Sex-specific differences in the expression levels of estrogen receptor subtypes in colorectal cancer

Background: Altered expression of estrogen receptors alpha and beta (ERα and ERβ) has been hypothesized to play a role in carcinogenesis. However, little is known about the sex-specific differences of ER expression in colorectal cancer (CRC).Objective: This study examined ERα and ERβ protein levels in male and female patients with CRC.Methods: Using Western blot analysis, the intensity of ERα and ERβ protein levels was determined in tumor tissue and in corresponding normal colon mucosa from patients with CRC.Results: All 64 white patients (33 men, mean [SEM] age 64.1 [13.1] years, age range 26-90 years; 31 women, mean age 68.5 [14.5] years, age range 39-91 years [4 were premenopausal at time of surgery]) expressed ERα and ERβ protein in normal colon mucosa, and there were no significant differences between men and women. In tumor tissue, a significantly increased ERα protein level was observed in men (P = 0.02 vs normal tissue), whereas in women, the ERα level did not differ significantly between tumor and normal tissue. The level of ERβ protein in CRC was significantly reduced in both men and women, but more so in men (P = 0.04 vs women). Furthermore, in men, the ERβ level was significantly lower in poorly differentiated tumors than in moderately differentiated tumors (P < 0.03), whereas in women, poor differentiation of the tumor was not associated with a significant decrease of ERβ level.Conclusions: Altered levels of ER subtypes resulting in an increased ERα:ERβ ratio were found in patients with CRC. The observation of significantly greater alterations in men than in women supports the hypothesis of sex-specific differences in the pathogenesis of CRC.     

Expression of estrogen receptor β increases integrin α1 and integrin β1 levels and enhances adhesion of breast cancer cells

Estrogen effects on mammary gland development and differentiation are mediated by two receptors (ERα and ERβ). Estrogen‐bound ERα induces proliferation of mammary epithelial and cancer cells, while ERβ is important for maintenance of the differentiated epithelium and inhibits proliferation in different cell systems. In addition, the normal breast contains higher ERβ levels compared to the early stage breast cancers, suggesting that loss of ERβ could be important in cancer development. Analysis of ERβ?/? mice has consistently revealed reduced expression of cell adhesion proteins. As such, ERβ is a candidate modulator of epithelial homeostasis and metastasis. Consequently, the aim of this study was to analyze estrogenic effects on adhesion of breast cancer cells expressing ERα and ERβ. As ERβ is widely found in breast cancer but not in cell lines, we used ERα positive T47‐D and MCF‐7 human breast cancer cells to generate cells with inducible ERβ expression. Furthermore, the colon cancer cell lines SW480 and HT‐29 were also used. Integrin α1 mRNA and protein levels increased following ERβ expression. Integrin β1—the unique partner for integrin α1—increased only at the protein level. ERβ expression enhanced the formation of vinculin containing focal complexes and actin filaments, indicating a more adhesive potential. This was confirmed by adhesion assays where ERβ increased adhesion to different extracellular matrix proteins, mostly laminin. In addition, ERβ expression was associated to less cell migration. These results indicate that ERβ affects integrin expression and clustering and consequently modulates adhesion and migration of breast cancer cells. J. Cell. Physiol. 222:156–167, 2010. © 2009 Wiley‐Liss, Inc.     

Expression of estrogen receptor α and β in rat astrocytes in primary culture: effects of hypoxia and glucose deprivation

Estrogen replacement therapy could play a role in the reduction of injury associated with cerebral ischemia in vivo, which could be, at least partially, a consequence of estrogen influence of glutamate buffering by astrocytes during hypoxia/ischemia. Estrogen exerts biological effects through interaction with its two receptors: estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), which are both expressed in astrocytes. This study explored effects of hypoxia and glucose deprivation (HGD), alone or followed by 1 h recovery, on ERα and ERβ expression in primary rat astrocyte cultures following 1 h exposure to: a) 5 % CO(2) in air (control group-CG); b) 2 % O(2)/5 % CO(2) in N(2) with glucose deprivation (HGD group-HGDG); or c) the HGDG protocol followed by 1 h CG protocol (recovery group-RG). ERα mRNA expression decreased in HGDG. At the protein level, full-length ERα (67 kDa) and three ERα-immunoreactive protein bands (63, 60 and 52 kDa) were detected. A significant decrease in the 52 kDa band was seen in HGDG, while a significant decrease in expression of the full length ERα was seen in the RG. ERβ mRNA and protein expression (a 54 kDa single band) did not change. The observed decrease in ERα protein may limit estrogen-mediated signalling in astrocytes during hypoxia and recovery.     

Effects of postnatal estrogen manipulations on juvenile alloparental behavior

Sex- and species-specific patterns of estrogen receptor (ER)-α expression are established early in development, which may contribute to sexual differentiation of behavior and determine male social organization. The current study investigated the effects of ERα and ERβ activation during the second postnatal week on subsequent alloparental behavior and ERα expression in juvenile prairie voles. Male and female pups were treated daily with 17β-estradiol (E2, ERα/ERβ agonist), PPT (selective ERα agonist), DPN (selective ERβ agonist), or the oil vehicle on postnatal days (PD) 8–14. Alloparental behavior and ERα expression were examined at PD21. PPT treatment inhibited prosocial motivation in males and increased pup-directed aggression in both sexes. E2 and DPN had no apparent effect on behavior in either sex. PPT-treated males had increased ERα expression in the medial preoptic area (MPN), medial amygdala (MEApd) and bed nucleus of the stria terminalis (BSTpr). DPN treatment also increased ERα expression in males, but only in the BSTpr. Female ERα expression was unaffected by treatment. These results support the hypothesis that ERα activation in early life is associated with less prosocial patterns of central ERα expression and alloparental behavior in males. The lack of an effect of E2 on behavior suggests that ERβ may antagonize the effects of ERα on alloparental behavior. The results in DPN-treated males suggest that ERα in the MEApd, and not the BSTpr, may be a primary determinant of alloparental behavior in males.     

Opposite effects of two estrogen receptors on tau phosphorylation through disparate effects on the miR‐218/PTPA pathway

The two estrogen receptors (ERs), ERα and ERβ, mediate the diverse biological functions of estradiol. Opposite effects of ERα and ERβ have been found in estrogen‐induced cancer cell proliferation and differentiation as well as in memory‐related tasks. However, whether these opposite effects are implicated in the pathogenesis of Alzheimer's disease (AD) remains unclear. Here, we find that ERα and ERβ play contrasting roles in regulating tau phosphorylation, which is a pathological hallmark of AD. ERα increases the expression of miR‐218 to suppress the protein levels of its specific target, protein tyrosine phosphatase α (PTPα). The downregulation of PTPα results in the abnormal tyrosine hyperphosphorylation of glycogen synthase kinase‐3β (resulting in activation) and protein phosphatase 2A (resulting in inactivation), the major tau kinase and phosphatase. Suppressing the increased expression of miR‐218 inhibits the ERα‐induced tau hyperphosphorylation as well as the PTPα decline. In contrast, ERβ inhibits tau phosphorylation by limiting miR‐218 levels and restoring the miR‐218 levels antagonized the attenuation of tau phosphorylation by ERβ. These data reveal for the first time opposing roles for ERα and ERβ in AD pathogenesis and suggest potential therapeutic targets for AD.     

Sex-associated difference in estrogen receptor β expression in N-methyl-N'-nitro-N-nitrosoguanidine-induced gastric cancers in rats

Epidemiologic studies indicate that the incidence of gastric cancer is higher in males than in females. Although the mechanisms mediating this difference are unclear, a role for estrogens has been proposed. We used Western blotting to evaluate the role of estrogen receptor (ER) subtypes ERα and ERβ and proliferating cell nuclear antigen (PCNA) in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in Wistar rats; ERα and ERβ mRNA levels also were analyzed by quantitative real-time RT-PCR analysis. The incidence of gastric cancer was significantly higher in male than female rats. In both sexes, ERα expression was similar in MNNG-treated cancerous and noncancerous tissues and normal gastric tissue. However, ERβ expression in MNNG-treated cancerous and noncancerous tissues was significantly lower in male rats and higher in female rats than that in normal gastric tissue; MNNG-induced cancerous tissue showed the highest ERβ expression. PCNA expression in MNNG-treated cancerous tissues was higher than that in noncancerous tissues, and was higher in male rats than female rats. Western blotting results were consistent with the mRNA changes determined by quantitative real-time RT-PCR. The present study provides evidence of a sex-associated difference in ERβ and PCNA expression in MNNG-induced gastric cancers in Wistar rats.     

Expression of estrogen receptors in the pelvic floor of pre- and post-menopausal women presenting pelvic organ prolapse

The precise role of estrogen in the pathogenesis of pelvic organ prolapse (POP) is still unclear, while the results concerning the effect of selective estrogen receptor modulators on pelvic organ prolapse are contradictory. Our aim was to test whether alteration in the expression of estrogen receptors in the pelvic floor of pre- and post-menopausal women is related to genital prolapse status. The mRNA levels of ERα and ERβ in 60 biopsy specimens were measured. Significantly higher expression of ERα and higher ERα/ERβ ratio were demonstrated in post-menopausal women compared to pre-menopausal women. Higher expression of ERα and higher ERα/ERβ ratio were detected in all studied groups with POP, thus it did not reach significance in the post-menopausal group. Pre-menopausal and post-menopausal women presenting pelvic organ prolapse had no difference in the ERα expression. Our preliminary study may indicate that pelvic organ prolapse is associated with higher expression of ERα/ERβ in the pelvic floor of both pre- and post-menopausal women; thus not reaching statistical significance in the post-menopausal women was probably due to the group's size. We believe that the inevitable changes in the estrogen receptor expression over women's different lifetimes may affect the risk of genital prolapse progression, and might contribute to the further search for appropriate selective estrogen receptor modulators as a treatment for women with pelvic organ prolapse.     

Chemoprevention of BBN-Induced Bladder Carcinogenesis by the Selective Estrogen Receptor Modulator Tamoxifen

Bladder cancer is the fifth most frequent tumor in men and ninth in women in the United States. Due to a high likelihood of recurrence, effective chemoprevention is a significant unmet need. Estrogen receptors (ERs), primarily ERβ, are expressed in normal urothelium and urothelial carcinoma, and blocking ER function with selective ER modulators such as tamoxifen inhibits bladder cancer cell proliferation in vitro. Herein, the chemoprotective potential of tamoxifen was evaluated in female mice exposed to the bladder-specific carcinogen, N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN). Carcinogen treatment resulted in a 76% tumor incidence and increased mean bladder weights in comparison to controls. In contrast, mice receiving tamoxifen concurrent (8–20 weeks) or concurrent and subsequent (8–32 weeks) to BBN administration had no change in bladder weight and only 10% to 14% incidence of tumors. Non-muscle-invasive disease was present in animals treated with tamoxifen before (5–8 weeks) or after (20–32 weeks) BBN exposure, while incidence of muscle-invasive bladder carcinoma was reduced. ERβ was present in all mice and thus is a potential mediator of the tamoxifen chemoprotective effect. Surprisingly, ERα expression, which was detected in 74% of the mice exposed to BBN alone but not in any controlmice, was correlated with tumor incidence, indicating a possible role for this receptor in carcinogen-induced urothelial tumorigenesis. Thus, these data argue that both ERα and ERβ play a role in modulating carcinogen-induced bladder tumorigenesis. Administration of tamoxifen should be tested as a chemopreventive strategy for patients at high risk for bladder cancer recurrence.     

Genetic variation in ESR2 and estrogen receptor-beta expression in lung tumors

Objective: To investigate the association between inherited variation in the estrogen receptor beta (ERβ) gene (ESR2) and ERβ lung tumor expression, a phenotype that possibly affects survival differently in men and women. Methods: We genotyped 135 lung cancer patients for 22 ESR2 single nucleotide polymorphisms (SNPs) and measured nuclear and cytoplasmic ERβ expression by immunohistochemistry (IHC) in their primary lung tumor. Distributing Allred ERβ IHC scores according to ESR2 genotype classified under a dominant genetic model, we used rank sum tests to identify ESR2 SNPs significantly associated (p < 0.05) with ERβ expression. Results: 35%, 35%, and 29% of lung tumors showed no/low (Allred < 6), intermediate (Allred 6–7), and maximal (Allred 8) cytoplasmic ERβ expression, whereas 13%, 27%, and 60% showed no/low, intermediate, and maximal nuclear ERβ expression. For SNPs rs8021944, rs1256061 and rs10146204, ERβ expression was higher according to the rank sum test in lung tumors from patients with at least one minor allele. For each of these three SNPs, the odds of maximal (Allred 8) relative to no/low (Allred < 6) ERβ expression was 3-fold higher in tumors from patients with at least one minor allele than in tumors from patients homozygous for the common allele. Conclusion: Inherited variability in ESR2 may determine ERβ lung tumor expression.     

The hepatitis B virus-associated estrogen receptor alpha (ERalpha) was regulated by microRNA-130a in HepG2.2.15 human hepatocellular carcinoma cells

The estrogen receptors (ERs) play important roles in hepatocarcinogenesis, which is always fostered by persistent hepatitis B virus (HBV) infection. Recent studies have linked microRNAs (miRNAs) to viral pathogenesis or oncogenesis. ERα could lead to cell cycle progression or inhibition of apoptosis, while ERβ had opposite effects. Here we proposed that HBV affected ERs expression in viral oncogenesis, which might be triggered by miRNAs. The protein expression of ERα in HepG2.2.15 cells was much stronger than that in HepG2 cells, which was not consistent with its mRNA expression in these cells. MicroRNA-130a (miR-130a) was predicted to be a regulator of ERα by targeting its 3' untranslated region (3'-UTR). The enhanced green fluorescence protein (EGFP) reporter experiment confirmed the direct interaction of miR-130a and ERα. Moreover, ERα protein level was inversely correlated with the miR-130a level. Taken together, our studies supported that HBV infection might attenuate miR-130a expression and ERα was a direct target of miR-130a. Difference in miR-130a levels between HepG2 and HepG2.2.15 cells resulted in the difference in ERα expression, implying host-virus crosstalk in viral pathogenesis mediated by miRNAs.     

雌激素受体α和β免疫反应在雄性和雌性棕色田鼠脑区分布的比较

单配制和多配制动物社会行为有差异,这些差异可能与雌激素受体类型有关（ERs）。虽然多配制大鼠和小鼠中枢神经雌激素受体α（ERα）和β（ERβ）免疫反应在大脑的分布已有报道,单配制雄性草原田鼠中枢神经ERα的分布也有报道,但单配制田鼠ERα和（或）ERβ在雌性和雄性分布差异未见报道。本研究对雄性和雌性棕色田鼠前脑区域ERα和ERβ免疫反应（IR）细胞数量进行比较。研究结果表明：（1）免疫反应主要分布在细胞核中。 （2）ERα-IR和ERβ-IR细胞广泛分布于整个雌性和雄性前脑区域,在许多脑区表达有重叠。然而,不同受体在雌雄不同脑核中的分布数量是不同的。（3）ERα 和ERβ的分布存在性别差异。例如,雌性ERα在视前核中部（MPN）,终纹床和（BNST）和杏仁内侧核（MeA）比雄性多,相反雄性ERβ在MPN和BNST比雌性多。这些研究结果可能为我们理解如何通过ERα和ERβ调节动物的社会行为,及雌性和雄性社会行为的差异提供一个重要的神经解剖学基础。     

Estrogen receptor beta in breast cancer—Diagnostic and therapeutic implications

More than 10 years have passed since the discovery of the second estrogen receptor, estrogen receptor β (ERβ). It is now evident that ERα is not the only ER in breast cancer cells; in fact, ERβ is expressed in the majority of breast cancers although at lower levels than in the normal breast. In addition, ERβ is expressed in breast cancer infiltrating lymphocytes, fibroblasts and endothelial cells, all known to influence tumor growth. By overexpressing or knocking-out ERβ in breast cancer cell lines, several researchers have investigated its function with respect to proliferation and tumor growth. It appears that ERβ is anti-proliferative, in many ways antagonising the function of ERα. Furthermore, phytoestrogens have a binding-preference for ERβ and several epidemiological studies indicate a breast cancer preventing effect of this class of compounds. Tamoxifen is one of the standard, adjuvant treatments for ERα positive breast cancer, classically thought to mediate its effect through ERα. However, in several recent studies, ERβ has been described as a potential marker for tamoxifen response. In summary, experimental, epidemiological as well as diagnostic studies point towards ERβ as an important factor in breast cancer, opening up the possibility for novel ERβ-selective therapies in the treatment of breast cancer.     

Estrogen signaling,through estrogen receptor β, regulates DNA methylation and its machinery in male germ line in adult rats

Estrogen, through its receptors, regulates various aspects of spermatogenesis and male fertility. To understand the roles of estrogen receptors (ERα and ERβ) in male fertility, we have developed in vivo selective ER agonist administration models. Treatment of adult male rats with ERα or ERβ agonist for 60 d decreases fertility and litter size mainly due to increased pre- and post-implantation embryo loss. Since epigenetic mechanisms like DNA methylation play a crucial role in male fertility, we investigated the effects of the ER agonists on DNA methylation in spermatozoa. Treatment with ERβ agonist causes a significant decrease in DNA methylation both at the global level and at the H19 differentially methylated region (DMR). This could be due to decrease in DNA methyltransferases in the testis upon ERβ agonist treatment. The hypomethylation observed at the H19 DMR corroborates with aberrant expression of Igf2 and H19 imprinted genes in the resorbed embryos sired by ERβ agonist-treated males. Thus, our study demonstrates that ERβ regulates DNA methylation and methylating enzymes during adult rat spermatogenesis. Activation of estrogen signaling through ERβ could therefore cause DNA methylation defects leading to impaired male fertility. These results define a role for estrogen in epigenetic regulation of male germ line, suggesting that epigenetic insults by exposure to environmental estrogens could potentially affect male fertility.