Role Of Estrogen Receptors Research Articles

Fulvestrant-mediated inhibition of estrogen receptor signaling slows lung cancer progression.

Estrogens are key signaling molecules that regulate various physiological processes such as cell growth, development, and differentiation. They also play a major role in many pathological conditions, such as hormone-dependent cancer. The importance of inhibiting estrogen receptor signaling in diseases of estrogen target tissues, such as breast cancer, is well documented. However, the role of estrogen signaling in diseases of nontarget tissues, such as lung cancer, is not well characterized. The aim of the current study is to examine the expression of estrogen receptor β (ERβ) and the roles of estradiol (E2) and fulvestrant on the progression of lung cancer. Tissue microarray (TMA) and immunohistochemistry (IHC) analyses were used to detect the expression of aromatase, ERα, and ERβ in 198 patients. We performed analyses to determine if there was any correlation among these three proteins. A mouse model of urethane-induced lung adenocarcinoma was used in the study. Mice were divided into three treatment groups: blank control, E2 alone, and E2 + fulvestrant (ERβ antagonist). Western blot analysis and fluorescence quantitative PCR (FQ-PCR) were used to measure expression of ERβ protein and mRNA levels, respectively. ERβ, but not ERα, was overexpressed in NSCLC samples. Lung cancer progression in mice treated with E2 was significantly increased compared to either the control group or the E2 + fulvestrant group. Mice in the E2 treatment group had significantly increased expression of ERβ at both the mRNA and protein levels compared to mice treated with E2 + fulvestrant or control. Our data suggest that ERβ promotes lung cancer progression in mice and that this progression can be inhibited with fulvestrant. These findings may help elucidate the role of ERβ in lung cancer and suggest that estrogen receptor antagonists, such as fulvestrant, may be therapeutically beneficial for the treatment of the disease.

Estrogen via estrogen receptor beta partially inhibits mandibular condylar cartilage growth

Temporomandibular joint (TMJ) diseases predominantly afflict women, suggesting a role for female hormones in the disease process. However, little is known about the role of estrogen receptor (ER) signaling in regulating mandibular condylar cartilage growth. Therefore, the goal of this study was to examine the effects of altered estrogen levels on the mandibular condylar cartilage in wild type (WT) and ER beta Knockout (KO) mice. 21-day-old female WT (n=37) and ER beta KO mice (n=36) were either sham operated or ovariectomized, and treated with either placebo or estradiol. The mandibular condylar cartilage was evaluated by histomorphometry, proliferation was analyzed by double ethynyl-2'-deoxyuridine/bromodeoxyuridine (EdU/BrdU) labeling, and assays on gene and protein expression of chondrocyte maturation markers were performed. In WT mice, ovariectomy caused a significant increase in mandibular condylar cartilage cell numbers, a significant increase in Sox9 expression and a significant increase in proliferation compared with sham operated WT mice. In contrast, ovariectomy did not cause any of these effects in the ER beta KO mice. Estrogen replacement treatment in ovariectomized WT mice caused a significant decrease in ER alpha expression and a significant increase in Sost expression compared with ovariectomized mice treated with placebo. Estrogen replacement treatment in ovariectomized ER beta KO mice caused a significant increase in Col2 expression, no change in ER alpha expression, and a significant increase in Sost expression. Estrogen via ER beta inhibits proliferation and ER alpha expression while estrogen independent of ER beta induces Col2 and Sost expression.

ERβ splice variant expression in four large cohorts of human breast cancer patient tumors.

Though the role of Estrogen Receptor (ER)α in breast cancer has been studied extensively, there is little consensus about the role of alternative ER isoform ERβ in breast cancer biology. ERβ has significant sequence homology to ERα but is located on a different chromosome and maintains both overlapping and unique functional attributes. Five variants exist, resulting from alternative splicing of the C-terminal region of ERβ. The relevance of ERβ variants in breast cancer outcomes and response to therapy is difficult to assess because of conflicting reports in the literature, likely due to variable methods used to assess ERβ in patient tumors. Here, we quantitatively assess expression of ERβ splice variants on over 2,000 breast cancer patient samples. Antibodies against ERβ variants were validated for staining specificity in cell lines by siRNA knockdown of ESR2 and staining reproducibility on formalin-fixed paraffin-embedded tissue by quantitative immunofluorescence (QIF) using AQUA technology. We found antibodies against splice variants ERβ1 and ERβ5, but not ERβ2/cx, which were sensitive, specific, and reproducible. QIF staining of validated antibodies showed both ERβ1 and ERβ5 QIF scores, which have a normal (bell shaped) distribution on most cohorts assessed, and their expression is significantly associated with each other. Extensive survival analyses show that ERβ1 is not a prognostic or predictive biomarker for breast cancer. ERβ5 appears to be a context-dependent marker of worse outcome in HER2-positive and triple-negative patients, suggesting an unknown biological function in the absence of ERα.

An animal model with a cardiomyocyte-specific deletion of estrogen receptor alpha: functional, metabolic, and differential network analysis.

Estrogen exerts diverse biological effects in multiple tissues in both animals and humans. Much of the accumulated knowledge on the role of estrogen receptor (ER) in the heart has been obtained from studies using ovariectomized mice, whole body ER gene knock-out animal models, ex vivo heart studies, or from isolated cardiac myocytes. In light of the wide systemic influence of ER signaling in regulating a host of biological functions in multiple tissues, it is difficult to infer the direct role of ER on the heart. Therefore, we developed a mouse model with a cardiomyocyte-specific deletion of the ERα allele (cs-ERα−/−). Male and female cs-ERα−/− mice with age/sex-matched wild type controls were examined for differences in cardiac structure and function by echocardiogram and differential gene expression microarray analysis. Our study revealed sex-differences in structural parameters in the hearts of cs-ERα−/− mice, with minimal functional differences. Analysis of microarray data revealed differential variations in the expression of 208 genes affecting multiple transcriptional networks. Furthermore, we report sex-specific differences in the expression of 56 genes. Overall, we developed a mouse model with cardiac-specific deletion of ERα to characterize the role of ERα in the heart independent of systemic effects. Our results suggest that ERα is involved in controlling the expression of diverse genes and networks in the cardiomyocyte in a sex-dependent manner.

17β-estradiol mediates upregulation of stromal cell-derived factor-1 in the retina through activation of estrogen receptor in an ischemia-reperfusion injury model

There is increasing evidence that suggests stromal cell-derived factor-1 (SDF-1) can induce a protective response against ischemic injury in various organs. In this study, we examined the expression of SDF-1 in a rat model of retinal ischemia-reperfusion (IR) injury. Further, we explored the effect of estrogen 17β-estradiol (E2), and the role of estrogen receptor (ER) in regulating SDF-1 expression. Retinal IR injury was established in Sprague-Dawley rats by elevating the intraocular pressure to 110 mmHg for 60 mins. Relative expression levels of SDF-1 mRNA and protein in the retina at 6 h, 12 h, and 24 h after reperfusion were determined by RT-PCR and western blot respectively. To investigate the influence of estrogen and ER on SDF-1 expression, E2 was administered intraperitoneally 30 mins before induction of ischemia, and the estrogen receptor antagonist ICI 182-780 was administered 1 h before E2 injection. SDF-1 expression in IR-injured retina is upregulated at 6 h, 12 h, and 24 h after injury, with maximum expression at 12 h. As expected, pretreatment of retinal IR rats with E2 enhanced the upregulation in SDF-1 expression after injury, through activation of the estrogen receptor. We proved this hypothesis by demonstrating that pretreatment of retinal IR rats with ICI 182-780 led to a partial decrease in E2-induced SDF-1 expression. Our findings suggest that 17β-estradiol offers protection against retinal ischemic injury by inducing an upregulation in SDF-1 expression through activation of the estrogen receptor.

The role of estrogen receptor β in prostate cancer.

Although androgen receptor (AR) signaling is the main molecular tool regulating growth and function of the prostate gland, estrogen receptor β (ERβ) is involved in the differentiation of prostatic epithelial cells and numerous antiproliferative actions on prostate cancer cells. However, ERβ splice variants have been associated with prostate cancer initiation and progression mechanisms. ERβ is promising as an anticancer therapy and in the prevention of prostate cancer. Herein, we review the recent experimental findings of ERβ signaling in the prostate.

Role of Estrogen Receptors and G Protein-Coupled Estrogen Receptor in Regulation of Hypothalamus–Pituitary–Testis Axis and Spermatogenesis

Male reproductive function is under the control of both gonadotropins and androgens through a negative feedback loop that involves the hypothalamus, pituitary, and testis known as hypothalamus–pituitary–gonadal axis (HPG). Indeed, estrogens also play an important role in regulating HPG axis but the study on relative contribution to the inhibition of gonadotropins secretion exerted by the amount of estrogens produced within the hypothalamus and/or the pituitary or by the amount of circulating estrogens is still ongoing. Moreover, it is known that the maintenance of spermatogenesis is controlled by gonadotropins and testosterone, the effects of which are modulated by a complex network of locally produced factors, including estrogens. Physiological effects of estrogens are mediated by the classical nuclear estrogen receptor alpha and estrogen receptor beta, which mediate both genomic and rapid signaling events. In addition, estrogens induce rapid non-genomic responses through a membrane-associated G protein-coupled estrogen receptor (GPER). Ours and other studies reported that, in the testis, GPER is expressed in both normal germ cells and somatic cells and it is involved in mediating the estrogen action in spermatogenesis controlling proliferative and/or apoptotic events. Interestingly, GPER expression has been revealed also in the hypothalamus and pituitary. However, its role in mediating estrogen rapid actions in this context is under investigation. Recent studies indicate that GPER is involved in modulating gonadotropin-releasing hormone (GnRH) release as well as gonadotropins secretion. In this review, we will summarize the current knowledge concerning the role of estrogen/estrogen receptors molecular pathways in regulating GnRH, follicle-stimulating hormone, and luteinizing hormone release at the hypothalamic and pituitary levels in males as well as in controlling specific testicular functions such as spermatogenesis, focusing our attention mainly on estrogen signaling mediated by GPER.

Quantitative Progesterone Receptor Expression and Efficacy of Anti-estrogen Therapy in Breast Cancer

The central role of estrogen receptor (ER) presence in predicting which breast cancer patients are likely to benefit from anti-estrogen therapies is well-established, but the added benefit of progesterone receptor (PR) and in particular low levels of PR is less well understood. The objective of this study was to determine the quantitative relationship between borderline levels of PR and subsequent benefit from anti-estrogen therapy. We examined data from 447 patients, age 50 or older. ER and PR levels were quantitated by conventional ligand binding assay and Scatchard plot analysis or by enzyme-linked immunoassay. Comparison of clinical outcome in relation with ER and PR status was calculated using Kaplan-Meier actuarial survival analysis and the log-rank test. Subpopulation treatment effect pattern plot (STEPP) analysis was used to explore the interaction between treatment effects and ER or PR levels for the 409 patients with ER values greater than 0. For anti-estrogen treated patients, when the ER and PR positivity cut-off was set at 1.0 fmole/mg protein, there was a statistically significant advantage for patients with ER+PR+ over ER+ PR- tumors for both breast cancer-free interval (BCFI) and overall survival (OS). STEPP analysis found no overall interaction between treatment outcome (5 year survival probability) and levels of hormone receptor. However, patients with borderline PR levels did not appear to benefit from anti-estrogen therapy. PR levels above borderline in addition to the presence of ER predicts an increased probability of benefit from anti-estrogen therapy in breast cancer patients.

Emerging Roles of Orphan Nuclear Receptors in Cancer

A growing body of evidence suggests that a subset of orphan nuclear receptors are amplified and prognostic for some human cancers. However, the specific roles of these orphan nuclear receptors in tumor progression and their utility as drug targets are not fully understood. In this review, we summarize recent progress in elucidating the direct and indirect involvement of orphan nuclear receptors in cancer as well as their therapeutic potential in a variety of human cancers. Furthermore, we contrast the role of orphan nuclear receptors in cancer with the known roles of estrogen receptor and androgen receptor in hormone-dependent cancers.

Harmful effect of ERβ on BCRP‐mediated drug resistance and cell proliferation in ERα/PR‐negative breast cancer

The role of estrogen receptor β (ERβ) in breast cancer is still under investigation. Various studies have provided evidence that ERβ behaves as a tumor suppressor in breast cancer, whereas some studies of estrogen receptor α (ERα) negative breast cancer reported a positive correlation between high ERβ expression and poor prognostic phenotypes, such as induced proliferation, invasion and metastasis. In the present immunohistochemistry study of 99 ERα/progesterone receptor (PR)-negative breast cancer samples, nuclear expression of ERβ was positively associated with membranous expression of breast cancer resistance protein (BCRP), Ki67 (proliferation marker) and tumor size. Moreover, both endogenous and exogenous ERβ upregulated BCRP expression which induced BCRP-mediated drug resistance and enhanced proliferation of ERα-/PR- breast cancer cells in the presence of 17β-estradiol, whereas these effects were reversed by additional use of tamoxifen (TAM). In addition, the regulation of BCRP via specific binding between ERβ and estrogen response element (ERE) was demonstrated in an electrophoretic mobility shift assay. Overall, our findings manifest that ERβ might act as a tumor promoter of cell proliferation and BCRP-mediated drug resistance in ERα-/PR- breast cancer. TAM routinely used for patients with ERα+/PR+, ERα+/PR- and ERα-/PR+ breast cancer might also be effective in ERα-/PR- but ERβ+ breast cancer. Therefore, the detection of ERβ in clinic is valuable and should not be neglected in breast cancer, especially for the ERα-/PR- phenotype.

Abstract 1575: Zebrafish embryos as a model for studying the role of estrogen receptor β in cancer metastasis.

Abstract Estrogen receptor β (ERβ) has been reported to impede cancer metastasis while estrogen receptor α (ERα) can promote cancer metastasis. Several splice variants of ERβ exist in humans and they may have different functions in different tissues, but the role of these differently spliced isoforms in cancer metastasis has not been well studied. Various model systems such as xenografting of cancer cells in mice and dogs have been used to study cancer metastasis. However, difficulties in monitoring living cancer cell metastasis in large non-transparent animals have been a limitation in these studies. Zebrafish embryos are transparent and their immune system is not fully developed until several days after post fertilization. These features make zebrafish a useful model for xenografting cancer cells and monitoring their migration. In addition, the large number of offspring and small size of the embryos make the zebrafish model amendable for high throughput screening and anti-metastasis drug discovery. In our studies, we co-microinjected breast cancer cell lines bearing ERβ constructs or control constructs, expressing fluorescent proteins of different colors, into zebrafish embryos at 48 hours post fertilization (hpf). After 2 hours recovery, fish embryos with cells circulating in the blood system were removed. Embryos that contained cells only in the original injection sites were incubated at 32°C to monitor the cancer cell migration daily using a fluorescence microscope. We found that ERβ expressing breast cancer cells were less migratory than the control cells and they remained at the original injection site to a large extent. We also examined the metastasis of prostate cancer cell lines expressing ERβ splice variants in our zebrafish xenograft model and found that cells with different ERβ splice variants exhibited different migration patterns. In conclusion, zebrafish embryos work as an effective model for studying the role of ERβ and its splice variants for cancer metastasis of diverse cancer cell lines. Citation Format: Ruixin Hao, Christoforos Thomas, Prasenjit Dey, Anders Ström, Catherine W. McCollum, Fotis Nikolos, Maria Bondesson, Jan-Ake Gustafsson. Zebrafish embryos as a model for studying the role of estrogen receptor β in cancer metastasis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1575. doi:10.1158/1538-7445.AM2013-1575

Abstract 3616: Androgen deprivation therapy and second primary lung cancer risk in prostate cancer patients in the US Veterans.

Abstract Background Previous observational studies have consistently reported decreased risk of lung cancers among prostate cancer patients. Recent literature suggests a role of estrogen receptor (ER) beta and aromatase, which can convert testosterone to estrogen, in development and progression of non small cell lung cancers. Second primary lung cancer risk among breast cancer patients appears to be higher in ER negative patients compared to ER positive patients probably from estrogen receptor blockade. As androgen deprivation therapy (ADT) has been well established for more than 70 years as an effective treatment modality for prostate cancer, we hypothesized the hormone modulation may decrease lung cancer risk and investigated the effect of ADT on second primary lung cancer risk among patients with prostate cancer. Methods We identified 62,589 men in VA Central Cancer Registry (VACCR) who were diagnosed with prostate cancer between 1999 and 2008, with follow-up available through 2010. The primary outcome was development of lung cancer, determined by VACCR. Descriptive statistics were used to compare basic characteristics between the groups. Cox proportional hazards model was used to assess the influence of ADT on the lung cancer incidence, adjusted for patient characteristics and prostate cancer stage. All the statistical analyses were performed using STATA 10 (Stata Corp, College Station, TX). Results Men who had ADT as part of their treatment for prostate cancer tend to be older (median age 71.3 vs 65.7, p < 0.01) and smoke slightly more (72.5% vs 71.4%, p=0.02). As expected, ADT group tend to have higher stage prostate cancers. There were 766 secondary lung cancers diagnosed in the cohort for the follow-up period. ADT group had significantly decreased secondary lung cancer risk by approximately 20% (HR 0.83, 95%CI=0.70-0.97) when adjusted for age, smoking status and prostate cancer stage at presentation. Conclusion Our study suggests that ADT in prostate cancer patients is associated with a decreased risk of second primary lung cancers. Independent validation studies and subgroup analyses to clarify the association is warranted. This work was supported by Veteran's Health Administration 1IK2BX001283-01 and NCI 5P50CA128613-02. Citation Format: Hyunseok Kang, Rathi N. Pillai, Johann C. Brandes. Androgen deprivation therapy and second primary lung cancer risk in prostate cancer patients in the US Veterans. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3616. doi:10.1158/1538-7445.AM2013-3616

Role of estrogen receptor α in estradiol‐induced cardiac growth

Contrary to its effects in the diseased heart, we recently discovered that estradiol (E2) unexpectedly exerts pro‐hypertrophic effects in the healthy heart of ovariectomized (OVX) mice. Our aim was to investigate the mechanism(s) involved in the regulation of cardiac growth by E2 testing the hypothesis that estrogen receptor α (ERα) mediates these E2 effects. Female wild‐type (WT) C57Bl/6J and estrogen receptor α knockout (ERKO) mice were ovariectomized at two months old and were fed an E2‐containing or soy‐free (Ctrl) diet for three months (n = 5–6/group). E2 supplementation in OVX mice led to a lower body weight (15% decrease; P < 0.05) and a higher uterus‐to‐body‐weight ratio (5‐fold increase; P < 0.001) compared with Ctrl mice, but these E2 effects were abrogated in ERKO mice. E2 led to a higher heart‐to‐body‐weight ratio compared with WT Ctrl mice (20% increase; P < 0.05). Deletion of ERα abolished this cardiac effect of E2. The expression of three E2 target genes in the heart was significantly induced by E2 in WT mice compared with Ctrl, whereas in ERKO mice E2 had no effect on Act2, Igf1 and Myocd expression. In conclusion, our study demonstrates that E2 regulates body weight and exerts significant effects on cardiac growth and gene expression via an ERα‐dependent mechanism. Funding: EUGeneHeart (LSHM‐CT‐2005–018833)

The Role of Estrogen Receptor β in Transplacental Cancer Prevention by Indole-3-Carbinol

In the present study, the efficacy of indole-3-carbinol (I3C), a key bioactive component of cruciferous vegetables, for prevention of cancer in offspring exposed in utero to the environmental carcinogen dibenzo[def,p]chrysene (DBC) was evaluated using an estrogen receptor β (ERβ) knockout mouse model. I3C was provided either through the maternal diet coincident with carcinogen exposure during pregnancy or directly to offspring postinitiation with DBC. I3C was effective at reducing T-cell acute lymphoblastic lymphoma/leukemia (T-ALL)-related mortality in offspring only if provided via the maternal diet, although a gender difference in the role of ERβ in mediating this response was evident. In female offspring, chemoprevention of T-ALL by maternal dietary I3C required expression of ERβ; survival in Esr2 wild-type and heterozygous female offspring was more than 90% compared with 66% in Esr2 null females. Alternatively, ERβ status did not significantly impact the transplacental chemoprevention by I3C in males. The possible role of ERβ in mediating lung carcinogenesis or chemoprevention by I3C was similarly complicated. Lung tumor incidence was unaltered by either dietary intervention, whereas lung tumor multiplicity was substantially reduced in Esr2 null females on the control diet and marginally lower in Esr2 null males exposed to I3C via the maternal diet compared with their wild-type and heterozygous counterparts. These findings suggest that I3C may act via ERβ to prevent or suppress DBC-initiated transplacental carcinogenesis but that the involvement of this receptor seems to differ depending on the cancer type and gender of the offspring.

The role of estrogen receptor α in the regulation of bone and growth plate cartilage.

Estrogens are important endocrine regulators of skeletal growth and maintenance in both females and males. Studies have demonstrated that the estrogen receptor (ER)-α is the main mediator of these estrogenic effects in bone. Therefore, estrogen signaling via ERα is a target both for affecting longitudinal bone growth and bone remodeling. However, treatment with estradiol (E2) leads to an increased risk of side effects such as venous thromboembolism and breast cancer. Thus, an improved understanding of the signaling pathways of ERα will be essential in order to find better bone specific treatments with minimal adverse effects for different estrogen-related bone disorders. This review summarizes the recent data regarding the intracellular signaling mechanisms, in vivo, mediated by the ERα activation functions (AFs), AF-1 and AF-2, and the effect on bone, growth plate and other estrogen responsive tissues. In addition, we review the recent cell-specific ERα-deleted mouse models lacking ERα specifically in neuronal cells or growth plate cartilage. The newly characterized signaling pathways of estrogen, described in this review, provide a better understanding of the ERα signaling pathways, which may facilitate the design of new, bone-specific treatment strategies with minimal adverse effects.

Role of estrogen receptor α and β in the induction of progesterone receptors in hypothalamic ventromedial neurons

The estrogen induction of progesterone receptors (PRs) in the ventrolateral division of the hypothalamic ventromedial nucleus (VMNvl) is critical for the regulation of female sexual behavior. VMNvl neurons express PRs and both types of estrogen receptors (ERα and ERβ), and their sequential activation initiates the molecular mechanisms underlying sexual behavior. To assess the relative importance of each ER subtype in the induction of PRs, we have estimated the total number of PR-immunoreactive neurons and quantified the total amount of PR protein in the VMNvl of adult ovariectomized rats that were injected with either estradiol benzoate (EB) or the specific agonists of the ERα, propyl-pyrazole triol (PPT), and of the ERβ, diaryl-propionitrile (DPN), in different doses and schedules. The administration of EB and of PPT alone, but not of DPN alone, increased the total number of PR-immunoreactive neurons and PR protein levels. When the specific agonists were administered sequentially, the total number of PR-immunoreactive neurons also increased, particularly when PPT was administered before DPN. Conversely, the concomitant administration of PPT and DPN did not increase the number of PR-immunoreactive neurons.The observation that PPT increases the number of PR-immunoreactive neurons and the levels of PR protein far less than EB shows that the estradiol induction of PRs in the VMNvl does not involve solely the activation of the ERα and suggests that it might also implicate the activation of membrane receptors. The present results also show that ERβ activation averts the action of ERα in the induction of PRs.

Role of Oestrogen Receptors on the Modulation of NADPH‐Diaphorase‐Positive Cell Number in Supraoptic and Paraventricular Nuclei of Ovariectomised Female Rats

Modulation of the nitric oxide producing system (demonstrated via the NADPH-diaphorase histochemical reaction) by oestradiol has been established in several structures of the rat brain. The present study aimed to explore the possible regulation of NADPH-diaphorase activity by oestradiol in neurones of the supraoptic (SON) and paraventricular (PVN) nuclei and the role of oestrogen receptors (ERα and ERβ) in this regulation. Adult ovariectomised rats were divided into six groups and injected either with vehicle or a single dose of oestradiol, a selective ERα agonist-PPT [4,4',4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol], a selective ERβ agonist-DPN [2,3-bis(4-hydroxyphenyl)-propionitrile], a selective ERα antagonist-MPP [1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1H-pyrazole dihydrochloride] or a selective ERβ antagonist-PHTPP (4-[2-phenyl-5,7-bis(trifluoromethyl)pyrazolo[1,5-a]pyrimidin-3-yl]phenol). The number of NADPH-diaphorase positive elements in the SON and the PVN was modulated by both ERs but, depending on the nucleus, ERα and ERβ ligands induced different effects. These results suggest that the regulation of nitrergic system by ERs may play a role in the control of oestrogen-dependent physiological mechanisms regulated by the SON and the PVN.

Role of estrogen receptor α and β in preserving hippocampal function during aging.

The expression of the ERα and ERβ estrogen receptors in the hippocampus may be important in the etiology of age-related cognitive decline. To examine the role of ERα and ERβ in regulating transcription and learning, ovariectomized wild-type (WT) and ERα and ERβ knockout (KO) mice were used. Hippocampal gene transcription in young ERαKO mice was similar to WT mice 6 h after a single estradiol treatment. In middle-age ERαKO mice, hormone deprivation was associated with a decrease in the expression of select genes associated with the blood-brain barrier; cyclic estradiol treatment increased transcription of these select genes and improved learning in these mice. In contrast to ERαKO mice, ERβKO mice exhibited a basal hippocampal gene profile similar to WT mice treated with estradiol and, in the absence of estradiol treatment, young and middle-age ERβKO mice exhibited preserved learning on the water maze. The preserved memory performance of middle-age ERβKO mice could be reversed by lentiviral delivery of ERβ to the hippocampus. These results suggest that one function of ERβ is to regulate ERα-mediated transcription in the hippocampus. This model is supported by our observations that knockout of ERβ under conditions of low estradiol allowed ERα-mediated transcription. As estradiol levels increased in the absence of ERα, we observed that other mechanisms, likely including ERβ, regulated transcription and maintained hippocampal-dependent memory. Thus, our results indicate that ERα and ERβ interact with hormone levels to regulate transcription involved in maintaining hippocampal function during aging.

Lack of estrogen receptors expression in malignant and pre-malignant colorectal lesions in Egyptian patients

Background: incidence of Colorectal cancer (CRC) is increasing globally. In Egypt, CRC ranks the sixth most common cancer in males and the fifth in females. Aim: To assess the expression of estrogen receptors (alpha and beta) in pre-malignant (adenomatous polyps and IBD), malignant colorectal lesions and normal colonic mucosa in group of Egyptian patients. Methods: This prospective study was done on 45 patients presenting with colonic symptoms, patients were divided into four groups; 15 CRC patients, 10 patients with adenomatous polyps, 10 IBD patients and 10 patients in the control group. Patients subjected to: Stool analysis, FOBT, CBC, CEA, Abdominal ultrasound & colonoscopy and biopsy (number = 80), Pathological, immunohistochemistry and RT- PCR quantification of ERα and ERβ were done. Results: Mean age: 39.2 (12 - 73), gender: M/F: 28/17. Bleeding per rectum was the commonest presentation; 29/45 (64.4%). CEA was significantly elevated in the CRC group compared with other studied groups (1692 mg/L vs. 4.0, 4.0 and 4.4 mg/L). Ultrasonography of the studied patients showed that metastatic CRC: 3/15 (20%); Colonic wall thickening: 5/15 (33.3%), 1/10 showed colonic polypoidal lesions in adenomatous polyps groups, in IBD group: 4/10 (40%) showed colonic and ileocecal thicknening. All the studied patients showed negative results for estrogen receptors (alpha and beta) by the use of immunohistochemistry staining and RT-PCR technique. Conclusion: Role of estrogen receptors in the colonic mucosa, precancerous and colorectal cancer is doubtful, contradictory results with some literature data could be due to racial and genetic difference in the studied population.

MNU-Induced Rat Mammary Carcinomas: Immunohistology and Estrogen Receptor Expression

Environmental exposure to nitrosamines is associated with the development of cancer in a variety of target organs. One such carcinogen, N-methyl-N-nitrosurea (MNU), has long been used to induce mammary tumors in rats, which provide a useful model to study mammary carcinogenesis. However, some poorly clarified issues remain, such as the lack of a clear description of morphological patterns of tumors and the distribution and role of estrogen receptors (ERs) during tumor progression, as tumors overexpressing ERs show a paradoxical tendency to recur after ovariectomy. Mammary carcinomas were induced in Sprague-Dawley rats using MNU. The tumors were studied histologically and distribution of smooth muscle actin and ERs was studied immunohistochemically. All tumors presented both an epithelial and a myoepithelial component, demonstrated by immunohistochemical detection of smooth muscle actin. Tumors showed distinct histological patterns: well-differentiated papillary and adenoid areas and poorly differentiated solid and spindle-cell foci. Overexpression of ERs (>75% of labelled cells vs. 0-75% in control tissue) occurred in papillary and adenoid areas but not in solid and spindle-cell foci. Poorly differentiated tumor foci are likely to represent a more advanced, estrogen-independent phase in cancer progression and constitute the basis for tumor recurrence after ovariectomy.