The androgen derivative 5alpha-androstane-3beta,17beta-diol inhibits prostate cancer cell migration through activation of the estrogen receptor beta subtype

Nuclear Estrogen Receptors in Prostate Cancer: From Genes to Function

Estrogens are almost ubiquitous steroid hormones that are essential for development, metabolism, and reproduction. They exert both genomic and non-genomic action through two nuclear receptors (ERα and ERβ), which are transcription factors with disregulated functions and/or expression in pathological processes. In the 1990s, the discovery of an additional membrane estrogen G-protein-coupled receptor augmented the complexity of this picture. Increasing evidence elucidating the specific molecular mechanisms of action and opposing effects of ERα and Erβ was reported in the context of prostate cancer treatment, where these issues are increasingly investigated. Although new approaches improved the efficacy of clinical therapies thanks to the development of new molecules targeting specifically estrogen receptors and used in combination with immunotherapy, more efforts are needed to overcome the main drawbacks, and resistance events will be a challenge in the coming years. This review summarizes the state-of-the-art on ERα and ERβ mechanisms of action in prostate cancer and promising future therapies.

AKR1C3 Converts Castrate and Post-Abiraterone DHEA-S into Testosterone to Stimulate Growth of Prostate Cancer Cells via 5-Androstene-3β,17β-Diol

Androgen receptor signaling inhibitors (ARSI) are used to treat castration-resistant prostate cancer (CRPC) to stop a resurgence of androgen receptor (AR) signaling. Despite early success, patients on ARSIs eventually relapse, develop drug resistance, and succumb to the disease. Resistance may occur through intratumoral steroidogenesis mediated by upregulation of aldo-keto reductase family 1C member 3 (AKR1C3). Patients treated with leuprolide (castrate) and those treated with leuprolide plus abiraterone (post-Abi) harbor a reservoir of DHEA-S which could fuel testosterone (T) biosynthesis via AKR1C3 to cause a resurgence of prostate cancer cell growth. We demonstrate that concentrations of DHEA-S found in castrate and post-Abi patients are (i) converted to T in an AKR1C3-dependent manner in prostate cancer cells, and (ii) in amounts sufficient to stimulate AKR1C3-dependent cell growth. We observed this in primary and metastatic prostate cancer cell lines, CWR22PC and DuCaP, respectively. Androgen measurements were made by stable isotope dilution LC-MS/MS. We demonstrate AKR1C3 dependence using stable short hairpin RNA knockdown and pharmacologic inhibitors. We also demonstrate that free DHEA is reduced to 5-androstene-3β,17β-diol (5-Adiol) by AKR1C3 and that this is a major metabolite, suggesting that in our cell lines 5-Adiol is a predominant precursor of T. We have identified a mechanism of ARSI resistance common to both primary and metastatic cell lines that is dependent on the conversion of DHEA to 5-Adiol on route to T catalyzed by AKR1C3.

SIGNIFICANCE

We show that reservoirs of DHEA-S that remain after ARSI treatment are converted into T in primary and metastatic prostate cancer cells in amounts sufficient to stimulate cell growth. Pharmacologic and genetic approaches demonstrate that AKR1C3 is required for these effects. Furthermore, the route to T proceeds through 5-Adiol. We propose that this is a mechanism of ARSI drug resistance.

Selective effects of estradiol on human corneal endothelial cells

In Fuchs endothelial corneal dystrophy (FECD), mitochondrial and oxidative stresses in corneal endothelial cells (HCEnCs) contribute to cell demise and disease progression. FECD is more common in women than men, but the basis for this observation is poorly understood. To understand the sex disparity in FECD prevalence, we studied the effects of the sex hormone 17-β estradiol (E2) on growth, oxidative stress, and metabolism in primary cultures of HCEnCs grown under physiologic ([O2]2.5) and hyperoxic ([O2]A) conditions. We hypothesized that E2 would counter the damage of oxidative stress generated at [O2]A. HCEnCs were treated with or without E2 (10 nM) for 7-10 days under both conditions. Treatment with E2 did not significantly alter HCEnC density, viability, ROS levels, oxidative DNA damage, oxygen consumption rates, or extracellular acidification rates in either condition. E2 disrupted mitochondrial morphology in HCEnCs solely from female donors in the [O2]A condition. ATP levels were significantly higher at [O2]2.5 than at [O2]A in HCEnCs from female donors only, but were not affected by E2. Our findings demonstrate the resilience of HCEnCs against hyperoxic stress. The effects of hyperoxia and E2 on HCEnCs from female donors suggest cell sex-specific mechanisms of toxicity and hormonal influences.

The role of androgens and estrogens in social interactions and social cognition

Gonadal hormones are becoming increasingly recognized for their effects on cognition. Estrogens, in particular, have received attention for their effects on learning and memory that rely upon the functioning of various brain regions. However, the impacts of androgens on cognition are relatively under investigated. Testosterone, as well as estrogens, have been shown to play a role in the modulation of different aspects of social cognition. This review explores the impact of testosterone and other androgens on various facets of social cognition including social recognition, social learning, social approach/avoidance, and aggression. We highlight the relevance of considering not only the actions of the most commonly studied steroids (i.e., testosterone, 17β-estradiol, and dihydrotestosterone), but also that of their metabolites and precursors, which interact with a plethora of different receptors and signalling molecules, ultimately modulating behaviour. We point out that it is also essential to investigate the effects of androgens, their precursors and metabolites in females, as prior studies have mostly focused on males. Overall, a comprehensive analysis of the impact of steroids such as androgens on behaviour is fundamental for a full understanding of the neural mechanisms underlying social cognition, including that of humans.

Age-related decrease in serum dihydrotestosterone concentration is accompanied by impaired vascular status

INTRODUCTION

The effect of androgens on the cardiovascular system in humans is ambiguous. Moreover, still little is known about the effects of the most potent androgen, dihydrotestosterone, on arterial stiffness and endothelial function. The aim of this study was to evaluate whether age-dependent alterations in serum concentration of dihydrotestosterone and its circulating metabolite are accompanied by changes in endothelial function and arterial stiffness.

METHODS

In 12 young and 11 older men, basal serum concentrations of testosterone, dehydroepiandrosterone sulfate (DHAE-S), androstenedione (AE), dihydrotestosterone (DHT) and androstanediol glucuronide (ADG) were analyzed in relation to vascular status including cIMT - carotid intima media thickness, cAI - central augmentation index, crPWV - carotid radial pulse wave velocity, SI - stiffness index, endothelial and inflammatory markers.

RESULTS

Although concentration of testosterone was not different between young and older group, it was demonstrated that DHT, DHEA-S, AE and ADG were significantly lower in older men in comparison to young men (p < 0.01). Interestingly the most surprising difference was found for DHT concentration, that was as much as 61 % lower in aged men that displayed significantly higher values of cIMT, AI, crPWV and SI (p < 10^-4), suggestive of arterial stiffness. Furthermore, DHT was negatively correlated to all arterial wall parameters (cAI, crPWV, SI and cIMT), c-reactive protein (CRP) and hyaluronic acid (HA) concentration, as well as positively correlated to markers of endothelial function (MNA and 6-keto-PGF_1α) in all studied individuals (n = 23).

CONCLUSIONS

We have shown that ageing leads to a significant decrease in DHT concentration that is accompanied by impaired arterial wall characteristics and worsened endothelial function. Therefore more attention should be paid to the DHT, DHEA-S and ADG concentrations as a biomarkers for vascular dysfunction in ageing men.

The Role of HSPB8, a Component of the Chaperone-Assisted Selective Autophagy Machinery, in Cancer

The cellular response to cancer-induced stress is one of the major aspects regulating cancer development and progression. The Heat Shock Protein B8 (HSPB8) is a small chaperone involved in chaperone-assisted selective autophagy (CASA). CASA promotes the selective degradation of proteins to counteract cell stress such as tumor-induced stress. HSPB8 is also involved in (i) the cell division machinery regulating chromosome segregation and cell cycle arrest in the G0/G1 phase and (ii) inflammation regulating dendritic cell maturation and cytokine production. HSPB8 expression and role are tumor-specific, showing a dual and opposite role. Interestingly, HSPB8 may be involved in the acquisition of chemoresistance to drugs. Despite the fact the mechanisms of HSPB8-mediated CASA activation in tumors need further studies, HSPB8 could represent an important factor in cancer induction and progression and it may be a potential target for anticancer treatment in specific types of cancer. In this review, we will discuss the molecular mechanism underlying HSPB8 roles in normal and cancer conditions. The basic mechanisms involved in anti- and pro-tumoral activities of HSPB8 are deeply discussed together with the pathways that modulate HSPB8 expression, in order to outline molecules with a beneficial effect for cancer cell growth, migration, and death.

Disruption of classical estrogenic targets in brown trout primary hepatocytes by the model androgens testosterone and dihydrotestosterone

Estrogenic effects triggered by androgens have been previously shown in a few studies. Aromatization and direct binding to estrogen receptors (ERs) are the most proposed mechanisms. For example, previously, a modulation of vitellogenin A (VtgA) by testosterone (T), an aromatizable androgen, was reported in brown trout primary hepatocytes. The effect was reversed by an ER antagonist. In this study, using the same model the disruption caused by T and by the non-aromatizable androgen - dihydrotestosterone (DHT), was assessed in selected estrogenic targets. Hepatocytes were exposed (96 h) to six concentrations of each androgen. The estrogenic targets were VtgA, ERα, ERβ1 and two zona pellucida genes, ZP2.5 and ZP3a.2. The aromatase CYP19a1 gene and the androgen receptor (AR) were also included. Modulation of estrogenic targets was studied by quantitative real-time PCR and immunohistochemistry, using an HScore system. VtgA and ERα were up-regulated by DHT (1, 10, 100 μM) and T (10, 100 μM). In contrast, ERβ1 was down-regulated by DHT (10, 100 μM), and T (100 μM). ZP2.5 mRNA levels were increased by DHT and T (1, 10, 100 μM), while ZP3a.2 was up-regulated by DHT (100 μM) and T (10, 100 μM). Positive correlations were found between VtgA and ERα mRNA levels and ZPs and ERα, after exposure to both androgens. The mRNA levels of CYP19a1 were not changed, while AR expression tended to increase after micromolar DHT exposures. HScores for Vtg and ZPs corroborated the molecular findings. Both androgens triggered estrogen signaling through direct binding to ERs, most probably ERα.

Roles for androgens in mediating the sex differences of neuroendocrine and behavioral stress responses

Estradiol and testosterone are powerful steroid hormones that impact brain function in numerous ways. During development, these hormones can act to program the adult brain in a male or female direction. During adulthood, gonadal steroid hormones can activate or inhibit brain regions to modulate adult functions. Sex differences in behavioral and neuroendocrine (i.e., hypothalamic pituitary adrenal (HPA) axis) responses to stress arise as a result of these organizational and activational actions. The sex differences that are present in the HPA and behavioral responses to stress are particularly important considering their role in maintaining homeostasis. Furthermore, dysregulation of these systems can underlie the sex biases in risk for complex, stress-related diseases that are found in humans. Although many studies have explored the role of estrogen and estrogen receptors in mediating sex differences in stress-related behaviors and HPA function, much less consideration has been given to the role of androgens. While circulating androgens can act by binding and activating androgen receptors, they can also act by metabolism to estrogenic molecules to impact estrogen signaling in the brain and periphery. This review focuses on androgens as an important hormone for modulating the HPA axis and behaviors throughout life and for setting up sex differences in key stress regulatory systems that could impact risk for disease in adulthood. In particular, impacts of androgens on neuropeptide systems known to play key roles in HPA and behavioral responses to stress (corticotropin-releasing factor, vasopressin, and oxytocin) are discussed. A greater knowledge of androgen action in the brain is key to understanding the neurobiology of stress in both sexes.

The Role of Sex and Sex Hormones in Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are a wide class of disorders of the central nervous system (CNS) with unknown etiology. Several factors were hypothesized to be involved in the pathogenesis of these diseases, including genetic and environmental factors. Many of these diseases show a sex prevalence and sex steroids were shown to have a role in the progression of specific forms of neurodegeneration. Estrogens were reported to be neuroprotective through their action on cognate nuclear and membrane receptors, while adverse effects of male hormones have been described on neuronal cells, although some data also suggest neuroprotective activities. The response of the CNS to sex steroids is a complex and integrated process that depends on (i) the type and amount of the cognate steroid receptor and (ii) the target cell type-either neurons, glia, or microglia. Moreover, the levels of sex steroids in the CNS fluctuate due to gonadal activities and to local metabolism and synthesis. Importantly, biochemical processes involved in the pathogenesis of NDs are increasingly being recognized as different between the two sexes and as influenced by sex steroids. The aim of this review is to present current state-of-the-art understanding on the potential role of sex steroids and their receptors on the onset and progression of major neurodegenerative disorders, namely, Alzheimer's disease, Parkinson's diseases, amyotrophic lateral sclerosis, and the peculiar motoneuron disease spinal and bulbar muscular atrophy, in which hormonal therapy is potentially useful as disease modifier.

Curcumin: a phytochemical modulator of estrogens and androgens in tumors of the reproductive system

Curcumin (Cur) is an active derivative extracted from turmeric which exerts a wide range of interactions with biomolecules through complex signaling pathways. Cur has been extensively shown to possess potential antitumor properties. In addition, there is growing body of evidence suggesting that Cur may exert potential anti-estrogen and anti-androgen activity. In vitro and in vivo studies suggest that anticancer properties of Cur against tumors affecting the reproductive system in females and males may be underlied by the Cur-mediated inhibition of androgen and estrogen signaling pathways. In this review we examine various studies assessing the crosstalk between Cur and both androgen and estrogen hormonal activity. Also, we discuss the potential chemopreventive and antitumor role of Cur in the most prevalent cancers affecting the reproductive system in females and males.

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.

ZFHX3 is indispensable for ERβ to inhibit cell proliferation via MYC downregulation in prostate cancer cells

Both estrogen receptor 2 (ESR2, also known as estrogen receptor beta (ERβ)) and the zinc-finger homeobox 3 (ZFHX3, also known as ATBF1 for AT motif-binding factor 1) modulate prostate development and suppress prostatic tumorigenesis in mice. ZFHX3 is integral to proper functions of ESR1 (i.e., estrogen receptor alpha (ERα)), which belongs to the same family of proteins as ESR2, but is hardly expressed in prostate epithelial cells. It is not clear how ZFHX3 suppresses prostatic tumorigenesis. In this study, we investigated whether ZFHX3 and ERβ functionally interact with each other in the suppression of prostatic tumorigenesis. In two androgen receptor (AR)-positive prostate cancer cell lines, C4-2B and LNCaP, we first validated ERβ’s tumor suppressor activity indicated by the inhibition of cell proliferation and repression of MYC expression. We found that loss of ZFHX3 increased cell proliferation and MYC expression, and downregulation of MYC was necessary for ZFHX3 to inhibit cell proliferation in the same cell lines. Importantly, loss of ZFHX3 prevented ERβ from suppressing cell proliferation and repressing MYC transcription. Biochemically, ERβ and ZFHX3 physically interacted with each other and they both occupied the same region of the common MYC promoter, even though ZFHX3 also bound to another region of the MYC promoter. Higher levels of ZFHX3 and ERβ in human prostate cancer tissue samples correlated with better patient survival. These findings establish MYC repression as a mechanism for ZFHX3’s tumor suppressor activity and ZFHX3 as an indispensable factor for ERβ’s tumor suppressor activity in prostate cancer cells. Our data also suggest that intact ZFHX3 function is required for using ERβ-selective agonists to effectively treat prostate cancer.

Structural and Functional Biology of Aldo-Keto Reductase Steroid-Transforming Enzymes

Aldo-keto reductases (AKRs) are monomeric NAD(P)(H)-dependent oxidoreductases that play pivotal roles in the biosynthesis and metabolism of steroids in humans. AKR1C enzymes acting as 3-ketosteroid, 17-ketosteroid, and 20-ketosteroid reductases are involved in the prereceptor regulation of ligands for the androgen, estrogen, and progesterone receptors and are considered drug targets to treat steroid hormone-dependent malignancies and endocrine disorders. In contrast, AKR1D1 is the only known steroid 5β-reductase and is essential for bile-acid biosynthesis, the generation of ligands for the farnesoid X receptor, and the 5β-dihydrosteroids that have their own biological activity. In this review we discuss the crystal structures of these AKRs, their kinetic and catalytic mechanisms, AKR genomics (gene expression, splice variants, polymorphic variants, and inherited genetic deficiencies), distribution in steroid target tissues, roles in steroid hormone action and disease, and inhibitor design.

Estrogen receptor β suppresses inflammation and the progression of prostate cancer

Previous studies demonstrated that estrogen receptor β (ERβ) signaling alleviates systemic inflammation in animal models, and suggested that ERβ-selective agonists may deactivate microglia and suppress T cell activity via downregulation of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB). In the present study, the role of ERβ in lipopolysaccharide (LPS)-induced inflammation and association with NF-κB activity were investigated in PC-3 and DU145 prostate cancer cell lines. Cells were treated with LPS to induce inflammation, and ELISA was performed to determine the expression levels of inflammatory cytokines, including tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein 1 (MCP-1), interleukin (IL)-1β and IL-6. MTT and Transwell assays, and Annexin V/propidium iodide staining were conducted to measure cell viability, apoptosis and migration, respectively. Protein expression was determined via western blot analysis. LPS-induced inflammation resulted in elevated expression levels of TNF-α, IL-1β, MCP-1 and IL-6 compared with controls. ERβ overexpression significantly inhibited the LPS-induced production of TNF-α, IL-1β, MCP-1 and IL-6. In addition, the results indicated that ERβ suppressed viability and migration, and induced apoptosis in prostate cancer cells, which was further demonstrated by altered expression of proliferating cell nuclear antigen, B-cell lymphoma 2-associated X protein, caspase-3, E-cadherin and matrix metalloproteinase-2. These effects were reversed by treatment with the ERβ antagonist PHTPP or ERβ-specific short interfering RNA. ERβ overexpression reduced the expression levels of p65 and phosphorylated NF-κB inhibitor α (IκBα), but not total IκBα expression in LPS-treated cells. In conclusion, ERβ suppressed the viability and migration of the PC-3 and DU145 prostate cancer cell lines and induced apoptosis. Furthermore, it reduced inflammation and suppressed the activation of the NF-κB pathway, suggesting that ERβ may serve roles as an anti-inflammatory and anticancer agent in prostate cancer.

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.

The small heat shock protein B8 (HSPB8) modulates proliferation and migration of breast cancer cells

Breast cancer (BC) is one of the major causes of cancer death in women and is closely related to hormonal dysregulation. Estrogen receptor (ER)-positive BCs are generally treated with anti hormone therapy using antiestrogens or aromatase inhibitors. However, BC cells may become resistant to endocrine therapy, a process facilitated by autophagy, which may either promote or suppress tumor expansion. The autophagy facilitator HSPB8 has been found overexpressed in some BC. Here we found that HSPB8 is highly expressed and differentially modulated by natural or synthetic selective ER modulators (SERMs), in the triple-positive hormone-sensitive BC (MCF-7) cells, but not in triple-negative MDA-MB-231 BC cells. Specific SERMs induced MCF-7 cells proliferation in a HSPB8 dependent manner whereas, did not modify MDA-MB-231 cell growth. ER expression was unaffected in HSPB8-depleted MCF-7 cells. HSPB8 over-expression did not alter the distribution of MCF-7 cells in the various phases of the cell cycle. Conversely and intriguingly, HSPB8 downregulation resulted in an increased number of cells resting in the G0/G1 phase, thus possibly reducing the ability of the cells to pass through the restriction point. In addition, HSPB8 downregulation reduced the migratory ability of MCF-7 cells. None of these modifications were observed, when another small HSP (HSPB1), also expressed in MCF-7 cells, was downregulated. In conclusion, our data suggest that HSPB8 is involved in the mechanisms that regulate cell cycle and cell migration in MCF-7 cells.

Activation of estrogen receptor beta (ERβ) regulates the expression of N-cadherin, E-cadherin and β-catenin in androgen-independent prostate cancer cells

The aim of the present study was to investigate the impact of the activation of estrogen receptors on expression and localization of N-cadherin, E-cadherin and non-phosphorylated β-catenin in androgen-independent prostate cancer cells (PC-3 and DU-145) and in human post pubertal prostate epithelial cells (PNT1A). Expression of N-cadherin was detected in PNT1A and PC-3 cells, but not in DU-145 cells. E-cadherin was detected only in DU-145 cells and β-catenin was detected in all cells studied. N-cadherin and β-catenin were located preferentially in the cellular membrane of PNT1A cells and in the cytoplasm of PC-3 cells. E-cadherin and β-catenin were located preferentially in the cellular membrane of DU-145 cells. 17β-estradiol (E2) or the ERα-selective agonist PPT did not affect the content and localization of N-cadherin in PC-3 and PNT1A cells or E-cadherin in DU-145 cells. In PC-3 cells, ERβ-selective agonist DPN decreased the expression of N-cadherin. DPN-induced downregulation of N-cadherin was blocked by pretreatment with the ERβ-selective antagonist (PHTPP), indicating that ERβ1 is the upstream receptor regulating the expression of N-cadherin. In DU-145 cells, the activation of ERβ1 by DPN increased the expression of E-cadherin. Taken together, these results suggest that activation of ERβ1 is required to maintain an epithelial phenotype in PC-3 and DU-145 cells. The activation of ERβ1 also increased the expression of β-catenin in cytoplasm of PC-3 and in the cellular membrane of DU-145 cells. In conclusion, our results indicate differential expression and localization of N-cadherin, E-cadherin and β-catenin in androgen-independent prostate cancer cells. The reduction of N-cadherin content by activation of ERβ, exclusively observed in androgen-independent prostate cancer cells (PC-3), may be related to the activation of signaling pathways, such as the release of β-catenin into the cytoplasm, translocation of β-catenin to the nucleus and activation of gene transcription.

Effect of estrogen receptor β agonists on proliferation and gene expression of ovarian cancer cells

Background

Estrogen receptor (ER) β has been suggested to affect ovarian carcinogenesis. We examined the effects of four ERβ agonists on proliferation and gene expression of two ovarian cancer cell lines.

Methods

OVCAR-3 and OAW-42 ovarian cancer cells were treated with the ERβ agonists ERB-041, WAY200070, Liquiritigenin and 3β-Adiol and cell growth was measured by means of the Cell Titer Blue Assay (Promega). ERβ expression was knocked down by transfection with specific siRNA. Additionally, transcriptome analyses were performed by means of Affymetrix GeneChip arrays. To confirm the results of DNA microarray analysis, Western blot experiments were performed.

Results

All ERβ agonists tested significantly decreased proliferation of OVCAR-3 and OAW-42 cells at a concentration of 10 nM. Maximum antiproliferative effects were induced by flavonoid Liquiritigenin, which inhibited growth of OVCAR-3 cells by 31.2% after 5 days of treatment, and ERB-041 suppressing proliferation of the same cell line by 29.1%. In OAW-42 cells, maximum effects were observed after treatment with the ERβ agonist WAY200070, inhibiting cell growth by 26.8%, whereas ERB-041 decreased proliferation by 24.4%. In turn, knockdown of ERβ with specific siRNA increased cell growth of OAW-42 cells about 1.9-fold. Transcriptome analyses revealed a set of genes regulated by ERβ agonists including ND6, LCN1 and PTCH2, providing possible molecular mechanisms underlying the observed antiproliferative effects.

Conclusion

In conclusion, the observed growth-inhibitory effects of all ERβ agonists on ovarian cancer cell lines in vitro encourage further studies to test their possible use in the clinical setting.

Agonists and knockdown of estrogen receptor β differentially affect invasion of triple-negative breast cancer cells in vitro

Background

Estrogen receptor β (ERβ) is expressed in the majority of invasive breast cancer cases, irrespective of their subtype, including triple-negative breast cancer (TNBC). Thus, ERβ might be a potential target for therapy of this challenging cancer type. In this in vitro study, we examined the role of ERβ in invasion of two triple-negative breast cancer cell lines.

Methods

MDA-MB-231 and HS578T breast cancer cells were treated with the specific ERβ agonists ERB-041, WAY200070, Liquiritigenin and 3β-Adiol. Knockdown of ERβ expression was performed by means of siRNA transfection. Effects on cellular invasion were assessed in vitro by means of a modified Boyden chamber assay. Transcriptome analyses were performed using Affymetrix Human Gene 1.0 ST microarrays. Pathway and gene network analyses were performed by means of Genomatix and Ingenuity Pathway Analysis software.

Results

Invasiveness of MBA-MB-231 and HS578T breast cancer cells decreased after treatment with ERβ agonists ERB-041 and WAY200070. Agonists Liquiritigenin and 3β-Adiol only reduced invasion of MDA-MB-231 cells. Knockdown of ERβ expression increased invasiveness of MDA-MB-231 cells about 3-fold. Transcriptome and pathway analyses revealed that ERβ knockdown led to activation of TGFβ signalling and induced expression of a network of genes with functions in extracellular matrix, tumor cell invasion and vitamin D3 metabolism.

Conclusions

Our data suggest that ERβ suppresses invasiveness of triple-negative breast cancer cells in vitro. Whether ERβ agonists might be useful drugs in the treatment of triple-negative breast cancer, has to be evaluated in further animal and clinical studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2973-y) contains supplementary material, which is available to authorized users.

Dihydrotestosterone synthesis pathways from inactive androgen 5α-androstane-3β,17β-diol in prostate cancer cells: Inhibition of intratumoural 3β-hydroxysteroid dehydrogenase activities by abiraterone

Intratumoural dihydrotestosterone (DHT) synthesis could be an explanation for castration resistance in prostate cancer (PC). By using liquid chromatography-mass spectrometry, we evaluated the intratumoral DHT synthesis from 5α-androstane-3β,17β-diol (3β-diol), which is inactive androgen metabolized from DHT. 3β-diol had biochemical potential to be converted to DHT via three metabolic pathways and could stimulate PC cell growth. Especially, 3β-diol was not only converted back to upstream androgens such as dehydroepiandrosterone (DHEA) or Δ5-androstenediol but also converted directly to DHT which is the main pathway from 3β-diol to DHT. Abiraterone had a significant influence on the metabolism of DHEA, epiandrosterone and 3β-diol, by the inhibition of the intratumoural 3β-hydroxysteroid dehydrogenase (3β-HSD) activities which is one of key catalysts in androgen metabolic pathway. The direct-conversion of 3β-diol to DHT was catalysed by 3β-HSD and abiraterone could inhibit this activity of 3β-HSD. These results suggest that PC had a mechanism of intratumoural androgen metabolism to return inactive androgen to active androgen and intratumoural DHT synthesis from 3β-diol is important as one of the mechanisms of castration resistance in PC. Additionally, the inhibition of intratumoural 3β-HSD activity could be a new approach to castration-resistant prostate cancer treatment.

Opposing Effects of Cyclooxygenase-2 (COX-2) on Estrogen Receptor β (ERβ) Response to 5α-Reductase Inhibition in Prostate Epithelial Cells

Current pharmacotherapies for symptomatic benign prostatic hyperplasia (BPH), an androgen receptor-driven, inflammatory disorder affecting elderly men, include 5α-reductase (5AR) inhibitors (i.e. dutasteride and finasteride) to block the conversion of testosterone to the more potent androgen receptor ligand dihydrotestosterone. Because dihydrotestosterone is the precursor for estrogen receptor β (ERβ) ligands, 5AR inhibitors could potentially limit ERβ activation, which maintains prostate tissue homeostasis. We have uncovered signaling pathways in BPH-derived prostate epithelial cells (BPH-1) that are impacted by 5AR inhibition. The induction of apoptosis and repression of the cell adhesion protein E-cadherin by the 5AR inhibitor dutasteride requires both ERβ and TGFβ. Dutasteride also induces cyclooxygenase type 2 (COX-2), which functions in a negative feedback loop in TGFβ and ERβ signaling pathways as evidenced by the potentiation of apoptosis induced by dutasteride or finasteride upon pharmacological inhibition or shRNA-mediated ablation of COX-2. Concurrently, COX-2 positively impacts ERβ action through its effect on the expression of a number of steroidogenic enzymes in the ERβ ligand metabolic pathway. Therefore, effective combination pharmacotherapies, which have included non-steroidal anti-inflammatory drugs, must take into account biochemical pathways affected by 5AR inhibition and opposing effects of COX-2 on the tissue-protective action of ERβ.

Phenotypic malignant changes and untargeted lipidomic analysis of long-term exposed prostate cancer cells to endocrine disruptors

Endocrine disruptors (EDs) are a class of environmental toxic molecules able to interfere with the normal hormone metabolism. Numerous studies involve EDs exposure to initiation and development of cancers, including prostate cancer. In this work, three different EDs (aldrin, aroclor 1254 and chlorpyrifos (CPF)) were investigated as potential inducers of a malignant phenotype in DU145 prostate cancer cells after a chronic exposure. Epithelial to mesenchymal transition (EMT) induction, proliferation, migration, colony formation and release of metalloproteinase 2 (MMP-2) were analyzed in 50-day exposed cells to the selected EDs. As a result, aldrin and CPF exposure led to an EMT induction (loss of 16% and 14% of E-cadherin levels, respectively, compared to the unexposed cells). Aroclor and CPF presented an increased migration (134% and 126%, respectively), colony formation (204% and 144%, respectively) and MMP-2 release (137% in both cases) compared to the unexposed cells. An untargeted lipidomic analysis was performed to decipher the lipids involved in the observed transformations. As general results, aldrin exposure showed a global decrease in phospholipids and sphingolipids, and aroclor and CPF showed an increase of certain phospholipids, glycosphingolipids as well as a remarkable increase of some cardiolipin species. Furthermore, the three exposures resulted in an increase of some triglyceride species. In conclusion, some significant changes in lipids were identified and thus we postulate that some lipid compounds and lipid metabolic pathways could be involved in the acquisition of the malignant phenotype in exposed prostate cancer cells to the selected EDs.

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.

DHEA - a precursor of ERβ ligands

What is DHEA and why is there so much public interest in this steroid which has been touted as the fountain of youth and is supposed to have all kinds of health benefits? Endocrinologists have been fascinated with DHEA for a long time because of its high production in the fetal adrenals and its continued high levels until the 7th decade of life. Yet there is still little agreement about its physiological functions. In its simplest terms endocrinology is the communication between at least three organs: one sends a message, one releases a hormone into the blood in response to the message and one responds to the hormone. DHEA is produced by a specific zone of the adrenal cortex, the zona reticularis, whose sole function is to produce this steroid. Glucocorticoids and mineralocorticoids which are C21 steroids are produced in two other zones of the adrenal cortex called the zona fasicularis and the zona glomerulosa, respectively. Being C21 steroids, they cannot be synthesized from DHEA which is a C19 steroid. To date there is no known hormone which specifically stimulates the zona reticularis and there is no known specific receptor for DHEA. Thus DHEA does not qualify as a hormone. DHEA could have autocrine or paracrine effects but, so far, there is no known effect of DHEA on either the cells of the zona glomerulosa or the zona fasicularis. Of course DHEA could have functions as a local precursor of androgens or estrogens and many studies have reported on the beneficial effects of transdermal or transvaginal administration of DHEA in postmenopausal women. This review will consider two of the potential functions of DHEA as a precursor of estrogen receptor beta (ERβ) ligands.

Effects of sex hormones on inflammatory response in male and female vascular endothelial cells

PURPOSE

Gender-related differences in sex hormones might have a key role in the development of atherosclerosis though direct vascular effects of sex hormones are not yet well understood. Thus, the main purpose of this study was to compare the effects of sex hormones on inflammatory response in Human Umbilical Vein Endothelial Cells (HUVECs) obtained from both male and female donors.

METHODS

We analyzed the expression of receptors and enzymes relevant to the action of androgens (AR, 5α-reductase 1 and 5α-reductase 2) and estrogens (ERα, ERβ, and aromatase) in male and female HUVECs. Furthermore, we analyzed the effect of testosterone (T), 17β-estradiol (E2), dihydrotestosterone (DHT), and several androgenic-anabolic steroids (AAS) on VCAM-1, ICAM-1, and E-selectin gene expression and on adhesion of U937 cells to TNF-α-stimulated male and female HUVECs.

RESULTS

Our results reveal that in HUVECs, regardless of gender, the components involved in the androgen action pathway are predominant as compared to those of estrogen action pathway. In both HUVEC genders, the inflammatory effect of TNF-α was amplified by co-administration of T or DHT and several AAS frequently used in doping, while E2 had no effect.

CONCLUSIONS

This is the first study analyzing, under identical culture conditions, the key components of sex hormone response in male and female HUVECs and the possible role of sex hormones in regulating the endothelial inflammatory response. The data obtained in our experimental system showed a pro-inflammatory effect of androgens, while conclusively excluding any protective effect for all the tested hormones.

Androgen biosynthesis in castration-resistant prostate cancer

Prostate cancer is the second leading cause of death in adult males in the USA. Recent advances have revealed that the fatal form of this cancer, known as castration-resistant prostate cancer (CRPC), remains hormonally driven despite castrate levels of circulating androgens. CRPC arises as the tumor undergoes adaptation to low levels of androgens by either synthesizing its own androgens (intratumoral androgens) or altering the androgen receptor (AR). This article reviews the major routes to testosterone and dihydrotestosterone synthesis in CRPC cells and examines the enzyme targets and progress in the development of isoform-specific inhibitors that could block intratumoral androgen biosynthesis. Because redundancy exists in these pathways, it is likely that inhibition of a single pathway will lead to upregulation of another so that drug resistance would be anticipated. Drugs that target multiple pathways or bifunctional agents that block intratumoral androgen biosynthesis and antagonize the AR offer the most promise. Optimal use of enzyme inhibitors or AR antagonists to ensure maximal benefits to CRPC patients will also require application of precision molecular medicine to determine whether a tumor in a particular patient will be responsive to these treatments either alone or in combination.

In vitro chronic administration of ERbeta selective ligands and prostate cancer cell growth: hypotheses on the selective role of 3beta-adiol in AR-positive RV1 cells

Prostate cancer (PC) progression from androgen-dependent (AD) to castration-resistant (CR) disease is a process caused by modifications of different signal transduction pathways within tumor microenvironment. Reducing cell proliferation, estrogen receptor beta (ERbeta) is emerging as a potential target in PC chemoprevention. Among the known selective ERbeta ligands, 3beta-Adiol, the endogenous ligand in the prostate, has been proved to counteract PC progression. This study compares the effects of chronic exposure (1–12 weeks) to different ERbeta selective ligands (DPN, 8beta-VE2, 3beta-Adiol) on proliferation of human androgen-responsive CWR22Rv1 cells, representing an intermediate phenotype between the AD- and CR-PC. 3beta-Adiol (10 nM) is the sole ligand decreasing cell proliferation and increasing p21 levels. In vitro transcriptional activity assays were performed to elucidate different behavior between 3beta-Adiol and the other ligands; in these experiments the endogenous and the main ERbeta subtype activation were considered. It is concluded that ERbeta activation has positive effects also in androgen-responsive PC. The underlying mechanisms are still to be clarified and may include the interplay among different ERbeta subtypes and the specific PC microenvironment. ERbeta agonists might be useful in counteracting PC progression, although the final outcome may depend upon the molecular pattern specific to each PC lesion.

Quality of Life and Sexual Health in the Aging of PCa Survivors

Prostate cancer (PCa) is the most common malignancy in elderly men. The progressive ageing of the world male population will further increase the need for tailored assessment and treatment of PCa patients. The determinant role of androgens and sexual hormones for PCa growth and progression has been established. However, several trials on androgens and PCa are recently focused on urinary continence, quality of life, and sexual function, suggesting a new point of view on the whole endocrinological aspect of PCa. During aging, metabolic syndrome, including diabetes, hypertension, dyslipidemia, and central obesity, can be associated with a chronic, low-grade inflammation of the prostate and with changes in the sex steroid pathways. These factors may affect both the carcinogenesis processes and treatment outcomes of PCa. Any treatment for PCa can have a long-lasting negative impact on quality of life and sexual health, which should be assessed by validated self-reported questionnaires. In particular, sexual health, urinary continence, and bowel function can be worsened after prostatectomy, radiotherapy, or hormone treatment, mostly in the elderly population. In the present review we summarized the current knowledge on the role of hormones, metabolic features, and primary treatments for PCa on the quality of life and sexual health of elderly Pca survivors.

Insight into the mechanisms of action of estrogen receptor β in the breast, prostate, colon, and CNS

Estrogen and its receptors (ERs) influence many biological processes in physiology and pathology in men and women. ERs are involved in the etiology and/or progression of cancers of the prostate, breast, uterus, ovary, colon, lung, stomach, and malignancies of the immune system. In estrogen-sensitive malignancies, ERβ usually is a tumor suppressor and ERα is an oncogene. ERβ regulates genes in several key pathways including tumor suppression (p53, PTEN); metabolism (PI3K); survival (Akt); proliferation pathways (p45(Skp2), cMyc, and cyclin E); cell-cycle arresting factors (p21(WAF1), cyclin-dependent kinase inhibitor 1 (CDKN1A)), p27(Kip1), and cyclin-dependent kinases (CDKs); protection from reactive oxygen species, glutathione peroxidase. Because they are activated by small molecules, ERs are excellent targets for pharmaceuticals. ERα antagonists have been used for many years in the treatment of breast cancer and more recently pharmaceutical companies have produced agonists which are very selective for ERα or ERβ. ERβ agonists are being considered for preventing progression of cancer, treatment of anxiety and depression, as anti-inflammatory agents and as agents, which prevent or reduce the severity of neurodegenerative diseases.

Effect of finasteride on serum levels of androstenedione, testosterone and their 5α-reduced metabolites in men at risk for prostate cancer

Studies show that treatment of men with 5α-reductase inhibitors such as finasteride is effective for the primary prevention of prostate cancer. Although it is known that finasteride treatment suppresses serum levels of dihydrotestosterone (DHT) and its distal metabolite, 5α-androstane-3α,17β-diol glucuronide (3α-diol G), and increases serum testosterone (T) levels, little is known about its effect on other precursors and metabolites of DHT, as well as on the relationship of these androgens to prostate specific antigen (PSA), a marker of prostatic intraepithelial neoplasia. The present study provides new data on the effect of finasteride on precursors and metabolites of DHT. Fifty-three men, ages 57-79 years, with elevated PSA levels (>4ng/ml), were randomized to treatment with finasteride (5mg/day) or observation (controls) for 12 months. Blood samples were obtained at baseline, 1, 3, 6 and 12 months for measurement of PSA, androstenedione (A), T, DHT, 3α-diol G, androsterone glucuronide (ADT G) and DHT sulfate (DHT S) in serum by validated, highly specific radioimmunoassays. Statistical analysis was carried out using mixed model ANOVA and t-tests. In the control group, PSA and androgen levels were unchanged throughout the 12 months of treatment. In the finasteride group, PSA, DHT, DHT S, 3α-diol G and ADT G decreased from baseline to 1 month by 23.2%, 78.7%, 71.0%, 75.7% and 43.0%, respectively. The change in PSA decreased further to 46.1% and 55.1% at 3 and 12 months of treatment, respectively, whereas the decrease in androgens observed at 1 month did not change by more than 6.9% for DHT, DHT S and 3α-diol G in the subsequent months of sampling. However, the decline in ADT G was only 22.2% at month 3, and remained essentially at this level after that time. In contrast, T and A increased significantly from baseline, and the increase in A of approximately 34.5% was about 1.9 times the increase in T (approximately 18.3%). The present data suggest that either 3α-diol G or DHT S may serve as a potential diagnostic marker of intraprostatic 5α-reductase activity during treatment of patients with 5α-reductase inhibitors.

Modulators of estrogen receptor inhibit proliferation and migration of prostate cancer cells

In the initial stages, human prostate cancer (PC) is an androgen-sensitive disease, which can be pharmacologically controlled by androgen blockade. This therapy often induces selection of androgen-independent PC cells with increased invasiveness. We recently demonstrated, both in cells and mice, that a testosterone metabolite locally synthetized in prostate, the 5α-androstane-3β, 17β-diol (3β-Adiol), inhibits PC cell proliferation, migration and invasion, acting as an anti-proliferative/anti-metastatic agent. 3β-Adiol is unable to bind androgen receptor (AR), but exerts its protection against PC by specifically interacting with estrogen receptor beta (ERβ). Because of its potential retro-conversion to androgenic steroids, 3β-Adiol cannot be used "in vivo", thus, the aims of this study were to investigate the capability of four ligands of ERβ (raloxifen, tamoxifen, genistein and curcumin) to counteract PC progression by mimicking the 3β-Adiol activity. Our results demonstrated that raloxifen, tamoxifen, genistein and curcumin decreased DU145 and PC3 cell proliferation in a dose-dependent manner; in addition, all four compounds significantly decreased the detachment of cells seeded on laminin or fibronectin. Moreover, raloxifen, tamoxifen, genistein and curcumin-treated DU145 and PC3 cells showed a significant decrease in cell migration. Notably, all these effects were reversed by the anti-estrogen, ICI 182,780, suggesting that their actions are mediated by the estrogenic pathway, via the ERβ, the only isoform present in these PCs. In conclusion, these data demonstrate that by selectively activating the ERβ, raloxifen, tamoxifen, genistein and curcumin inhibit human PC cells proliferation and migration favoring cell adesion. These synthetic and natural modulators of ER action may exert a potent protective activity against the progression of PC even in its androgen-independent status.

AKR1C3 as a target in castrate resistant prostate cancer

Aberrant androgen receptor (AR) activation is the major driver of castrate resistant prostate cancer (CRPC). CRPC is ultimately fatal and more therapeutic agents are needed to treat this disease. Compounds that target the androgen axis by inhibiting androgen biosynthesis and or AR signaling are potential candidates for use in CRPC treatment and are currently being pursued aggressively. Aldo-keto reductase 1C3 (AKR1C3) plays a pivotal role in androgen biosynthesis within the prostate. It catalyzes the 17-ketoreduction of weak androgen precursors to give testosterone and 5α-dihydrotestosterone. AKR1C3 expression and activity has been implicated in the development of CRPC, making it a rational target. Selective inhibition of AKR1C3 will be important, however, due to the presence of closely related isoforms, AKR1C1 and AKR1C2 that are also involved in androgen inactivation. We examine the evidence that supports the vital role of AKR1C3 in CRPC and recent developments in the discovery of potent and selective AKR1C3 inhibitors. This article is part of a Special Issue entitled 'CSR 2013'.

Local endocrine, paracrine and redox signaling networks impact estrogen and androgen crosstalk in the prostate cancer microenvironment

Androgen receptor (AR) signaling is essential for the initial development and progression of prostate cancer (PCa) as well as the growth and survival of castration-resistant tumors. However, AR action may be opposed by estrogen receptor beta (ERß) that responds to androgen metabolites produced in the prostate. The balance between the activity of these two receptors is not only influenced by the steroidogenic capacity of the prostatic microenvironment but also by its redox status and local paracrine signals such as transforming growth factor-beta (TGF-ß). In this review, we highlight the studies that revealed select roles for AR and ERß in distinct compartments of the prostate cancer microenvironment. We also discuss new work that identified stromal-epithelial crosstalk through TGF-ß1 signaling that drives the production of reactive oxygen species in stromal cells thereby selectively limiting the anti-tumor activity of ERß in cancer cells. Therefore, any new therapeutic approaches that seek to limit AR but enhance ERß activity in PCa, must take into account potential adaptive changes in the tumor microenvironment that utilize paracrine signals and altered redox balance to divert local androgen metabolites towards AR at the expense of ERß.

A bi-faceted role of estrogen receptor β in breast cancer

Despite over 15 years of research, the exact role, if any, played by estrogen receptor β (ERβ) in human breast cancer remains elusive. A large body of data both in vitro and in vivo supports its role as an antiproliferative, pro-apoptotic factor especially when co-expressed with ERα. However, there is a smaller body of data associating ERβ with growth and survival in breast cancer. In clinical studies and most often in cell culture studies, the pro-growth and pro-survival activity of ERβ occurs in ERα-negative breast cancer tissue and cells. This bi-faceted role of ERβ is discussed in this review.

The androgen metabolite, 5α-androstane-3β,17β-diol (3β-diol), activates the oxytocin promoter through an estrogen receptor-β pathway

Testosterone has been shown to suppress the acute stress-induced activation of the hypothalamic-pituitary-adrenal axis; however, the mechanisms underlying this response remain unclear. The hypothalamic-pituitary-adrenal axis is regulated by a neuroendocrine subpopulation of medial parvocellular neurons in the paraventricular nucleus of the hypothalamus (PVN). These neurons are devoid of androgen receptors (ARs). Therefore, a possibility is that the PVN target neurons respond to a metabolite in the testosterone catabolic pathway via an AR-independent mechanism. The dihydrotestosterone metabolite, 5α-androstane-3β,17β-diol (3β-diol), binds and activates estrogen receptor-β (ER-β), the predominant ER in the PVN. In the PVN, ER-β is coexpressed with oxytocin (OT). Therefore, we tested the hypothesis that 3β-diol regulates OT expression through ER-β activation. Treatment of ovariectomized rats with estradiol benzoate or 3β-diol for 4 days increased OT mRNA selectively in the midcaudal, but not rostral PVN compared with vehicle-treated controls. 3β-Diol treatment also increased OT mRNA in the hypothalamic N38 cell line in vitro. The functional interactions between 3β-diol and ER-β with the human OT promoter were examined using an OT promoter-luciferase reporter construct (OT-luc). In a dose-dependent manner, 3β-diol treatment increased OT-luc activity when cells were cotransfected with ER-β, but not ER-α. The 3β-diol-induced OT-luc activity was reduced by deletion of the promoter region containing the composite hormone response element (cHRE). Point mutations of the cHRE also prevented OT-luc activation by 3β-diol. These results indicate that 3β-diol induces OT promoter activity via ER-β-cHRE interactions.

Inferring the metabolism of human orphan metabolites from their metabolic network context affirms human gluconokinase activity

Metabolic network reconstructions define metabolic information within a target organism and can therefore be used to address incomplete metabolic information. In the present study we used a computational approach to identify human metabolites whose metabolism is incomplete on the basis of their detection in humans but exclusion from the human metabolic network reconstruction RECON 1. Candidate solutions, composed of metabolic reactions capable of explaining the metabolism of these compounds, were then identified computationally from a global biochemical reaction database. Solutions were characterized with respect to how metabolites were incorporated into RECON 1 and their biological relevance. Through detailed case studies we show that biologically plausible non-intuitive hypotheses regarding the metabolism of these compounds can be proposed in a semi-automated manner, in an approach that is similar to de novo network reconstruction. We subsequently experimentally validated one of the proposed hypotheses and report that C9orf103, previously identified as a candidate tumour suppressor gene, encodes a functional human gluconokinase. The results of the present study demonstrate how semi-automatic gap filling can be used to refine and extend metabolic reconstructions, thereby increasing their biological scope. Furthermore, we illustrate how incomplete human metabolic knowledge can be coupled with gene annotation in order to prioritize and confirm gene functions.

Estrogen receptor β sustains epithelial differentiation by regulating prolyl hydroxylase 2 transcription

Estrogen receptor β (ERβ) promotes the degradation of hypoxia inducible factor 1α (HIF-1α), which contributes to the ability of this hormone receptor to sustain the differentiation of epithelial and carcinoma cells. Although the loss of ERβ and consequent HIF-1 activation occur in prostate cancer with profound consequences, the mechanism by which ERβ promotes the degradation of HIF-1α is unknown. We report that ERβ regulates the ligand (3β-adiol)-dependent transcription of prolyl hydroxylase 2 (PHD2) also known as Egl nine homolog 1 (EGLN1), a 2-oxoglutarate-dependent dioxygenase that hydroxylates HIF-1α and targets it for recognition by the von Hippel-Lindau tumor suppressor and consequent degradation. ERβ promotes PHD2 transcription by interacting with a unique estrogen response element in the 5' UTR of the PHD2 gene that functions as an enhancer. PHD2 itself is critical for maintaining epithelial differentiation. Loss of PHD2 expression or inhibition of its function results in dedifferentiation with characteristics of an epithelial-mesenchymal transition, and exogenous PHD2 expression in dedifferentiated cells can restore an epithelial phenotype. Moreover, expression of HIF-1α in cells that express PHD2 does not induce dedifferentiation but expression of HIF-1α containing mutations in the proline residues that are hydroxylated by PHD2 induces dedifferentiation. These data describe a unique mechanism for the regulation of HIF-1α stability that involves ERβ-mediated transcriptional regulation of PHD2 and they highlight an unexpected role for PHD2 in maintaining epithelial differentiation.

Estrogen receptor β agonists affect growth and gene expression of human breast cancer cell lines

Expression of estrogen receptor β (ERβ) has been described to reduce growth of cancer cell lines derived from hormone-dependent tumors, like breast cancer. In this study we tested to what extent two ERβ agonists, androgen derivative 3β-Adiol and flavonoid Liquiritigenin, would affect growth and gene expression of different ERβ-positive human breast cancer cell lines. Under standard cell culture conditions, we observed 3β-Adiol to inhibit growth of MCF-7 cells in a dose-dependent manner, whereas growth of BT-474 and MCF-10A cells was suppressed by the maximum concentration (100 nM) only. When treated in serum-free medium, all cell lines except of MDA-MB-231 were responsive to 1 nM 3β-Adiol, and ZR75-1 cells exhibited a dose-dependent antiproliferative response. Providing putative mechanisms underlying the observed growth-inhibitory effect, expression of Ki-67 or cyclins A2 and B1 was downregulated after 3β-Adiol treatment in all responsive lines. In contrast, treatment with lower doses of Liquiritigenin did not affect growth. In MCF-7 cells, the highest dose of this flavonoid exerted proliferative effects accompanied by increased expression of cyclin B1, PR and PS2, indicating unspecific activation of ERα. In conclusion, the ERβ agonists tested exerted distinct concentration-dependent and cell line-specific effects on growth and gene expression. The observed inhibitory effects of 3β-Adiol on breast cancer cell growth encourage further studies on the potential of this and other ERβ agonists as targeted drugs for breast cancer therapy.

The mouse as a model to investigate sex steroid metabolism in the normal and pathological prostate

Metabolism of sex steroids within the prostate is an important factor affecting its growth and pathology. Mouse models with genetic gain- and especially loss-of-function have characterised different steroid metabolic pathways and their contribution to prostate pathology. With reference to the human prostate, this review aims to summarize the steroidogenic pathways in the mouse prostate as the basis for using the mouse as a model for intraprostatic steroid signalling. In this review we summarize the current information for three main components of the steroid signalling pathway in the mouse prostate: circulating steroids, steroid receptors and steroidogenic enzymes with regard to signalling via androgen, estrogen, progesterone and glucocorticoid pathways. This review reveals many opportunities for characterisation steroid metabolism in various mouse models. The knowledge of steroid metabolism within prostate tissue and in a lobe (rodent)/region (human) specific manner, will give valuable information for future, novel hypotheses of intraprostatic control of steroid actions. This review summarizes knowledge of steroid metabolism in the mouse prostate and its relevance to the human.

Aggressive prostate cancer is prevented in ERαKO mice and stimulated in ERβKO TRAMP mice

Previous evidence suggests soy genistein may be protective against prostate cancer, but whether this protection involves an estrogen receptor (ER)-dependent mechanism is unknown. To test the hypothesis that phytoestrogens may act through ERα or ERβ to play a protective role against prostate cancer, we bred transgenic mice lacking functional ERα or ERβ with transgenic adenocarcinoma of mouse prostate (TRAMP) mice. Dietary genistein reduced the incidence of cancer in ER wild-type (WT)/transgenic adenocarcinoma of mouse prostate mice but not in ERα knockout (KO) or ERβKO mice. Cancer incidence was 70% in ERWT mice fed the control diet compared with 47% in ERWT mice fed low-dose genistein (300 mg/kg) and 32% on the high-dose genistein (750 mg/kg). Surprisingly, genistein only affected the well differentiated carcinoma (WDC) incidence but had no effect on poorly differentiated carcinoma (PDC). No dietary effects have been observed in either of the ERKO animals. We observed a very strong genotypic influence on PDC incidence, a protective effect in ERαKO (only 5% developed PDC), compared with 19% in the ERWT, and an increase in the incidence of PDC in ERβKO mice to 41%. Interestingly, immunohistochemical analysis showed ERα expression changing from nonnuclear in WDC to nuclear in PDC, with little change in ERβ location or expression. In conclusion, genistein is able to inhibit WDC in the presence of both ERs, but the effect of estrogen signaling on PDC is dominant over any dietary treatment, suggesting that improved differential targeting of ERα vs. ERβ would result in prevention of advanced prostate cancer.

Androgen receptor (AR) expression in prostate cancer and progression of the tumor: Lessons from cell lines, animal models and human specimens

Prostate cancer (PC) is among the most frequent causes of death for cancer in men in western countries. In about 30% of cases, the disease is very aggressive rapidly leading to a metastatic disease. In these cases, prostatectomy is not possible and the patient is usually directed to androgen deprivation therapy (ADT) which is only palliative as a castration resistant PC (CRPC) usually develops within 2-3 years of treatment. At present there are no prognostic markers of PC progression. The role of the androgen receptor (AR) in initiation and development of PC is well established and documented. In particular, it is now recognized that androgens actions are mediated by an integration of classical (genomic) and non-classical (extragenomic) activity of AR. The picture about AR and PC become less clear when CRPC is considered. Indeed, the role of AR in the progression of PC and in CRPC is controversial. Results of studies on the role of AR in the progression of PC in cell lines, xenografts, animal models and even clinical specimens are conflicting reflecting the high heterogeneity of PC. Recent evidence in AR conditional KO in mouse models of PC shows possible contrasting roles of AR depending on its location in the two (epithelial or stromal) compartments of PC. Here, we review this evidence and report preliminary data of a study performed in microdissected areas of epithelia and stromal compartments of human PC.

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

AIMS

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

MAIN METHODS

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

KEY FINDINGS

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

SIGNIFICANCE

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

A local paracrine and endocrine network involving TGFβ, Cox-2, ROS, and estrogen receptor β influences reactive stromal cell regulation of prostate cancer cell motility

The tumor microenvironment plays a critical role in supporting cancer cells particularly as they disengage from limitations on their growth and motility imposed by surrounding nonreactive stromal cells. We show here that stromal-derived androgenic precursors are metabolized by DU145 human prostate cancer (PCa) cells to generate ligands for estrogen receptor-β, which act to limit their motility through transcriptional regulation of E-cadherin. Although primary human PCa-associated fibroblasts and the human WPMY-1-reactive prostate stromal cell line maintain this inherent estrogen receptor (ER)β-dependent motility inhibitor activity, they are subverted by TGF-β1 pro-oxidant signals derived from cocultured DU145 PCa cells. Specifically, stromal-produced H(2)O(2), which requires Cox-2, acts as a second paracrine factor to inhibit ERβ activity in adjacent DU145 cells. Chromatin immunoprecipitation analysis reveals that ERβ recruitment to the E-cadherin promoter is inhibited when H(2)O(2) is present. Both neutralization of H(2)O(2) with catalase and prevention of its production by silencing Cox-2 expression in stromal cells restore the motility-suppression activity of stromal-derived ERβ ligand precursors. These data suggest that reactive stromal cells may still have a capacity to limit cancer cell motility through a local endocrine network but must be protected from pro-oxidant signals triggered by cancer cell-derived TGF-β1 to exhibit this cancer-suppressive function.

Effects of CYP7B1-related steroids on androgen receptor activation in different cell lines

The widely expressed steroid hydroxylase CYP7B1 is involved in metabolism of a number of steroids reported to influence estrogen and androgen signaling. Several studies by us and other investigators have linked this enzyme to effects on estrogen receptor activation. In a previous report we examined the effect of CYP7B1-mediated hormone metabolism for estrogen-mediated response in kidney-derived HEK293 cells. In the current study we used an androgen response element (ARE) reporter system to examine androgen-dependent response of some CYP7B1 substrates and CYP7B1-formed metabolites in several cell lines derived from different tissues. The results indicate significantly lower androgen receptor activation by CYP7B1-formed steroid metabolites than by the corresponding steroid substrates, suggesting that CYP7B1-mediated catalysis may decrease some androgenic responses. Thus, CYP7B1-dependent metabolism may be of importance not only for estrogenic signaling but also for androgenic. This finding, that CYP7B1 activity may be a regulator of androgenic signaling by converting AR ligands into less active metabolites, is also supported by real-time RT-PCR experiment where a CYP7B1 substrate, but not the corresponding product, was able to stimulate known androgen-sensitive genes. Furthermore, our data indicate that the effects of some steroids on hormone response element reporter systems are cell line-specific. For instance, despite transfection of the same reporter systems, 5-androstene-3β,17β-diol strongly activates an androgen-dependent response element in prostate cancer cells whereas it elicits only ER-dependent responses in kidney HEK293 cells. Potential roles of cell-specific metabolism or comodulator expression for the observed differences are discussed.

Involvement of estrogen receptors in prostatic diseases

Accumulating evidence shows that estrogens participate in the pathogenesis and development of benign prostatic hyperplasia and prostate cancer by activating estrogen receptor α. In contrast, estrogen receptor β is involved in the differentiation and maturation of prostatic epithelial cells, and thus possesses antitumor effects in prostate cancer. However, the natural ligands of estrogen receptor β are not fully understood, and its mode of action according to its ligands and the binding sites located in the promoter regions of downstream genes remains to be elucidated. Here, we review recent experimental investigations of estrogen receptors and their urological relevance. Estrogen receptor-mediated signaling in the prostate is essential together with the androgen receptor-mediated pathway, providing a new therapeutic target for prostatic diseases.