4-hydroxyestradiol and Breast-Neoplasms

Long-term exposure to estrogens influences the development of breast cancer in women, but the precise mechanisms involved are not clearly defined. Our working hypothesis is that estrogen modulates this process by two separate processes. One involves the binding of estradiol to estrogen receptor (ER) alpha with stimulation of cell proliferation. Errors in DNA occurring during replication result in fixed mutations when not repaired. The other process results from the formation of genotoxic metabolites of estradiol, which can bind to DNA, cause depurination, and result in mutations. Our collaborative group, funded by a Department of Defense Center of Excellence grant, has examined this hypothesis using a variety of experimental methods. Estradiol and its catechol-estrogen metabolite 4-OH-estradiol causes mutations in cell culture systems and can transform benign MCF-10F cells, allowing them to cause tumors in SCID mice. We have demonstrated loss of heterozygosity and gains and losses of DNA segments by comparative genomic hybridization methodology. The depurinated estradiol-guanine and -adenine adducts are measurable in MCF-7 breast cancer cells in culture and in mouse mammary tissue. The double transgenic, alpha estrogen receptor knockout/Wnt-1 knockin mouse model allows us to dissect out the separate effects of ER-mediated and ER-independent actions of estradiol. Knock out of the ER alpha delays the onset of breast tumors in this model, demonstrating a role of receptor-mediated actions. Oophorectomy delays the onset of tumors and reduces overall incidence, providing evidence for an ER-independent effect. Taken together, these data suggest that both ER-dependent and genotoxic ER-independent effects of estradiol mediate breast cancer development.

Topics: Animals; Breast Neoplasms; Estradiol; Estrogen Receptor alpha; Estrogens; Estrogens, Catechol; Female; Humans; Mice; Mice, SCID; Mutation

C2- and C4-position 17beta-estradiol metabolites play an important role in breast carcinogenesis. 2-Hydroxyestradiol and 4-hydroxyestradiol are implicated in tumorigenesis via two pathways. These pathways entail increased cell proliferation and the formation of reactive oxygen species that trigger an increase in the likelihood of deoxyribonucleic acid mutations. 2-Methoxyestradiol, a 17beta-estradiol metabolite, however, causes induction of apoptosis in transformed and tumor cells; thus exhibiting an antiproliferative effect on tumor growth. The 4-hydroxyestradiol:2-methoxyestradiol and 2-hydroxyestradiol:2-methoxyestradiol ratios therefore ought to be taken into account as possible indicators of carcinogenesis.

Topics: 2-Methoxyestradiol; Animals; Breast Neoplasms; Cell Proliferation; Estradiol; Estrogens, Catechol; Humans

Certain estrogen metabolites can act as carcinogens in in vitro and animal experiments. The clinical relevance remains unclear. However, in the presence of factors that could influence estradiol metabolism, such as smoking or genetic polymorphisms, it seems prudent to prefer transdermal therapy to minimize the production of possible toxic metabolites. In addition, various defense mechanisms operate in the physiologic human body that prevent the formation of possible toxic intermediate products of estradiol metabolism, especially during oxidative stress. Only under rare special conditions is it conceivable that the human body cannot react sufficiently.

Topics: Administration, Cutaneous; Animals; Breast Neoplasms; Carcinogens; Estradiol; Estriol; Estrogen Replacement Therapy; Estrogens, Catechol; Female; Humans; Steroid 16-alpha-Hydroxylase

Topics: Breast Neoplasms; Carcinogenesis; Carcinogens; Cytochrome P-450 CYP1B1; Down-Regulation; Estradiol; Estrogens, Catechol; Female; Flavanones; Flavonoids; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Humans; MCF-7 Cells

Estrogen (17β-estradiol, E2) undergoes oxidative metabolism by CYP1B1 to form 4-hydroxyestradiol (4-OHE2), a putative carcinogenic metabolite of estrogen. Our previous study showed that 4-OHE2-induced production of reactive oxygen species contributed to neoplastic transformation of human breast epithelial (MCF-10A) cells. In this study, 4-OHE2, but not E2, increased the expression of heme oxygenase-1 (HO-1), a sensor and regulator of oxidative stress, in MCF-10A cells. Silencing the HO-1 gene in MCF-10A cells suppressed 4-OHE2-induced cell proliferation and transformation. In addition, subcutaneous administration of 4-OHE2 markedly enhanced the growth of the MDA-MB-231 human breast cancer xenografts, which was retarded by zinc protoporphyrin, a pharmacological inhibitor of HO-1. 4-OHE2-induced HO-1 expression was mediated by NF-E2-related factor 2 (Nrf2). We speculate that an electrophilic quinone formed as a consequence of oxidation of 4-OHE2 binds directly to Kelch-like ECH-associated protein 1 (Keap1), an inhibitory protein that sequesters Nrf2 in the cytoplasm. This will diminish association between Nrf2 and Keap1. 4-OHE2 failed to interrupt the interaction between Keap1 and Nrf2 and to induce HO-1 expression in Keap1-C273S or C288S mutant cells. Lano-LC-ESI-MS/MS analysis in MCF-10A-Keap1-WT cells which were treated with 4-OHE2 revealed that the peptide fragment containing Cys288 gained a molecular mass of 287.15 Da, equivalent to the addition of a single molecule of 4-OHE2-derived ortho-quinones.

Topics: Animals; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Cell Transformation, Neoplastic; Disease Models, Animal; Epithelial Cells; Estrogens, Catechol; Female; Gene Expression; Gene Expression Regulation, Neoplastic; Heme Oxygenase-1; Heterografts; Humans; Mice; Mice, Knockout; NF-E2-Related Factor 2; Protein Binding; Response Elements; Tumor Burden

Clinical study of breast cancer patients in Chicago, IL, USA.. Ascertain the utility of measurements of single-strand breaks (SSB) in DNA for assessment of breast cancer risk.. Fine-needle aspirates of the breast, SSB by nick translation, percent breast density (PBD), Gail model risk, cumulative methylation index (CMI), enzymes of DNA repair and tissue antioxidants.. DNA repair enzymes and 4-hydroxyestradiol were negatively associated with SSB; CMI and PBD were positively associated.. Quantitative measurement of SSBs by this procedure indicates the relative number of SSBs and is related to promoter methylation, antioxidant availability and percent breast density.

Topics: Adult; Breast Density; Breast Neoplasms; DNA Breaks, Single-Stranded; DNA Damage; DNA Repair Enzymes; Estrogens; Estrogens, Catechol; Female; Humans; Middle Aged; Risk

Leptin, a hormone with multiple biological actions, is produced predominantly by adipose tissue. Among its functions, leptin can stimulate tumour cell growth. Oestrogen receptor α (ERα), which plays an essential role in breast cancer development, can be transcriptionally activated in a ligand-independent manner. In this study, we investigated the effect of leptin on CYP1B1 expression and its mechanism in breast cancer cells. Leptin induced CYP1B1 protein, messenger RNA expression and promoter activity in ERα-positive MCF-7 cells but not in ERα-negative MDA-MB-231 cells. Additionally, leptin increased 4-hydroxyoestradiol in MCF-7 cells. Also, ERα knockdown by siRNA significantly blocked the induction of CYP1B1 expression by leptin, indicating that leptin induced CYP1B1 expression via an ERα-dependent mechanism. Transient transfection with CYP1B1 deletion promoter constructs revealed that the oestrogen response element (ERE) plays important role in the up-regulation of CYP1B1 by leptin. Furthermore, leptin stimulated phosphorylation of ERα at serine residues 118 and 167 and increased ERE-luciferase activity, indicating that leptin induced CYP1B1 expression by ERα activation. Finally, we found that leptin activated ERK and Akt signalling pathways, which are upstream kinases related to ERα phosphorylation induced by leptin. Taken together, our results indicate that leptin-induced CYP1B1 expression is mediated by ligand-independent activation of the ERα pathway as a result of the activation of ERK and Akt in MCF-7 cells.

Topics: Aryl Hydrocarbon Hydroxylases; Breast Neoplasms; Cell Line, Tumor; Cytochrome P-450 CYP1B1; Estrogen Receptor alpha; Estrogens, Catechol; Female; Humans; Leptin; MCF-7 Cells; Phosphorylation; Response Elements; RNA, Messenger; RNA, Small Interfering; Signal Transduction; Transcriptional Activation; Transfection; Up-Regulation

Germline mutations in BRCA1 predispose carriers to a high incidence of breast and ovarian cancers. BRCA1 functions to maintain genomic stability through critical roles in DNA repair, cell-cycle arrest, and transcriptional control. A major question has been why BRCA1 loss or mutation leads to tumors mainly in estrogen-regulated tissues, given that BRCA1 has essential functions in all cell types. Here, we report that estrogen and estrogen metabolites can cause DNA double-strand breaks (DSB) in estrogen receptor-α-negative breast cells and that BRCA1 is required to repair these DSBs to prevent metabolite-induced genomic instability. We found that BRCA1 also regulates estrogen metabolism and metabolite-mediated DNA damage by repressing the transcription of estrogen-metabolizing enzymes, such as CYP1A1, in breast cells. Finally, we used a knock-in human cell model with a heterozygous BRCA1 pathogenic mutation to show how BRCA1 haploinsufficiency affects these processes. Our findings provide pivotal new insights into why BRCA1 mutation drives the formation of tumors in estrogen-regulated tissues, despite the general role of BRCA1 in DNA repair in all cell types.

Topics: BRCA1 Protein; Breast; Breast Neoplasms; Cytochrome P-450 CYP1A1; DNA Breaks, Double-Stranded; DNA Repair; Estradiol; Estrogens; Estrogens, Catechol; Female; Genomic Instability; Humans; MCF-7 Cells

The current study was undertaken to determine the involvement of cAMP/PKA and MAPK-mediated signalling pathways in the regulation of cell proliferation by hydroxylated metabolites of 17β-estradiol (E2).. MCF-7, human breast cancer cells, were cultured in phenol red-free DMEM and treated with 1 nM 2-OH-E2 or 4-OH-E2. E2 was used as a positive control. Cell proliferation was measured using the BrdU incorporation assay. Cellular levels of cAMP and PKA were determined using ELISA kits. ERK1/2 protein expression was evaluated by Western Blot analysis. To determine the involvement of different intracellular pathways in the regulation of cell proliferation appropriate activators or inhibitors were used.. Hydroxylated estrogens, as E2, exhibited no influence on cAMP accumulation and PKA activation. In concomitant treatments with forskolin, cell proliferation decreased to the amount noted under the influence of forskolin alone. A PKA inhibitor (PKI) had no statistically significant effect on proliferation stimulated by E2 and its hydroxylated metabolites. Phospho-ERK1/2 protein expression in cells stimulated with E2, 2-OH-E2 and 4-OH-E2 was not significantly different from the control. However, co-treatment with both PD98059 and E2 or its hydroxylated metabolites reversed the effect of tested compounds on cell proliferation.. We have shown that E2 hydroxylated metabolites do not activate cAMP/PKA in breast cancer cells and confirm previously published data, which showed a lack of ERK1/2 activation in a breast cancer cell line. The observed reversible action of PD98059 on cell proliferation can be explained by the fact that hydroxylated estrogens, as E2, stimulate secretion of a number of growth factors, which affect MAPK activity, suggested by Lobenhofer et al. (2000).

Topics: Breast Neoplasms; Carcinoma; Cell Line, Tumor; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Drug Evaluation, Preclinical; Enzyme Activation; Estradiol; Estrogens; Estrogens, Catechol; Female; Humans; Hydroxylation; MAP Kinase Signaling System; Signal Transduction

Evidence is accumulating that certain estradiol metabolites may play a more important role in enhancing breast cancer risk than their parent substance - 17 β-estradiol (E2). Of special interest are the metabolites 2-hydroxyestradiol (2-OH-E2), which can show anticarcinogenic effect, while that of 4-hydroxyestradiol (4-OH-E2) may be rather procarcinogenic. We suggest that local activation of cytochrome P450 enzymes - CYP1A1 and/or CYP1B1 - by E2 could generate active metabolites that affect the apoptosis and thereby promote mammary carcinogenesis. Over the last several years, there has been accumulating evidence that, apart from the receptor-mediated (extrinsic) pathway, also the mitochondrial (intrinsic) pathway plays a role in E2-induced apoptosis. In the present study, we have compared the effect of these metabolites and their parent substance E2 on caspase-8 and caspase-9 activity as well as on the end step of apoptosis DNA fragmentation.. MCF-7 human breast cancer cells (ATCC) were routinely cultured in DMEM supplemented with 10 % heat-inactivated FBS. Forty-eight hours before experiments, the medium was removed and replaced by DMEM without phenol red supplemented with 5 % heat-inactivated fetal bovine serum. For determination of caspase-8 and caspase-9 activities, MCF-7 cells were seeded in 48-well culture plates at a density of 15 x 104 cells/well and incubated with 1 nM E2 and its metabolites for 24 h. DNA fragmentation, caspase-8 and caspase-9 activities were determined in cell lysates by ELISAs. The CYP1A1 and CYP1B1 protein expression was evaluated by Western blotting.. E2 had no effect on CYP1A1 protein levels. However an increase in CYP1B1 protein expression was observed within 48 hrs of exposure. None of the compounds tested changed caspase-8 activity as compared to the controls. Statistically significant decrease in caspase-9 activity and DNA fragmentation was observed in the presence of E2 and 4-OH-E2, but no significant effect was found for the metabolite 2-OH-E2.. It was found that local activation of cytochrome P450 enzyme CYP1B1 by E2 may change the local metabolic activation pathway into 4-OH-E2 as well as the activation of caspase-9 (a part of the intrinsic mitochondrial apoptotic pathway) in the antiapoptotic effect of E2 and 4-OH-E2.

Topics: Apoptosis; Aryl Hydrocarbon Hydroxylases; Breast Neoplasms; Caspase 8; Caspase 9; Cell Line, Tumor; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1B1; DNA Fragmentation; Enzyme Activation; Estradiol; Estrogens; Estrogens, Catechol; Female; Humans; Mitochondria

Current models of breast cancer risk prediction do not directly reflect mammary estrogen metabolism or genetic variability in exposure to carcinogenic estrogen metabolites.. We developed a model that simulates the kinetic effect of genetic variants of the enzymes CYP1A1, CYP1B1, and COMT on the production of the main carcinogenic estrogen metabolite, 4-hydroxyestradiol (4-OHE(2)), expressed as area under the curve metric (4-OHE(2)-AUC). The model also incorporates phenotypic factors (age, body mass index, hormone replacement therapy, oral contraceptives, and family history), which plausibly influence estrogen metabolism and the production of 4-OHE(2). We applied the model to two independent, population-based breast cancer case-control groups, the German GENICA study (967 cases, 971 controls) and the Nashville Breast Cohort (NBC; 465 cases, 885 controls).. In the GENICA study, premenopausal women at the 90th percentile of 4-OHE(2)-AUC among control subjects had a risk of breast cancer that was 2.30 times that of women at the 10th control 4-OHE(2)-AUC percentile (95% CI: 1.7-3.2, P = 2.9 × 10(-7)). This relative risk was 1.89 (95% CI: 1.5-2.4, P = 2.2 × 10(-8)) in postmenopausal women. In the NBC, this relative risk in postmenopausal women was 1.81 (95% CI: 1.3-2.6, P = 7.6 × 10(-4)), which increased to 1.83 (95% CI: 1.4-2.3, P = 9.5 × 10(-7)) when a history of proliferative breast disease was included in the model.. The model combines genotypic and phenotypic factors involved in carcinogenic estrogen metabolite production and cumulative estrogen exposure to predict breast cancer risk.. The estrogen carcinogenesis-based model has the potential to provide personalized risk estimates.

Topics: Adult; Algorithms; Area Under Curve; Aryl Hydrocarbon Hydroxylases; Breast Neoplasms; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1B1; Estradiol; Estrogens; Estrogens, Catechol; Female; Genetic Predisposition to Disease; Genotype; Humans; Middle Aged; Models, Theoretical; Phenotype; Risk Factors

Sex Hormone-Binding Globulin (SHBG) - specific carrier for sex steroids - regulates hormone bioavailable fraction and estrogen signaling system in breast cancer cells. This study was conducted to elucidate the effects of hydroxylated estrogen (E2) metabolites (2-OH-E2 and 4-OH-E2) on sex hormone binding globulin (SHBG) mRNA and protein expression as well as on intracellular and extracellular SHBG levels.. MCF-7 human breast cancer cells were cultured with 2-OH-E2 or 4-OH-E2 in concentration of 1, 10 and 100 nM for 24 h, 17β-estradiol being used as a positive control. SHBG levels were measured in medium and cells by ELISA, SHBG mRNA expression was evaluated by real-time-PCR and protein expression by Western blot analysis.. 4-OH-E2 in high doses and 2-OH-E2 in the highest dose, while 17β-estradiol in all doses used increased intracellular but not extracellular SHBG levels. Both metabolites increased SHBG mRNA expression, the rank order of potency being E2 > 4-OH-E2 > 2-OH-E2. Both E2 and its metabolites increased SHBG protein expression.. Although the metabolites showed a lower potency than 17β-estradiol, further studies are needed to clarify whether hydroxylated metabolites of E2 are potent ligands for SHBG.

Topics: Blotting, Western; Breast Neoplasms; Cell Line, Tumor; Estradiol; Estrogens, Catechol; Female; Gene Expression; Humans; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sex Hormone-Binding Globulin

A 17beta-estradiol (E(2)) is hydrolyzed to 2-hydroxy-E(2) (2-OHE(2)) and 4-hydroxy-E(2) (4-OHE(2)) via cytochrome P450 (CYP) 1A1 and 1B1, respectively. In estrogen target tissues including the mammary gland, ovaries, and uterus, CYP1B1 is highly expressed, and 4-OHE(2) is predominantly formed in cancerous tissues. In this study, we investigated the inhibitory effects of chrysoeriol (luteorin-3'-methoxy ether), which is a natural methoxyflavonoid, against activity of CYP1A1 and 1B1 using in vitro and cultured cell techniques. Chrysoeriol selectively inhibited human recombinant CYP1B1-mediated 7-ethoxyresorufin-O-deethylation (EROD) activity 5-fold more than that of CYP1A1-mediated activity in a competitive manner. Additionally, chrysoeriol inhibited E(2) hydroxylation was catalyzed by CYP1B1, but not by CYP1A1. Methylation of 4-OHE(2), which is thought to be a detoxification process, was not affected by the presence of chrysoeriol. In human breast cancer MCF-7 cells, chrysoeriol did not affect the gene expression of CYP1A1 and 1B1, but significantly inhibited the formation of 4-methoxy E(2) without any effects on the formation of 2-methoxy E(2). In conclusion, we present the first report to show that chrysoeriol is a chemopreventive natural ingredient that can selectively inhibit CYP1B1 activity and prevent the formation of carcinogenic 4-OHE(2) from E(2.).

Topics: 2-Methoxyestradiol; Aryl Hydrocarbon Hydroxylases; Biocatalysis; Breast Neoplasms; Carcinogens; Catechol O-Methyltransferase; Cell Line, Tumor; Chemoprevention; Culture Media, Conditioned; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1B1; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; Cytosol; Enzyme Inhibitors; Estradiol; Estrogens, Catechol; Female; Flavones; Flavonoids; Gene Expression; Glucuronidase; Humans; Hydroxylation; Kinetics; Methylation; Oxazines; Recombinant Proteins; Sulfatases

Catechol estrogens, especially 4-hydroxylated metabolites of 17beta-estradiol (E(2)), are responsible for estrogen-induced carcinogenesis. 4-Hydroxyestradiol (4-OHE(2)), a major metabolite of E(2) formed preferentially by cytochrome P-450 1B1, is oxidized to E(2)-3,4-quinone, which can react with DNA to yield the depurinating adducts 4-OHE(2)-1-N3Ade and 4-OHE(2)-1-N7Gua. The apurinic sites generated by the loss of these depurinating adducts induce mutations that could lead to cancer initiation. In this study, we have evaluated the effects of N-acetylcysteine (NAcCys) on the metabolism of two cell lines, MCF-10F (a normal human breast epithelial cell line) and E6 (a normal mouse mammary epithelial cell line), treated with 4-OHE(2) or its reactive metabolite, E(2)-3,4-quinone. Extensive HPLC with electrochemical detection and UPLC-MS/MS analyses of the cell media demonstrated that the presence of NAcCys very efficiently shifted the estrogen metabolism toward protective methoxylation and conjugation pathways in multiple ways, whereas formation of depurinating DNA adducts was inhibited. Protection by NAcCys seems to be similar in both cell lines, irrespective of their origin (human or mouse) or the presence of estrogen receptor-alpha. This finding suggests that NAcCys, a common dietary supplement, could be used as a potential chemopreventive agent to block the initial step in the genotoxicity caused by catechol estrogen quinones.

Topics: Acetylcysteine; Animals; Antioxidants; Breast; Breast Neoplasms; Cell Line; DNA Adducts; Estradiol; Estrogens, Catechol; Female; Humans; Mammary Glands, Animal; Mammary Neoplasms, Experimental; Mice

Estrogen is converted by cytochrome P450 1B1 to 4-hydroxyestradiol (4-OHE(2)), a putative carcinogenic metabolite of estrogen. This catechol estrogen metabolite is oxidized further to produce a reactive quinone via semiquinone. Redox cycling between 4-OHE(2) and its quinoid generates reactive oxygen species (ROS). ROS not only causes oxidative DNA damage but also promotes neoplastic transformation of initiated cells. In the present study, 4-OHE(2) induced anchorage-independent colony formation in human mammary epithelial cells (MCF-10A). MCF-10A cells treated with 4-OHE(2) exhibited increased accumulation of intracellular ROS. The antioxidant N-acetyl-l-cysteine inhibited the neoplastic transformation induced by 4-OHE(2). ROS overproduced by 4-OHE(2) increased the nuclear translocation of nuclear factor-kappaB (NF-kappaB) and its DNA binding through induction of IkappaB kinase alpha (IKKalpha) and IKKbeta activities. The inhibition of the IKK activities with Bay 11-7082 significantly reduced the anchorage-independent growth induced by 4-OHE(2). The 4-OHE(2)-induced activation of extracellular signal-regulated kinase and Akt resulted in enhanced IKK activities and phosphorylation of IkappaBalpha, thereby inducing NF-kappaB activation and anchorage-independent growth of MCF-10A cells. In conclusion, ROS, concomitantly overproduced during redox cycling of 4-OHE(2), activates IKK signaling, which may contribute to neoplastic transformation of MCF-10A cells.

Topics: Breast; Breast Neoplasms; Cell Adhesion; Cell Growth Processes; Cell Transformation, Neoplastic; DNA; Enzyme Activation; Epithelial Cells; Estradiol; Estrogens, Catechol; Extracellular Signal-Regulated MAP Kinases; Humans; I-kappa B Kinase; NF-kappa B; Oncogene Protein v-akt; Oxidation-Reduction; Phosphorylation; Reactive Oxygen Species; Signal Transduction

The tissue concentrations of the female sex hormone 17beta-estradiol (E2) and its reactive catechol metabolites such as 4-hydroxyestradiol (4-HO-E2) play important roles in hormonal carcinogenesis. They are influenced by the activity of local enzymes involved in the metabolic activation and inactivation of E2. In the mammary gland, catechol estrogens are predominately inactivated by catechol-O-methyltransferase (COMT). Food supplements containing the soy isoflavones genistein and daidzein are consumed because they are believed to protect from breast cancer; however, this proposed benefit is controversial. The aim of the present study was to investigate the influence of soy isoflavones on the gene expression and activity of COMT in cultured human mammary adenocarcinoma MCF-7 cells. Levels of COMT messenger RNA (mRNA) were determined by reverse transcription/competitive polymerase chain reaction and COMT activity was determined by high-performance liquid chromatography analysis of the methylation products of both the model substrate quercetin and the physiological relevant substrate 4-HO-E2. Our study demonstrates for the first time that soy isoflavones at hormonally active concentrations cause a significant reduction of both COMT mRNA levels and COMT activity as well as of the methylation of 4-HO-E2. Experiments using the estrogen receptor (ER) antagonist ICI 182,780 support a role of the ER in the isoflavone-induced down-regulation of COMT expression. Thus, this study not only demonstrates that hormonally active concentrations of soy isoflavones inhibit the detoxification of catechols in this human breast cancer cell line but also implies that diet might influence COMT activity to a greater extent than heretofore recognized.

Topics: Breast Neoplasms; Catechol O-Methyltransferase; Cell Line, Tumor; Cell Proliferation; Diet; Estradiol; Estrogens, Catechol; Female; Fulvestrant; Gene Expression Regulation, Neoplastic; Glycine max; Humans; Models, Biological; Models, Chemical; Receptors, Estrogen

Certain estradiol metabolites may play a pivotal role in breast carcinogenesis. Of special interest are the metabolites 2-hydroxyestradiol (2-OHE2), which can react anti-carcinogenically, and 4-hydroxyestradiol (4-OHE1) and 16a-hydroxyestrone (16-OHE1), which may have procarcinogenic potential. In the present study, we have compared for the first time the effect of these metabolites and their parent substance 17beta-estradiol (E2) on proliferation, apoptosis, apoptosis markers and markers of metastatic property of human breast cancer cells.. MCF-7 cells (human estrogen-receptor positive metastatic breast cancer cell line) were incubated with the estrogens at concentrations of 0.1-100 nM. Cell proliferation rate was measured by the ATP-assay. Apoptosis was measured by cell death assay and the apoptosis markers cytochrome C, Bcl-2, Fasl and p53 were determined in cell lysates by ELISAs. The markers of metastatic property of the cell line, VEGF and MCP-1 were measured in the cell supernatant by ELISAs.. The estrogens E2, 4-OHE2 and 16-OHE1 display a proliferative effect on MCF-7 cells which is accompanied by a down-regulation of apoptosis. Various markers of apoptosis such as Bcl-2, cytochrome C and p53 appear to be involved. No significant effect was found for the metabolite 2-OHE2. VEGF and MCP-1 were up-regulated by E2 and 16-OHE1, whereas 2-OHE2 and 4-OHE2 did not show any effect.. The most potent estrogen regarding proliferation, apoptosis and metastasis of breast cancer cells seems to be estradiol. However, the estradiol metabolites 4-OHE2 and 16-OHE1 elicit similar properties on cell proliferation, apoptosis and metastasis as compared to estradiol but only at higher concentrations. In contrast 2-OHE2 did not show any significant effect on these parameters. Thus, intracellular estradiol metabolism may determine an individual's risk for breast carcinogenesis.

Topics: Apoptosis; Biomarkers, Tumor; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Cytochromes c; Down-Regulation; Enzyme-Linked Immunosorbent Assay; Estradiol; Estriol; Estrogens; Estrogens, Catechol; Fas Ligand Protein; Female; Humans; Membrane Glycoproteins; Proto-Oncogene Proteins c-bcl-2; Tumor Necrosis Factors; Tumor Suppressor Protein p53; Up-Regulation

An elevated incidence of breast cancer in women has been associated with prolonged exposure to high levels of estrogens. Our laboratory demonstrated that treatment of the immortalized human breast epithelial cells MCF-10F with 17beta-estradiol (E2), 4-hydroxyestradiol (4-OHE2) or 2-hydroxyestradiol (2-OHE2) induces phenotypical changes indicative of neoplastic transformation. MCF-10F cells treated with E2, 4-OHE2 or 2-OHE2 formed colonies in agar methocel and lost their ductulogenic capacity in collagen, expressing phenotypes similar to those induced by the carcinogen benzo[a]pyrene. To investigate whether the transformation phenotypes were associated with genomic changes, cells treated with E2, 4-OHE2 or 2-OHE2 at different doses were analyzed using microsatellite markers. Since microsatellite instability (MSI) and loss of heterozygosity (LOH) in chromosomes 13 and 17 have been reported in human breast carcinomas, we tested these parameters in MCF-10F cells treated with E2, 2-OHE2, or 4-OHE2 alone or in combination with the antiestrogen ICI182780. MCF-10F cells treated with E2 or 4-OHE2, either alone or in combination with ICI182780, exhibited LOH in the region 13q12.3 with the marker D13S893 located at approximately 0.8 cM telomeric to BRCA2. Cells treated with E2 or 4-OHE2 at doses of 0.007 and 70 nM and 2-OHE2 only at a higher dose (3.6 microM) showed a complete loss of 1 allele with D13S893. For chromosome 17, differences were found using the marker TP53-Dint located in exon 4 of p53. Cells treated with E2 or 4-OHE2 at doses of 0.007 nM and 70 nM and 2-OHE2 only at a higher dose (3.6 microM) exhibited a 5 bp deletion in p53 exon 4. Our results show that E2 and its catechol estrogen metabolites are mutagenic in human breast epithelial cells. ICI182780 did not prevent these mutations, indicating that the carcinogenic effect of E2 is mainly through its reactive metabolites 4-OHE2 and 2-OHE2, with 4-OHE2 and E2 being mutagenic at lower doses than 2-OHE2.

Topics: Base Sequence; Breast; Breast Neoplasms; Cell Culture Techniques; Cell Transformation, Neoplastic; Epithelial Cells; Estradiol; Estrogens, Catechol; Female; Humans; Loss of Heterozygosity; Molecular Sequence Data; Mutagenesis; Phenotype

In malignant breast cancer, estrogen metabolism is altered, favoring the accumulation of hydroxyestradiols, which can generate free radicals. These reactive species can activate matrix metalloproteinases (MMPs), which in turn can hydrolyze the proteins of the extracellular matrix (ECM) that act as a barrier to tumor cell passage. The aim of this study was to determine whether reactive oxygen species generated by 4-hydroxyestradiol (4-OHE(2)) can activate MMP-2 and then enhance the invasiveness of breast cancer cells MDA-MB-231 in vitro. Enzymatic assay and gel zymography demonstrated that 4-OHE(2) at a concentration as low as 10(-8) M led to the conversion of proMMP-2 to active MMP-2. Activation of proMMP-2 by 4-OHE(2) was inhibited by the Cu,Zn-SOD supporting the involvement of the free radical superoxide anion (O(2)(*-)). Using invasion chambers coated with matrigel (artificial ECM), 4-OHE(2) (10(-8) M) enhanced the invasiveness of MDA-MB-231 breast cancer cells by 3-fold. The addition of Cu,Zn-SOD reduced the invasiveness of MDA-MB-231 cells by more than 2-fold, supporting the involvement of O(2)(*-) generated by 4-OHE(2). Addition of an MMP-2 inhibitor completely inhibited the enhancement of invasiveness induced by 4-OHE(2), which demonstrates the importance of activating MMP-2 by 4-OHE(2). On the other hand, estradiol, which does not have a catechol structure, did not generate free radicals, and it could not activate proMMP-2 or enhance the invasiveness of beast cancer cells. Although these data need to be confirmed in an animal model, this study suggests that the accumulation of 4-OHE(2) in breast tumors could enhance the invasiveness of breast cancer cells.

Topics: Breast Neoplasms; Collagen; Culture Media, Conditioned; Drug Combinations; Enzyme Activation; Estradiol; Estrogens, Catechol; Extracellular Matrix; Female; Humans; Laminin; Matrix Metalloproteinase 2; Neoplasm Invasiveness; Oxygen; Peptide Fragments; Proteoglycans; Reactive Oxygen Species; Superoxide Dismutase; Superoxides

A novel mechanistic hypothesis is proposed which suggests that hyperhomocysteinemia is a risk factor for the development of estrogen-induced hormonal cancer in humans. Mechanistically, hyperhomocysteinemia may exert its pathogenic effects largely through metabolic accumulation of intracellular S-adenosyl-L-homocysteine, a strong non-competitive inhibitor of the catechol-O-methyltransferase-mediated methylation metabolism of endogenous and exogenous catechol estrogens (mainly 2-hydroxyestradiol and 4-hydroxyestradiol). While a strong inhibition of the methylation metabolism of 2-hydroxyestradiol would decrease the formation of 2-methoxyestradiol (an antitumorigenic endogenous metabolite of 17beta-estradiol), an inhibition of the methylation of 4-hydroxyestradiol would lead to accumulation of this hormonally-active and strongly procarcinogenic catechol estrogen metabolite. Both of these effects resulting from inhibition of the methylation metabolism of catechol estrogens would facilitate the development of estrogen-induced hormonal cancer in the target organs. This hypothesis also predicts that adequate dietary intake of folate, vitamin B6, and vitamin B12 may reduce hyperhomocysteinemia-associated risk for hormonal cancer. Experimental studies are warranted to determine the relations of hyperhomocysteinemia with the altered circulating or tissue levels of 4-hydroxyestradiol and 2-methoxyestradiol and also with the altered risk for estrogen-induced hormonal cancer.

Topics: Anticarcinogenic Agents; Breast Neoplasms; Catechol O-Methyltransferase; Catechol O-Methyltransferase Inhibitors; Estradiol; Estrogens; Estrogens, Catechol; Female; Folic Acid; Humans; Hyperhomocysteinemia; Kinetics; Methylation; Models, Biological; Mutagenicity Tests; Neoplasms, Experimental; Neoplasms, Hormone-Dependent; Risk Factors; S-Adenosylhomocysteine; Uterine Neoplasms; Vitamin B 12; Vitamin B 6

The main goal of our study was to assess estrogen contents of breast tumor tissues, having different estrogen receptor status, in relation to long-term follow-up of patients.. Twenty-one breast cancer cases, all collected from January 1986 to January 1988 at the M. Ascoli Cancer Hospital Centre in Palermo, were included in the study and compared with 6 healthy women as a control group. Average follow-up time of patients was 144 +/- 10 months. The estrogen receptor status of tissues was determined by both ligand binding and immunohistochemical assays. A high performance liquid chromatography-based approach, jointly with gas chromatography/mass spectrometry, was used to identify and measure main estrogens, various hydroxyestrogens, and their methoxy derivatives in both normal and tumor tissues.. Although variable concentrations of hydroxylated estrogens were detected, they consistently accounted for >80% of all of the estrogens. Significantly greater amounts of both 2- and 4-hydroxyestradiol, along with a marked increase of 16 alpha-hydroxyestrone (OHE(1)), were observed in cancer with respect to normal breast tissues. A significant positive association was observed with elevated 16 alpha OHE(1) (P = 0.015) in patients alive, leading to significantly lower (P = 0.043) 2OHE(1):16 alpha OHE(1) ratio values. Conversely, ratio values of 4:2 hydroxy+methoxy estrogens was significantly lower (P = 0.006) in deceased patients. Using cutoff values of 1.2 for 4:2 hydroxy+methoxy ratio and 150 fmol/mg tissue for 16 alpha OHE(1) we achieved a clear-cut separation of patients, with over-cutoff patients having 147 months and under cutoff patients showing only 47 months median survival time (P = 0.00008).. Our data imply that individual hydroxyestrogens may have a distinct role in the onset and the clinical progression of breast cancer, with greater 16 alpha OHE(1) levels being in turn associated to cancer with respect to normal tissues and to a prolonged survival of breast cancer patients.

Topics: Adult; Aged; Binding Sites; Breast Neoplasms; Chromatography, High Pressure Liquid; Estradiol; Estrogens; Estrogens, Catechol; Female; Follow-Up Studies; Humans; Hydroxyestrones; Immunoenzyme Techniques; Middle Aged; Receptors, Estrogen; Survival Rate

Certain estrogen metabolites are involved in carcinogenesis and the development of resistance to methotrexate (MTX). In this study, we determined whether these well-established biological effects correlate with the relative efficiency of several estrogen metabolites to induce DNA strand breaks in the presence of copper, and investigated the potential enhancing effect of reduced nicotinamide adenine dinucleotide (NADH). DNA strand breaks induced by estradiol metabolites were measured by the conversion of supercoiled phage phiX-174 RF1 DNA to open circular and linear forms. The most active catecholestrogens were the 4-hydroxy derivatives, which produced about 2.5 times more DNA double strand breaks than the 2-hydroxy derivatives, while estradiol and 16alpha-hydroxyestrone were inactive. In addition, our results show that 4-hydroxyestradiol (4-OHE2) at physiological concentrations was capable of exhibiting DNA cleaving activity. The formation of these catecholestrogen-induced DNA strand breaks was associated with the utilization of oxygen and the generation of H2O2, because catalase inhibited the DNA cleaving activity of 4-OHE2. Interestingly, we also observed that NADH enhanced the induction of DNA strands breaks by 4-OHE2/Cu(II), probably by perpetuating the redox cycle between the quinone and the semiquinone forms of the catecholestrogen. In conclusion, this study demonstrated that the relative efficiency of 2-, and 4-hydroxyestrogen in carcinogenesis and for the enhancement of MTX resistance correlates with their relative capability to induce DNA strand breaks. In order to inhibit these estrogen-mediated biological effects, it may be important to develop different strategies to block the production of reactive oxygen species by the catecholestrogen-redox cycle.

Topics: Bacteriophage phi X 174; Breast Neoplasms; Copper; DNA Damage; DNA, Superhelical; DNA, Viral; Electrophoresis, Agar Gel; Estradiol; Estrogens, Catechol; Humans; Hydrogen Peroxide; NAD; Oxidation-Reduction; Oxygen Consumption; Reactive Oxygen Species; Superoxides

A series of synthetic estrogens containing hydroxyalkyl side chains at the C-4 position of the A ring were designed as metabolically stable analogs of 4-hydroxyestradiol, a catechol estrogen. These synthetic steroids would facilitate investigations on the potential biological role of catechol estrogens and also enable further examination of the structural and electronic constraints on the A ring in the interaction of estrogens with the estrogen receptor. Catechol estrogens are implicated as possible causative agents in estrogen-induced tumorigenesis. 4-Hydroxyestradiol has weaker affinity for the estrogen receptor and exhibits lower estrogenic activity in vivo; on the other hand, the catechol estrogens are prone to further oxidative metabolism and can form reactive intermediates. This report describes the synthesis and initial biochemical evaluation of 4-(hydroxyalkyl)estrogens and 4-(aminoalkyl)estradiols. The 4-(hydroxyalkyl)estrogens were prepared by oxidative hydroboration of 4-alkenylestradiols. The alkenylestradiols were obtained via a Stille cross-coupling between a MOM-protected 4-bromoestradiol and an alkenylstannane. The (4-aminoalkyl)estrogens were prepared from the hydroxyalkyl derivatives with phthalimide under Mitsunobu conditions. The substituted estradiols were evaluated for estrogen receptor binding activity in MCF-7 human mammary carcinoma cells, and 4-(hydroxymethyl)estradiol 1 exhibited the highest affinity with an apparent EC50 value of 364 nM. The relative activities for mRNA induction of the pS2 gene in MCF-7 cell cultures by the 4-(hydroxyalkyl)estrogens closely parallel the relative binding affinities. 4-(Hydroxymethyl)estradiol 1 did not stimulate the growth of MCF-7 cells at concentrations up to 1 microM. Thus, 4-(hydroxymethyl)estradiol 1 exhibited similar estrogen receptor affinity as the catechol estrogen, 4-hydroxyestradiol, and may prove useful in the examination of the biological effects of 4-hydroxyestrogens.

Topics: Adenocarcinoma; Breast Neoplasms; Cell Division; Estradiol; Estrogens, Catechol; Humans; Kinetics; Neoplasms, Hormone-Dependent; Receptors, Estrogen; Structure-Activity Relationship; Tumor Cells, Cultured

Estrogen is a known risk factor in human breast cancer. In rodent models, estradiol has been shown to induce tumors in those tissues in which this hormone is predominantly converted to the catechol metabolite 4-hydroxyestradiol by a specific 4-hydroxylase enzyme, whereas tumors fail to develop in organs in which 2-hydroxylation predominates. We have now found that microsomes prepared from human mammary adenocarcinoma and fibroadenoma predominantly catalyze the metabolic 4-hydroxylation of estradiol (ratios of 4-hydroxyestradiol/2-hydroxyestradiol formation in adenocarcinoma and fibroadenoma, 3.8 and 3.7, respectively). In contrast, microsomes from normal tissue obtained either from breast cancer patients or from reduction mammoplasty operations expressed comparable estradiol 2- and 4-hydroxylase activities (corresponding ratios, 1.3 and 0.7, respectively). An elevated ratio of 4-/2-hydroxyestradiol formation in neoplastic mammary tissue may therefore provide a useful marker of benign or malignant breast tumors and may indicate a mechanistic role of 4-hydroxyestradiol in tumor development.

Topics: Adenocarcinoma; Animals; Biomarkers, Tumor; Breast; Breast Neoplasms; Cytochrome P-450 CYP1A1; Cytochrome P-450 Enzyme System; Estradiol; Estrogens; Estrogens, Catechol; Female; Fibroadenoma; Humans; Hydroxylation; In Vitro Techniques; Microsomes; Steroid Hydroxylases

The catechol estrogens (CE), 2-hydroxyestradiol (2-OH-E2) and 4-hydroxyestradiol (4-OH-E2) were analyzed for their binding affinity to the estrogen receptor of MCF-7 cells. Applying a competitive binding assay to cytosols prepared from MCF-7 breast cancer cells, we measured a relative binding affinity of 23% (2-OH-E2) and 26% (4-OH-E2) compared to E2. Nuclear binding assays with the same cell line demonstrated a high specific binding with Kd's of 0.31 nM (2-OH-E2) and 0.21 nM (4-OH-E2). The relative binding affinity measured was 25% and 42% for 2-OH-E2 and 4-OH-E2, respectively. Based on this nuclear binding it can be concluded that the estrogen receptor occupied by CE is bound within the nucleus and might therefore be transcriptionally active.

Topics: Binding, Competitive; Breast Neoplasms; Cell Nucleus; Cytosol; Estradiol; Estrogens, Catechol; Humans; Prolactin; Receptors, Estrogen; Receptors, Progesterone; Tumor Cells, Cultured

Catecholestrogens are important metabolites of estradiol and estrone in the human. Considerable interest has focused on the catecholestrogens 2-hydroxy- and 4-hydroxyestradiol since they bind to the estrogen receptor with an affinity in the range of estradiol. Using the MCF-7 cell line, we analysed the capacity of purified catecholestrogens to transform the estrogen receptor into its high affinity nuclear binding form and to affect receptor-dependent processes such as proliferation and expression of the progesterone receptor (PR). Incubations with 2-hydroxy- and 4-hydroxyestradiol at 10(-8) M for 1 h resulted in tight nuclear binding of the estrogen receptor. During treatment of the cells with catecholestrogens we obtained a marked increase in proliferation rate of 36 and 76% for 2-hydroxy- and 4-hydroxyestradiol, respectively, relative to the inductive effect of estradiol (100%). The PR level, was slightly increased by treatment with 2-hydroxyestradiol (10%), whereas treatment with 4-hydroxyestradiol increased the PR level at 28%, compared to estradiol (100%). From these results we conclude that the 2- and 4-hydroxylated derivatives of estradiol are active hormones and are able to initiate estrogen receptor mediated processes in MCF-7 cells.

Topics: Breast Neoplasms; Cell Division; Cell Nucleus; Estradiol; Estrogens, Catechol; Female; Humans; Kinetics; Receptors, Estrogen; Receptors, Progesterone; Tamoxifen; Time Factors; Tumor Cells, Cultured

The binding of catechol estrogens, epoxyenones and methoxyestrogens was evaluated using estrogen receptors in cytosol prepared from human breast cancers. The relative affinity of 2-hydroxyestradiol, a metabolite formed in vitro from estradiol-17 beta by breast cancer cells, was indistinguishable from that of estradiol-17 beta. 4-Hydroxyestradiol, which is also a metabolite of estradiol-17 beta, associated with the estrogen receptor with a relative affinity approximately 1.5-fold greater than that of estradiol-17 beta. Epoxyenones and methoxyestrogens were weak competitors compared to the binding of estradiol-17 beta, exhibiting relative affinities 3% or less than the affinity of estradiol-17 beta. Sucrose density gradient centrifugation revealed that both 2- and 4-hydroxyestradiol inhibited the binding of estradiol-17 beta to both the 4S and 8S isoforms of the estrogen receptor in a competitive manner, with a Ki = 0.94 nM for 2-hydroxyestradiol and a Ki = 0.48 nM for 4-hydroxyestradiol. It can be concluded that these data demonstrate a specific receptor-mediated estrogenic action for both of these catechol estrogens.

Topics: Binding, Competitive; Breast Neoplasms; Centrifugation, Density Gradient; Cytosol; Estradiol; Estrogens, Catechol; Female; Humans; Kinetics; Receptors, Estrogen; Tumor Cells, Cultured

Topics: Animals; Breast Neoplasms; Equilenin; Equilin; Estradiol; Estrogens; Estrogens, Catechol; Ethinyl Estradiol; Female; Humans; Hydroxyestrones; Hydroxylation; Microsomes, Liver; Papio