Specific association of estrogen receptor beta with the cell cycle spindle assembly checkpoint protein, MAD2

Estrogens—Origin of Centrosome Defects in Human Cancer?

Estrogens are associated with a variety of diseases and play important roles in tumor development and progression. Centrosome defects are hallmarks of human cancers and contribute to ongoing chromosome missegragation and aneuploidy that manifest in genomic instability and tumor progression. Although several mechanisms underlie the etiology of centrosome aberrations in human cancer, upstream regulators are hardly known. Accumulating experimental and clinical evidence points to an important role of estrogens in deregulating centrosome homeostasis and promoting karyotype instability. Here, we will summarize existing literature of how natural and synthetic estrogens might contribute to structural and numerical centrosome defects, genomic instability and human carcinogenesis.

Synthesis and Discovery of Estra-1,3,5(10),6,8-pentaene-2,16α-diol

A metallacycle-centered approach to the assembly of partially aromatic synthetic steroids was investigated as a means to prepare a boutique collection of unique steroidal agents. The synthesis and discovery of estra-1,3,5(10),6,8-pentaene-2,16α-diol (VII) is described, along with structure-activity relationships related to its cytotoxic properties. Overall, VII was found to have a GI50 = 0.2 μg/mL (∼800 nM) in MDA-MB-231 human breast cancer cells, be an efficacious estrogen receptor agonist with potency for ERβ > ERα (ERβ EC50 = 21 nM), possess selective affinity to the cdc-2-like kinase CLK4 (Kd = 350 nM), and be phenotypically related to paclitaxel by an unbiased panel assessment.

In Vivo Study of the Effects of ERβ on Apoptosis and Proliferation of Hormone-Independent Prostate Cancer Cell Lines PC-3M

OBJECTIVE

To evaluate the in vivo therapeutic effects of attenuated Salmonella carrying PCDNA3.1-ERβ plasmid in hormone-independent prostatic cancer in nude mice and to clarify the mechanism by which estrogen receptor β (ERβ) induces apoptosis and proliferation in prostatic cancer cells in mice.

METHODS

The orthotopic prostatic cancer models of mice were randomly divided as follows: MOCK group, treated with PBS, PQ group, treated with attenuated Salmonella alone, PQ-PCDNA3.1 group, treated with attenuated Salmonella carrying PCDNA3.1 plasmid, and PQ-PCDNA3.1-ERβ group, treated with the attenuated Salmonella carrying PCDNA3.1-ERβ plasmid. Then, 10 μl of the plasmid-containing solution, comprising 1 × 107 cfu of the bacteria, was administered via intranasal delivery to each group except the MOCK group. The experimental methods included flow cytometry and terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling (TUNEL) assay, immunohistochemistry, and western blotting.

RESULTS

Compared with the MOCK, PQ, and PQ-PCDNA3.1 groups, the weights of tumors in the PQ-PCDNA3.1-ERβ group were significantly reduced. The results of flow cytometry and TUNEL assay revealed that the number of apoptotic cells in the PQ-PCDNA3.1-ERβ group significantly increased. Compared with PQ-PCDNA3.1 group, the protein expression levels of ERβ, Bad, p-caspase 9, p-caspase 3, and cleaved PARP in the PQ-PCDNA3.1-ERβ group were significantly increased, while the expression levels of Akt, p-Akt, and Bcl-xl were decreased (P < 0.05).

CONCLUSION

The attenuated Salmonella carrying PCDNA3.1-ERβ plasmid could inhibit the growth of orthotopic prostatic cancer in mice by increasing the expression of ERβ.

The association between MAD2 and prognosis in cancer: a systematic review and meta-analyses

This systematic review and meta-analyses investigates the expression of the cell checkpoint regulator, mitotic arrest deficiency protein 2 (MAD2) in cancerous tissue and examines whether an association exists between MAD2 levels and cancer survival and recurrence. Studies investigating MAD2 expression in cancer tissue utilising immunohistochemistry (IHC) were identified by systematic literature searches of Medline, Embase and Web of Science databases by October 2015. Random effects meta-analyses were performed to generate pooled hazard ratios (HRs) with 95% confidence intervals (CIs) of overall and progression-free survival according to MAD2 expression. Forty-three studies were included in the overall review. In 33 studies investigating MAD2 expression by IHC in cancer tissue, a wide range of expression positivity (11–100%) was reported. Higher MAD2 expression was not associated with an increased risk of all-cause mortality in a range of cancers (pooled HR 1.35, 95% CI 0.97–1.87; P = 0.077, n = 15). However, when ovarian cancer studies were removed, a significant pooled HR of 1.59 for risk of all-cause mortality in other cancer patients with higher expressing MAD2 tumours was evident (95% CI, 1.17–2.17; P = 0.003, n = 12). In contrast, higher MAD2 expression was associated with significant decreased risk of all-cause mortality in ovarian cancer patients (pooled HR = 0.50, 95% CI, 0.25–0.97; P = 0.04, n = 3). In conclusion, with the exception of ovarian cancer, increased MAD2 expression is associated with increased risk of all-cause mortality and recurrence in cancer. For ovarian cancer, reduced levels of MAD2 are associated with poorer outcome. Further studies are critical to assess the clinical utility of a MAD2 IHC biomarker.

Regulation of steroid hormone receptors and coregulators during the cell cycle highlights potential novel function in addition to roles as transcription factors

Cell cycle progression is tightly controlled by several kinase families including Cyclin-Dependent Kinases, Polo-Like Kinases, and Aurora Kinases. A large amount of data show that steroid hormone receptors and various components of the cell cycle, including cell cycle regulated kinases, interact, and this often results in altered transcriptional activity of the receptor. Furthermore, steroid hormones, through their receptors, can also regulate the transcriptional expression of genes that are required for cell cycle regulation. However, emerging data suggest that steroid hormone receptors may have roles in cell cycle progression independent of their transcriptional activity. The following is a review of how steroid receptors and their coregulators can regulate or be regulated by the cell cycle machinery, with a particular focus on roles independent of transcription in G2/M.

ERα regulates chromosome alignment and spindle dynamics during mitosis

Estrogen receptors are activated by the hormone estrogen and they control cell growth by altering gene expression as a transcription factor. So far two estrogen receptors have been found: ERα and ERβ. Estrogen receptors are also implicated in the development and progression of breast cancer. Here, we found that ERα localized on the spindle and spindle poles at the metaphase during mitosis. Depletion of ERα generated unaligned chromosomes in metaphase cells and lagging chromosomes in anaphase cells in a transcription-independent manner. Furthermore, the levels of β-tubulin and γ-tubulin were reduced in ERα-depleted cells. Consistent with this, polymerization of microtubules in ERα-depleted cells and turnover rate of α/β-tubulin were decreased than in control cells. We suggest that ERα regulates chromosome alignment and spindle dynamics by stabilizing microtubules during mitosis.

Estrogen induces Vav1 expression in human breast cancer cells

Vav1, a guanine nucleotide exchange factor (GEF) for Rho family GTPases, is a hematopoietic protein involved in a variety of cellular events. In recent years, aberrant expression of Vav1 has been reported in non-hematopoietic cancers including human breast cancer. It remains to be answered how Vav1 is expressed and what Vav1 does in its non-resident tissues. In this study, we aimed to explore the mechanism for Vav1 expression in breast cancer cells in correlation with estrogen-ER pathway. We not only verified the ectopic expression of Vav1 in human breast cancer cell lines, but also observed that Vav1 expression was induced by 17β-estradiol (E₂), a typical estrogen receptor (ER) ligand, in ER-positive cell lines. On the other hand, Tamoxifen, a selective estrogen receptor modulator (SERM), and ICI 182,780, an ER antagonist, suppressed the expression of Vav1. The estrogen receptor modulating Vav1 expression was identified to be α form, not β. Furthermore, treatment of E₂ increased the transcription of vav1 gene by enhancing the promoter activity, though there was no recognizable estrogen response element (ERE). Nevertheless, two regions at the vav1 gene promoter were defined to be responsible for E₂-induced activation of vav1 promoter. Chromatin immunoprecipitation (ChIP) and co-immunoprecipitation (Co-IP) analyses suggested that ERα might access to the vav1 promoter via interacting with transcription factors, c-Myb and ELF-1. Consequently, the enhanced expression of Vav1 led to the elevation of Cyclin D1 and the progression of cell cycle. The present study implies that estrogen-ER modulates the transcription and expression of Vav1, which may contribute to the proliferation of cancerous cells.

Estrogen receptors are involved in polychlorinated biphenyl-induced apoptosis on mouse spermatocyte GC-2 cell line

Polychlorinated biphenyls (PCBs) are widespread persistent environmental contaminants which have been shown to have reproductive toxicity and to disturb spermatogenesis. But the precise mechanism is not clear. A mouse pachytene spermatocyte-derived cell line, GC-2 cells were used in the present study to investigate the toxic effect of PCBs (Aroclor 1254) and explore the underlying molecular mechanism. Results showed that Aroclor 1254 inhibited cell proliferation, caused the arrest of cells in G0/G1 phase and induced apoptosis which might be partly explained by the decreased expression of Bcl-2 and cell cycle regulator cyclin D1 together with the activation of caspase-3. Besides, the treatment of Aroclor 1254 decreased the protein expression of estrogen receptor (ER)-α while increasing that of ERβ. Then the administration of selective ERα agonist PPT partly reversed Aroclor 1254-induced alteration in Bcl-2, caspase-3 and cyclin D1 protein expression while selective ERβ agonist DPN accelerated it. These results suggest that Aroclor 1254, working through ERα and ERβ, interferes with the expression of proteins involved in the balance between cellular apoptosis and proliferation.

Genetic polymorphisms associated with carotid artery intima-media thickness and coronary artery calcification in women of the Kronos Early Estrogen Prevention Study

Menopausal hormone treatment (MHT) may limit progression of cardiovascular disease (CVD) but poses a thrombosis risk. To test targeted candidate gene variation for association with subclinical CVD defined by carotid artery intima-media thickness (CIMT) and coronary artery calcification (CAC), 610 women participating in the Kronos Early Estrogen Prevention Study (KEEPS), a clinical trial of MHT to prevent progression of CVD, were genotyped for 13,229 single nucleotide polymorphisms (SNPs) within 764 genes from anticoagulant, procoagulant, fibrinolytic, or innate immunity pathways. According to linear regression, proportion of European ancestry correlated negatively, but age at enrollment and pulse pressure correlated positively with CIMT. Adjusting for these variables, two SNPs, one on chromosome 2 for MAP4K4 gene (rs2236935, β = 0.037, P value = 2.36 × 10(-06)) and one on chromosome 5 for IL5 gene (rs739318, β = 0.051, P value = 5.02 × 10(-05)), associated positively with CIMT; two SNPs on chromosome 17 for CCL5 (rs4796119, β = -0.043, P value = 3.59 × 10(-05); rs2291299, β = -0.032, P value = 5.59 × 10(-05)) correlated negatively with CIMT; only rs2236935 remained significant after correcting for multiple testing. Using logistic regression, when we adjusted for waist circumference, two SNPs (rs11465886, IRAK2, chromosome 3, OR = 3.91, P value = 1.10 × 10(-04); and rs17751769, SERPINA1, chromosome 14, OR = 1.96, P value = 2.42 × 10(-04)) associated positively with a CAC score of >0 Agatston unit; one SNP (rs630014, ABO, OR = 0.51, P value = 2.51 × 10(-04)) associated negatively; none remained significant after correcting for multiple testing. Whether these SNPs associate with CIMT and CAC in women randomized to MHT remains to be determined.

Investigation on association and expression of ESR2 as a candidate gene for boar sperm quality and fertility

ESR2 is involved in oestrogen-related apoptosis in cell cycle spermatogenesis but their effects have not yet confirmed in pig. Therefore, this study was aimed to investigate the association of ESR2 polymorphism with sperm quality and boar fertility traits and to analyse the ESR2 mRNA and protein expressions in boar reproductive tissues. DNA samples from 203 Pietrain (PI) and 100 Pietrain × Hampshire (PIHA) pigs with records of sperm quality [sperm concentration (SCON), motility (MOT), semen volume (VOL), plasma droplet rate (PDR) and abnormal spermatozoa rate (ASR)] and fertility [non-return rate (NRR) and number of piglet born alive (NBA)] traits were available. A SNP in coding region of ESR2 g.35547A>G in exon 5 was associated with MOT and PDR in the PI and with SCON, VOL, MOT and PDR in PIHA population. For mRNA and protein expression study, a total of six boars were divided into two groups with group I (G-I) and group II (G-II) where G-I characterized for relatively a better sperm quality according to the mean of two groups. mRNA expression was higher in brain and testis than that in all parts of epididymis. Both qRT-PCR and western blot analysis revealed that the ESR2 gene expression and protein expression were significantly higher in testis collected from G-II compared with that of G-I boars. Moreover, ESR2 protein localization in germ cell, Leydig and Sertoli cells, epithelial cells and spermatozoa was remarkable, which indicated the important role of ESR2 in spermatogenesis process. These results might shed new light on the roles of ESR2 in spermatogenesis as candidate for boar fertility, but still the lack of association across populations should be considered.

Breaking the cycle: An insight into the role of ERα in eukaryotic cell cycles

There have been numerous reviews written to date on estrogen receptor (ER), focusing on topics such as its role in the etiology of breast cancer, its mode of regulation, its role as a transcriptional activator and how to target it therapeutically, just to name a few. One reason for so much attention on this nuclear receptor is that it acts not only as a prognostic marker, but also as a target for therapy. However, a relatively undiscovered area in the literature regarding ER is how its activity in the presence and absence of ligand affects its role in proliferation and cell cycle transition. In this review, we provide a brief overview of ER signaling, ligand dependent and independent, genomic and non-genomic, and how these signaling events affect the role of ER in the mammalian cell cycle.

Estrogen receptor β: switching to a new partner and escaping from estrogen

Estrogen receptor (ER) β, the "second" ER, plays a gatekeeper role by inhibiting cell proliferation, promoting apoptosis, and impeding the progression of prostate cancer. Ironically, its presumed ligand, 17β-estradiol, promotes cancer development in experimental models. The mechanisms underlying the interplay between estrogens and ERβ in prostate cancer remain largely unclear. Research on a previously unknown tethering partner of ERβ, Krüppel-like zinc finger transcription factor 5 (KLF5), and its downstream gene target (FOXO1) helps to unlock this puzzle. 17β-Estradiol is not required to maintain the tumor-suppressive function of ERβ in the prostate, a tissue with limited estrogen availability; moreover, the presence of 17β-estradiol abrogates ERβ- and KLF5-mediated signaling and promotes cellular proliferation. Future research into ERβ will likely involve this estrogen independency and the preference for binding nonclassical DNA elements through tethering. The development of ERβ-based therapies may lead to improved drug efficacy.

Systems genetics analyses predict a transcription role for P2P-R: molecular confirmation that P2P-R is a transcriptional co-repressor

Background

The 250 kDa P2P-R protein (also known as PACT and Rbbp6) was cloned over a decade ago and was found to bind both the p53 and Rb1 tumor suppressor proteins. In addition, P2P-R has been associated with multiple biological functions, such as mitosis, mRNA processing, translation and ubiquitination. In the current studies, the online GeneNetwork system was employed to further probe P2P-R biological functions. Molecular studies were then performed to confirm the GeneNetwork evaluations.

Results

GeneNetwork and associated gene ontology links were used to investigate the coexpression of P2P-R with distinct functional sets of genes in an adipocyte genetic reference panel of HXB/BXH recombinant strains of rats and an eye genetic reference panel of BXD recombinant inbred strains of mice. The results establish that biological networks of 75 and 135 transcription-associated gene products that include P2P-R are co-expressed in a genetically-defined manner in rat adipocytes and in the mouse eye, respectively. Of this large set of transcription-associated genes, >10% are associated with hormone-mediated transcription. Since it has been previously reported that P2P-R can bind the SRC-1 transcription co-regulatory factor (steroid receptor co-activator 1, [Ncoa1]), the possible effects of P2P-R on estrogen-induced transcription were evaluated. Estrogen-induced transcription was repressed 50-70% by the transient transfection of P2P-R plasmid constructs into four different cell types. In addition, knockdown of P2P-R expression using an antisense oligonucleotide increased estrogen-mediated transcription. Co-immunoprecipitation assays confirmed that P2P-R interacts with SRC-1 and also demonstrated that P2P-R interacts with estrogen receptor α.

Conclusions

The findings presented in this study provide strong support for the value of systems genetics, especially GeneNetwork, in discovering new functions of genes that can be confirmed by molecular analysis. More specifically, these data provide evidence that the expression of P2P-R co-varies in a genetically-defined manner with large transcription networks and that P2P-R can function as a co-repressor of estrogen-dependent transcription.

The unliganded long isoform of estrogen receptor beta stimulates brain ryanodine receptor single channel activity alongside with cytosolic Ca2+

Ca(2+) release from intracellular stores mediated by endoplasmic reticulum membrane ryanodine receptors (RyR) plays a key role in activating and synchronizing downstream Ca(2+)-dependent mechanisms, in different cells varying from apoptosis to nuclear transcription and development of defensive responses. Recently discovered, atypical "nongenomic" effects mediated by estrogen receptors (ER) include rapid Ca(2+) release upon estrogen exposure in conditions implicitly suggesting involvement of RyRs. In the present study, we report various levels of colocalization between RyR type 2 (RyR2) and ER type beta (ER beta) in the neuronal cell line HT-22, indicating a possible functional interaction. Electrophysiological analyses revealed a significant increase in single-channel ionic currents generated by mouse brain RyRs after application of the soluble monomer of the long form ER beta (ER beta 1). The effect was due to a strong increase in open probability of RyR higher open channel sublevels at cytosolic [Ca(2+)] concentrations of 100 nM, suggesting a synergistic action of ER beta 1 and Ca(2+) in RyR activation, and a potential contribution to Ca(2+)-induced Ca(2+) release rather than to basal intracellular Ca(2+) concentration level at rest. This RyR/ER beta interaction has potential effects on cellular physiology, including roles of shorter ER beta isoforms and modulation of the RyR/ER beta complexes by exogenous estrogens.

Quantitative RT-PCR analysis of estrogen receptor gene expression in laser microdissected prostate cancer tissue

BACKGROUND

Real-time quantitative RT-PCR analysis of laser microdissected tissue is considered the most accurate technique for determining tissue gene expression. The discovery of estrogen receptor beta (ERbeta) has focussed renewed interest on the role of estrogen receptors in prostate cancer, yet few studies have utilized the technique to analyze estrogen receptor gene expression in prostate cancer.

METHODS

Fresh tissue was obtained from 11 radical prostatectomy specimens and from 6 patients with benign prostate hyperplasia. Pure populations of benign and malignant prostate epithelium were laser microdissected, followed by RNA isolation and electrophoresis. Quantitative RT-PCR was performed using primers for androgen receptor (AR), estrogen receptor beta (ERbeta), estrogen receptor alpha (ERalpha), progesterone receptor (PGR) and prostate specific antigen (PSA), with normalization to two housekeeping genes. Differences in gene expression were analyzed using the Mann-Whitney U-test. Correlation coefficients were analyzed using Spearman's test.

RESULTS

Significant positive correlations were seen when AR and AR-dependent PSA, and ERalpha and ERalpha-dependent PGR were compared, indicating a representative population of RNA transcripts. ERbeta gene expression was significantly over-expressed in the cancer group compared with benign controls (P < 0.01). In contrast, PGR expression was significantly down-regulated in the cancer group (P < 0.05). There were no significant differences in AR, ERalpha or PSA expression between the groups. This study represents the first to show an upregulation of ERbeta gene expression in laser microdissected prostate cancer specimens.

CONCLUSIONS

In concert with recent studies the findings suggest differential production of ERbeta splice variants, which may play important roles in the genesis of prostate cancer.

Estrogen receptor (ER) beta regulates ERalpha expression in stromal cells derived from ovarian endometriosis

CONTEXT

Estradiol and its nuclear receptors, estrogen receptor (ER) alpha and ERbeta, play critical roles in endometrium and endometriosis. Levels of ERbeta, due to pathological hypomethylation of its promoter, are significantly higher in endometriotic vs. endometrial tissue and stromal cells, whereas ERalpha levels are lower in endometriosis. Estradiol regulates ERalpha gene expression via its alternatively used promoters A, B, and C.

OBJECTIVE

The aim of the study was to determine whether high levels of ERbeta in endometriotic stromal cells from ovarian endometriomas regulate ERalpha gene expression.

RESULTS

ERbeta knockdown significantly increased ERalpha mRNA and protein levels in endometriotic stromal cells. Conversely, ERbeta overexpression in endometrial stromal cells decreased ERalpha mRNA and protein levels. ERbeta knockdown significantly decreased proliferation of endometriotic stromal cells. Chromatin immunoprecipitation assays demonstrated that estradiol enhanced ERbeta binding to nonclassical activator protein 1 and specificity protein 1 motifs in the ERalpha gene promoters A and C and a classic estrogen response element in promoter B in endometriotic stromal cells.

CONCLUSIONS

High levels of ERbeta suppress ERalpha expression and response to estradiol in endometrial and endometriotic stromal cells via binding to classic and nonclassic DNA motifs in alternatively used ERalpha promoters. ERbeta also regulates cell cycle progression and might contribute to proliferation of endometriotic stromal cells. We speculate that a significantly increased ratio of ERbeta:ERalpha in endometriotic tissues may also suppress progesterone receptor expression and contribute to progesterone resistance. Thus, ERbeta may serve as a significant therapeutic target for endometriosis.

DNA demethylation and histone deacetylation inhibition co-operate to re-express estrogen receptor beta and induce apoptosis in prostate cancer cell-lines

INTRODUCTION

Epigenetic silencing mechanisms are increasingly thought to play a major role in the development of human cancers, including prostate cancer. Promoter CpG island hypermethylation and histone hypoacetylation, catalyzed by DNA methyltransferase (DNMT) and histone deacetylase (HDAC), respectively, are associated with transcriptional repression in a number of cancers. Evidence is accumulating the two mechanisms are dynamically linked, yet few studies have examined a potential interaction in prostate cancer.

METHODS

LNCaP, DU-145, and PC-3 prostate cancer cells were co-treated with a DNMT inhibitor, 5'-aza-2'-deoxycytidine (5-AZAC), and an HDAC inhibitor, trichostatin A (TSA). Following treatment cells were processed for cell proliferation/apoptosis assays, or harvested for real-time RT-PCR. Assessed target genes were estrogen receptor beta (ERbeta), estrogen receptor alpha (ERalpha), androgen receptor (AR), progesterone receptor (PGR), and prostate specific antigen (PSA).

RESULTS

In all cell-lines, co-treatment was associated with reduced cell proliferation compared with control groups (P<0.05). A reciprocal rise in caspase activation was identified, indicating apoptosis was the major mechanism of cell death. Most marked effects were seen in the androgen-dependent, AR-positive LNCaP cell-line. In all cell-lines, an additive re-expression of ERbeta was identified in the co-treatment group, a finding not seen for either AR or PSA.

CONCLUSION

At concentrations associated with gene re-expression, the DNA demethylating agent 5-AZAC and the HDAC inhibitor TSA co-operate to induce apoptosis in prostate cancer cell-lines. Increased apoptosis in the co-treatment group was associated with marked re-expression of ERbeta, raising the possibility of further targeting of prostate cancer cells with ERbeta-selective agents.

Promoter methylation regulates estrogen receptor 2 in human endometrium and endometriosis

Steroid receptors in the stromal cells of endometrium and its disease counterpart tissue endometriosis play critical physiologic roles. We found that mRNA and protein levels of estrogen receptor 2 (ESR2) were strikingly higher, whereas levels of estrogen receptor 1 (ESR1), total progesterone receptor (PGR), and progesterone receptor B (PGR B) were significantly lower in endometriotic versus endometrial stromal cells. Because ESR2 displayed the most striking levels of differential expression between endometriotic and endometrial cells, and the mechanisms for this difference are unknown, we tested the hypothesis that alteration in DNA methylation is a mechanism responsible for severely increased ESR2 mRNA levels in endometriotic cells. We identified a CpG island occupying the promoter region (-197/+359) of the ESR2 gene. Bisulfite sequencing of this region showed significantly higher methylation in primary endometrial cells (n = 8 subjects) versus endometriotic cells (n = 8 subjects). The demethylating agent 5-aza-2'-deoxycytidine significantly increased ESR2 mRNA levels in endometrial cells. Mechanistically, we employed serial deletion mutants of the ESR2 promoter fused to the luciferase reporter gene and transiently transfected into both endometriotic and endometrial cells. We demonstrated that the critical region (-197/+372) that confers promoter activity also bears the CpG island, and the activity of the ESR2 promoter was strongly inactivated by in vitro methylation. Taken together, methylation of a CpG island at the ESR2 promoter region is a primary mechanism responsible for differential expression of ESR2 in endometriosis and endometrium. These findings may be applied to a number of areas ranging from diagnosis to the treatment of endometriosis.

Spindle proteins Aurora A and BUB1B, but not Mad2, are aberrantly expressed in dysplastic mucosa of patients with longstanding ulcerative colitis

BACKGROUND

Long term ulcerative colitis (UC) increases the risk of colorectal cancer (CRC). DNA aneuploidy is a common feature of both dysplastic and non-dysplastic colonic epithelia from patients with longstanding UC, and is regarded as an early sign of possible malignant transformation. The spindle proteins Aurora A, BUB1B and Mad2 have been implicated as contributors to aneuploidy and carcinogenesis.

AIMS

To investigate the role of these spindle proteins in relation to DNA aneuploidy and during the progressive morphological changes in ulcerative colitis associated colorectal cancer (UCCRC).

METHODS

Tissue microarrays were made from 31 colectomy specimens from patients with longstanding UC. Expression of Aurora A, BUB1B and Mad2 was investigated by immunohistochemistry and their relation to ploidy status, mucosal morphology and Ki67 levels was explored.

RESULTS

Expression of Aurora A and BUB1B was significantly associated with the progressive morphological changes of UCCRC. In the progression from non-dysplastic to dysplastic mucosa, Aurora A expression decreased while BUB1B expression increased. There was an increasing incidence of aneuploidy with progression towards cancer; expression of all spindle proteins was associated with the level of Ki67 but not with aneuploidy.

CONCLUSION

Due to the significant differences in Aurora A and BUB1B expression in dysplastic compared non-dysplastic mucosa, these proteins may serve as putative biological markers for the progressive morphological changes in UC associated carcinogenesis. The close relationship to Ki67 levels reflect that spindle proteins are expressed in tissues with a high proliferative rate; a role for these proteins in the development of aneuploidy was not found.

NM23-H2, an estrogen receptor β-associated protein, shows diminished expression with progression of atherosclerosis

While estrogen receptor (ER) profile plays an important role in response to estrogens, receptor coregulators act as critical determinants of signaling. Although the clinical effects of ovarian hormones on various normal and pathological processes are an active area of research, the exact signaling effects on, for example, the vessel wall, are incompletely understood. Hence, we sought to discover proteins that associate with ERβ, the isoform that shows upregulated mRNA expression after arterial injury. Using a yeast two-hybrid screen we identified NM23-H2, a multifaceted metastasis suppressor candidate protein, as an ERβ-associated protein. Although NM23-H2 was immunodetected in arteries from young subjects (27 ± 6 yr, 14 men and 6 women) with benign intimal hyperplasia, expression was diminished in fatty streaks/atheromas and altogether absent in advanced atherosclerotic lesions. Both nm23-H2 mRNA and protein were expressed by vascular cells in vitro. Treatment with 17β-estradiol and an ERβ-selective agonist, diarylpropionitrile, increased protein expression of NM23-H2; an effect that was not seen with an ERα-selective agonist, propylpyrazole-triol. Estrogen also prompted nuclear localization of NM23-H2 protein in human coronary smooth muscle cells (SMCs). An in vitro mimic of inflammation decreased the expression of NM23-H2 in SMCs, which was restored on addition of estrogen and dependent on the estrogen receptor. In summary, we report the novel association of NM23-H2 with ERβ and show for the first time its expression in vascular cells and demonstrate regulation of its expression and localization by estrogen. In that the abundance of NM23-H2 diminishes with both the advancement of atherosclerosis and inflammation, this ERβ-associated protein may play an important role in mediating the vasculoprotective effects of estrogens.

Estrogens and Antiestrogens as Etiological Factors and Therapeutics for Prostate Cancer

Mounting evidence supports a key role played by estrogen or estrogen in synergy with an androgen, in the pathogenesis of prostate cancer (PCa). New experimental data suggest that this process could begin as early as prenatal life. During adulthood, estrogen carcinogenicity is believed to be mediated by the combined effects of hormone-induced, unscheduled cell proliferation and bioactivation of estrogens to genotoxic carcinogens. Increased bioavailability of estrogen through age-dependent increases in conversion from androgen could also be a contributing factor. Individual variations and race-/ethnic-based differences in circulating or locally formed estrogens or in tissue estrogen responsiveness may explain differential PCa risk among individuals or different populations. Estrogen receptor (ER)-alpha and ER-beta are the main mediators of estrogen action in the prostate. However, ER-beta is the first ER subtype expressed in the fetal prostate. During cancer development, ER-beta expression is first lost as tumors progress into high grade in the primary site. Yet, its reexpression occurs in all metastatic cases of PCa. A change in cytosine methylation in a regulatory CpG island located in the proximal promoter of ER-beta may constitute an "on/off" switch for reversible regulation of ER-beta expression. A variety of estrogenic/antiestrogenic/selective estrogen receptor modulator (SERM)-like compounds have been shown to use non-ERE pathways, such as tethering of ER-beta to NF-kappaB binding proteins, Sp2, or Ap1 for gene transactivation. These findings open new avenues for drug design that now focuses on developing a new generation of estrogen-based PCa therapies with maximal proapoptotic action but few or no side effects.

Mad2 is required for optimal hematopoiesis: Mad2 associates with c-Kit in MO7e cells

Mitotic arrest deficiency 2 (Mad2) is a component of mitotic spindle checkpoint proteins and is essential for accurate chromosome segregation. We investigated a role for Mad2 in hematopoiesis using Mad2-haploinsufficient (Mad2+/-) mice. Mad2+/- bone marrow (BM) and spleen manifested decreased absolute numbers and cycling status of immature, but not mature, hematopoietic progenitor cells. Mad2+/- BM granulocyte-macrophage colony-forming units (CFU-GMs) did not manifest synergistic proliferation in response to stem cell factor (SCF) plus GM-CSF. The percentage of annexin V+ cells was higher in Mad2+/- than Mad2+/+c-Kit+lin- BM after culture with SCF and GM-CSF. However, no significant difference in phosphorylation of extracellular signal-related kinase (Erk1/2) at Thr202/Tyr204 and Akt at Ser473 between Mad2+/- and Mad2+/+BM c-Kit+lin- cells was observed. Immunoprecipitation assays performed in human MO7e cells demonstrated physical association of c-Kit with Mad2. Moreover, stimulation with SCF plus GM-CSF led to dissociation of Mad2 from c-Kit. Confocal microscopy demonstrated that Mad2 colocalized with c-Kit in the cytoplasm of MO7e cells. These results suggest that Mad2 is involved in synergistic growth of immature hematopoietic progenitor cells in response to SCF plus GM-CSF, effects that may be mediated via physical association of Mad2 with c-Kit.

Estrogen therapy and thrombotic risk

Post-menopausal hormone therapy increases the risk for venous thrombosis, and possibly myocardial infarction (MI) and ischemic stroke. However, most women using hormone therapy do not suffer thrombosis, and to date our ability to identify women at risk is limited. Thrombosis, arterial or venous, has 2 requisites: a vascular anomaly and a response of the hemostasis system to the anomaly. Consequently, experimental approaches to understand the pathophysiology of thrombosis require definition of vascular anatomy and function as well as characteristics of the blood within the context of genetic background, lifestyle choices and environmental exposures, which influence gene expression. Defining interactions among factors that affect individual propensity to thrombosis will allow physicians to better identify at-risk individuals, for example a woman contemplating estrogen therapy for symptoms of menopause, and prevent adverse thrombotic events.

Sex steroids have differential effects on growth and gene expression in primary human prostatic epithelial cell cultures derived from the peripheral versus transition zones

The majority of human prostate cancers arise from the peripheral zone (PZ). Prostate epithelial stem cells have been localized to the basal epithelial cell compartment. In addition, basal cells have been shown to maintain luminal epithelial cell differentiation and may mediate signals between the stromal and luminal cell compartments. Therefore, the study of adult prostate basal cells derived from different prostate zones may give insights into the mechanisms underlying normal and abnormal prostate growth. We herein compare the basal and sex steroid-stimulated expression and activity of several genes/proteins that are known to be critical in prostate cancer development in primary cultures of basal cells derived from the transition zone (TZ) and PZ of prostatectomy specimens. Our results demonstrate that prostate basal cells derived from the PZ versus TZ are more viable in culture, particularly in response to sex steroid addition. PZ cells exhibit higher telomerase activity and increased expression levels of androgen receptor, the anti-apoptotic protein bcl-2, and the dominant-negative splice variant of Kruppel-like Factor 6. PZ cells have lower basal expression levels of estrogen receptor-beta, the pro-apoptotic protein Bax, and cell-cycle inhibitor proteins (p53, p21(waf1/Cip1)). Finally, we demonstrate divergent responses to sex hormones in the two basal cell populations. The gene expression pattern in the PZ cells may partially explain the predominance of prostate cancer development in this region.

Preliminary array analysis reveals novel genes regulated by ovarian steroids in the monkey raphe region

We hypothesize that ovarian hormones may improve serotonin neuron survival. We sought the effect of estradiol (E) and progesterone (P) on novel gene expression in the macaque dorsal raphe region with Affymetrix array analysis. Nine spayed rhesus macaques were treated with either placebo, E or E+P via Silastic implant for 1 month prior to euthanasia (n=3 per treatment). RNA was extracted from a small block of midbrain containing the dorsal raphe and examined on an Agilent Bioanalyzer. The RNA from each monkey was labeled and hybridized to an Affymetrix HG_U95AV Human GeneChip Array. After filtering and sorting, 25 named genes remained that were regulated by E, and 24 named genes remained that were regulated by supplemental P. These genes further sorted into functional categories that would promote neuronal plasticity, transmitter synthesis, and trafficking, as well as reduce apoptosis. The relative abundance of four pivotal genes was examined in all nine animals with quantitative RT-PCR and normalized by glyceraldehyde 3-phosphate dehydrogenase (GAPDH). E+/-P caused a significant threefold reduction in JNK-1 (a pro-apoptosis gene, p<0.007); and a significant sixfold decrease in kynurenine mono-oxygenase (produces neurotoxic quinolones, p<0.05). GABA-A receptor (alpha3 subunit; benzodiazepine site) and E2F1 (interferes with cytokine signaling) were unaffected by E, but increased sevenfold (p<0.02) and fourfold (p<0.009), respectively, upon treatment with P. In summary, subsets of genes related to tissue remodeling or apoptosis were up- or down-regulated by E and P in a tissue block containing the dorsal raphe. These changes could promote cellular resilience in the region where serotonin neurons originate.

Mad2 and p27 expression profiles in colorectal cancer and its clinical significance

AIM: To investigate the expression of tumor suppressor gene p27 and spindle checkpoint gene Mad2 and to demonstrate their expression difference in colorectal cancer and normal mucosa and to evaluate its clinical significance.

METHODS: Immunohistochemical staining was used for detection of expression of Mad2 and p27 in colorectal cancer and its corresponding normal mucosa.

RESULTS: Mad2 was significantly overexpressed in colorectal cancer compared with corresponding normal mucosa (P < 0.01, χ² = 7.5), and it was related to the differentiation of adenocarcinoma, lymph node metastasis and survival period after excision (P < 0.05, χ² = 7.72, χ² = 4.302, χ² = 6.234). The rate of p27 positive expression in adenocarcinomas and normal mucosa was 40% and 80% respectively. There was a significant difference in p27 expression between adenocarcinomas and normal mucosa (P < 0.001, χ² = 13.333), which was related to the differentiation degree of adenoca rcinoma and lymph node metastasis (P < 0.05, χ² = 8.901, χ² = 4). The positive expression of p27 was not correlated with survival period after excision.

CONCLUSION: Defect of spindle checkpoint gene Mad2 and mutation of p27 gene are involved mainly in colorectal carcinogenesis and associated with prognosis of colorectal cancer.

Estrogen Receptor β Expression and Apoptosis of Spermatocytes of Mice Overexpressing a Rat Androgen-Binding Protein Transgene1

Progression of the first meiotic division in male germ cells is regulated by a variety of factors, including androgens and possibly estrogens. When this regulation fails, meiosis is arrested and primary spermatocytes degenerate by apoptosis. Earlier studies showed that overexpression of rat androgen-binding protein (ABP) in the testis of transgenic mice results in a partial meiotic arrest and apoptosis of pachytene spermatocytes. In view of the recent localization of estrogen receptor beta (ERbeta) in primary spermatocytes and data suggesting the ability of ERbeta to repress cellular proliferation, we tested the hypothesis that variations in the testicular steroid microenvironment caused by excess ABP produce changes in ERbeta expression in this cellular type that could be associated to the meiotic arrest and, eventually, to the induction of germ cell apoptosis observed in the ABP transgenic mice. Increased levels of ERbeta mRNA and protein were demonstrated in the testis of rat ABP transgenic mice compared with nontransgenic littermates by reverse transcriptase-polymerase chain reaction (RT-PCR) experiments, Northern blotting, and Western Blotting. The major differences were found when isolated germ cells of transgenic and nontransgenic littermates were analyzed by RT-PCR. In keeping with this finding, ERbeta was strongly immunolabeled in pachytene spermatocytes of rat ABP transgenic mice and localized in tubular stages in which TUNEL labeling was maximal. Confocal microscopy analysis of a fluorescent TUNEL assay and ERbeta immunohistochemistry revealed that degenerating pachytene spermatocytes overexpressed ERbeta. The present results are consistent with the interpretation that ERbeta is associated with the events that regulate negatively the progression of meiosis or that lead to spermatocyte apoptosis.

Hormone-induced chromosomal instability in p53-null mammary epithelium

The absence of p53 function increases risk for spontaneous tumorigenesis in the mammary gland. Hormonal stimulation enhances tumor risk in p53-null mammary epithelial cells as well as the incidence of aneuploidy. Aneuploidy appears in normal p53-null mammary epithelial cells within 5 weeks of hormone stimulation. Experiments reported herein assessed a possible mechanism of hormone-induced aneuploidy. Hormones increased DNA synthesis equally between wild-type (WT) and p53-null mammary epithelial cells. There were two distinct responses in p53-null cells to hormone exposure. First, Western blot analysis demonstrated that the levels of two proteins involved in regulating sister chromatid separation and the spindle checkpoint, Mad2 and separase (ESPL1) were increased in null compared with WT cells. In contrast, the levels of securin and Rad21 proteins were not increased in hormone-stimulated p53-null compared with WT cells. ESPL1 RNA was also increased in p53-null mouse mammary cells in vivo by 18 h of hormone stimulation and in human breast MCF7 cells in monolayer culture by 8 h of hormone stimulation. Furthermore, both promoters contained p53 and steroid hormone response elements. Mad2 protein was increased as a consequence of the absence of p53 function. The increase in Mad2 protein was observed also at the cellular level by immunohistochemistry. Second, hormones increased gene amplication in the distal arm of chromosome 2, as shown by comparative genomic hybridization. These results support the hypothesis that hormone stimulation acts to increase aneuploidy by several mechanisms. First, by increasing mitogenesis in the absence of the p53 checkpoint in G2, hormones allow the accumulation of cells that have experienced chromosome missegregation. Second, the absolute rate of chromosome missegregation may be increased by alterations in the levels of two proteins, separase and Mad2, which are important for maintaining chromosomal segregation and the normal spindle checkpoint during mitosis.

Estrogens and anti-estrogens: Key mediators of prostate carcinogenesis and new therapeutic candidates

Despite the historical use of estrogens in the treatment of prostate cancer (PCa) little is known about their direct biological effects on the prostate, their role in carcinogenesis, and what mechanisms mediate their therapeutic effects on PCa. It is now known that estrogens alone, or in synergism with an androgen, are potent inducers of aberrant growth and neoplastic transformation in the prostate. The mechanisms of estrogen carcinogenicity could be mediated via induction of unscheduled cell proliferation or through metabolic activation of estrogens to genotoxic metabolites. Age-related changes and race-/ethnic-based differences in circulating or locally formed estrogens may explain differential PCa risk among different populations. Loss of expression of estrogen receptor (ER)-beta expression during prostate carcinogenesis and prevention of estrogen-mediated oxidative damage could be exploited in future PCa prevention strategies. Re-expression of ER-beta in metastatic PCa cells raises the possibility of using ER-beta-specific ligands in triggering cell death in these malignant cells. A variety of new estrogenic/anti-estrogenic/selective estrogen receptor modulator (SERM)-like compounds, including 2-methoxyestradiol, genistein, resveratrol, licochalcone, Raloxifene, ICI 182,780, and estramustine are being evaluated for their potential in the next generation of PCa therapies. Increasing numbers of patients self-medicate with herbal formulations such as PC-SPES. Some of these compounds are selective ER-beta ligands, while most of them have minimal interaction with ER-alpha. Although many may inhibit testosterone production by blockade of the hypothalamal-pituitary-testis axis, the most effective agents also exhibit direct cytostatic, cytotoxic, or apoptotic action on PCa cells. Some of them are potent in interfering with tubulin polymerization, blocking angiogenesis and cell motility, suppressing DNA synthesis, and inhibiting specific kinase activities. Further discovery of other compounds with potent apoptotic activities but minimal estrogen action should promote development of a new generation of effective PCa preventive or treatment regimens with few or no side-effects due to estrogenicity. Further advancement of our knowledge of the role of estrogens in prostate carcinogenesis through metabolic activation of estrogens and/or ER-mediated pathways will certainly result in better preventive or therapeutic modalities for PCa.

Steroid receptor and aromatase expression in baboon endometriotic lesions

OBJECTIVE

To evaluate steroid receptor and aromatase gene expression in endometriotic lesions, and determine the effects of endometriosis on uterine receptivity in a baboon model for endometriosis.

DESIGN

Prospective study to determine the expression of steroid receptors, and aromatase in ectopic endometriotic lesions and endometrial genes in the eutopic endometrium of baboons with induced endometriosis by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunocytochemistry.

SETTING

University research laboratory and primate research facility.

ANIMAL(S)

Normally cycling baboons inoculated intraperitoneally with menstrual endometrium to induce endometriosis.

INTERVENTION(S)

Endometriotic lesions were resected during laparotomy, and endometrium was obtained by endometrectomy or after hysterectomy.

MAIN OUTCOME MEASURE(S)

Steroid receptor and aromatase expression by RT-PCR and immunocytochemistry in endometriotic lesions and glycodelin and alpha-smooth muscle actin expression and localization in endometrium after chorionic gonadotropin (CG) stimulation.

RESULT(S)

This study demonstrated that estrogen receptor-alpha (ERalpha) and progesterone receptor (PR) were expressed in both ectopic and eutopic endometrium between 1 and 10 months after inoculation. In contrast, ERbeta was only expressed in the ectopic endometriotic lesions. Aromatase expression was only evident in lesions obtained 10 months after inoculation. Infusion of CG during the luteal phase failed to induce the expression of glycodelin in the glandular epithelium or alpha-smooth muscle actin (alpha-SMA) in stromal cells in animals with endometriosis as early as 1 and 4 months after inoculation.

CONCLUSION(S)

The ERbeta expression is selectively up-regulated in the endometriotic lesions at all stages of the disease, whereas aromatase expression is not evident until the disease progresses. However, expression of uterine receptivity markers was down-regulated as early as 1 and 4 months after inoculation.

Mad2 and p53 expression profiles in colorectal cancer and its clinical significance

AIM: To investigate the expression of tumor suppressor gene p53 and spindle checkpoint gene Mad2, and to demonstrate their expression difference in colorectal cancer and normal mucosa and to evaluate its clinical significance.

METHODS: Western blot and immunohistochemistry methods were used to analyze the expression of Mad2 in colorectal cancer and its corresponding normal mucosa. The expression of p53 was detected by immunohistochemistry method in colorectal cancer and its corresponding normal mucosa.

RESULTS: Mad2 was significantly overexpressed in colorectal cancer compared with corresponding normal mucosa (P < 0.001), and it was not related to the differentiation of adenocarcinoma and other clinical factors (P > 0.05).The ratio of Mad2 protein in cancer tissue (C) to that in its normal mucosa tissue (N) was higher than 2, which was more frequently observed in patients with lymph gland metastasis (P < 0.05). p53 protein expression was not observed in normal mucosa. The rate of p53 positive expression in adenocarcinomas was 52.6%. There was a significant difference between adenocarcinomas and normal mucosa(P < 0.001), which was not related to the differentiation degree of adenocarcinoma and other clinical factors (P > 0.05).

CONCLUSION: Defect of spindle checkpoint gene Mad2 and mutation of p53 gene are involved mainly in colorectal carcinogenesis and C/N > 2 is associated with prognosis of colorectal cancer.

Evaluation of seven oestrogen receptor beta antibodies for immunohistochemistry, western blotting, and flow cytometry in human breast tissue

Two oestrogen receptors, ER alpha and ER beta, exist. While much is known about ER alpha, the role of ER beta is still undefined, especially at the protein level. The aim of this study was to determine the utility of seven ER beta antibodies (14C8, 8D5, PAI313, PPG5/10, N19, 9.88, and D7N) raised against different domains of ER beta in three commonly used laboratory applications, namely immunohistochemistry, western blot, and flow cytometry, using human breast material. For immunohistochemical analysis of frozen material, PAI313 and D7N gave stronger and more specific signals than 14C8, 8D5, and PPG5/10. In paraffin sections, 14C8, closely followed by PPG5/10, gave by far the most superior nuclear immunoreactivity, compared with the other antibodies tested. In general, flow cytometry results mirrored the immunohistochemistry data for paraffin sections, with antibodies ranked 14C8 > 8D5> or = PAI-313 > PPG5/10 >D7N. For western blotting, 8D5 and D7N yielded the strongest and most consistent bands, with weaker bands seen with the others. It is concluded that ER beta protein can be detected using specific antibodies. However, there is considerable variation between the specificity and application of these antibodies, highlighting the fact that careful optimization is required when selecting an antibody for use in a particular laboratory technique.

Molecular cloning of porcine estrogen receptor-beta complementary DNAs and developmental expression in periimplantation embryos

In the pig, estrogens transiently produced by embryos and progestins of maternal origin target the uterine endometrium, causing alterations in gene expression and secretory activity, both of which are important for the initiation of embryo attachment. The potential direct embryotrophic roles of estrogens and progestins are, however, unknown. Here we report the cloning of porcine embryonic estrogen receptor-beta (ER-beta) mRNA by reverse transcription-polymerase chain reaction (RT-PCR) using specific primer sets designed initially within conserved regions of human and bovine ER-beta mRNAs, and subsequently within regions of identified porcine ER-beta cDNA sequences. The ER-beta mRNA has an open reading frame of 1578 nucleotides and encodes a 526 amino acid polypeptide that displays greater than 90% identity with other mammalian ER-beta proteins. Northern and Western blot analyses using porcine filamentous embryos from Day 12 of pregnancy demonstrated the presence of multiple ER-beta mRNA transcripts of approximately 9.5, 4.9, and 3.5 kilobases, and a similar 64-kDa protein corresponding in size to human ovarian granulosa cell ER-beta, respectively. In Day 12 filamentous embryos, ER-beta expression was immunolocalized to trophoblastic cell nuclei, coincident with that of proliferative cell nuclear antigen (PCNA). The developmental ontogeny of ER-beta mRNA was evaluated in embryos of different morphologies (spherical, tubular, and filamentous) by semiquantitative RT-PCR, along with those for other steroid hormone receptors (ER-alpha and progesterone receptor) and known embryonic genes associated with cell differentiation (cytochrome P450 aromatase type III) and growth (cyclin D1). ER-beta mRNA levels varied with embryo morphology (filamentous maximum at Day 12), coincident with that of cyclin D1. Progesterone receptor mRNA levels were maximal in tubular embryos, similar to that of P450 aromatase, whereas the expression of the ER-alpha gene was barely detectable and appeared constitutive for all developmental stages examined. Estradiol-17 beta treatment of Day 12 filamentous embryos in culture up-regulated ER-beta and P450 aromatase (type III) mRNA levels, respectively, but decreased those of PCNA, and had no effect on cyclin D1 mRNA levels. These studies taken together suggest that embryonic ER-beta likely mediates the autocrine functions of estrogens in the dynamic regulation of embryonic growth and development at periimplantation.

Role of estrogen receptors in the vascular system

Estrogens have been shown to exert significant benefits on the cardiovascular system both in animals and in postmenopausal women. However, the exact mechanism of these effects are, for the most part, still unknown. The goal of this paper is to evaluate the role of estrogen receptors (ER) in mediating some of the cardiovascular beneficial actions of 17 beta-estradiol (E2). This analysis was possible because of the availability of ER alpha (ER alpha KO) and ER beta-deficient (ER beta KO) mice, and access to a patient with ER alpha-deficiency. Experimental results obtained in our laboratory demonstrated that the ER alpha subtype mediates E2-induced increase in endothelial nitric oxide production and facilitation of fibroblast growth factor-elicited angiogenesis in vivo. Others have confirmed these findings. Experiments using a novel ER-antagonist and ApoExER alpha double-knockout mice proved that ER alpha mediates some of the antiatherosclerotic effects of E2 as well. In contrast, both the ER alpha and ER beta subtypes appear to mediate the beneficial effects of E2 on vascular smooth muscle proliferation after vessel injury. The young male patient with ER alpha-deficiency exhibited reduced endothelial nitric oxide production and premature coronary arteriosclerosis. These studies in mice and a male human subject suggest that absence of functional ER may represent a novel risk factor for cardiovascular diseases.

Cell cycle-dependent interaction of Mad2 with conserved Box1/2 region of human granulocyte-macrophage colony-stimulating factor receptor common betac

Box1 and 2 (box1/2) are conserved cytoplasmic motifs located in the membrane proximal region of cytokine receptors, including the human granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor common betac. Deletion of box1/2 abrogated all the examined activities of GM-CSF, and this phenomenon is explained by the loss of binding by Jak2. To test if a molecule other than Jak2 interacting with the box1/2 region plays a role in GM-CSF receptor signal transduction, we screened for molecules interacting with the box1/2 region by a pull-down assay using recombinant purified protein of GST fused with the betac box1/2 region and a Ba/F3 cell lysate. The mouse homologue of Mad2 protein, which plays an important role in the M phase of the cell cycle, was revealed to associate with the box1/2 region specifically. Peptides corresponding to the box1 sequence also bound to Mad2, and mutation of the box1 decreased the Mad2 interaction. Deletion analysis indicated that interaction with box1/2 occurred through the C-terminal portion of Mad2. Mad2 is known to change affinity for binding partners cell cycle dependently. Binding affinity of Mad2 to box1/2 increased in the late M phase, suggesting the possibility that GM-CSF participates in regulation of the M phase check point through interaction with Mad2.

Estrogen receptors: orchestrators of pleiotropic cellular responses

Estrogen receptors (ERs) orchestrate both transcriptional and non-genomic functions in response to estrogens, xenoestrogens and signals emanating from growth factor signalling pathways. The pleiotropic and tissue-specific effects of estrogens are likely to be mediated by the differential expression of distinct estrogen receptor subtypes (ERalpha and ERbeta) and their coregulators. The recent analysis of transcription complexes associated with estrogen-responsive promoters has revealed unexpected levels of complexity in the dynamics of ER-mediated transcription. Furthermore, a small fraction of ERs also appears to directly interact with components of the cytosolic signalling machinery. Analysis of the interrelationship between these distinct modes of ER action is likely to reveal novel aspects of estrogen signalling that will impact on nuclear receptor biology and human health.

Effects of estrogen on the vascular injury response in estrogen receptor alpha, beta (double) knockout mice

The two known estrogen receptors, ERalpha and ERbeta, mediate the effects of estrogen in all target tissues, including blood vessels. We have shown previously that estrogen inhibits vascular injury response to the same extent in female wild-type (WT), ERalpha knockout (ERalphaKO(CH)), and ERbeta knockout (ERbetaKO(CH)) mice. We generated mice harboring disruptions of both ERalpha and ERbeta genes (ERalpha,betaKO(CH)) by breeding and studied the effect of 17beta-estradiol (E2) on vascular injury responses in ovariectomized female ERalpha,betaKO(CH) mice and WT littermates. E2 inhibited increases in vascular medial area following injury in the WT mice but not in the ERalpha,betaKO(CH) mice, demonstrating for the first time that the two known estrogen receptors are necessary and sufficient to mediate estrogen inhibition of a component of the vascular injury response. Surprisingly, as in WT littermates, E2 still significantly increased uterine weight and inhibited vascular smooth muscle cell (VSMC) proliferation following injury in the ERalpha,betaKO(CH) mice. These data support that the role of estrogen receptors differs for specific components of the vascular injury response in the ERalpha,betaKO(CH) mice. The results leave unresolved whether E2 inhibition of VSMC proliferation in ERalpha,betaKO(CH) mice is caused by a receptor-independent mechanism, an unidentified receptor responsive to estrogen, or residual activity of the ERalpha splice variant reported previously in the parental ERalphaKO(CH) mice. These possibilities may be resolved by studies of mice in which ERalpha has been fully disrupted (ERalphaKO(St)), which are in progress.

Estrogen receptor beta is expressed in human colorectal adenocarcinoma

Estrogen receptor beta (ER-beta) has recently been detected in a human colon cancer cell line. The aim of this work was to determine whether ER-beta is expressed in human colorectal carcinoma (CRC) tissue and the extent of this expression. ER-beta expression in CRC was investigated by immunohistochemical staining of sections of formalin-fixed, paraffin-embedded tissue from 55 CRC. The percent of positive cells was recorded. ER-beta immunoreactivity was always present in normal epithelium and adenomas in the same sections of some CRC and was always nuclear. In CRC, nuclear ER-beta immunoreactivity was detected in >10% of the cancer cells in 67% of the cases and was almost always associated with cytoplasmic immunoreactivity. There were no statistically significant differences between the ER-beta-positive and -negative groups in regard to depth of invasion, nodal metastases, or survival, regardless of the cut-off value used. We conclude that (1) a significant number of CRCs are positive for ER-beta. (2) estrogen may play an important role in the proliferation of normal colonic epithelium, and (3) there is differential localization of ER-beta immunoreactivity between normal colon, adenomas, and CRCs. Whether different ER-beta isoforms are differentially expressed in CRCs, and whether human CRCs respond to treatment with antiestrogens, is the subject of studies currently in progress.

Mitotic checkpoint protein hsMAD2 as a marker predicting liver metastasis of human gastric cancers

hsMAD2, the human homologue of mitotic arrest deficient 2 (MAD2), is a key component of the mitotic checkpoint system. Recently, mutations and decreased expression of mitotic checkpoint genes including hsMAD2 have been reported in cancer cell lines with defective mitotic checkpoint. However, the genetic alterations in the genomic hsMAD2 gene have not been determined in gastric cancers. Moreover, the biological implications of the overexpressed hsMAD2 in primary cancers are unknown. In this study, we analyzed 32 primary gastric cancers with polymerase chain reaction (PCR) amplification of all exons, including flanking intronic sequences, of the genomic hsMAD2 gene followed by direct DNA sequencing. We also measured the hsMAD2 protein levels in cancer and normal tissues by semi-quantitative immunoblotting. No mutations were found in the coding sequences, although three single nucleotide polymorphisms (SNPs) were identified in the noncoding sequences in 13 of 32 patients. These SNPs were not associated with either hsMAD2 expression or disease progression. The semi-quantitative western blot analysis showed hsMAD2 was significantly overexpressed in gastric cancer tissues compared with corresponding normal tissues (P < 0.001). The calculated ratio of the hsMAD2 protein in cancer tissue (C) to that in corresponding normal tissue (N) (C / N ratio) was significantly higher in patients with well differentiated adenocarcinoma (P = 0.0274) or with synchronous liver metastasis (P = 0.0025). A C / N ratio greater than 3 was observed more frequently in patients with synchronous liver metastasis. Therefore, C / N ratio > 3 may be clinically important as a predictive indicator for metachronous liver metastasis of gastric cancers.

Estrogen receptor beta dominates in baboon carotid after endothelial denudation injury

Increasing evidence, mainly from rodents, suggests that the predominant estrogen receptor (ER) in arteries is the newly-described ERbeta. We have investigated the expression of the two ERs in baboon carotid artery before and after denudation injury. Prior to denudation, both full length receptors were detected in semiquantitative RT-PCR; in addition two ERalpha but no ERbeta splicing variants were found. After denudation, ERbeta mRNA increased five-fold and declined, whereas ERalpha mRNA expression remained low. Prior to and after denudation, two ERalpha-specific antibodies showed no reaction with the vessel wall. Instead, two affinity purified antisera to ERbeta demonstrated a weak but distinct reaction over vascular smooth muscle cells with predenudation specimens, escalating post-denudation and declining thereafter. The results suggest that selective targeting to ERbeta should be attempted when designing estrogen-based vasculoprotective drug therapies devoid of uterotrophic side effects.

Activation of estrogen receptor beta is a prerequisite for estrogen-dependent upregulation of nitric oxide synthases in neonatal rat cardiac myocytes

Physiological effects of estrogen on myocardium are mediated by two intracellular estrogen receptors, ERalpha and ERbeta, that regulate transcription of target genes through binding to specific DNA target sequences. To define the role of ERbeta in the transcriptional activation of both endothelial (eNOS) and inducible nitric oxide synthase (iNOS) in cardiac myocytes, we used the complete ER-specific antagonist R,R-tetrahydrochrysene (R,R-THC). R,R-THC inhibited activation of iNOS/eNOS promoter-luciferase reporter constructs (iNOS/eNOS-Luc) in a dose-dependent fashion in COS7 cells selectively transfected with ERbeta, but failed to influence ERalpha-mediated increase of iNOS/ eNOS-Luc. In neonatal rat cardiomyocytes transfected with eNOS-Luc or iNOS-Luc, incubation with 17betaestradiol (E2, 10(-8) M) for 24 h stimulated expression of eNOS and iNOS. R,R-THC (10(-5) M) completely inhibited this effect. Furthermore, eNOS and iNOS protein expression in cardiac myocytes induced by E2 was completely blocked by R,R-THC as shown by immunoblot analysis. Taken together, these results show that ERbeta mediates transcriptional activation of eNOS and iNOS by E2.

Estrogen changes mitosis orientation in the uterine epithelia

OBJECTIVES

Estrogens can lead to hyperplasia and cancer formation in the uterus, ovary and mammary gland. However, key factors involved in this process are not defined at present. It is possible that estrogens primarily affect more global tissue-organising parameters as composition of tissues in three-metric space, that is brought about changes in the orientation of the plane of cell division. There are no data about estrogen action on mitosis orientation in the uterus.

STUDY DESIGN

Mitosis orientation, proliferative activity and general histology were examined in the uterus, jejunal and colonic crypts, and epidermis of ovariectomized rats 0, 24, 36 and 48h after a single injection of estradiol, and in the uterus of ovariectomized mice received injections with estradiol once-a-week for 30, 60 and 90 days.

RESULTS

All mitoses in luminal and glandular epithelia of the uterus of ovariectomized rats aligned parallel to the basement membrane, and estradiol treatment leads to appearing of mitoses oriented perpendicular to the basement membrane of the epithelium. Together with increase in the proliferative activity, the number of perpendicular oriented mitoses in uterine epithelia of ovariectomized rats is significantly increased after a single injection of estradiol. During endometrial hyperplasia formation in mice, that is induced by chronic estrogen treatment, the number of perpendicular oriented mitoses in uterine epithelia become much more higher. In jejunal and colonic crypts, epidermis of ovariectomized rats, most of mitoses disposed parallel to the basement membrane and an injection of estradiol did not affect mitosis orientation and activity of proliferation.

CONCLUSIONS

Estradiol effect on mitosis orientation may be considered as specific. Changes in mitosis orientation are probably responsible for estrogen-dependent hyperplasia and cancer formation in the uterus.

Comparative studies of the estrogen receptors beta and alpha and the androgen receptor in normal human prostate glands, dysplasia, and in primary and metastatic carcinoma

An antibody, GC-17, thoroughly characterized for its specificity for estrogen receptor-beta (ER-beta), was used to immunolocalize the receptor in histologically normal prostate, prostatic intraepithelial neoplasia, primary carcinomas, and in metastases to lymph nodes and bone. Comparisons were made between ER-beta, estrogen receptor-alpha (ER-alpha), and androgen receptor (AR) immunostaining in these tissues. Concurrently, transcript expression of the three steroid hormone receptors was studied by reverse transcriptase-polymerase chain reaction analysis on laser capture-microdissected samples of normal prostatic acini, dysplasias, and carcinomas. In Western blot analyses, GC-17 selectively identified a 63-kd protein expressed in normal and malignant prostatic epithelial cells as well as in normal testicular and prostatic tissues. This protein likely represents a posttranslationally modified form of the long-form ER-beta, which has a predicted size of 59 kd based on polypeptide length. In normal prostate, ER-beta immunostaining was predominately localized in the nuclei of basal cells and to a lesser extent stromal cells. ER-alpha staining was only present in stromal cell nuclei. AR immunostaining was variable in basal cells but strongly expressed in nuclei of secretory and stromal cells. Overall, prostatic carcinogenesis was characterized by a loss of ER-beta expression at the protein and transcript levels in high-grade dysplasias, its reappearance in grade 3 cancers, and its diminution/absence in grade 4/5 neoplasms. In contrast, AR was strongly expressed in all grades of dysplasia and carcinoma. Because ER-beta is thought to function as an inhibitor of prostatic growth, androgen action, presumably mediated by functional AR and unopposed by the beta receptor, may have provided a strong stimulus for aberrant cell growth. With the exception of a small subset of dysplasias in the central zone and a few carcinomas, ER-alpha-stained cells were not found in these lesions. The majority of bone and lymph node metastases contained cells that were immunostained for ER-beta. Expression of ER-beta in metastases may have been influenced by the local microenvironment in these tissues. In contrast, ER-alpha-stained cells were absent in bone metastases and rare in lymph nodes metastases. Irrespective of the site, AR-positive cells were found in all metastases. Based on our recent finding of anti-estrogen/ER-beta-mediated growth inhibition of prostate cancer cells in vitro, the presence of ER-beta in metastatic cells may have important implications for the treatment of late-stage disease.

Quantitative analysis of estrogen receptor proteins in rat mammary gland

Estrogen receptor alpha and beta proteins (ERalpha and ERbeta) at various stages of development of the rat mammary gland were quantified by Western blotting. ERalpha and ERbeta recombinant proteins were used as standards, and their molar concentrations were measured by ligand binding assays. In 3-week-old pregnant, lactating, and postlactating rats the ERalpha content ranged from 0.30-1.55 fmol/microg total protein (mean values). The ERbeta content of the same samples ranged between 1.06-7.50 fmol/microg total protein. At every developmental stage, the ERbeta content of the mammary gland was higher than that of ERalpha. When receptor levels were normalized against beta-actin, it was evident that ER expression changed during development, with maximum expression of both receptors during the lactation period. With an antibody raised against the 18-amino acid insert of the ERbeta variant, originally called ERbeta2 but named ERbetains in this paper, Western blots revealed that ERbetains protein was up-regulated during the lactation period. RT-PCR showed that the levels of messenger RNA of ERbetains paralleled those of the protein. Double immunohistochemical staining with anti-ERalpha and anti-ERbetains antibodies revealed that ERbetains protein colocalized with ERalpha in 70-80% of the ERalpha-expressing epithelial cells during lactation and with 30% of these cells during pregnancy. These observations indicate that expression of ERbetains is regulated not only quantitatively, but also with regard to its cellular distribution. As ERbetains acts as the dominant repressor of ERalpha, we suggest that its coexpression with ERalpha quenches ERalpha function and may be one of the factors that contribute to the previously described insensitivity of the mammary gland to estrogens during lactation.

Mitotic checkpoint proteins HsMAD1 and HsMAD2 are associated with nuclear pore complexes in interphase

Mad1 was first identified in budding yeast as an essential component of the checkpoint system that monitors spindle assembly in mitosis and prevents premature anaphase onset. Using antibodies to the human homologue of Mad1 (HsMAD1), we have begun to characterize this protein in mammalian cells. HsMad1 is found localized at kinetochores in mitosis. The labeling is brightest in prometaphase and is absent from kinetochores at metaphase and anaphase. In cells where most chromosomes have reached the metaphase plate, those aligned at the plate show no labeling while remaining, unaligned chromosomes are still brightly labeled. We find HsMad1 associated with HsMad2. Association with p55CDC, a protein previously shown to bind HsMad2, was not detected. Surprisingly, unlike any other known mitotic checkpoint proteins, HsMad1 and HsMAD2 were found localized at nuclear pores throughout interphase. This was confirmed by co-labeling with an antibody to known nuclear pore complex proteins and by their co-purification with enriched nuclear envelope fractions. HsMad1 was identified serendipitously by its binding to a viral protein, HTLV-1 Tax, which affects transcription of viral and human proteins. The localization of HsMad1 to nuclear pore complexes suggests an alternate, non-mitotic role for the Mad1/Tax interaction in the viral transformation of cells.

Estrogen receptor beta expression in invasive breast cancer

The aim of this work was to determine the extent of estrogen receptor beta (ER-beta) expression in invasive breast cancer (BrCA) and whether ER-beta expression is correlated with response to adjuvant hormonal therapy with tamoxifen (AHTT). Immunohistochemical staining (IHC) for estrogen receptor alpha (ER-alpha) and ER-beta was performed on sections of formalin-fixed and paraffin-embedded tissue from 47 unselected invasive breast carcinomas (BrCA). IHC for ER-beta was also performed on sections of BrCA from 118 women who were treated with mastectomy and AHTT. Survival analysis was performed using the Kaplan-Meier method and the log-rank test. Of the 47 unselected BrCA, 17 (36%) were negative for ER-alpha and of these, 8 (47% of ER-alpha negative cases and 17% of all 47 patients) were ER-beta positive. Five of the 8 ER-alpha negative and ER-beta positive cases were positive for ER biochemically. There was no correlation between ER-beta positivity and overall survival in the unselected group. By contrast, in the group of women treated with AHTT, expression of ER-beta in more than 10% of cancer cells was associated with better survival (P = .0077), even in women with node-negative BrCA (P = .0069). In conclusion, our results show that a significant number of women with BrCA are positive for ER-beta only, and may be determined to be ER-negative when currently available IHC is used. ER-beta status is a significant predictor of response to AHTT in women with BrCA. Larger studies with multivariate analysis are needed to confirm these findings.