Transcriptional regulation of the human quinone reductase gene by antiestrogen-liganded estrogen receptor-alpha and estrogen receptor-beta

Roles of NAD(P)H:quinone Oxidoreductase 1 in Diverse Diseases

NAD(P)H:quinone oxidoreductase (NQO) is an antioxidant flavoprotein that catalyzes the reduction of highly reactive quinone metabolites by employing NAD(P)H as an electron donor. There are two NQO enzymes—NQO1 and NQO2—in mammalian systems. In particular, NQO1 exerts many biological activities, including antioxidant activities, anti-inflammatory effects, and interactions with tumor suppressors. Moreover, several recent studies have revealed the promising roles of NQO1 in protecting against cardiovascular damage and related diseases, such as dyslipidemia, atherosclerosis, insulin resistance, and metabolic syndrome. In this review, we discuss recent developments in the molecular regulation and biochemical properties of NQO1, and describe the potential beneficial roles of NQO1 in diseases associated with oxidative stress.

Effects of bisphenol A exposure during cardiac cell differentiation

Heart development requires a precise temporal regulation of gene expression in cardiomyoblasts. Therefore, the transcriptional changes in differentiating cells can lead to congenital heart diseases. Although the genetic mutations underlie most of these alterations, exposure to environmental contaminants, such as bisphenol A (BPA), has been recently considered as a risk factor as well. In this study we investigated the genotoxic and epigenotoxic effects of BPA throughout cardiomyocyte differentiation. H9c2 cells (rat myoblasts) were exposed to 10 and 30 μM BPA before and during the last two days of cardiac-driven differentiation. Then, we have analysed the phenotypic and molecular modifications (at transcriptional, genetic and epigenetic level). The results showed that treated myoblasts developed a skeletal muscle cell-like phenotype. The transcriptional changes induced by BPA in genes codifying proteins involved in heart differentiation and function depend on the window of exposure to BPA. The exposure before differentiation repressed the expression of heart transcription factors (Hand2 and Gata4), whereas exposure during differentiation reduced the expression of cardiac-specific genes (Tnnt2, Myom2, Sln, and Atp2a1). Additionally, significant effects were observed regarding DNA damage and histone acetylation levels after the two periods of BPA exposure: in cells exposed to the toxicant the percentage of DNA repair foci (formed by the co-localization of γH2AX and 53BP1) increased in a dose-dependent manner, whereas the treatment with the toxicant triggered a decrease in the epigenetic marks H3K9ac and H3K27ac. Our in vitro results reveal that BPA seriously interferes with the process of cardiomyocyte differentiation, which could be related to the reported in vivo effects of this toxicant on cardiogenesis.

The diverse functionality of NQO1 and its roles in redox control

In this review, we summarize the multiple functions of NQO1, its established roles in redox processes and potential roles in redox control that are currently emerging. NQO1 has attracted interest due to its roles in cell defense and marked inducibility during cellular stress. Exogenous substrates for NQO1 include many xenobiotic quinones. Since NQO1 is highly expressed in many solid tumors, including via upregulation of Nrf2, the design of compounds activated by NQO1 and NQO1-targeted drug delivery have been active areas of research. Endogenous substrates have also been proposed and of relevance to redox stress are ubiquinone and vitamin E quinone, components of the plasma membrane redox system. Established roles for NQO1 include a superoxide reductase activity, NAD+ generation, interaction with proteins and their stabilization against proteasomal degradation, binding and regulation of mRNA translation and binding to microtubules including the mitotic spindles. We also summarize potential roles for NQO1 in regulation of glucose and insulin metabolism with relevance to diabetes and the metabolic syndrome, in Alzheimer's disease and in aging. The conformation and molecular interactions of NQO1 can be modulated by changes in the pyridine nucleotide redox balance suggesting that NQO1 may function as a redox-dependent molecular switch.

Reciprocal interference between the NRF2 and LPS signaling pathways on the immune-metabolic phenotype of peritoneal macrophages

The metabolic and immune adaptation to extracellular signals allows macrophages to carry out specialized functions involved in immune protection and tissue homeostasis. Nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor that coordinates cell redox and metabolic responses to stressors. However, the individual and concomitant activation of NRF2 and inflammatory pathways have been poorly investigated in isolated macrophages. We here took advantage of reporter mice for the transcriptional activities of NRF2 and nuclear factor-kB (NFκB), a key transcription factor in inflammation, and observe a persisting reciprocal interference in the response of peritoneal macrophages to the respective activators, tert-Butylhydroquinone (tBHQ) and lipopolysaccharide (LPS). When analyzed separately by gene expression studies, these pathways trigger macrophage-specific metabolic and proliferative target genes that are associated with tBHQ-induced pentose phosphate pathway (PPP) with no proliferative response, and with opposite effects observed with LPS. Importantly, the simultaneous administration of tBHQ + LPS alters the effects of each individual pathway in a target gene-specific manner. In fact, this co-treatment potentiates the effects of tBHQ on the antioxidant enzyme, HMOX1, and the antibacterial enzyme, IRG1, respectively; moreover, the combined treatment reduces tBHQ activity on the glycolytic enzymes, TALDO1 and TKT, and decreases LPS effects on the metabolic enzyme IDH1, the proliferation-related proteins KI67 and PPAT, and the inflammatory cytokines IL-1β, IL-6, and TNFα. Altogether, our results show that the activation of NRF2 redirects the metabolic, immune, and proliferative response of peritoneal macrophages to inflammatory signals, with relevant consequences for the pharmacological treatment of diseases that are associated with unopposed inflammatory responses.

Ascorbic Acid and Alpha-Tocopherol Contribute to the Therapy of Polycystic Ovarian Syndrome in Mouse Models

Polycystic ovary syndrome (PCOS) affects up to 10% of women within reproductive ages and has been a cause of infertility and poor quality of life. Alteration in the oxidant-antioxidant profile occurs in PCOS. This study, therefore, investigates the contribution of ascorbic acid (AA) and alpha-tocopherol(ATE) on different PCOS parameters. The mifepristone and letrozole models were used, and young mature female mice were randomly assigned to groups of six per group. On PCOS induction with either mifepristone or letrozole, mice were administered AA and ATE at doses ranging from 10-1000mg/kg to 0.1-1000 mg/kg in the respective models. Vaginal cytology, body weights, and temperature, as well as blood glucose, testosterone, and insulin levels, were measured. Total antioxidant capacity and malondialdehyde levels were analyzed. Determination of gene expression of some reactive oxygen species and histomorphological analysis on the ovaries and uteri were performed. At the end of the experiments, AA and ATE restored reproductive cycling, with AA being more effective. AA and ATE increased fasting blood glucose but had no significant effect on serum insulin levels. AA decreased testosterone levels, but ATE caused slight increases. AA and ATE both increased total antioxidant capacity and decreased malondialdehyde levels. AA and ATE also slightly upregulated the mRNA expressions of catalase, superoxide dismutase, and heme oxygenase 1 mainly. AA and ATE also decreased ovarian weight and mostly resolved cysts in the ovaries and congestion in the uterus. This study has shown that AA and ATE are beneficial in the therapy of PCOS.

Expression of NAD(P)H quinone dehydrogenase 1 (NQO1) is increased in the endometrium of women with endometrial cancer and women with polycystic ovary syndrome

OBJECTIVE

Women with a prior history of polycystic ovary syndrome (PCOS) have an increased risk of endometrial cancer (EC).

AIM

To investigate whether the endometrium of women with PCOS possesses gene expression changes similar to those found in EC.

DESIGN AND METHODS

Patients with EC, PCOS and control women unaffected by either PCOS or EC were recruited into a cross-sectional study at the Nottingham University Hospital, UK. For RNA sequencing, representative individual endometrial biopsies were obtained from women with EC, PCOS and a woman unaffected by PCOS or EC. Expression of a subset of differentially expressed genes identified by RNA sequencing, including NAD(P)H quinone dehydrogenase 1 (NQO1), was validated by quantitative reverse transcriptase PCR validation (n = 76) and in the cancer genome atlas UCEC (uterine corpus endometrioid carcinoma) RNA sequencing data set (n = 381). The expression of NQO1 was validated by immunohistochemistry in EC samples from a separate cohort (n = 91) comprised of consecutive patients who underwent hysterectomy at St Mary's Hospital, Manchester, between 2011 and 2013. A further 6 postmenopausal women with histologically normal endometrium who underwent hysterectomy for genital prolapse were also included. Informed consent and local ethics approval were obtained for the study.

RESULTS

We show for the first that NQO1 expression is significantly increased in the endometrium of women with PCOS and EC. Immunohistochemistry confirms significantly increased NQO1 protein expression in EC relative to nonmalignant endometrial tissue (P < .0001).

CONCLUSIONS

The results obtained here support a previously unrecognized molecular link between PCOS and EC involving NQO1.

Importance of Estrogenic Signaling and Its Mediated Receptors in Prostate Cancer

Prostate cancer (PCa) treatment was first established by Huggins and Hodges in 1941, primarily described as androgen deprivation via interference of testicular androgen production. The disease remains incurable with relapse of hormone-refractory cancer after treatments. Epidemiological and clinical studies disclosed the importance of estrogens in PCa. Discovery of estrogen receptor ERβ prompted direct estrogenic actions, in conjunction with ERα, on PCa cells. Mechanistically, ERs upon ligand binding transactivate target genes at consensus genomic sites via interactions with various transcriptional co-regulators to mold estrogenic signaling. With animal models, Noble revealed estrogen dependencies of PCa, providing insight into potential uses of antiestrogens in the treatment. Subsequently, various clinical trials were conducted and molecular and functional consequences of antiestrogen treatment in PCa were delineated. Besides, estrogens can also trigger rapid non-genomic signaling responses initiated at the plasma membrane, at least partially via an orphan G-protein-coupled receptor GPR30. Activation of GPR30 significantly inhibited in vitro and in vivo PCa cell growth and the underlying mechanism was elucidated. Currently, molecular networks of estrogenic and antiestrogenic signaling via ERα, ERβ and GPR30 in PCa have not been fully deciphered. This crucial information could be beneficial to further developments of effective estrogen- and antiestrogen-based therapy for PCa patients.

Oxidative stress contributes to the tamoxifen-induced killing of breast cancer cells: implications for tamoxifen therapy and resistance

Tamoxifen is the accepted therapy for patients with estrogen receptor-α (ERα)-positive breast cancer. However, clinical resistance to tamoxifen, as demonstrated by recurrence or progression on therapy, is frequent and precedes death from metastases. To improve breast cancer treatment it is vital to understand the mechanisms that result in tamoxifen resistance. This study shows that concentrations of tamoxifen and its metabolites, which accumulate in tumors of patients, killed both ERα-positive and ERα-negative breast cancer cells. This depended on oxidative damage and anti-oxidants rescued the cancer cells from tamoxifen-induced apoptosis. Breast cancer cells responded to tamoxifen-induced oxidation by increasing Nrf2 expression and subsequent activation of the anti-oxidant response element (ARE). This increased the transcription of anti-oxidant genes and multidrug resistance transporters. As a result, breast cancer cells are able to destroy or export toxic oxidation products leading to increased survival from tamoxifen-induced oxidative damage. These responses in cancer cells also occur in breast tumors of tamoxifen-treated mice. Additionally, high levels of expression of Nrf2, ABCC1, ABCC3 plus NAD(P)H dehydrogenase quinone-1 in breast tumors of patients at the time of diagnosis were prognostic of poor survival after tamoxifen therapy. Therefore, overcoming tamoxifen-induced activation of the ARE could increase the efficacy of tamoxifen in treating breast cancer.

Identification of estrogen-responsive genes based on the DNA binding properties of estrogen receptors using high-throughput sequencing technology

Estrogens are important endocrine hormones that control physiological functions in reproductive organs, and play a pivotal role in the generation and progression of breast cancer. Therapeutic drugs including anti-estrogen and aromatase inhibitors are used to treat patients with breast cancer. The estrogen receptors, ERα and ERβ, function as hormone-dependent transcription factors that directly regulate the expression of their target genes. Therefore, a better understanding of the function and regulation of estrogen-responsive genes provides insight into the gene regulation network associated with breast cancer. Recent technological developments in high-throughput sequencing have enabled the genome-wide identification of estrogen-responsive genes. Further elucidating the estrogen gene cascade is critical for advancements in the diagnosis and treatment of breast cancer.

Chemical and biological mechanisms of phytochemical activation of Nrf2 and importance in disease prevention

Plants are an incredibly rich source of compounds that activate the Nrf2 transcription factor, leading to upregulation of a battery of cytoprotective genes. This perspective surveys established and proposed molecular mechanisms of Nrf2 activation by phytochemicals with a special emphasis on a common chemical property of Nrf2 activators: the ability as "soft" electrophiles to modify cellular thiols, either directly or as oxidized biotransformants. In addition, the role of reactive oxygen/nitrogen species as secondary messengers in Nrf2 activation is discussed. While the uniquely reactive C151 of Keap1, an Nrf2 repressor protein, is highlighted as a key target of cytoprotective phytochemicals, also reviewed are other stress-responsive proteins, including kinases, which play non-redundant roles in the activation of Nrf2 by plant-derived agents. Finally, the perspective presents two key factors accounting for the enhanced therapeutic windows of effective phytochemical activators of the Keap1-Nrf2 axis: enhanced selectivity toward sensor cysteines and reversibility of addition to thiolate molecules.

Estrogen receptor and PI3K/Akt signaling pathway involvement in S-(-)equol-induced activation of Nrf2/ARE in endothelial cells

S-(-)equol, a natural product of the isoflavone daidzein, has been reported to offer cytoprotective effects with respect to the cardiovascular system, but how this occurs is unclear. Interestingly, S-(-)equol is produced by the human gut, suggesting a role in physiological processes. We report that treatment of human umbilical vein endothelial cells and EA.hy926 cells with S-(-)equol induces ARE-luciferase reporter gene activity that is dose and time dependent. S-(-)equol (10-250 nM) increases nuclear factor-erythroid 2-related factor 2 (Nrf2) as well as gene products of Nrf2 target genes heme oxygenase-1 (HO-1) and NAD(P)H (nicotinamide-adenine-dinucleotide-phosphate) quinone oxidoreductase 1 (NQO1). Endothelial cells transfected with an HA-Nrf2 expression plasmid had elevated HA-Nrf2, HO-1, and NQO1 in response to S-(-)equol exposure. S-(-)equol treatment affected Nrf2 mRNA only slightly but significantly increased HO-1 and NQO1 mRNA. The pretreatment of cells with specific ER inhibitors or PI3K/Akt (ICI182,780 and LY294002) increased Nrf2, HO-1, and NQO1 protein, impaired nuclear translocation of HA-Nrf2, and decreased ARE-luciferase activity. Identical experiments were conducted with daidzein, which had effects similar to S-(-)equol. In addition, DPN treatment (an ERβ agonist) induced the ARE-luciferase reporter gene, promoting Nrf2 nuclear translocation. Cell pretreatment with an ERβ antagonist (PHTPP) impaired S-(-)equol-induced Nrf2 activation. Pre-incubation of cells followed by co-treatment with S-(-)equol significantly improved cell survival in response to H2O2 or tBHP and reduced apoptotic and TUNEL-positively-stained cells. Notably, the ability of S-(-)equol to protect against H2O2-induced cell apoptosis was attenuated in cells transfected with an siRNA against Nrf2. Thus, beneficial effects of S-(-)equol with respect to cytoprotective antioxidant gene activation may represent a novel strategy to prevent and treat cardiovascular diseases.

Induction of quinone reductase by tamoxifen or DPN protects against mammary tumorigenesis

We have previously shown that estrogen receptor β (ERβ)-mediated up-regulation of quinone reductase (QR) is involved in the protection against estrogen-induced mammary tumorigenesis. Our present study provides evidence that the ERβ agonist, 2,3-bis-(4-hydroxy-phenyl)-propionitrile (DPN), and the selective estrogen receptor modulator tamoxifen (Tam), inhibit estrogen-induced DNA damage and mammary tumorigenesis in the aromatase transgenic (Arom) mouse model. We also show that either DPN or Tam treatment increases QR levels and results in a decrease in ductal hyperplasia, proliferation, oxidative DNA damage (ODD), and an increase in apoptosis. To corroborate the role of QR, we provide additional evidence in triple transgenic MMTV/QR/Arom mice, wherein the QR expression is induced in the mammary glands via doxycycline, causing a decrease in ductal hyperplasia and ODD. Overall, we provide evidence that up-regulation of QR through induction by Tam or DPN can inhibit estrogen-induced ODD and mammary cell tumorigenesis, representing a novel mechanism of prevention against breast cancer. Thus, our data have important clinical implications in the management of breast cancer; our findings bring forth potentially new therapeutic strategies involving ERβ agonists.

The exonuclease activity of hPMC2 is required for transcriptional regulation of the QR gene and repair of estrogen-induced abasic sites

We have previously reported that the expression of antioxidative stress enzymes are upregulated by trans-hydroxytamoxifen (TOT) in breast epithelial cell lines providing protection against estrogen-induced DNA damage. This regulation involves Estrogen Receptor beta (ERβ) recruitment to the Electrophile Response Element (EpRE) and a novel protein, human homolog of Xenopus gene which Prevents Mitotic Catastrophe (hPMC2). We have also demonstrated that ERβ and hPMC2 are required for TOT-dependent recruitment of poly (ADP-ribose) polymerase 1 (PARP-1) and Topoisomerase IIβ (Topo IIβ) to the EpRE. Sequence analysis reveals that the C-terminus of hPMC2 encodes a putative exonuclease domain. Using in vitro kinetic assays, we found that hPMC2 is a 3'–5' non-processive exonuclease that degrades both single stranded and double stranded substrates. Mutation of two conserved carboxylate residues drastically reduced the exonuclease activity of hPMC2 indicating the relative importance of the catalytic residues. Western blot analysis of breast cancer cell lines for Quinone Reductase (QR) levels revealed that the intrinsic exonuclease activity of hPMC2 was required for TOT-induced QR upregulation. Chromatin immunoprecipitation assays (ChIP) also indicated that hPMC2 was involved in the formation of strand breaks observed with TOT-treatment and is specific for the EpRE-containing region of the QR gene. We also determined that the transcription factor NF-E2-related factor-2 (Nrf2) is involved in the specificity of hPMC2 for the EpRE. In addition, we determined that the catalytic activity of hPMC2 is required for repair of abasic sites that result from estrogen-induced DNA damage. Thus our study provides a mechanistic basis for transcriptional regulation by hPMC2 and provides novel insights into its role in cancer prevention.

Inhibition of estrogen signaling activates the NRF2 pathway in breast cancer

Exposure to higher levels of estrogen produces genotoxic metabolites that can stimulate mammary tumorigenesis. Induction of NF-E2-related factor 2 (NRF2)-dependent detoxifying enzymes (e.g., NAD(P)H-quinone oxidoreductase 1 (NQO1)) is considered an important mechanism of protection against estrogen-associated carcinogenesis because they would facilitate removal of toxic estrogens. Here, we studied the impact of estrogen-receptor (ER) signaling on NRF2-dependent gene transcription. In luciferase assay experiments using the 5-flanking region of the human NQO1 gene promoter, we observe that ERα ligand-binding domain (LBD) is required for estrogen inhibition of NQO1 promoter activity in estrogen-dependent breast cancer cells. Chromatin immunoprecipitation (ChIP) assay shows that estrogen recruits ERα and a class III histone deacetylase SIRT1 at the NQO1 promoter, leading to inhibition of NQO1 transcription. Inhibition of ERα expression by the antiestrogen shikonin reverses the inhibitory effect of estrogen on NQO1 expression. As a consequence, a chemoprevention study was undertaken to monitor the impact of shikonin on DNA lesions and tumor growth. Treatment of MCF-7 breast cancer cells with shikonin inhibits estrogen-induced 8-hydroxy-2-deoxyguanosine (8-OHdG), a marker of DNA damage. NQO1 deficiency promotes estrogen-dependent tumor formation, and shikonin inhibits estrogen-dependent tumor growth in an NQO1-dependent manner in MCF-7 xenografts. These results suggest that estrogen-receptor signaling pathway has an inhibitory effect on NRF2-dependent enzymes. Moreover, shikonin reverses the inhibitory effects of estrogen on this pathway and may contribute to breast cancer prevention.

Minireview: Estrogen receptor-beta: mechanistic insights from recent studies

The discovery of estrogen receptor-beta (ERbeta) in 1996 stimulated great interest in the physiological roles and molecular mechanisms of ERbeta action. We now know that ERbeta plays a major role in mediating estrogen action in several tissues and organ systems, including the ovary, cardiovascular system, brain, and the immune system, and that ERbeta and ERalpha generally play distinct physiological roles in the body. Although significant progress has been made toward understanding the molecular mechanisms of ERbeta action, particularly in vitro, there remains a large gap in our understanding of the mechanisms by which ERbeta elicits its biological functions in a true physiological context.

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.

hPMC2 is required for recruiting an ERbeta coactivator complex to mediate transcriptional upregulation of NQO1 and protection against oxidative DNA damage by tamoxifen

In the presence of ERbeta, trans-hydroxytamoxifen (TOT) protects cells against 17beta-estradiol (E(2))-induced oxidative DNA damage (ODD) and this correlates with increased expression of the antioxidative enzyme quinone reductase (QR). Here, we investigate the molecular mechanism responsible for ERbeta-mediated protection against ODD. We observe constitutive interaction between ERbeta and the novel protein hPMC2. Using a combination of breast epithelial cell lines that are either positive or negative for ERalpha, we demonstrate TOT-dependent recruitment of both ERbeta and hPMC2 to the EpRE (electrophile response element)-regulated antioxidative enzyme QR. We further demonstrate TOT-dependent corecruitment of the coactivators Nrf2, PARP-1 (poly (ADP-ribose) polymerase 1) and topoisomerase IIbeta, both in the presence and absence of ERalpha. However, absence of either ERbeta or hPMC2 results in nonrecruitment of PARP-1 and topoisomerase IIbeta, loss of antioxidative enzyme induction and attenuated protection against ODD by TOT even in the presence of Nrf2 and ERalpha. These findings indicate minor role for Nrf2 and ERalpha in TOT-dependent antioxidative gene regulation. However, downregulation of PARP-1 attenuates TOT-dependent antioxidative gene induction. We conclude that ERbeta and hPMC2 are required for TOT-dependent recruitment of coactivators such as PARP-1 to the EpRE resulting in the induction of antioxidative enzymes and subsequent protection against ODD.

Agonist-like SERM effects on ERalpha-mediated repression of MMP1 promoter activity predict in vivo effects on bone and uterus

Estradiol receptors (ER), ERalpha and ERbeta, are ligand-dependent transcription factors that regulate gene expression. Human and murine genetics suggest that ERalpha is the key target for estradiol action on bone, uterus and breast. To date, the molecular mode of action of estradiol and selective estradiol receptor modulators (SERMs) on bone is not fully understood. This is exemplified by a lack of in vitro assays that reliably predict SERM agonist activities in vivo. We hypothesized that ligand-dependent ERalpha transrepression, via protein-protein interactions at AP1, may predict estrogenic effects on bone. We modeled this using the MMP1 promoter, which encodes an AP1 binding site. We show that ICI-182780, raloxifene, 4-hydroxytamoxifen and estradiol all exhibit differential agonistic activities on the MMP1 promoter by suppressing activity by 20-80%. Transrepression efficacy and potency correlated with both uterotrophic (R(2)=0.98) and osteoprotective (R(2)=0.80) potential in the ovariectomized rat. This identifies MMP1 promoter transrepression as an agonist activity commonly shared by AF2 agonists and "antagonists" alike. Mutation analysis showed that the repression by estradiol and SERMs required correct amino acid sequences in the AF-2 domain. For instance, L540Q AF2 mutation did not alter responses to raloxifene, although it greatly increased responses to ICI-182780 (threefold) and reduced estradiol's effect by 20%. Furthermore, all tested ligands repressed the MMP1 promoter through the L540Q mutant with identical efficacy. Together, these data suggest that estradiol and SERMs share common agonist transcriptional activity via protein-protein interactions at AP1.

Hyperglycaemia, stress oxidant, liver dysfunction and histological changes in diabetic male rat pancreas and liver: protective effect of 17 beta-estradiol

Oxidative stress is thought to play a crucial role in the pathogenesis of chronic diabetic complications. We investigated the protective effects of 17 beta-estradiol (E2) on alloxan-induced stress oxidant, hepatic dysfunction and histological changes in male rats liver and pancreas. Our results showed that 17 beta-estradiol could attenuate the increase of blood glucose in plasma and normalise the hepatic glycogen level. In addition, E2 enhanced superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) (by 207, 52 and 72%, respectively, as compared to diabetic rats), reduced lipid peroxidation in the hepatic tissue (by 54%) and improved the liver dysfunction parameters by the significant decrease of gamma-glytamyl transferase (GGT), phosphatases alkalines (PAL), lactate deshydrogenase (LDH) and aspartate and lactate transaminases (AST and ALT) activities which increased in diabetic rats. Moreover, 17 beta-estradiol treatment in diabetic rats protects against alloxan-induced pancreatic beta-cells and hepatic cells damages.

The role of estrogens and estrogen receptors in normal prostate growth and disease

Estrogens have significant direct and indirect effects on prostate gland development and homeostasis and have been long suspected in playing a role in the etiology of prostatic diseases. Direct effects are mediated through prostatic estrogen receptors alpha (ERalpha) and beta (ERbeta) with expression levels changing over time and with disease progression. The present review examines the evidence for a role of estrogens and specific estrogen receptors in prostate growth, differentiation and disease states including prostatitis, benign prostatic hyperplasia (BPH) and cancer and discusses potential therapeutic strategies for growth regulation via these pathways.

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.

Metabolic activation of carcinogenic aristolochic acid, a risk factor for Balkan endemic nephropathy

Aristolochic acid (AA), a naturally occurring nephrotoxin and carcinogen, is associated with tumor development in patients suffering from Chinese herbs nephropathy (now termed aristolochic acid nephropathy, AAN) and may also be a cause for the development of a similar type of nephropathy, the Balkan endemic nephropathy (BEN). Major DNA adducts [7-(deoxyadenosin-N6-yl)-aristolactam and 7-(deoxyguanosin-N2-yl)aristolactam] formed from AA after reductive metabolic activation were found in renal tissues of patients with both diseases. Understanding which human enzymes are involved in AA activation and/or detoxication is important in the assessment of an individual's susceptibility to this plant carcinogen. This paper reviews major hepatic and renal enzymes responsible for AA-DNA adduct formation in humans. Phase I biotransformation enzymes play a crucial role in the metabolic activation of AA to species forming DNA adducts, while a role of phase II enzymes in this process is questionable. Most of the activation of AA in human hepatic microsomes is mediated by cytochrome P450 (CYP) 1A2 and, to a lower extent, by CYP1A1; NADPH:CYP reductase plays a minor role. In human renal microsomes NADPH:CYP reductase is more effective in AA activation. Prostaglandin H synthase (cyclooxygenase, COX) is another enzyme activating AA in human renal microsomes. Among the cytosolic reductases, NAD(P)H:quinone oxidoreductase (NQO1) is the most efficient in the activation of AA in human liver and kidney. Studies with purified enzymes confirmed the importance of CYPs, NADPH:CYP reductase, COX and NQO1 in the AA activation. The orientation of AA in the active sites of human CYP1A1, -1A2 and NQO1 was predicted from molecular modeling and explains the strong reductive potential of these enzymes for AA detected experimentally. We hypothesized that inter-individual variations in expressions and activities of enzymes activating AA may be one of the causes responsible for the different susceptibilities to this carcinogen reflected in the development of AA-induced nephropathies and associated urothelial cancer.

Therapeutic effect of phytoecdysteroids rich extract from Ajuga iva on alloxan induced diabetic rats liver, kidney and pancreas

In the current study, the effect of Ajuga iva extract on blood glucose, lipid profile, hepatic and renal toxicity and antioxidant enzyme activities in alloxan-induced diabetic rats was investigated. Diabetes was confirmed by measuring the glucoserua concentration 15 days after alloxan administration. Ajuga iva extract was administrated orally 3 weeks after alloxan injection. Our results investigate that Ajuga iva extract supplementation increased the levels of both enzymatic antioxidant (superoxide dismutase, catalase and glutathione peroxidase) and metals antioxidants (iron, copper, magnesium, calcium) and decreased lipid peroxidation level (TBARs). Besides Ajuga iva ameliorated diabetes provoked hepatic and renal toxicity appeared by a lower level in total and direct bilirubin, urea, creatinine, triglyceride (TG), cholesterol and a higher level in HDL-cholesterol. Besides, the activities of phosphatase alkalines (PAL), aspartate and lactate transaminase (AST & ALT) were decreased. The benefices effects of phytoecdysteroids of Ajuga iva confirmed by histological observation in pancreatic tissues. In conclusion, Ajuga iva phytoecdysteroids supplements seem to be beneficial for correcting the hyperglycemia and preventing diabetic complications in liver, pancreas and kidneys.

ERRbeta: a potent inhibitor of Nrf2 transcriptional activity

The orphan nuclear receptor, estrogen-related receptor beta (ERRbeta), shares a high degree of amino acid identity with estrogen receptor alpha (ERalpha). Although ERRbeta has been shown to be critical in embryo development, little is known about its functions and target genes. Here we report that the newly identified and most common human ortholog of ERRbeta--short-form hERRbeta (SFhERRbeta) potently represses the transcriptional activity of NF-E2 Related Factor 2 (Nrf2) on antioxidant response element (ARE)-mediated gene expression. Nrf2 is a main regulator of the expression of phase II detoxifying enzymes and antioxidant proteins in the cellular protection against oxidative stress. SFhERRbeta is the most potent inhibitor of Nrf2 transcriptional activity among the three ERR family members, ERRalpha, ERRbeta and ERRgamma. Additional analyses revealed that SFhERRbeta repressed Nrf2 activity likely through physical interaction in a complex with Nrf2, not by competing for the ARE DNA-binding sites, nor by decreasing Nrf2 protein concentration. By confocal immunofluorescence microscopy, SFhERRbeta alters the subcellular localization of Nrf2. Analyses using SFhERRbeta deletion mutants showed that SFhERRbeta interacts with Nrf2 through multiple sites. Our findings suggest that ERRbeta plays a novel functional role in the Nrf2-ARE pathway. By acting as a repressor of Nrf2, ERRbeta may be useful as a therapeutic target in cancer chemoprevention studies.

Modulation of transcription factors by curcumin

Curcumin is the active ingredient of turmeric that has been consumed as a dietary spice for ages. Turmeric is widely used in traditional Indian medicine to cure biliary disorders, anorexia, cough, diabetic wounds, hepatic disorders, rheumatism, and sinusitis. Extensive investigation over the last five decades has indicated that curcumin reduces blood cholesterol, prevents low-density lipoprotein oxidation, inhibits platelet aggregation, suppresses thrombosis and myocardial infarction, suppresses symptoms associated with type II diabetes, rheumatoid arthritis, multiple sclerosis, and Alzheimer's disease, inhibits HIV replication, enhances wound healing, protects from liver injury, increases bile secretion, protects from cataract formation, and protects from pulmonary toxicity and fibrosis. Evidence indicates that the divergent effects of curcumin are dependent on its pleiotropic molecular effects. These include the regulation of signal transduction pathways and direct modulation of several enzymatic activities. Most of these signaling cascades lead to the activation of transcription factors. Curcumin has been found to modulate the activity of several key transcription factors and, in turn, the cellular expression profiles. Curcumin has been shown to elicit vital cellular responses such as cell cycle arrest, apoptosis, and differentiation by activating a cascade of molecular events. In this chapter, we briefly review the effects of curcumin on transcription factors NF-KB, AP-1, Egr-1, STATs, PPAR-gamma, beta-catenin, nrf2, EpRE, p53, CBP, and androgen receptor (AR) and AR-related cofactors giving major emphasis to the molecular mechanisms of its action.

The prevention of prostate cancer

From our better understanding of the natural history of prostate cancer, it is not unreasonable to believe that the disease is preventable. Prostate cancer has become a major healthcare problem worldwide, as life expectancy increases. Moreover, the cancer is slow growing, with a period of about 20-25 years from initiation to the stage when the clinically detectable phenotype can be identified. This review provides a simple overview of the endocrinology of prostate cancer and discusses some of the pharmaceutical agents that have been or are being tested to restrain, possibly arrest, the progression of this slowly growing cancer. Also discussed are many of the dietary factors that may influence the molecular or endocrine events implicated in its development. Dietary factors are considered responsible for the geographical differences in prostate cancer incidence and mortality. Since about 50% of all men worldwide, from both East and West, show evidence of microscopic cancer by 50 years of age, growth restraint would appear to be the pragmatic option to the possibility of preventing initiation.

The Anticancer Drug Ellipticine is an Inducer of Rat NAD(P)H:Quinone Oxidoreductase

The antineoplastic agent ellipticine was investigated for its ability to induce the biotransformation enzyme NAD(P)H:quinone oxidoreductase (DT-diaphorase, EC 1.6.99.2) in male Wistar rats. Using the real-time polymerase chain reaction, the levels of NAD(P)H:quinone oxidoreductase mRNA were determined in livers, kidneys and lungs of rats treated intraperitoneally with ellipticine (40 mg/kg body weight) and of control (untreated) rats. Cytosolic fractions were isolated from the same tissues of control and ellipticine-treated rats and tested for NAD(P)H:quinone oxidoreductase protein expression and its enzymatic activity. The results demonstrate that ellipticine is a potent inducer of NAD(P)H:quinone oxidoreductase in rat livers and kidneys, while no induction of this enzyme was detectable in rat lungs. The increase in levels of NAD(P)H:quinone oxidoreductase mRNA correlates with the increase in expression of its protein and enzymatic activity, measured with menadione and 3-nitrobenzanthrone as substrates. The results, the identification of the potential of ellipticine to induce NAD(P)H:quinone oxidoreductase, suggest that this drug is capable of modulating biological efficiencies of the toxicants and/or drugs that are reductively metabolized by this enzyme.

Estrogens and aspects of prostate disease

Estrogens have long been associated with the processes involved in prostate carcinogenesis, particularly in cancer suppression. However, the synergistic influence of low concentrations of estrogens, together with androgens, in promoting aberrant growth of the gland has also been recognized. As new insights into the complex molecular events implicated in growth regulation of the prostate are revealed, the role of the estrogens has become clearer. The present review considers this role in relation to the pathogenesis of prostate cancer and the potential cancer-repressive influence of the dietary estrogens.

Protective roles of quinone reductase and tamoxifen against estrogen-induced mammary tumorigenesis

We previously reported that antiestrogen-liganded estrogen receptor beta (ERbeta) transcriptionally activates the major detoxifying enzyme quinone reductase (QR) (NAD(P)H:quinone oxidoreductase). Further studies on the functional role of ERbeta-mediated upregulation of antioxidative enzymes indicated protective effects against estrogen-induced oxidative DNA damage (ODD). We now report on in vivo and in vitro studies that show that ERbeta-mediated upregulation of QR are involved in the protection against estrogen-induced mammary tumorigenesis. Using the August Copenhagen Irish (ACI) model of estrogen-induced carcinogenesis, we observed that increased ODD and decreased QR expression occur early in the process of estrogen-induced mammary tumorigenesis. Prevention of ACI mammary gland tumorigenesis by tamoxifen was accompanied by decreased ODD and increased QR levels. These correlative findings were supported by our findings that downregulation of QR levels led to increased levels of estrogen quinone metabolites and enhanced transformation potential of 17beta-estradiol treated MCF10A non-tumorigenic breast epithelial cells. Concurrent expression of ERbeta and treatment with 4-hydroxytamoxifen decreased tumorigenic potential of these MCF10A cells. We conclude that upregulation of QR, through induction by tamoxifen, can inhibit estrogen-induced ODD and mammary cell tumorigenesis, representing a possible novel mechanism of tamoxifen prevention against breast cancer.

Estrogen receptor-beta regulates psoriasin (S100A7) in human breast cancer

We have previously observed a paradoxical relationship of the psoriasin/S100A7 gene with estrogen response in-vitro in ERalpha positive cells but its association with ERalpha negative status in-vivo raising the possibility that S100A7 might be regulated by ERbeta in breast cancer. Using doxycycline-inducible ERbeta and ERalpha expressing MCF-7 cells the hypothesis that psoriasin/S100A7 is ERbeta regulated was investigated To explore the relationship between psoriasin/S100A7 and ERbeta expression in-vivo, we also assessed a cohort of 233 ERalpha negative breast tumors using tissue microarrays and immunohistochemistry. Psoriasin/S100A7 was increased by 17beta-estradiol (E2) following ERbeta induction, in several clones of ERbeta over-expressing but not in the original MCF-7 cells, nor clones over-expressing ERalpha. The effect of E2 on psoriasin/S100A7 was inhibited by 4-hydroxytamoxifen and ICI 182780 but not with a selective ERalpha antagonist. An ERbeta selective-agonist but not an ERalpha selective-agonist, induced psoriasin/S100A7. This induction still occurred after stable down-regulation of ERalpha using siRNA in ERbeta inducible cells. E2 increased psoriasin/S100A7 mRNA but cycloheximide treatment inhibited this effect. A relationship between ERbeta and psoriasin/S100A7 was observed in the p53 immunohistochemically negative subset of invasive breast tumors in-vivo (r = 0.225, p = 0.046, n = 79). In conclusion we demonstrate that E2 induction of psoriasin/S100A7 can be specifically regulated through ERbeta in-vitro and associated with ERbeta in-vivo. These data support the hypothesis that psoriasin/S100A7 is specifically regulated by ERbeta activity and could be useful to guide future therapies targeting ERbeta in certain phenotypic subsets of breast cancers in-vivo.

Estrogen-occupied Estrogen Receptor Represses Cyclin G2 Gene Expression and Recruits a Repressor Complex at the Cyclin G2 Promoter

Estrogens, acting through their nuclear receptors have a broad impact on target cells, eliciting a transcriptional response program that involves gene repression as well as gene stimulation. While much is known about the mechanisms by which the estrogen-occupied estrogen receptor (ER) stimulates gene expression, the molecular events that lead to gene repression by the hormone-ER complex are largely unknown. Because estradiol represses expression of the cyclin G2 gene, which encodes a negative regulator of the cell cycle, our aim was to understand the mechanism by which cyclin G2 is repressed by estrogen. We show that cyclin G2 is a primary ER target gene in MCF-7 breast cancer cells that is rapidly and robustly down-regulated by estrogen. Promoter analysis reveals a responsive region containing a half-estrogen response element and GC-rich region that interact with ER and Sp1 proteins. Mutation of the half-ERE abrogates hormone-mediated repression. Mutational mapping of receptor reveals a requirement for its N-terminal region and DNA binding domain to support cyclin G2 repression. Following estradiol treatment of cells, chromatin immunoprecipitation analyses reveal recruitment of ER to the cyclin G2 regulatory region, dismissal of RNA polymerase II, and recruitment of a complex containing N-CoR and histone deacetylases, leading to a hypoacetylated chromatin state. Our study provides evidence for a mechanism by which the estrogen-occupied ER is able to actively repress gene expression in vivo and indicates a role for nuclear receptor corepressors and associated histone deacetylase activity in mediating negative gene regulation by this hormone-occupied nuclear receptor.

DNA sequence determinants of nuclear protein binding to the c-Ha-ras antioxidant/electrophile response element in vascular smooth muscle cells: identification of Nrf2 and heat shock protein 90 beta as heterocomplex components

The antioxidant/electrophile response element (ARE/EpRE) is a cis-acting element involved in redox regulation of c-Ha-ras gene. Protein binding to the ARE/EpRE may be credited to deoxyribonucleic acid sequence; therefore, studies were conducted to evaluate the influence of internal and flanking regions to the 10-bp human c-Ha-ras ARE/EpRE core (hHaras10) on nuclear protein binding in oxidant-treated vascular smooth muscle cells. A protein doublet bound to an extended oligonucleotide comprising the ARE/EpRE core in genomic context (hHaras27), whereas a single complex bound to hHarasl0. Protein binding involved specific interactions of 25- and 23-kDa proteins with hHarasl0, and binding of 80-, 65-, and 55-kDa proteins to hHaras27. Competition assays with hNQO1 and rGSTA2 confirmed the specificity of deoxyribonucleic acid-protein interactions and indicated preferred binding of p25 and p23 to the c-Ha-ras ARE/EpRE. "NNN" sequences within the core afforded unique protein-binding profiles to the c-Ha-ras ARE/EpRE. In addition, Nrf2 and heat shock protein 90beta (p80) were identified as components of the c-Ha-ras ARE/EpRE heterocomplex. We conclude that both internal bases and flanking sequences regulate nuclear protein recruitment and complex assembly on the c-Ha-ras ARE/EpRE.

17beta-estradiol induces apoptosis in the developing rodent prostate independently of ERalpha or ERbeta

Estrogens induce both proliferative and antiproliferative responses in the prostate gland. To date, antiproliferative effects of estrogens are generally considered to be due to systemic antiandrogenic actions. However, estrogen action mediated through estrogen receptor (ER) beta was recently suggested as another mechanism of induction of apoptosis in the prostate. This study aimed to explore the hypothesis that the antiproliferative effects of estrogen are directly mediated through ERbeta using a prostate organ culture system. We previously reported effects of 17beta-estradiol (E2) using rat ventral prostate (VP) tissues, and adapted the system for culturing mouse tissues. In both rat and mouse models, estrogen-induced apoptosis was detected that was spatially and regionally localized to the epithelium of the distal tips. Using organ cultures of alphaER knockout (alphaERKO) and betaERKO prostates, we failed to demonstrate that apoptosis induced by E2 was mediated through either receptor subtype. Activation of ER-selective ligands (ERalpha, propyl pyrazole triol, ERbeta, diaryl-proprionitrile, and 5alpha-androstane-3beta,17beta-diol) in organ culture experiments failed to induce apoptosis, as did the membrane impermeable conjugate E2:BSA, discounting the possibility of nongenomic effects. Consequently, E2 regulation of androgen receptor (AR) expression was examined and, in the presence of nanomolar testosterone levels, E2 caused a specific reduction in AR protein expression in wild-type, alphaERKO, and betaERKO mice, particularly in the distal region where apoptosis was detected. This down-regulation of AR protein provides a possible mechanism for the proapoptotic action of E2 that is independent of ERs or nongenomic effects.

Metal complex SERMs (selective oestrogen receptor modulators). The influence of different metal units on breast cancer cell antiproliferative effects

The selective oestrogen receptor modulator tamoxifen is a leading agent in the adjuvant treatment of breast cancer. Several organometallic moieties have been vectorised with tamoxifen, in order to improve on the latter's antiproliferative properties by the addition of a potentially cytotoxic moiety, and have been evaluated versus both oestrogen receptor positive (MCF7) and oestrogen receptor negative (MDA-MB231) breast cancer cells. For tamoxifen analogues with ((R,R)-trans-1,2-diaminocyclohexane)platinum(II), cyclopentadienyl rhenium tricarbonyl, and ruthenocene tethers, there was no enhancement of the antiproliferative effect on oestrogen receptor positive cells, nor any cytotoxic effect on oestrogen receptor negative cells, while those containing cyclopentadienyl titanium dichloride showed an oestrogenic effect. However, compounds where ferrocene replaces tamoxifen's phenyl ring were strongly cytotoxic against both cell lines. The synthesis and biological results of these compounds is reviewed and placed in the historic context of inorganic compounds in therapy.

Repression of cancer protective genes by 17beta-estradiol: ligand-dependent interaction between human Nrf2 and estrogen receptor alpha

Repression of cancer-protective phase II enzymes may help explain why estrogen exposure leads to the development of cancer. In an earlier report we described the ability of 17beta-estradiol (E(2)) to repress phase II enzyme activity in vivo. Phase II enzymes are coordinately regulated via the presence of the antioxidant response element (ARE) in their promoter. We wanted to determine if estrogen receptors (ER) repress ARE-dependent gene expression through a mechanism that requires interaction with Nrf2, the transcription factor that regulates ARE-mediated gene transcription. E(2)-bound ERalpha, but not ERbeta, represses ARE-regulated gene expression in the presence of exogenously expressed Nrf2 as well as when the transactivation domain of Nrf2 was fused to a heterologous DNA-binding domain. Deletion of the activation function-2 (AF-2) and the ligand-binding domain of ERalpha result in a constitutive repression of Nrf2-mediated transcription. Finally, E(2)-bound ERalpha co-immunoprecipitates with Nrf2. Repression of Nrf2-mediated transcription by E(2)-bound ERalpha expands our knowledge of E(2)-regulated genes and provides a potential drug-screening target for the development of selective estrogen receptor modulators with a lower risk of causing cancer.

Use of binding energy in comparative molecular field analysis of isoform selective estrogen receptor ligands

A diverse set of 30 estrogen receptor ligands whose relative binding affinities (RBA) with respect to 17beta-estradiol were available in both isoforms of the nuclear estrogen receptor (ERalpha, ERbeta) were studied with a combination of comparative molecular field analysis (CoMFA) and binding energy calculations. The ligands were docked inside the ligand-binding domain (LBD) of both ERalpha and ERbeta utilizing the docking program Gold. The binding energy (DeltaE) and corresponding non-bonded interactions (NB) of the subsequent protein-ligand complexes were calculated in both the gas-phase and implicit aqueous solution using the generalized born surface area (GB/SA) model. A partial least-squares analysis of the calculated energies indicated that the NB(g) were sufficiently predictive in ERalpha, but performed poorly in ERbeta. Further analysis of the calculated energies by dissecting the ligands into two distinct classes, estrogen-like and heterocyclic, yielded more predictive models. In particular the DeltaE calculated in solution proved particularly predictive for the estrogen-like ligands in ERbeta. Finally the estrogen subtype selective nature RBA (ERalpha/ERbeta) of a test-set consisting of six of the original ligands was predicted. The combined CoMFA and non-bonded interaction energy model ranked correctly the ligands in order of increasing RBA (ERalpha/ERbeta), illustrating the utility of this method as a prescreening tool in the development of novel estrogen receptor subtype selective ligands.

Differential induction of quinone reductase by phytoestrogens and protection against oestrogen-induced DNA damage

Quinone reductase (QR) is a phase II detoxification enzyme that plays an important role in detoxifying quinones and may help maintain the antioxidant function of the cell. We have previously observed that QR is up-regulated by anti-oestrogens, but not oestrogen, in breast cancer cells via ERbeta (oestrogen receptor beta) transactivation. Such QR induction appears to protect breast cells against oestrogen-induced oxidative DNA damage, most likely by reducing reactive oestrogen metabolites termed catecholestrogen-quinones back to the hydroxy-catecholestrogens which may be conjugated. We now report that the phytoestrogens biochanin A, genistein and resveratrol also up-regulate QR expression in breast cancer cells. We observe that regulation can occur at the transcriptional level, preferentially through ERbeta transactivation at the electrophile response element of the QR gene promoter. By chromatin immunoprecipitation analysis, we show binding of ERalpha and ERbeta to the QR promoter, with increased ERbeta binding in the presence of resveratrol. Functional studies show that biochanin A and resveratrol, but not genistein, can significantly protect against oestrogen-induced oxidative DNA damage in breast cancer cells. Antisense technology was used to determine whether such protection was dependent on ERbeta or QR. Our results with resveratrol are consistent with our hypothesis that the protective ability of resveratrol is partially dependent on the presence of ERbeta and QR. In conclusion, we postulate that phytoestrogen-mediated induction of QR may represent an additional mechanism for breast cancer protection, although the effects may be specific for a given phytoestrogen.

Modification of the Estrogenic Properties of Diphenols by the Incorporation of Ferrocene. Generation of Antiproliferative Effects in Vitro

We report here the synthesis and the strong and unexpected antiproliferative effect of the organometallic diphenolic compound 1,1-bis(4'-hydroxyphenyl)-2-ferrocenyl-but-1-ene (4) on both hormone-dependent (MCF7) and -independent (MDA-MB231) breast cancer cells (IC(50) = 0.7 and 0.6 microM). Surprisingly, 6 [1,2-bis(4'-hydroxyphenyl)-2-ferrocenyl-but-1-ene], the regioisomer of 4, shows only a modest effect on these cell lines. This pertinent organometallic modification seems to trigger an intracellular oxidation of the structurally favorable compound 4, leading to the generation of a potent cytotoxic compound.

Pomegranate extracts potently suppress proliferation, xenograft growth, and invasion of human prostate cancer cells

We completed a multicenter study of the effects of pomegranate cold-pressed (Oil) or supercritical CO(2)-extracted (S) seed oil, fermented juice polyphenols (W), and pericarp polyphenols (P) on human prostate cancer cell xenograft growth in vivo, and/or proliferation, cell cycle distribution, apoptosis, gene expression, and invasion across Matrigel, in vitro. Oil, W, and P each acutely inhibited in vitro proliferation of LNCaP, PC-3, and DU 145 human cancer cell lines. The dose of P required to inhibit cell proliferation of the prostate cancer cell line LNCaP by 50% (ED(50)) was 70 microg/mL, whereas normal prostate epithelial cells (hPrEC) were significantly less affected (ED(50) = 250 g/mL). These effects were mediated by changes in both cell cycle distribution and induction of apoptosis. For example, the androgen-independent cell line DU 145 showed a significant increase from 11% to 22% in G(2)/M cells (P <.05) by treatment with Oil (35 microg/mL) with a modest induction of apoptosis. In other cell lines/treatments, the apoptotic response predominated, for example, in PC-3 cells treated with P, at least partially through a caspase 3-mediated pathway. These cellular effects coincided with rapid changes in mRNA levels of gene targets. Thus, 4-hour treatment of DU 145 cells with Oil (35 microg/mL) resulted in significant 2.3 +/- 0.001-fold (mean +/- SEM) up-regulation of the cyclin-dependent kinase inhibitor p21((waf1/cip1)) (P <.01) and 0.6 +/- 0.14-fold down-regulation of c-myc (P <.05). In parallel, all agents potently suppressed PC-3 invasion through Matrigel, and furthermore P and S demonstrated potent inhibition of PC-3 xenograft growth in athymic mice. Overall, this study demonstrates significant antitumor activity of pomegranate-derived materials against human prostate cancer.

Differential expression of steroid receptors in prostate tissues before and after radiation therapy for prostatic adenocarcinoma

The expression, distribution and the role of steroid receptors in benign and malignant untreated prostate tissues is well recognized, however, the status of steroid receptors in prostate after radiotherapy (RT) for adenocarcinoma has not yet been studied fully. Immunohistochemical evaluation of androgen receptor (AR), estrogen receptor-alpha (ER-alpha), estrogen receptor-beta (ER-beta), and progesterone receptor (PR) was carried out in prostate needle biopsies obtained before and after radiotherapy from 60 patients with adenocarcinoma. The ER-beta transcripts were also studied by RT-PCR in LNCaP prostate carcinoma cell line before and 24 hr after gamma-irradiation at 0.5 Gy and 8.0 Gy. Significantly higher level of ER-beta expression was found in post-radiation samples of prostate adenocarcinoma and benign epithelium. After RT, all steroid receptors were upregulated in prostatic stroma. Tumor AR expression did not change significantly. Although a positive association between AR and ER-beta expression was observed in pre-treatment prostate adenocarcinoma, it was lost after RT suggesting that these 2 steroid receptors respond differently to RT. High levels of pretreatment tumor ER-beta were associated with local recurrence after RT and decreased biochemical recurrence-free survival (p = 0.028). LNCaP cell line that expressed no ER-beta mRNA before gamma-irradiation, clearly expressed ER-beta mRNA 24 hr after 0.5 Gy and 8.0 Gy. Upregulation of all steroid receptors in the prostate stroma and upregulation of ER-beta in the tumor epithelium after RT, may represent a protective tissue response to radiation-induced tissue injury. Although stromal AR was doubled after RT, the tumor and benign epithelium expression of AR seemed resistant to change by RT.

CoMFA and docking study of novel estrogen receptor subtype selective ligands

We present the results from a Comparative Molecular Field Analysis (CoMFA) and docking study of a diverse set of 36 estrogen receptor ligands whose relative binding affinities (RBA) with respect to 17beta-Estradiol were available in both isoforms of the nuclear estrogen receptors (ER alpha, ER beta). Initial CoMFA models exhibited a correlation between the experimental relative binding affinities and the molecular steric and electrostatic fields; ER alpha: r2 = 0.79, q2 = 0.44 ER beta: r2 = 0.93, q2 = 0.63. Addition of the solvation energy of the isolated ligand improved the predictive nature of the ER beta model initially; r2 = 0.96, q2 = 0.70 but upon rescrambling of the data-set and reselecting the training set at random, inclusion of the ligand solvation energy was found to have little effect on the predictive nature of the CoMFA models. The ligands were then docked inside the ligand binding domain (LBD) of both ER alpha and ER beta utilizing the docking program Gold, after-which the program CScore was used to rank the resulting poses. Inclusion of both the Gold and CScore scoring parameters failed to improve the predictive ability of the original CoMFA models. The subtype selectivity expressed as RBA(ER alpha/ER beta) of the test sets was predicted using the most predictive CoMFA models, as illustrated by the cross-validated r2. In each case the most selective ligands were ranked correctly illustrating the utility of this method as a prescreening tool in the development of novel estrogen receptor subtype selective ligands.

Estrogen and neuroprotection: higher constitutive expression of glutaredoxin in female mice offers protection against MPTP-mediated neurodegeneration

Incidence of Parkinson's disease is lower in women as compared with men. Although neuroprotective effect of estrogen is recognized, the underlying molecular mechanisms are unclear. MPTP (1-methyl-4-phenyl-1, 2, 3, 6, tetrahydro-pyridine), a neurotoxin that causes Parkinson's disease-like symptoms acts through inhibition of mitochondrial complex I. Administration of MPTP to male mice results in loss of dopaminergic neurons in substantia nigra, whereas female mice are unaffected. Oxidation of critical thiol groups by MPTP disrupts mitochondrial complex I, and up-regulation of glutaredoxin (a thiol disulfide oxidoreductase) is essential for recovery of complex I. Early events following MPTP exposure, such as increased AP1 transcription, loss of glutathione, and up-regulation of glutaredoxin mRNA is seen only in male mice, indicating that early response to neurotoxic insult does not occur in females. Pretreatment of female mice with ICI 182,780, estrogen receptor (ER) antagonist sensitizes them to MPTP-mediated complex I dysfunction. Constitutive expression of glutaredoxin is significantly higher in female mice as compared with males. ICI 182,780 down-regulates glutaredoxin activity in female mouse brain regions (midbrain and striatum), indicating that glutaredoxin expression is regulated through estrogen receptor signaling. Higher constitutive expression of glutaredoxin could potentially contribute to the neuroprotection seen in female mouse following exposure to neurotoxins, such as MPTP.

Therapeutic targeting in the estrogen receptor hormonal pathway

Estrogens work along with genetic changes to promote the development and growth of breast cancers. Because estrogenic hormones act via the estrogen receptors (ERs), ER-alpha and ER-beta, and the ER is present in more than half of breast tumors, this receptor has been the most widely targeted protein in breast cancer therapy. The presence of the ER in breast tumors predicts improved disease-free survival and response to selective ER modulators (SERMs), such as tamoxifen, or other forms of endocrine therapy. Suppression of ER activity by SERMs has proven to be a great benefit in the treatment of breast cancers and also in the prevention of breast cancer in women at high risk for the disease. The Study of Tamoxifen and Raloxifene trial comparing tamoxifen versus raloxifene effectiveness in breast cancer prevention is currently under way. To understand the balance of beneficial and undesirable effects of SERMs and to optimize their effectiveness, current investigations seek to characterize the genes activated or suppressed by these agents. Elucidation of the gene networks and cell signaling pathways under estrogen and SERM regulation and a clearer definition of the respective roles of ER-alpha and ER-beta and their coregulators in the actions of selective ER ligands, should enable the identification of new gene targets for therapeutic intervention and the development of novel drugs for the optimal treatment and prevention of breast cancer.

In vitro and in vivo regulation of antioxidant response element-dependent gene expression by estrogens

Understanding estrogen's regulation of phase II detoxification enzymes is important in explaining how estrogen exposure increases the risk of developing certain cancers. Phase II enzymes such as glutathione-S-transferases (GST) and quinone reductase protect against developing chemically induced cancers by metabolizing reactive oxygen species. Phase II enzyme expression is regulated by a cis-acting DNA sequence, the antioxidant response element (ARE). It has previously been reported that several antiestrogens, but not 17beta-estradiol, could regulate ARE-mediated gene transcription. Our goal was to determine whether additional estrogenic compounds could regulate ARE-mediated gene expression both in vitro and in vivo. We discovered that physiological concentrations (10 nm) of 17beta-estradiol repressed GST Ya ARE-dependent gene expression in vitro. Treatment with other endogenous and anti-, xeno-, and phytoestrogens showed that estrogen receptor/ARE signaling is ligand, receptor subtype, and cell type specific. Additionally, GST and quinone reductase activities were significantly lowered in a dose-dependent manner after 17beta-estradiol exposure in the uteri of mice. In conclusion, we have shown that 17beta-estradiol, and other estrogens, down-regulate phase II enzyme activities. We propose estrogen-mediated repression of phase II enzyme activities may increase cellular oxidative DNA damage that ultimately can result in the formation of cancer in some estrogen-responsive tissues.

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.

Transcriptional regulation by the estrogen receptor of antioxidative stress enzymes and its functional implications

We previously reported that antiestrogen-liganded estrogen receptor beta (ERbeta) transcriptionally activates the major detoxifying enzyme quinone reductase (QR) (NAD(P)H:quinone oxidoreductase). Our studies also indicate that upregulation of QR, either by overexpression or induction by tamoxifen, can protect breast cells against oxidative DNA damage caused by estrogen metabolites. We now report on the upregulation of glutathione S-transferases Pi (GST-Pi) and gamma-glutamylcysteine synthetase heavy subunit (GCSh) expression by antiestrogens. Studies indicate the regulation of GST-Pi and GCSh transcriptional activity by ER. While ER regulation is mediated by an electrophile response element (EpRE), we identified mechanistic differences in the involvement of other transcription factors. Regardless of these differences, ER beta-mediated regulation of GST-Pi and GCSh point towards an important role for ER beta in cellular protection against oxidative stress. A protective role is supported by our observation of inhibition of estrogen-induced DNA damage upon upregulation of GST-Pi and GCSh expression.

Nrf2, not the estrogen receptor, mediates catechol estrogen-induced activation of the antioxidant responsive element

The antioxidant responsive element (ARE) plays an important role in the gene expression of phase II detoxification enzymes, such as NAD(P)H:quinone oxidoreductase 1 (NQO1), and NF-E2-related factor2 (Nrf2) is the transcription factor for the ARE-driven genes. Interestingly, estrogen receptor (ER) was reported to increase NQO1 gene expression through the ARE. In this study, we investigated the role of ER and Nrf2 in ARE activation using IMR-32 cells and mouse primary astrocytes. Among tested estrogen-related compounds, only catechol estrogens (i.e. 4-hydroxyestradiol) activated the ARE. Since 4-hydroxyestradiol-induced ARE activation was not inhibited by either 17beta-estradiol or tamoxifen, and overexpression of ER-alpha decreased 4-hydroxyestradiol-induced ARE activation, ARE activation by catechol estrogen was independent of ER. Nrf2, however, was very important in the 4-hydroxyestradiol-induced ARE activation. 4-Hydroxyestradiol did not activate the ARE in Nrf2 knockout (-/-) primary astrocytes, but did activate the ARE when Nrf2 was transfected into Nrf2-/- astrocytes. In addition, dominant negative Nrf2 completely blocked 4-hydroxyestradiol-induced ARE activation in Nrf2+/+ astrocytes, and only 4-hydroxyestradiol induced Nrf2 nuclear translocation in IMR-32 cells. A selective phosphatidylinositol 3-kinase (PI3-kinase) inhibitor (LY294002) blocked 4-hydroxyestradiol-induced Nrf2 nuclear translocation and NQO1 activity induction in IMR-32 cells. Taken together, these observations suggest that 4-hydroxyestradiol activates the ARE by a PI3-kinase-Nrf2 dependent mechanism, not involving ER.

Functional implications of antiestrogen induction of quinone reductase: inhibition of estrogen-induced deoxyribonucleic acid damage

Recent studies have shown that the antiestrogens tamoxifen and raloxifene may protect against breast cancer, presumably because of a blockade of estrogen receptor (ER)-mediated transcription. Another possible explanation is that antiestrogen-liganded ER transcriptionally induces genes that are protective against cancer. We previously reported that antiestrogen-liganded ERbeta transcriptionally activates the major detoxifying enzyme quinone reductase (QR) [NAD(P)H:quinone oxidoreductase]. It has been established that metabolites of estrogen, termed catecholestrogens, can form DNA adducts and cause oxidative DNA damage. We hypothesize that QR inhibits estrogen-induced DNA damage by detoxification of reactive catecholestrogens. We report here that physiological concentrations of 17beta-estradiol cause oxidative DNA damage, as measured by levels of 8- hydroxydeoxyguanine, in ER-positive MCF7 breast cancer cells, MDA-MB-231 breast cancer cells (ERalpha negative/ERbeta positive) and nontumorigenic MCF10A breast epithelial cells (very low ER), which is dependent on estrogen metabolism. Estrogen-induced 8-hydroxydeoxyguanine was inversely correlated to QR and ERbeta levels and was followed by downstream induction of the DNA repair enzyme XPA. Trans-hydroxytamoxifen, raloxifene, and the pure antiestrogen ICI-182,780 protected against estradiol-mediated damage in breast cancer cells containing ERbeta. This is most likely due to the ability of these antiestrogens to activate expression of QR via ERbeta. We conclude that up-regulation of QR, either by overexpression or induction by tamoxifen, can protect breast cells against oxidative DNA damage caused by estrogen metabolites, representing a possible novel mechanism of tamoxifen prevention against breast cancer.