a long-term study on orchiectomized rats bearing Dunning R3327 PC grafts. This effect cannot be ascribed to cytotoxic effects of meso-4-PtLL' because of its inactivity on the human LNCaP/FGC PC cell line. Therefore, the contribution of an additional mechanism to the anti-prostate cancer activity of meso-4-PtLL', presumably owing to its estrogenic potency, must be considered. This assumption was supported by test results with diethylstilbestrol (DES) (non-steroidal estrogen) on the Dunning R3327 PC of the rat relapsed after orchiectomy. This tumor model was strongly inhibited by DES. The possible mode of action of meso-4-PtLL' is thoroughly discussed.

Progress in chemoprevention drug development: the promise of molecular biomarkers for prevention of intraepithelial neoplasia and cancer--a plan to move forward

This article reviews progress in chemopreventive drug development, especially data and concepts that are new since the 2002 AACR report on treatment and prevention of intraepithelial neoplasia. Molecular biomarker expressions involved in mechanisms of carcinogenesis and genetic progression models of intraepithelial neoplasia are discussed and analyzed for how they can inform mechanism-based, molecularly targeted drug development as well as risk stratification, cohort selection, and end-point selection for clinical trials. We outline the concept of augmenting the risk, mechanistic, and disease data from histopathologic intraepithelial neoplasia assessments with molecular biomarker data. Updates of work in 10 clinical target organ sites include new data on molecular progression, significant completed trials, new agents of interest, and promising directions for future clinical studies. This overview concludes with strategies for accelerating chemopreventive drug development, such as integrating the best science into chemopreventive strategies and regulatory policy, providing incentives for industry to accelerate preventive drugs, fostering multisector cooperation in sharing clinical samples and data, and creating public-private partnerships to foster new regulatory policies and public education.

Optimizing outcomes and quality of life in the hormonal treatment of prostate cancer

We review the effectiveness of androgen-deprivation therapy (ADT) in the management of prostate cancer, and the effect that this treatment has on a patient's quality of life (QoL), based on discussions held at a European symposium on the management of prostate cancer. The overall QoL is reduced in asymptomatic men, and there are known decreases in cognitive function, self-esteem, libido and sexual function. Hot flashes are also a frequent problem. Prolonged ADT can lead to osteoporosis and subsequently fractures. Various effective methods exist to manage and minimize these side-effects; some are specific to the side-effect, whereas other more general methods include lifestyle changes, specific drugs and added hormonal manipulations. Intermittent ADT for patients taking luteinizing hormone-releasing hormone agonists offers a promising method to reduce adverse effects, and possibly increases the time to androgen independence. Initial studies indicate that prostate-specific antigen-based progression with intermittent ADT is similar to that seen with continuous ADT, but there is a reduction in side-effects, leading to an improvement in QoL.

Chemoprevention of prostate cancer

Prostate cancer is an attractive target for chemoprevention because of its ubiquity, treatment-related morbidity, long latency between premalignant lesions and clinically evident cancer, and defined molecular pathogenesis. The Prostate Cancer Prevention Trial has provided the first firm evidence that this cancer can be prevented by a relatively nontoxic oral agent. Additional agents, many of which are antioxidants with antiandrogenic effects, are being tested (or soon will be) in large clinical trials. The current body of evidence is insufficient to make a routine recommendation of any dietary or nutritional supplement for the prevention of prostate cancer.

[Implications of estrogens and their receptors for the development and progression of prostate cancer]

The recent discovery of the estrogen receptors alpha and beta (ERalpha, ERbeta) and the progesterone receptor (PR) in human prostate tissue offers new insights into the role of estrogens and their receptors in prostate cancer development and tumor progression. The differentiation compartment of the prostatic epithelium (secretory luminal cells) expresses high levels of ERbeta, while the ERalpha is restricted to the proliferation compartment (basal cells). In high grade prostatic intraepithelial neoplasia (HGPIN), ERalpha gene expression extends to luminal cells and thus may mediate cancerogenic effects of estrogens on the dysplastic epithelium. Conversely, the ERbeta is downregulated in HGPIN indicating that the chemopreventive effects of phytoestrogens mediated by the ERbeta are partially lost. Irrespective of grades and stages, prostate cancer retains high levels of the ERbeta which is partially lost in androgen-insensitive stages of the disease. In contrast with breast cancer, the presence of the ERalpha and the PR is a late event in prostate cancer progression. At least 30% of metastatic and androgen-insensitive tumors express high levels of the PR indicating that these tumors harbor a functional ERalpha. The antiestrogen Raloxifene has growth-inhibitory effects on androgen-insensitive prostate cancer cells in vitro and induces the apoptotic cell death in a dose-dependent fashion. These data provide a rational for clinical trials to study the efficiency of antiestrogens in the medical treatment of advanced prostate cancer.

Effects of estradiol-17β, testosterone and a black cohosh preparation on bone and prostate in orchidectomized rats

Estradiol (E2) and testosterone (T) effectively prevent orchidectomy (orx) induced osteoporosis. T, however, stimulates prostate proliferation which may lead to malignancy. We showed that a Cimicifuga racemosa (CR) preparation had bone-sparing effects without exerting estrogenic effects in the uterus. We studied therefore whether a CR preparation has also antiosteoporotic effects in orx rats substituted with E2, T or CR via pelleted food over a period of 3 months. Average daily intake per animal was: T: 25 mg; E2: 0.325 mg, CR low dose: 33 mg; CR high dose: 133 mg. E2, T and CR at the high dose partially prevented development of osteoporosis as measured by quantitative computer tomography in the metaphysis of the tibia. E2, but not T or CR reduced serum osteocalcin and the metabolic products of collagen-1alpha1. Gene expression of collagen-1alpha1 and tartrate-resistant acid phosphatase was decreased by E2 and the higher dose of the CR extract but increased in the T-treated animals. In the prostate T inhibited androgen receptor, estrogen receptor alpha and insulin-like growth factor-1 gene expression but stimulated the expression of the ERbeta gene. These effects were not shared by E2 or both doses of the CR extract. It is concluded that E2, T and CR exert antiosteoporotic effects in the metaphysis of the tibia of orx rats. T has profound effects in the prostate which were not seen in the E2- and CR-treated animals. Therefore, the Cimicifuga racemosa extract BNO 1055 may be useful to prevent osteoporosis in aged male patients with reduced testosterone production.

Lack of significant modifying effect of arctiin on prostate carcinogenesis in probasin/SV40 T antigen transgenic rats

Arctiin, a plant lignan that can be extracted from the Arctium lappa (burdock) seeds, is a possible environmental endocrine disruptor compounds and have been shown to influence sex hormone metabolism as well as protein synthesis, steroid biosynthesis. Modifying effects of arctiin on prostate carcinogenesis in probasin/SV 40 T antigen (Tag) transgenic (TG) rats were examined. A total of 64 male TG rats, 6 weeks old, were randomly divided to three experimental groups (soybean free Oriental MF diet with 0.1, 0.02, or 0.004% arctiin) and a control group (soybean free Oriental MF diet). Animals were killed at the end of week 18. Histopathological evaluation of prostate revealed that all the rats in any group developed adenocarcinoma in dorsolateral lobe of prostate, except two rats in 0.1% arctiin treated and one rat in 0.002% arctiin treated groups without prostate adenocarcinoma development. However, there were no definite treatment-related changes with statistical significance in all parameters for prostate carcinomas measured in this experiment. These results indicated that arctiin might not exert significant modifying effect on prostate carcinogenesis in SV 40 Tag TG rats at least under the present experiment.

Tectorigenin and other phytochemicals extracted from leopard lily Belamcanda chinensis affect new and established targets for therapies in prostate cancer

Isoflavones have been shown to exert antiproliferative effects on cancer cells by steroid receptor signaling. In this study, we demonstrate the potential of plant constituents extracted from Belamcanda chinensis as anticancer drugs, which regulate the aberrant expression of genes relevant in proliferation, invasion, immortalization and apoptosis. LNCaP cells were treated with B.chinensis extract, tectorigenin or other isoflavones and mRNA expression was quantified by using real time RT-PCR. In addition, ELISA, TRAP assays and western blots were used to measure protein expression or activity. Male nude mice (n=18) were injected subcutaneously with LNCaP cells and were fed with extracts from B.chinensis, and tumor development was monitored versus a control animal group (n=18). Tectorigenin and several other phytochemicals downregulated PDEF, PSA and IGF-1 receptor mRNA expression in vitro. Furthermore, PSA secretion and IGF-1 receptor protein expression were diminished, and hTERT mRNA expression and telomerase activity decreased after tectorigenin treatments. However, TIMP-3 mRNA was upregulated on tectorigenin treatment. Growth of subcutaneous tumors in nude mice was delayed and diminished in animals fed with extracts from B.chinensis. The downregulation of PDEF, PSA, hTERT and IGF-1 receptor gene expression by tectorigenin demonstrates the antiproliferative potential of these agents. The upregulation of TIMP-3 gene expression indicates a pro-apoptotic function of the drug and a reduction of the invasiveness of tumors. The animal experiments demonstrate that B.chinensis markedly inhibited the development of tumors in vivo. Thus, these compounds may be useful for the prevention or treatment of human prostate cancer.

Chemoprevention of prostate cancer

Prostate cancer is an attractive target for chemoprevention because of its ubiquity, treatment-related morbidity, long latency between premalignant lesions and clinically evident cancer, and defined molecular pathogenesis. Prevention of this disease would have a major impact on disease-associated cost, morbidity, and mortality for a large segment of the population. A major advance in prevention of prostate cancer came in 2003 with the publication of the Prostate Cancer Prevention Trial (PCPT). This overview summarizes the results of that trial, the design of other large-scale trials, and advances in understanding of the molecular mechanisms underlying the effect of other promising agents, including dutasteride, selenium, Vitamin E, Vitamin D, COX-2 inhibitors, lycopene, and green tea.

Can prostate cancer be prevented?

The goal of primary chemoprevention is to decrease the incidence of a given cancer, simultaneously reducing both treatment-related adverse events and mortality. Prostate cancer is an attractive and appropriate target for primary prevention because of its incidence, prevalence, and disease-related mortality; its long latency and molecular pathogenesis; and epidemiologic data indicating that modifiable environmental factors may decrease risk. The Prostate Cancer Prevention Trial (PCPT) demonstrated that finasteride can prevent prostate cancer, albeit with an apparently increased risk of high-grade disease. A substantial amount of epidemiologic, molecular, and clinical evidence suggests that both selenium and vitamin E might also prevent prostate cancer, and this combination is being tested in the Selenium and Vitamin E Cancer Prevention Trial (SELECT). Ultimately, the adoption of a preventive strategy hinges on its potential benefits weighed against the potential risks of the specific agents used.

Review article Testosterone therapy in the ageing male: what about the prostate?

The concerns about testosterone therapy in ageing men with late-onset hypogonadism mainly address the risk of prostatic disease, i.e. either benign prostatic hyperplasia (BPH) or prostate cancer (PCa). Both conditions are highly dependent on androgen action and recent clinical data on the cancer-preventive effect of the 5alpha-reductase inhibitor finasteride have supported the possible role of androgens in PCa. However, the clinical data especially on the long-term effects of exogenous androgen substitution in regard to prostate safety are nonconclusive in many respects. As sufficient clinical studies on these risks will not be available in the near future, the approach of testosterone therapy towards prostate complications should be kept on a safe but practical basis. This review includes some recommendations in regard to testosterone therapy and prostate monitoring in patients with BPH and bladder outlet obstruction, with previous history of curative treatment for PCa or with prostatic intraepithelial neoplasia.

CYP1B1 expression in prostate is higher in the peripheral than in the transition zone

Prostate cancer (CaP) mostly occurs in the peripheral zone whereas benign prostatic hypertrophy (BPH) occurs in the transition zone. Human prostates (n = 12) were obtained, with ethical approval, from radical retropubic prostatectomies. Following resection, tissue sets consisting of peripheral zone and transition zone were isolated from a lobe pre-operatively identified as negative for CaP. Real-time RT-PCR was employed to quantitatively examine CYP1A1, CYP1A2 and CYP1B1. Quantifiable CYP1A1 expression was observed (in nine out of twelve tissue sets) whilst CYP1A2 mRNA transcripts, although detectable (in six out of twelve tissue sets), were unquantifiable. In ten tissue sets, 2- to 6-fold higher CYP1B1 expression in peripheral zone as compared to transition zone was observed. In the other two, equal CYP1B1 expression levels were observed; retrospective examination identified malignancy in one of the zones. Inter-individual variations (up to 10-fold) in CYP1B1 were also noted. Immunohistochemistry for CYP1B1 showed epithelial and stromal nuclear staining. Since CYP1B1 metabolises hormones and carcinogens our results, if confirmed, suggest that this enzyme may influence susceptibility to CaP.

Role of estrogens in development of prostate cancer

Estrogens have previously been extensively used in prostate cancer treatment. Serious side effects, primarily in cardiovascular system have, however, limited their use. The therapeutic effect of estrogen in preventing prostate cancer growth was mainly obtained indirectly by feedback inhibition of the hypothalamic release of LRH leading to lowered serum androgen levels and castration like effects. Prostate tissue is also most probably a target for direct regulation by estrogens. Prostate contains estrogen receptor alpha (ERalpha) and beta (ERbeta), which are localized characteristically in stroma and epithelium, respectively. The physiological function of these receptors is not known but there is evidence of the role of estrogens in prostatic carcinogenesis. Developing prostate seems particularly sensitive to increased level of endogenous and/or exogenous estrogens. Perinatal or neonatal exposure of rats and mice to estrogens leads to "imprinting" of prostate associated with increased proliferation, inflammation and dysplastic epithelial changes later in life. Prolonged treatment of adult rodents with estrogens along with androgens also leads to epithelial metaplasia, PIN-like lesions and even adenocarcinoma of prostate speaking for the role of estrogen in prostate cancer development. Recent results concerning antiestrogen inhibition of prostate cancer development beyond PIN-type lesions in transgenic mouse models further suggests a role for estrogens in prostate cancer progression. These results also suggest that direct inhibition of estrogen action at the level of prostate tissue may provide an important novel principle of development of prostate cancer therapies.

[New insights into the role of estogens and their receptors in prostate cancer]

The present review gives a survey on the differential expression of estrogen receptors alpha and beta (ERalpha, ERbeta) and the progesterone receptor (PR) in human prostate tissue and discusses their potential implications for normal and abnormal prostatic growth. The differentiation compartment of the prostatic epithelium (secretory luminal cells) expresses high levels of ERbeta, while the ERalpha is restricted to the proliferation compartment (basal cells). In high-grade prostatic intraepithelial neoplasia (HGPIN), ERalpha gene expression extends to luminal cells and thus may mediate cancerogenic effects of estrogens on the dysplastic epithelium. Conversely, the ERbeta is downregulated in HGPIN indicating that the chemopreventive effects of phytoestrogens mediated by the ERbeta are partially lost. Irrespective of grades and stages, prostate cancer retains high levels of the ERbeta, which is partially lost in androgen-insensitive stages of the disease. In contrast with breast cancer, the presence of the ERalpha and the progesterone receptor (PR) is a late event in prostate cancer progression. At least 30% of metastatic and androgen-insensitive tumors express high levels of the PR indicating that these tumors harbor a functional ERalpha. The antiestrogen raloxifene has growth-inhibitory effects on androgen-insensitive prostate cancer cells in vitro and induces apoptotic cell death in a dose-dependent fashion. These data provide a rationale for clinical trials to study the efficiency of antiestrogens in the medical treatment of advanced prostate cancer.

Localization of estrogen and androgen receptors in male reproductive tissues of mice and rats

Using immunohistochemical methods, we studied the cell-type- and species-specific expressions of estrogen receptor (ER) isoforms (ER alpha and ER beta) and androgen receptors (ARs) in the male reproductive tract and accessory sex glands of mature mice and rats. ER alpha and ER beta showed cell-type- and species-specific distributions, respectively. In contrast, AR was localized in the epithelial and stroma cells of all tissues examined in this study, in both species. In mice, the epithelial cells of the ductuli efferentes showed a strong ER alpha-immunoreaction, and those of the caput epididymis, coagulating glands, and prostate also exhibited a positive reaction. Stroma cells, except in the ductuli efferentes, showed a positive ER alpha-immunostaining. In rats, ER alpha was detected in very few cell types: the epithelial cells of the ductuli efferentes showed a strong reaction, and the stroma cells of the ampullary and urethral glands exhibited a weak reaction. ER beta was localized in the epithelial cells of the prostate in mice, while the reaction was faint or negative in both the epithelial and stroma cells of other tissues. In rats, the ER beta-immunoreaction was strongest in the epithelial cells of the ventral prostate. The epithelial cells of the corpus and cauda epididymis, ductus deferens, and urethral glands, and the stroma cells of the urethral glands were also positively ER beta-immunostained. Almost the same AR distribution pattern was observed in both species. In particular, strong AR-immunostaining was present in the epithelial cells of the caput and corpus epididymis, seminal vesicle, and ventral prostate. These results indicate that species and tissues differences should be taken into careful consideration in assessing the physiological and pharmacological effects of sex steroids (particularly estrogens) on the reproductive tissues of male rodents.

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.