Estrogens downregulate urocortin 2 expression in rat uterus

Urocortin 2 (Ucn2) is a member of the corticotropin-releasing factor peptide family and is expressed by various tissues, including reproductive tissues such as the uterus, ovary, and placenta. However, the regulatory mechanisms of Ucn2 expression and the physiological significance of Ucn2 in these tissues remain unclear. We previously showed that passive immunization of immature female rats by i.p. injection of anti-Ucn2 IgG induces earlier onset of puberty. Therefore, this study was designed to clarify the site and regulatory mechanisms of Ucn2 expression in the uterus. Expression levels of Ucn2 mRNA in the uterus were higher in immature (2- and 4-week-old) and aged (17-month-old) rats than in mature (9-week-old) rats in the proestrus phase. In 9-week-old rats, mRNA expression levels and contents in the uterus were lower in the proestrus phase than in the diestrus phase, while plasma Ucn2 concentrations did not differ between the two phases. Ucn2-like immunoreactivitiy was detected in the endometrial gland epithelial cells of the uterus. S.c. injection of estradiol benzoate or an estrogen receptor α (ERα) agonist significantly reduced mRNA expression levels and contents of Ucn2 in the uterus when compared with vehicle-injected ovariectomized rats. By contrast, estradiol benzoate increased Ucn2 mRNA expression levels in the lung. Thus, estrogens downregulate Ucn2 expression in the uterus in a tissue-specific manner, and Ucn2 may play a role in the regulatory mechanisms of maturation of the uterus through ERα and estrous cycle.

ErbB3 downregulation enhances luminal breast tumor response to antiestrogens

Aberrant regulation of the erythroblastosis oncogene B (ErbB) family of receptor tyrosine kinases (RTKs) and their ligands is common in human cancers. ErbB3 is required in luminal mammary epithelial cells (MECs) for growth and survival. Since breast cancer phenotypes may reflect biological traits of the MECs from which they originate, we tested the hypothesis that ErbB3 drives luminal breast cancer growth. We found higher ERBB3 expression and more frequent ERBB3 gene copy gains in luminal A/B breast cancers compared with other breast cancer subtypes. In cell culture, ErbB3 increased growth of luminal breast cancer cells. Targeted depletion of ErbB3 with an anti-ErbB3 antibody decreased 3D colony growth, increased apoptosis, and decreased tumor growth in vivo. Treatment of clinical breast tumors with the antiendocrine drug fulvestrant resulted in increased ErbB3 expression and PI3K/mTOR signaling. Depletion of ErbB3 in fulvestrant-treated tumor cells reduced PI3K/mTOR signaling, thus decreasing tumor cell survival and tumor growth. Fulvestrant treatment increased phosphorylation of all ErbB family RTKs; however, phospho-RTK upregulation was not seen in tumors treated with both fulvestrant and anti-ErbB3. These data indicate that upregulation of ErbB3 in luminal breast cancer cells promotes growth, survival, and resistance to fulvestrant, thus suggesting ErbB3 as a target for breast cancer treatment.

Silencing MED1 sensitizes breast cancer cells to pure anti-estrogen fulvestrant in vitro and in vivo

Pure anti-estrogen fulvestrant has been shown to be a promising ER antagonist for locally advanced and metastatic breast cancer. Unfortunately, a significant proportion of patients developed resistance to this type of endocrine therapy but the molecular mechanisms governing cellular responsiveness to this agent remain poorly understood. Here, we’ve reported that knockdown of estrogen receptor coactivator MED1 sensitized fulvestrant resistance breast cancer cells to fulvestrant treatment. We found that MED1 knockdown further promoted cell cycle arrest induced by fulvestrant. Using an orthotopic xenograft mouse model, we found that knockdown of MED1 significantly reduced tumor growth in mice. Importantly, knockdown of MED1 further potentiated tumor growth inhibition by fulvestrant. Mechanistic studies indicated that combination of fulvestrant treatment and MED1 knockdown is able to cooperatively inhibit the expression of ER target genes. Chromatin immunoprecipitation experiments further supported a role for MED1 in regulating the recruitment of RNA polymerase II and transcriptional corepressor HDAC1 on endogenous ER target gene promoter in the presence of fulvestrant. These results demonstrate a role for MED1 in mediating resistance to the pure anti-estrogen fulvestrant both in vitro and in vivo.

Antiestrogens suppress effects of transforming growth factor-β in breast cancer cells via the signaling axis estrogen receptor-α and Y-box Binding Protein-1

BACKGROUND

Multifunctional Y-box Binding Protein-1 (YB1) is correlated with a poor outcome in breast cancer. We found YB1 expression to be regulated by antiestrogens commonly used in the hormonal therapy of breast cancer and known as activators of Transforming Growth Factor-β (TGFβ). Thus, a putative influence of YB1 on TGFβ signaling should be investigated.

MATERIALS AND METHODS

The effect of YB1 on TGFβ signaling was monitored by expression analysis and reporter gene assays in breast cancer cells overexpressing YB1 and treated with antiestrogens.

RESULTS

Antiestrogen-mediated inhibition of estrogen receptor-α led to a suppression of YB1 protein synthesis. On the other hand, YB1 was found to be an enhancer of TGFβ signaling.

CONCLUSION

High levels of YB1 expression lead to a stimulation of TGFβ pathways, thereby counteracting antihormonal breast cancer therapy and representing a putative resistance mechanism.

Effects of tibolone or continuous combined oestradiol/norethisterone acetate on glucose and insulin metabolism

OBJECTIVE

To determine the effects of tibolone or oestradiol (E(2) )/norethisterone acetate (NETA) hormone replacement therapy on glucose and insulin metabolism in postmenopausal women.

DESIGN

Single-centre double-blind placebo-controlled randomized clinical trial.

SUBJECTS/METHODS

We randomized 105 healthy postmenopausal women to tibolone 2·5 mg daily, continuous combined oral E(2) 2 mg/NETA 1 mg daily or placebo over a 2-year study. We performed intravenous glucose tolerance tests (IVGTT) with measurements of plasma glucose, insulin and C-peptide concentrations and the IVGTT glucose elimination rate, k. Mathematical modelling was performed to determine measures of insulin sensitivity, S(i) , pancreatic insulin secretion and hepatic and plasma insulin elimination.

RESULTS

Tibolone decreased S(i) to 53-63% and k to 72-79% of baseline values but increased IVGTT phase 2 C-peptide concentrations 1·6-1·8-fold and pancreatic insulin secretion 2·2-2·4-fold, so overall IVGTT glucose concentrations were unaffected. Similar, but for k, significantly smaller changes in insulin and C-peptide secretion were seen with E(2) /NETA, also with no effect on overall IVGTT glucose concentrations.

CONCLUSIONS

Tibolone reduces insulin sensitivity. Healthy postmenopausal women seem able to compensate for this and maintain normal postload glucose concentrations, but it may not be advisable to prescribe tibolone to women with, or at increased risk for, diabetes.

A new soy germ fermented ingredient displays estrogenic and protease inhibitor activities able to prevent irritable bowel syndrome-like symptoms in stressed female rats

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) often associated with psychological distress, is characterized by increased gut permeability and visceral sensitivity. In animals, stress increases intestinal paracellular permeability (IPP), visceral sensitivity and colonic proteolytic activity. Estradiol reduces IPP and affects visceral sensitivity in non-stressed ovariectomized rats, but whether estrogens affect stress-induced hyperpermeability and hypersensitivity in cyclic females remains unclear. We aimed to evaluate (i) the effects of a phytoestrogen-rich soy germ fermented ingredient (SG) on visceral hypersensitivity, hyperpermeability and other symptoms in stressed intact female rats, (ii) the mechanisms of action involved on the basis of both estrogenic and protease inhibitor activities of SG.

METHODS

Female rats received orally for 15-d either SG, 17β-estradiol benzoate (EB), or vehicles, with or without the estrogen receptor (ER) antagonist ICI182.780 before stress. Visceral sensitivity, IPP, faecal proteolytic activity, plasma corticosterone, rat mast cell protease II immunostaining, and occludin expression were assessed.

RESULTS

Stress increased IPP (concomitantly to a drop in occludin expression), visceral sensitivity, faecal proteolytic activity and plasma corticosterone. Similarly to EB, SG prevented the stress-induced hyperpermeability, and hypersensitivity, without changes in plasma corticosterone. SG inhibited the increase in faecal proteolytic activity, enhanced occludin expression, and reduced the colonic mast cell density. All SG effects, except decrease on faecal proteolytic activity, were blocked by ICI182.780.

CONCLUSION

A 2-wk oral treatment with SG prevented the stress-induced hyperpermeability and visceral hypersensitivity in cyclic rats through ER activation, and blocked the increase in colonic proteolytic activity, suggesting that SG can be promising in IBS management.

Endocrine resistance: what do we know?

Adjuvant therapy with antiestrogens targeting estrogen receptor α (ER) signaling prevents disease recurrence in many patients with early-stage ER+ breast cancer. However, a significant number of cases exhibit de novo or acquired endocrine resistance. While other clinical subtypes of breast cancer (HER2+, triple-negative) have disproportionately higher rates of mortality, ER+ breast cancer is responsible for at least as many deaths because it is the most common subtype. Therefore, identifying mechanisms that drive endocrine resistance is a high clinical priority. A large body of experimental evidence indicates that oncogenic signaling pathways underlie endocrine resistance, including growth factor receptor tyrosine kinases (HER2, epidermal growth factor receptor [EGFR], fibroblast growth factor receptor 1/2 [FGFR], insulin-like growth factor-1 receptor [IGF-1R]/ insulin receptor [InsR]), PI3K/AKT/ mTOR, MAPK/ERK, Src, CDK4/CDK6, and ER itself. Combined targeting of ER and such pathways may be the most effective means to combat antiestrogen resistance, and clinical trials testing such strategies show promising results. Herein, we discuss pathways associated with endocrine resistance, biomarkers that may be useful to predict response to targeted agents, and avenues for further exploration to identify strategies for the treatment of patients with endocrine-resistant disease.

The neuropeptide y y(1) receptor: a diagnostic marker? Expression in mcf-7 breast cancer cells is down-regulated by antiestrogens in vitro and in xenografts

The neuropeptide Y (NPY) Y(1) receptor (Y(1)R) has been suggested as a tumor marker for in vivo imaging and as a therapeutic target. In view of the assumed link between estrogen receptor (ER) and Y(1)R in mammary carcinoma and with respect to the development of new diagnostic tools, we investigated the Y(1)R protein expression in human MCF-7 cell variants differing in ER content and sensitivity against antiestrogens. ER and Y(1)R expression were quantified by radioligand binding using [(3)H]-17β-estradiol and the Y(1)R selective antagonist [(3)H]-UR-MK114, respectively. The latter was used for cellular binding studies and for autoradiography of MCF-7 xenografts. The fluorescent ligands Cy5-pNPY (universal Y(1)R, Y(2)R and Y(5)R agonist) and UR-MK22 (selective Y(1)R antagonist), as well as the selective antagonists BIBP3226 (Y(1)R), BIIE0246 (Y(2)R) and CGP71683 (Y(5)R) were used to identify the NPY receptor subtype(s) by confocal microscopy. Y(1)R functionality was determined by mobilization of intracellular Ca(2+). Sensitivity of MCF-7 cells against antiestrogen 4-hydroxytamoxifen correlated directly with the ER content. The exclusive expression of Y(1)Rs was confirmed by confocal microscopy. The Y(1)R protein was up-regulated (100%) by 17β-estradiol (EC(50) 20 pM) and the predominant role of ERα was demonstrated by using the ERα-selective agonist "propylpyrazole triol". 17β-Estradiol-induced over-expression of functional Y(1)R protein was reverted by the antiestrogen fulvestrant (IC(50) 5 nM) in vitro. Furthermore, tamoxifen treatment of nude mice resulted in an almost total loss of Y(1)Rs in MCF-7 xenografts. In conclusion, the value of the Y(1)R as a target for therapy and imaging in breast cancer patients may be compromised due to Y(1)R down-regulation induced by hormonal (antiestrogen) treatment.

Estrogens promote cell-cell adhesion of normal and malignant mammary cells through increased desmosome formation

The association of estrogen receptor alpha (ERα) expression with differentiated breast tumors presenting a lower metastasis risk could be explained by the estrogen modulation of cell adhesion, motility and invasiveness. Since desmosomes play a crucial role in cell-cell adhesion and may interfere in tumor progression, we studied their regulation by estrogens in human breast cancer and normal mammary cells. Estrogens increased the formation of desmosomes in normal and malignant cells. Furthermore, four desmosomal proteins (desmocollin, γ-catenin, plakophilin and desmoplakin) appeared significantly up-regulated by estrogens in three ERα-expressing cancer cell lines and this effect was reversed by a pure antiestrogen. Finally, silencing of ERα or desmoplakin expression by specific siRNA revealed that estrogen-modulated desmosomal proteins are essential for the estrogenic control of intercellular adhesion. This estrogen modulation of desmosome formation could contribute to the lower invasiveness of ERα-positive tumors and to the integrity of epithelial layers in estrogen target tissues.

Disruption of 3D MCF-12A breast cell cultures by estrogens--an in vitro model for ER-mediated changes indicative of hormonal carcinogenesis

Introduction

Estrogens regulate the proliferation of normal and neoplastic breast epithelium. Although the intracellular mechanisms of estrogens in the breast are largely understood, little is known about how they induce changes in the structure of the mammary epithelium, which are characteristic of breast cancer. In vitro three dimensional (3D) cultures of immortalised breast epithelial cells recapitulate features of the breast epithelium in vivo, including formation of growth arrested acini with hollow lumen and basement membrane. This model can also reproduce features of malignant transformation and breast cancer, such as increased cellular proliferation and filling of the lumen. However, a system where a connection between estrogen receptor (ER) activation and disruption of acini formation can be studied to elucidate the role of estrogens is still missing.

Methods/Principal Findings

We describe an in vitro 3D model for breast glandular structure development, using breast epithelial MCF-12A cells cultured in a reconstituted basement membrane matrix. These cells are estrogen receptor (ER)α, ERβ and G-protein coupled estrogen receptor 1 (GPER) competent, allowing the investigation of the effects of estrogens on mammary gland formation and disruption. Under normal conditions, MCF-12A cells formed organised acini, with deposition of basement membrane and hollow lumen. However, treatment with 17β-estradiol, and the exogenous estrogens bisphenol A and propylparaben resulted in deformed acini and filling of the acinar lumen. When these chemicals were combined with ER and GPER inhibitors (ICI 182,780 and G-15, respectively), the deformed acini recovered normal features, such as a spheroid shape, proliferative arrest and luminal clearing, suggesting a role for the ER and GPER in the estrogenic disruption of acinar formation.

Conclusion

This new model offers the opportunity to better understand the role of the ER and GPER in the morphogenesis of breast glandular structure as well as the events implicated in breast cancer initiation and progression.

Antiestrogenic activity of flavonoid phytochemicals mediated via the c-Jun N-terminal protein kinase pathway. Cell-type specific regulation of estrogen receptor alpha

Flavonoid phytochemicals act as both agonists and antagonists of the human estrogen receptors (ERs). While a number of these compounds act by directly binding to the ER, certain phytochemicals, such as the flavonoid compounds chalcone and flavone, elicit antagonistic effects on estrogen signaling independent of direct receptor binding. Here we demonstrate both chalcone and flavone function as cell type-specific selective ER modulators. In MCF-7 breast carcinoma cells chalcone and flavone suppress ERα activity through stimulation of the stress-activated members of the mitogen-activated protein kinase (MAPK) family: c-Jun N-terminal kinase (JNK)1 and JNK2. The use of dominant-negative mutants of JNK1 or JNK2 in stable transfected cells established that the antiestrogenic effects of chalcone and flavone required intact JNK signaling. We further show that constitutive activation of the JNK pathway partially suppresses estrogen (E2)-mediated gene expression in breast, but not endometrial carcinoma cells. Our results demonstrate a role for stress-activated MAPKs in the cell type-specific regulation of ERα function.

Oldenlandia diffusa extracts exert antiproliferative and apoptotic effects on human breast cancer cells through ERα/Sp1-mediated p53 activation

Breast cancer is the most frequent tumor and a major cause of death among women. Estrogens play a crucial role in breast tumor growth, which is the rationale for the use of hormonal antiestrogen therapies. Unfortunately, not all therapeutic modalities are efficacious and it is imperative to develop new effective antitumoral drugs. Oldenlandia diffusa (OD) is a well-known medicinal plant used to prevent and treat many disorders, especially cancers. The aim of this study was to investigate the effects of OD extracts on breast cancer cell proliferation. We observed that OD extracts strongly inhibited anchorage-dependent and -independent cell growth and induced apoptosis in estrogen receptor alpha (ERα)-positive breast cancer cells, whereas proliferation and apoptotic responses of MCF-10A normal breast epithelial cells were unaffected. Mechanistically, OD extracts enhance the tumor suppressor p53 expression as a result of an increased binding of ERα/Sp1 complex to the p53 promoter region. Finally, we isolated ursolic and oleanolic acids as the bioactive compounds able to upregulate p53 expression and inhibit breast cancer cell growth. These acids were greatly effective in reducing tamoxifen-resistant growth of a derivative MCF-7 breast cancer cell line resistant to the antiestrogen treatment. Our results evidence how OD, and its bioactive compounds, exert antiproliferative and apoptotic effects selectively in ERα-positive breast cancer cells, highlighting the potential use of these herbal extracts as breast cancer preventive and/or therapeutic agents.

Dissecting rapid estrogen signaling with conjugates

Hypothesizing that rapid estrogen signaling could be modulated from different estrogen receptors with unique localization patterns, a number of groups have attempted to design drug conjugates that target or restrict compounds to specific subcellular compartments. This article will briefly discuss the history of using conjugates to dissect rapid estrogen signaling and different strategies to attempt to target estrogens and antiestrogens to different locations. It will also detail some of the potential issues that can arise with different types of conjugates, using examples drawn from the authors' own work.

Glucose-regulated protein 78 controls cross-talk between apoptosis and autophagy to determine antiestrogen responsiveness

While more than 70% of breast cancers express estrogen receptor-α (ER+), endocrine therapies targeting these receptors often fail. The molecular mechanisms that underlie treatment resistance remain unclear. We investigated the potential role of glucose-regulated protein 78 (GRP78) in mediating estrogen resistance. Human breast tumors showed increased GRP78 expression when compared with normal breast tissues. However, GRP78 expression was reduced in ER+ breast tumors compared with HER2-amplifed or triple-negative breast tumors. ER+ antiestrogen-resistant cells and ER+ tumors with an acquired resistant antiestrogen phenotype were both shown to overexpress GRP78, which was not observed in cases of de novo resistance. Knockdown of GRP78 restored antiestrogen sensitivity in resistant cells, and overexpression of GRP78 promoted resistance in sensitive cells. Mechanistically, GRP78 integrated multiple cellular signaling pathways to inhibit apoptosis and stimulate prosurvival autophagy, which was dependent on TSC2/AMPK-mediated mTOR inhibition but not on beclin-1. Inhibition of autophagy prevented GRP78-mediated endocrine resistance, whereas caspase inhibition abrogated the resensitization that resulted from GRP78 loss. Simultaneous knockdown of GRP78 and beclin-1 synergistically restored antiestrogen sensitivity in resistant cells. Together, our findings reveal a novel role for GRP78 in the integration of cellular signaling pathways including the unfolded protein response, apoptosis, and autophagy to determine cell fate in response to antiestrogen therapy.

Screening for in vivo (anti)estrogenic and (anti)androgenic activities of Tropaeolum majus L. and its effect on uterine contractility

ETHNOPHARMACOLOGICAL RELEVANCE

Tropaeolum majus L. (Tropaeolaceae) is a medicinal herb popularly used in Brazil for treatment of inflammatory and cardiovascular diseases. Despite some published data on its efficacy, there are still few toxicological data describing the safety of this plant. The aim of this study was to evaluate the (anti)estrogenic and (anti)androgenic activity of the hydroethanolic extract obtained from Tropaeolum majus L. (HETM), as well as its possible effects on uterine contractility.

MATERIALS AND METHODS

Three experimental protocols were performed, (a) uterotrophic assay, (b) Hershberger assay and (c) an ex vivo test to investigate the effects of maternal administration of HETM on uterine contractility at the end of pregnancy. In all protocols three doses of the HETM were administered to Wistar rats: 3, 30 and 300mg/kg.

RESULTS

In vivo tests for detection of (anti)androgenic and (anti)estrogenic activities did not show any significant alterations. Similarly, no alterations were observed on uterine contractility induced by oxytocin and arachidonic acid.

CONCLUSIONS

HETM was unable to produce (anti)estrogenic or (anti)androgenic activities in the short-term in vivo screening assays performed. In addition, there was no evidence that HETM can affect uterine contractility following gestational exposure of rats.

Tamoxifen and CYP2D6: a contradiction of data

Tamoxifen is an effective antiestrogen used in the treatment of hormone receptor-positive breast cancer. Bioconversion of tamoxifen to endoxifen, its most abundant active metabolite, is primarily dependent on the activity of cytochrome P450 2D6 (CYP2D6), which is highly polymorphic. Over 20 published studies have reported on the potential association between CYP2D6 polymorphism and tamoxifen treatment outcome, with highly inconsistent results. The purpose of this review is to explore differences among 17 independent studies to identify factors that may have contributed to the discrepant findings. This report discusses six putative factors that are grouped into two categories: (a) clinical management criteria: hormone receptor classification, menopausal status, and tamoxifen combination therapy; (b) pharmacologic criteria: genotyping comprehensiveness, CYP2D6 inhibitor coadministration, and tamoxifen adherence. Comparison of these factors between the positive and negative studies suggests that tamoxifen combination therapy, genotyping comprehensiveness, and CYP2D6 inhibitor coadministration may account for some of the contradictory results. Future association studies on the link between CYP2D6 genotype and tamoxifen treatment efficacy should account for combination therapy and CYP2D6 inhibition, and interrogate as many CYP2D6 alleles as possible.

Proliferation assays for estrogenicity testing with high predictive value for the in vivo uterotrophic effect

Proliferation assays based on human cell lines are the most used in vitro tests to determine estrogenic properties of compounds. Our objective was to characterise to what extent these in vitro tests provide alternatives for the in vivo Allen and Doisy test, a uterotrophic assay in immature or ovariectomised rodents with uterus weight as a crucial read-out parameter. In the present study four different human cell lines derived from three different female estrogen-sensitive tissues, i.e. breast (MCF-7/BOS and T47D), endometrial (ECC-1) and ovarian (BG-1) cells, were characterised by investigating their relative ERα and ERβ amounts, as the ERα/ERβ ratio is a dominant factor determining their estrogen-dependent proliferative responses. All four cell lines clearly expressed the ERα type and a very low but detectable amount of ERβ on both the mRNA and protein level, with the T47D cell line expressing the highest level of the ERβ type. Subsequently, a set of reference compounds representing different modes of estrogen action and estrogenic potency were used to investigate the proliferative response in the four cell lines, to determine which cell line most accurately predicts the effect observed in vivo. All four cell lines revealed a reasonable to good correlation with the in vivo uterotrophic effect, with the correlation being highest for the MCF-7/BOS cell line (R²=0.85). The main differences between the in vivo uterotrophic assay and the in vitro proliferation assays were observed for tamoxifen and testosterone. The proliferative response of the MCF-7/BOS cells to testosterone was partially caused by its conversion to estradiol by aromatase or via androstenedione to estrone. It is concluded that of the four cell lines tested, the best assay to include in an integrated testing strategy for replacement of the in vivo uterotrophic assay is the human MCF-7/BOS breast cancer cell line.

Comparison of tibolone and 17beta-estradiol administration on the expression of zonula occludens-1, occludin, glial fibrillary acidic protein and c-fos levels in the brain cortex and hippocampus of female rats

OBJECTIVES

To compare the effect exerted by oral tibolone or intramuscular 17β-estradiol administration on the expression of ZO-1, occludin, GFAP and c-fos levels in the brain cortex and hippocampus of ovariectomized rats.

RESULTS

Immunostaining for ZO-1 and occludin revealed similar staining patterns between controls and tibolone rats and between controls and E2 rats. When staining in tibolone and E2 rats were compared both for ZO-1 and occludin, staining patterns were again identical. Positive staining for the GFAP was detected in the controls, tibolone rats and E2 rats. Staining was more intense in the tibolone rats than controls and in the E2 rats than controls. In sections from the controls, tibolone rats and E2 rats, number of reactive cells for c-fos were 1.75±0.25, 3.75±0.36 and 4.50±0.50, respectively. There was a statistically significant difference between the three groups (p=0.0001). Comparison of tibolone and E2 rats revealed no statistically significant difference (p=0.246).

CONCLUSIONS

It is well known that natural hormones like E2 regulate brain development and function. Our results provide further information on the mechanism of action of tibolone in the brain cortex and hippocampus. These results will allow us to continue with further studies with different post-ovariectomy intervals, because tibolone can be proposed as an attractive alternative for hormone replacement therapy, acting as a neuroprotective agent for the prevention of neurodegenerative diseases in menopausal women.

Estrogen activity as a preventive and therapeutic target in thyroid cancer

Thyroid cancer is the most common endocrine-related cancer with increasing incidences during the last five years. Interestingly, according to the American Thyroid Association, the incidences of thyroid proliferative diseases occur four to five times more in women than in men with the risk of developing thyroid disorders being one in every eight females. Several epidemiological studies have suggested a possible correlation between incidences of thyroid malignancies and hormones but the precise contribution of estrogen in thyroid proliferative disease initiation, and progression is not well understood. This review is an attempt to define the phenotypic and genotypic modulatory effects of estrogen on thyroid proliferative diseases. The significance and relevance of expression of estrogen receptors, α and β, in normal and malignant thyroid tissues and their effects on different molecular pathways involved in growth and function of the thyroid gland are discussed. These novel findings open up areas of developing alternative therapeutic treatments and preventive approaches which employ the use of antiestrogen to treat thyroid malignancies.

Protective effect of tamoxifen, a synthetic non-steroidal antiestrogen, on phenelzine and 1-methyl-4-phenylpyridinium ion (MPP+)-induced hydroxyl radical generation in rat striatum

The present study examined whether tamoxifen could suppress antidepressant drug phenelzine can increase an active dopaminergic neurotoxin, 1-methyl-4-phenylpyridinium ion (MPP+)-induced hydroxyl radical (*OH) generation in the extracellular fluid of rat striatum, using in vivo microdialysis system. Rats were anesthetized, and sodium salicylate (0.5 nmol/microl/min) was infused through a microdialysis probe to detect the generation of *OH as reflected by the non-enzymatic formation of 2,3-dihydroxybenzoic acid (DHBA) in the striatum. Infusion of phenelzine (0.1 mM or 0.1 nmol/microl/min) into the striatum drastically increased dopamine (DA) efflux and the *OH formation, trapped as 2,3-DHBA by the possible increased production of MPP+. However, tamoxifen (100 microM) significantly suppressed phenelzine enhanced DA efflux and *OH formation by MPP+. These results in the pressent study is the first demonstration showing the protective effect of tamoxifen on *OH generation induced by phenelzine enhanced MPP+ by suppressing DA efflux.

Lignans as food constituents with estrogen and antiestrogen activity

Phytoestrogens are plant-derived food ingredients assumed to contribute to the prevention of hormone-dependent cancers, osteoporosis, cardiovascular disease, and menopausal symptoms. Lignans occur in numerous food plants and various structures; they are common constituents of human diet, and estrogen activity has been assessed for lignan metabolites formed in the mammalian intestine. We examined natural lignans and semisynthetic norlignans for estrogen and antiestrogen activity. A transformed yeast strain (Saccharomyces cerevisiae) expressing the estrogen receptor alpha and a reporter system was applied as test system. Some plant lignans showed estrogen activity while others and the semisynthetic norlignans were moderately active antiestrogens. Docking of lignans to protein models of estrogen receptor alpha in the active and inactive form sustained the results of the yeast estrogen assay and supported the concept of plant lignans as phytoestrogens.

Inhibition of FOSL1 overexpression in antiestrogen-resistant MCF-7 cells decreases cell growth and increases vacuolization and cell death

Elevated activator protein-1 (AP-1) activity in breast cancer cells has been linked to Tamoxifen (TAM) resistance. Fos-like antigen-1 (FOSL1) is a member of the AP-1 transcription factor and is overexpressed in a variety of human cancers including breast tumors. We have previously established an estrogen-independent and antiestrogen Toremifene (TOR)-resistant subline of MCF-7 breast cancer cells. In these cells, the expression of FOSL1 is upregulated when compared to the parental cells. In the present study, partial inhibition of FOSL1 expression in these cells by small interfering RNA resulted in a marked decrease of cell growth. The inhibition of cell growth paralleled with changes in cell morphology such as increased formation of vacuoles followed by an increase in the number of dead cells. The inhibition of FOSL1 expression in these cells also restored sensitivity to TOR. Our results suggest that chemotherapy targeting overexpression of FOSL1 could be a potent strategy for treating endocrine resistant breast cancers.

Alpha-defensins 1-3 release by dendritic cells is reduced by estrogen

BACKGROUND

During pregnancy the immune system of the mother must protect any activation that may negatively affect the fetus. Changes in susceptibility to infection as well as resolution of some autoimmune disorders represent empirical evidence for pregnancy related alterations in immunity. Sex hormones reach extremely high levels during pregnancy and have been shown to have direct effects on many immune functions including the antiviral response of dendritic cells. Among the immunologically active proteins secreted by monocyte derived DCs (MDDC) are the alpha-defensins 1-3. This family of cationic antimicrobial peptides has a broad spectrum of microbicidal activity and has also been shown to link innate to adaptive immunity by attracting T cells and immature DCs, which are essential for initiating and polarizing the immune response.

METHODS

We compare culture-generated monocyte derived DCs (MDDCs) with directly isolated myeloid dendritic cells (mDCs) and plasmacytoid dendritic cells (pDCs) and measure their alpha-defensins 1-3 secretion by ELISA both, in basal situations and after hormone (E2 or PG) treatments. Moreover, using a cohort of pregnant women we isolated mDCs from blood and also measure the levels of these anti-microbial peptides along pregnancy.

RESULTS

We show that mDCs and pDCs constitutively produce alpha-defensins 1-3 and at much higher levels than MDDCs. Alpha-defensins 1-3 production from mDCs and MDDCs but not pDCs is inhibited by E2. PG does not affect alpha-defensins 1-3 in any of the populations. Moreover, alpha-defensins 1-3 production by mDCs was reduced in the later stages of pregnancy in 40% of the patients.

CONCLUSIONS

Here, we demonstrate that mDCs and pDCs secrete alpha-defensins 1-3 and present a novel effect of E2 on the secretion of alpha-defensins 1-3 by dendritic cells.

Estrogen protection in Friedreich's ataxia skin fibroblasts

Estrogens have been shown to have protective effects on a wide range of cell types and animal models for many neurodegenerative diseases. The present study demonstrates the cytoprotective effects of 17β-estradiol (E2) and estrogen-like compounds in an in vitro model of Friedreich's ataxia (FRDA) using human donor FRDA skin fibroblasts. FRDA fibroblasts are extremely sensitive to free radical damage and oxidative stress, produced here using l-buthionine (S,R)-sulfoximine to inhibit de novo glutathione synthesis. We have shown that the protective effect of E2 in the face of l-buthionine (S,R)-sulfoximine -induced oxidative stress is independent of estrogen receptor-α, estrogen receptor-β or G protein-coupled receptor 30 as shown by the inability of either ICI 182,780 or G15 to inhibit the E2-mediated protection. These cytoprotective effects appear to be dependent on antioxidant properties and the phenolic structure of estradiol as demonstrated by the observation that all phenolic compounds tested were protective, whereas all nonphenolic compounds were inactive, and the observation that the phenolic compounds reduced the levels of reactive oxygen species, whereas the nonphenolic compounds did not. These data show for the first time that phenolic E2-like compounds are potent protectors against oxidative stress-induced cell death in FRDA fibroblasts and are possible candidate drugs for the treatment and prevention of FRDA symptoms.

Nicotine-mediated suppression of the retinoic acid metabolizing enzyme CYP26A1 limits the oncogenic potential of breast cancer

Tobacco smoke influences cancer development in tissues that are not directly exposed, and epidemiological studies have indicated that smoking women might experience decreased risk of breast cancer as a result of antiestrogenic effects. However, it remains to be clarified whether nicotine, one of the major addictive and best-investigated constituents of tobacco smoke, has any effect on breast cancer. Our recent work demonstrated that the retinoic acid metabolizing enzyme CYP26A1 enhances oncogenic and cell survival properties of breast carcinoma cells, implying a role as an oncogene. Here, we present evidence that nicotine significantly suppresses constitutive expression of CYP26A1, and that cells treated with nicotine exhibit enhanced sensitivity to apoptosis. In addition, nicotine may inhibit anchorage independent growth, cellular invasiveness and motility. These data show that nicotine can limit CYP26A1-mediated oncogenic characteristics, and suggest mechanisms by which nicotine might inhibit breast cancer development.