Opposite effects of estrogen and catecholestrogen on hormone-sensitive breast cancer cell growth and differentiation

Urinary estrogen metabolites and breast cancer risk in Chinese population

BACKGROUND

In China, the association between estrogen metabolism and breast cancer risk and the differences in metabolic pattern between breast cancer patients and controls are poorly understood.

METHODS

A total of 84 patients with invasive breast cancer and 47 controls with benign breast diseases were included in this study. Estrogen metabolites from their morning urine were determined by HPLC-MS/MS and evaluated in both groups, and the predictive value of each estrogen metabolite in the malignant group according to their menstrual status was analyzed.

RESULTS

Urinary concentration of estrogen metabolites 2-hydroxyestrone (2-OHE1), 2-hydroxyestradiol (2-OHE2), 4-hydroxyestradiol (4-OHE2), 4-methoxyestrone (4-MeOE1), and 16α-hydroxyestrone were lower in postmenopausal patients with breast cancer, compared with benign controls. In logistic regression model, breast cancer risk increased with the decline in the levels of 4-OHE2 and 4-MeOE1. In premenopausal patients, a difference in the level of 2-OHE2 was observed between both groups, and 2-OHE2 was found to have predictive value for breast cancer. Additionally, urinary 2-OHE2 level in premenopausal hormone receptor positive (HR+) patients was considerably higher compared with hormone receptor negative patients.

CONCLUSIONS

We found that lower urinary levels of 4-OHE2 and 4-MeOE1 had predictive value for breast cancer, and higher 2-OHE1 were associated with HR+ breast cancer in premenopausal women.

Endogenous estrogens-breast cancer and chemoprevention

Breast cancer is the most common female malignancy and the second leading cause of cancer related deaths. It is estimated that about 40% of all cancer in women is hormonally mediated. Both estrogens and androgens play critical roles in the initiation and development of breast cancer. Estrogens influence normal physiological growth, proliferation, and differentiation of breast tissues, as well as the development and progression of breast malignancy. Breast cancer is caused by numerous endo- and exogenous risk factors. The paper presents estrogen metabolism, in particular 17β-estradiol and related hormones. The mechanisms of estrogen carcinogenesis include the participation of estrogen receptors, the genotoxic effect of the estrogen metabolites, and epigenetic processes that are also presented. The role of reactive oxygen species in breast cancer has been described. It called attention to a role of numerous signaling pathways in neoplastic transformation. Chemoprotective agents, besides other phytoestrogens, classical antioxidants, synthetic compounds, and their mechanisms of action have been shown.

The 2-/16α-Hydroxylated Estrogen Ratio-Breast Cancer Risk Hypothesis: Insufficient Evidence for its Support

During the past 25 years or so a number of studies have been carried out to address the hypothesis that the ratio of 2-hydroxyestrone (2-hydroxy-E₁) to 16α-hydroxyestrone (16α-hydroxy-E₁) is associated with breast cancer risk. The rationale for this hypothesis is based on data from studies that suggest a tumorigenic and genotoxic effect of 16α-hydroxy-E₁ and a protective effect of 2-hydroxy-E₁ regarding breast cancer risk. The adverse effect of 16α-hydroxy-E₁ has been attributed to its potential to form covalent adducts with macromolecules. Initial studies used radiometric assays and enzyme immunoassays to test the hypothesis. However, concerns about the accuracy of these assays led to the development of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay that is capable of measuring 5 unconjugated and 15 conjugated endogenous estrogens, which include 2- and 16-hydroxylated estrogen metabolites, in serum or urine. The conjugated estrogens are quantified following a deconjugation (hydrolysis) step to remove the sulfate and glucuronide groups. Epidemiologic studies have been using the LC-MS/MS assay to determine whether there is an association between breast cancer risk and the ratio of the sum of the concentrations of metabolites in the 2-hydroxylated estrogen pathway and in the 16-hydroxylated estrogen pathway. However, the validity of the pathways as biomarkers was not evaluated. The 16-hydroxylated estrogen pathway includes estriol, 16-epiestriol, 17-epiestriol and 16-ketoestradiol, in addition to 16α-hydroxy-E₁. However, with the exception of 16α-hydroxy-E₁, there is no evidence that any of the other estrogens in the pathway have tumorigenic or genotoxic properties, and they do not form covalent adducts with macromolecules. Another deficiency in the epidemiological studies pertains to the accuracy of estrogen metabolite measurements obtained after the hydrolysis step in the LC-MS/MS assays. No validation was performed to demonstrate that a constant efficiency of hydrolysis is found for all the different structural forms of sulfated and glucuronidated conjugates. Other deficiencies in the assays include the need for greater sensitivity so that the very low concentrations of unconjugated 2-hydroxy-E₁, 2-hydroxy-E₂, and 16α-hydroxy-E₁ can be measured in serum. There is also a need to develop assays to measure intact forms of conjugated estrogens in both serum and urine, particularly the sulfates and glucuronides of 2-hydroxylated, 2-methoxylated, and 16α-hydroxylated E₁ and E₂. This will avoid inaccuracies that stem from hydrolysis procedures. Improvements in LC-MS/MS assay methodology to obtain accurate measurements of unconjugated and conjugated 2-hydroxylated, 2-methoxylated, and 16α-hydroxylated estrogen metabolites are needed. This should provide valuable data for testing the 2-/16α-hydroxylated estrogen-breast cancer risk hypothesis.

A randomized, placebo-controlled trial of diindolylmethane for breast cancer biomarker modulation in patients taking tamoxifen

PURPOSE

Diindolylmethane (DIM), a bioactive metabolite of indole-3-carbinol found in cruciferous vegetables, has proposed cancer chemoprevention activity in the breast. There is limited evidence of clinically relevant activity of DIM or long-term safety data of its regular use. A randomized, double-blind, placebo-controlled trial was conducted to determine the activity and safety of combined use of BioResponse DIM® (BR-DIM) with tamoxifen.

METHODS

Women prescribed tamoxifen (n = 130) were randomly assigned oral BR-DIM at 150 mg twice daily or placebo, for 12 months. The primary study endpoint was change in urinary 2/16α-hydroxyestrone (2/16α-OHE1) ratio. Changes in 4-hydroxyestrone (4-OHE1), serum estrogens, sex hormone-binding globulin (SHBG), breast density, and tamoxifen metabolites were assessed.

RESULTS

Ninety-eight women (51 placebo, 47 DIM) completed intervention; compliance with treatment was >91%. BR-DIM increased the 2/16α-OHE1 ratio (+3.2 [0.8, 8.4]) compared to placebo (-0.7 [-1.7, 0.8], P < 0.001). Serum SHBG increased with BR-DIM compared to placebo (+25 ± 22 and +1.1 ± 19 nmol/L, respectively). No change in breast density measured by mammography or by MRI was observed. Plasma tamoxifen metabolites (endoxifen, 4-OH tamoxifen, and N-desmethyl-tamoxifen) were reduced in women receiving BR-DIM versus placebo (P < 0.001). Minimal adverse events were reported and did not differ by treatment arm.

CONCLUSION

In patients taking tamoxifen for breast cancer, daily BR-DIM promoted favorable changes in estrogen metabolism and circulating levels of SHBG. Further research is warranted to determine whether BR-DIM associated decreases in tamoxifen metabolites, including effects on endoxifen levels, attenuates the clinical benefit of tamoxifen.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01391689.

Estrogen metabolism and breast cancer

There is currently accumulating evidence that endogenous estrogens play a critical role in the development of breast cancer. Estrogens and their metabolites have been studied in both pre- and postmenopausal women with more consistent results shown in the latter population, in part because of large hormonal variations during the menstrual cycle and far fewer studies having been performed in premenopausal women. In this review we describe in detail estrogen metabolism and associated genetic variations, and provide a critical review of the current literature regarding the role of estrogens and their metabolites in breast cancer risk.

Circulating estrogen metabolites and risk of breast cancer in postmenopausal women

BACKGROUND

It has been hypothesized that predominance of the 2-hydroxylation estrogen metabolism pathway over the 16α-hydroxylation pathway may be inversely associated with breast cancer risk.

METHODS

We examined the associations of invasive breast cancer risk with circulating 2-hydroxyestrone (2-OHE1), 16α-hydroxyestrone (16α-OHE1), and the 2-OHE1:16α-OHE1 ratio in a case-control study of postmenopausal women nested within two prospective cohorts: the New York University Women's Health Study (NYUWHS) and the Northern Sweden Mammary Screening Cohort (NSMSC), with adjustment for circulating levels of estrone, and additional analyses by tumor estrogen receptor (ER) status. Levels of 2-OHE1 and 16α-OHE1 were measured using ESTRAMET 2/16 assay in stored serum or plasma samples from 499 incident breast cancer cases and 499 controls, who were matched on cohort, age, and date of blood donation.

RESULTS

Overall, no significant associations were observed between breast cancer risk and circulating levels of 2-OHE1, 16α-OHE1, or their ratio in either cohort and in combined analyses. For 2-OHE1, there was evidence of heterogeneity by ER status in models adjusting for estrone (P ≤ 0.03). We observed a protective association of 2-OHE1 with ER+ breast cancer [multivariate-adjusted OR for a doubling of 2-OHE1, 0.67 (95% confidence interval [CI], 0.48-0.94; P = 0.02)].

CONCLUSIONS

In this study, higher levels of 2-OHE1 were associated with reduced risk of ER+ breast cancer in postmenopausal women after adjustment for circulating estrone.

IMPACT

These results suggest that taking into account the levels of parent estrogens and ER status is important in studies of estrogen metabolites and breast cancer.

Cancer morbidity in rheumatoid arthritis: role of estrogen metabolites

Estrogen metabolites have been implicated in rheumatoid arthritis (RA) and cancer, although the mechanism remains unestablished. Some estrogen metabolites, which are used for the assessment of cancer risk, play an important role in RA. The pathways by which malignancies associated with RA remain elusive. Possible mechanism involves enzymatic or nonenzymatic oxidation of estrogen into catecholestrogen metabolites through semiquinone and quinone redox cycle to produce free radicals that can cause DNA modifications. Modifications of DNA alter its immunogenicity and trigger various immune responses leading to elevated levels of cancer and RA antibodies. However, the role of different estrogen metabolites as a mediator of immune response cannot be ruled out in various immune-related diseases.

Serum free estradiol and estrogen receptor-α mediated activity are related to decreased incident hip fractures in older women

There is paucity of data from Asian women on the association between serum estrogens and osteoporotic hip fracture risk. We conducted a case-control study nested within a population-based prospective cohort, The Singapore Chinese Health Study, to evaluate serum estrogens levels, ERα-mediated estrogenic activity and hip fracture risk in postmenopausal Asian women. Among 35,298 women who were recruited between 1993 and 1998, 15,410 women donated blood for research between 1999 and 2004. From this subcohort, we identified 140 cases who subsequently suffered hip fracture after blood donation, and 278 age-matched controls. Serum levels of total estrone, estradiol and sex hormone binding globulin levels were measured in a blinded fashion among cases and controls. ERα-mediated estrogenic activity of serum samples was quantified using a sensitive ERα-driven cell bioassay. Women with hip fracture had lower serum estrogens than control women. Compared to the lowest quintile, women in the highest quintile of free estradiol exhibited a statistically significant 57% reduction in risk of hip fracture (95% confidence interval (CI), 6-80%), with a dose-dependent relationship (p for trend=0.021). High levels of ERα-mediated estrogenic activity were also associated with decreased risk of hip fracture (p for trend=0.048). Overall, women with relatively high levels of both free estradiol and ERα-mediated estrogenic activity had a 55% reduction in hip fracture risk (95% CI, 17-76%) compared to women with low levels of both. High levels of free estradiol and ERα-mediated estrogen activity in sera were associated with reduced hip fracture risk in Chinese postmenopausal women.

Urinary estrogens and estrogen metabolites and subsequent risk of breast cancer among premenopausal women

Endogenous estrogens and estrogen metabolism are hypothesized to be associated with premenopausal breast cancer risk but evidence is limited. We examined 15 urinary estrogens/estrogen metabolites and breast cancer risk among premenopausal women in a case-control study nested within the Nurses' Health Study II (NHSII). From 1996 to 1999, urine was collected from 18,521 women during the mid-luteal menstrual phase. Breast cancer cases (N = 247) diagnosed between collection and June 2005 were matched to two controls each (N = 485). Urinary estrogen metabolites were measured by liquid chromatography-tandem mass spectrometry and adjusted for creatinine level. Relative risks (RR) and 95% confidence intervals (CI) were estimated by multivariate conditional logistic regression. Higher urinary estrone and estradiol levels were strongly significantly associated with lower risk (top vs. bottom quartile RR: estrone = 0.52; 95% CI, 0.30-0.88; estradiol = 0.51; 95% CI, 0.30-0.86). Generally inverse, although nonsignificant, patterns also were observed with 2- and 4-hydroxylation pathway estrogen metabolites. Inverse associations generally were not observed with 16-pathway estrogen metabolites and a significant positive association was observed with 17-epiestriol (top vs. bottom quartile RR = 1.74; 95% CI, 1.08-2.81; P(trend) = 0.01). In addition, there was a significant increased risk with higher 16-pathway/parent estrogen metabolite ratio (comparable RR = 1.61; 95% CI, 0.99-2.62; P(trend) = 0.04). Other pathway ratios were not significantly associated with risk except parent estrogen metabolites/non-parent estrogen metabolites (comparable RR = 0.58; 95% CI, 0.35-0.96; P(trend) = 0.03). These data suggest that most mid-luteal urinary estrogen metabolite concentrations are not positively associated with breast cancer risk among premenopausal women. The inverse associations with parent estrogen metabolites and the parent estrogen metabolite/non-parent estrogen metabolite ratio suggest that women with higher urinary excretion of parent estrogens are at lower risk.

Towards non-surgical therapy for uterine fibroids: catechol-O-methyl transferase inhibitor shrinks uterine fibroid lesions in the Eker rat model

BACKGROUND

Uterine leiomyomas (fibroids) are the most common pelvic tumors in women. We assessed the potential therapeutic utility of Ro 41-0960, a synthetic catechol-O-methyl transferase inhibitor (COMTI), in the Eker rat.

METHODS

We randomized uterine fibroid-bearing Eker rats for treatment with Ro 41-0960 (150 mg/kg/12 h) versus vehicle for 2 and 4 weeks. The fibroids were measured by caliper and subjected to histological evaluation. Urinary levels of 2-hydroxy estrogen (E(2)), 16-hydroxy E2 and DPD (osteoporosis marker) and serum liver enzymes were evaluated. Expressions of Cyclin D1, proliferating cell nuclear antigen (PCNA), Poly [ADP-ribose] polymerase1 (PARP1), tumor suppressor gene (P53) and transforming growth factor (TGFβ3) were assessed in fibroids using immunohistochemical analysis or RT-PCR. Apoptosis was confirmed using terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling (TUNEL).

RESULTS

Ro 41-0960-treated rats exhibited fibroid volumes of 86 ± 7% and 105 ± 12% of initial burden, at 2 and 4 weeks post-treatment, respectively, significantly lower than control group (240 ± 15% and 300 ± 18%; P< 0.01). Ro 41-0960 increased the urinary 2-hydroxy E2/16-hydroxy E(2) ratio, level of p53 mRNA and TUNEL positivity (P< 0.05) and decreased PARP1, PCNA and cyclin D1 proteins and TGFβ3 mRNA (P< 0.05). Ro 41-0960 did not change normal tissue histology, liver functions or urinary DPD level.

CONCLUSIONS

Ro 41-0960 (COMTI) arrested growth/shrunk uterine fibroids in Eker rats. This result may be related to modulation of estrogen-dependent genes involved in apoptosis, proliferation and extracellular matrix deposition via accumulation of 2-hydroxy estrogen. The efficacy and safety of Ro 41-0960 in rats suggest its candidacy for treatment of uterine fibroids.

Vitamin D inhibits proliferation of human uterine leiomyoma cells via catechol-O-methyltransferase

OBJECTIVE

To evaluate the effects and mechanisms of action of vitamin D on human uterine leiomyoma (HuLM) cell proliferation in vitro.

DESIGN

Laboratory study.

SETTING

University hospitals.

PATIENTS(S)

Not applicable.

INTERVENTIONS(S)

Not applicable.

MAIN OUTCOME MEASURE(S)

HuLM cells were treated with 1,25-dihydroxyvitamin D3 (vitamin D), and cell proliferation was assayed by the methylthiazolyl tetrazolium technique. proliferating cell nuclear antigen (PCNA), BCL-2, BCL-w, cyclin-dependent kinase (CDK) 1, and catechol-O-methyltransferase (COMT) protein levels were analyzed by Western blotting. COMT mRNA and enzyme activity were assayed by quantitative reverse-transcription polymerase chain reaction (RT-PCR) and high-performance liquid chromatography analysis, respectively. The role of COMT was evaluated in stable HuLM cells by silencing COMT expression.

RESULT(S)

Vitamin D inhibited the growth of HuLM cells by 47±0.03% at 1 μM and by 38±0.02% at 0.1 μM compared with control cells at 120 hours of treatment. Vitamin D inhibited extracellular signal-regulated kinase activation and down-regulated the expression of BCL-2, BCL-w, CDK1, and PCNA. Western blot, RT-PCR, and enzyme assay of COMT demonstrated inhibitory effects of vitamin D on COMT expression and enzyme activity. Silencing endogenous COMT expression abolished vitamin D-mediated inhibition of HuLM cell proliferation.

CONCLUSION(S)

Vitamin D inhibits growth of HuLM cells through the down-regulation of PCNA, CDK1, and BCL-2 and suppresses COMT expression and activity in HuLM cells. Thus, hypovitaminosis D appears to be a risk factor for uterine fibroids.

Circulating sex steroids and breast cancer risk in premenopausal women

Evidence from both laboratory and epidemiologic studies indicate a key role of hormones in the etiology of breast cancer. In epidemiologic studies, indirect data, including the consistent associations observed between reproductive factors and breast cancer risk, support an important contribution of hormones to risk. Recently, the associations between circulating hormones in premenopausal women and subsequent risk of breast cancer have been evaluated. To date, both positive and null associations have been observed for estrogens and inverse and null associations for progesterone with breast cancer risk. For estrogens, the relationships may vary by menstrual cycle phase (e.g., follicular versus luteal phase), although this requires confirmation. Few studies have evaluated estrogen metabolites in relation to breast cancer risk; hence, no conclusions can yet be drawn. Findings for the largely adrenal-derived dehydroepiandrosterone (DHEA) and DHEA sulfate also are inconsistent and may vary by age. However, relatively consistent positive associations have been observed between testosterone (or free testosterone) levels and breast cancer risk; these associations are of similar magnitude to those confirmed among postmenopausal women. In this review, we summarize current evidence and identify gaps and inconsistencies that need to be addressed in future studies of sex steroids and premenopausal breast cancer risk.

Reproducibility of fifteen urinary estrogens and estrogen metabolites over a 2- to 3-year period in premenopausal women

Endogenous estrogens play an integral role in the etiology of breast, endometrial, and, possibly, ovarian cancers. Estrogen metabolism yields products that are potentially both estrogenic and genotoxic, yet individual metabolic patterns are just beginning to be explored in epidemiologic studies. Within the Nurses' Health Study II, we examined reproducibility of 15 urinary estrogens and estrogen metabolites (EM) among 110 premenopausal women with three luteal-phase urine samples collected over 3 years. EM were measured by a recently developed high-performance liquid chromatography-tandem mass spectrometry (LC-MS(2)) method with high sensitivity, specificity, and precision. We assessed Spearman correlations and intraclass correlation coefficients (ICC) across the three samples. Correlations between urinary estrone or estradiol and EM were only modest (r = 0.1-0.5). The 2- and 4-hydroxylation pathways were highly correlated (r = 0.9) but weakly inversely correlated with the 16-hydroxylation pathway (r = -0.2). Within-woman reproducibility over time was fairly high for the three pathways, with ICCs ranging from 0.52 (16-hydroxylation pathway) to 0.72 (2-hydroxylation pathway). ICCs were similarly high for 2-catechols and the individual catechols (ICCs = 0.58-0.72). Individual and grouped methylated 2-catechols had fairly high ICCs (0.51-0.62), but methylated 4-catechols had low ICCs (0.14-0.27). These data indicate that, in general, urinary EM levels vary substantially among individuals compared with intraindividual variability. Within-person reproducibility over time for most EM measures is comparable to or better than that for well-vetted biomarkers such as plasma cholesterol and, in postmenopausal women, estradiol.

Elevated expression of catechol-O-methyltransferase is associated with labor and increased prostaglandin E(2) production by human fetal membranes

OBJECTIVE

The purpose of this study was to evaluate the expression and function of catechol-O-methyltransferase in human fetal membranes at term.

STUDY DESIGN

Fetal membranes obtained from women between 38-42 weeks of gestation, after (1) vaginal delivery with spontaneous labor and (2) prelabor elective cesarean section (no labor), were assayed for catechol-O-methyltransferase expression using quantitative real-time polymerase chain reaction analysis, immunohistochemistry, and Western blot analysis. Prostaglandin E(2) secretion from amnion and choriodecidua explants treated with or without catechol-O-methyltransferase inhibitor was assayed by enzyme-linked immunosorbent analysis.

RESULTS

Amnion layer of fetal membranes from laboring women expressed significantly higher levels of catechol-O-methyltransferase, compared with those from women with no labor. Catechol-O-methyltransferase was higher in the amnion layer than in choriodecidua. Selective catechol-O-methyltransferase inhibition significantly decreased prostaglandin E(2) production from fetal membranes.

CONCLUSION

Labor increases catechol-O-methyltransferase expression in the amnion of human fetal membranes. Selective catechol-O-methyltransferase inhibition decreased prostaglandin E(2) secretion in fetal explant cultures, suggesting a role for catechol-O-methyltransferase in human labor and delivery.

Circulating estrogen metabolites and risk for breast cancer in premenopausal women

BACKGROUND

It has been proposed that a shift toward 2-hydroxyestrone from 16alpha-hydroxyestrone metabolic pathway may be inversely associated with breast cancer risk because 2-hydroxyestrone is thought to be less genotoxic and estrogenic than 16alpha-hydroxyestrone.

METHODS

We examined the associations of invasive breast cancer risk with circulating 2-hydroxyestrone, 16alpha-hydroxyestrone, and the 2-hydroxyestrone:16alpha-hydroxyestrone ratio in a case-control study on premenopausal women nested within a prospective cohort the New York University Women's Health Study. The serum levels of 2-hydroxyestrone and 16alpha-hydroxyestrone were measured in 377 incident premenopausal breast cancer cases and 377 premenopausal controls, who were matched on age at enrollment, number and dates of blood donations, and day and phase of menstrual cycle.

RESULTS

Overall, no significant associations were observed between breast cancer risk and serum levels of 2-hydroxyestrone, 16alpha-hydroxyestrone, or their ratio. The 2-hydroxyestrone:16alpha-hydroxyestrone ratio was positively associated with risk for estrogen receptor-positive breast cancer in the analyses controlling for matching factors. However, the association was attenuated and not significant after adjustment for potential confounders (odds ratio for the highest versus the lowest quartile, 2.15; 95% CI, 0.88-5.27; P(trend) = 0.09).

CONCLUSIONS

The results of the current study do not support the hypothesis that a metabolic shift from 16alpha-hydroxyestrone toward 2-hydroxyestrone in premenopausal women is associated with reduced risk for breast cancer. The association between the 2-hydroxy:16alpha-hydroxyestrone ratio and estrogen receptor-positive breast cancer needs to be explored in future studies.

Circulating 2-hydroxy- and 16alpha-hydroxy estrone levels and risk of breast cancer among postmenopausal women

Circulating estrogens are associated with breast cancer risk in postmenopausal women. Given that estrogen metabolites are potentially both mitogenic and genotoxic, it is possible that plasma levels of estrogen metabolites are related to breast cancer risk. We conducted a prospective, nested case-control study within the Nurses' Health Study. Blood samples, collected in 1989 to 1990, were assayed for 2-OH and 16alpha-OH estrone among 340 cases and 677 matched controls not taking postmenopausal hormones. Multivariate relative risks (RR) and 95% confidence intervals (95% CI) were calculated by conditional logistic regression, adjusting for breast cancer risk factors. Neither 2-OH nor 16alpha-OH estrone concentrations were significantly associated with breast cancer risk overall (top versus bottom quartile: RR, 1.19; 95% CI, 0.80-1.79; P(trend) = 0.40 for 2-OH estrone and RR, 1.04; 95% CI, 0.71-1.53; P(trend) = 0.81 for 16alpha-OH estrone). The ratio between the two metabolites (2-OH:16alpha-OH estrone) was similarly unrelated to risk overall (1.30; 95% CI, 0.87-1.95; P(trend) = 0.35). Although no associations were detected among women with estrogen receptor (ER)-positive/progesterone receptor (PR)-positive tumors, significant positive associations were observed for 2-OH estrone and the 2-OH:16alpha-OH estrone ratio among women with ER-negative/PR-negative tumors (RR, 3.65; 95% CI, 1.23-10.81; P(trend) = 0.01; P(heterogeneity) = 0.02 for 2-OH estrone; RR, 3.70; 95% CI, 1.24-11.09; P(trend) = 0.004; P(heterogeneity) = 0.005 for 2-OH:16alpha-OH estrone). These data do not support the hypothesized inverse associations with 2-OH estrone and the 2-OH:16alpha-OH estrone ratio or the hypothesized positive association with 16alpha-OH estrone. The significant positive associations with 2-OH estrone and the 2-OH:16-OH estrone ratio among women with ER-negative/PR-negative tumors needs to be replicated in future studies.

Molecular genetics and racial disparities of uterine leiomyomas

Uterine leiomyomas (ULMs) are benign oestrogen-dependent tumours of the myometrium. They are the most common tumours of the female genital tract, affecting around 77% of the female population. ULMs are more common in Black women than White women. These tumours tend to develop earlier and be more numerous, larger in size and more symptomatic in Black women than other ethnic groups. The molecular mechanism underlying this ethnic disparity is not fully understood. Polymorphism of genes involved in oestrogen synthesis and/or metabolism (COMT, CYP17), variation in the expression levels or function of oestrogen and progesterone receptors or retinoic acid nuclear receptors (retinoid acid receptor-alpha, retinoid X receptor-alpha), or aberrant expression of micro-RNAs are some of the molecular mechanisms that may be involved.

Treatment with an inhibitor of catechol-O-methyltransferase activity reduces preterm birth and impedes cervical resistance to stretch in pregnant rats

Catechol-O-methyltransferase (COMT) enzyme catalyzes the methylation of the 2- or 4-hydroxyestrogens to 2- or 4-methoxyestrogens. Both the hydroxyestrogens and methoxyestrogens have been shown to block or enhance the effects of estrogen respectively. Our objective was to investigate the potential role of COMT in parturition and cervical ripening using a rat model. Immunohistochemistry was conducted to detect and localize the COMT protein in rat uterine tissues during pregnancy. We measured the longitudinal changes in urinary 2-hydroxyestrogen before, during, and after pregnancy in rats. Animal studies were conducted to determine the effect of treatment with a selective COMT inhibitor on (1) mifepristone-induced preterm birth and (2) cervical resistance to stretch in pregnant rats. The intensity of staining for the COMT protein differed within the luminal epithelium, uterine gland epithelium, endometrium, and myometrium during pregnancy. Levels of staining for the COMT protein in rat myometrium were highest on day 1 and lowest on days 8 and 13, but high levels returned by days 16 and 19 of pregnancy. The levels of urinary 2-hydroxyestrogen gradually increased in the first 2 weeks of pregnancy, peaked from days 16 to 18 of pregnancy, and then gradually returned to pre-pregnancy levels after delivery. The percentage of pups retained in the uterus of pregnant rats treated with both mifepristone and COMT inhibitor (48 ± 15%) was significantly higher (P< 0.05) when compared with the value of pregnant rats treated with mifepristone alone (12 ± 4%). The resistance to stretch was significantly higher (P< 0.05) in cervical tissues from the pregnant rats treated with COMT inhibitor (0.28) when compared with cervical tissues taken from rats treated with vehicle control (0.18). Modulation of COMT activity may play a role in the regulation of myometrial contractility and cervical ripening during pregnancy.

Lower levels of urinary 2-hydroxyestrogens in polycystic ovary syndrome

CONTEXT

Women with polycystic ovary syndrome (PCOS) have anovulation due to arrested follicular maturation. The substrate (2-hydroxyestrogen) and product (2-methoxyestrogen) of catechol-O-methyl transferase (COMT) have been shown to modulate proliferation and angiogenesis of granulosa cells.

OBJECTIVE

The objective of the study was to evaluate COMT ovarian expression as well as the production of estrogen metabolites (2-hydroxyestrogen and 2-methoxyestrogen) in subjects with PCOS.

DESIGN

Immunohistochemistry was used to assess COMT expression in ovarian tissues. Urinary levels of 10 different estrogens and estrogen metabolites were measured using enzyme-labeled immunoassays and/or liquid chromatography with tandem mass spectrometry.

SETTING

The study was conducted at a tertiary university referral center.

PATIENTS AND OTHER PARTICIPANTS

Ovarian tissues were obtained from six control subjects and six subjects with PCOS. Fasting first-void urinary samples were collected from 49 subjects with PCOS and 36 healthy control subjects.

MAIN OUTCOME MEASURE(S)

COMT protein expression in ovarian tissues was measured. Urinary levels of 2-hydroxyestrogen and 2-methoxyestrogen levels in PCOS patients were also measured.

RESULTS

Whereas immunohistochemistry showed that COMT was expressed in ovaries from control and PCOS subjects, its expression was significantly higher in ovaries from subjects with PCOS, in both the follicular structures and ovarian stroma. The urinary 2-hydroxyestrogen level was significantly lower in subjects with PCOS, compared with normal controls (P = 0.009). Additionally, urinary 2-hydroxyestrogen levels negatively correlated with serum insulin levels in subjects with PCOS (r = -0.333, P =0 .031).

CONCLUSIONS

Urinary 2-hydroxyestrogen is decreased in subjects with PCOS, which could be due in part to increased ovarian expression of COMT. Further studies are needed to ascertain the role of estrogen metabolism in PCOS before this information can be used in clinical settings.

Regulation of catechol-O-methyltransferase expression in human myometrial cells

OBJECTIVE

The catechol-O-methyltransferase enzyme catalyzes the methylation of the catechol estrogens, 2- or 4-hydroxyestrogen, to 2- or 4-methoxyestrogen. Both the hydroxy estrogens and methoxy estrogens were shown to modulate the effects of estrogen. Because catechol-O-methyltransferase activity controls levels of these metabolites, it may help regulate the cellular estrogenic milieu. In this study, we examined the regulation of catechol-O-methyltransferase expression in human myometrial cells.

METHODS

Catechol-O-methyltransferase expression was assessed by reverse transcription-polymerase chain reaction, Western blot, and luciferase assays in human myometrial cells after treatment with estrogen or progesterone. Catechol-O-methyltransferase expression was measured in cells after treatment with tumor necrosis factor alpha (TNFalpha) alone or with lactacystin, a proteasome inhibitor. Luciferase assays were also conducted using human myometrial cells containing an estrogen response element-luciferase reporter gene to measure levels of estrogen-mediated transactivation after treatment with estrogen and increasing concentrations of 2-hydroxestrogen.

RESULTS

Catechol-O-methyltransferase expression was down-regulated by progesterone or estrogen. Tumor necrosis factor alpha upregulated catechol-O-methyltransferase expression, whereas cotreatment with lactacystin attenuated this response, suggesting that TNFalpha activated nuclear factor kappa B to induce catechol-O-methyltransferase expression. Increased concentrations of 2-hydroxyestrogen attenuated estrogen-mediated transcription in the myometrial cells.

CONCLUSION

Catechol-O-methyltransferase expression may be regulated in the myometrium to control the local action of estrogen. Low levels of catechol-O-methyltransferase in the myometrium would result in an accumulation of 2-hydroxyestrogen and may antagonize the local effect of estrogen. High levels of catechol-O-methyltransferase in the myometrium would result in lower levels of 2-hydroxyestrogen and may increase sensitivity to estrogen.

Role of polymorphic human cytochrome P450 enzymes in estrone oxidation

Estrogen and its metabolites are believed to play important roles in breast cancer. The influence of genetic polymorphisms in the enzymes responsible for formation and disposition of estrogen on breast cancer risk may shed light on the importance of estrogen metabolites in this disease. However, for such studies to be valid, it is important to correctly identify the enzymes involved in estrogen bioactivation. Therefore, we assessed the human cytochrome P450-dependent oxidation of estrone using substrate concentrations that more closely approximate the maximum expected concentrations in breast tissue. The in vitro metabolism of estrone by recombinant human cytochrome P450 enzymes and human liver microsomes was studied. The formation of estrone metabolites (2-hydroxyestrone, 4-hydroxyestrone, and 16alpha-hydroxyestrone) was monitored by high-performance liquid chromatography. 2-Hydroxyestrone formation was catalyzed predominantly by CYP1A2, CYP1A1, and CYP1B1 enzymes; 4-hydroxyestrone formation was catalyzed predominantly by CYP1B1, CYP1A2, and CYP1A1 enzymes; and 16alpha-hydroxyestrone formation was catalyzed predominantly by CYP2C19, CYP1A1, and CYP3A5. This study confirms the important role of members of the CYP1 family in the 2-hydroxylation and 4-hydroxylation of estrone, but the enzymes identified as responsible for the 16alpha-hydroxylation of estrone are different from those previously identified. The relative importance of these enzymes in vivo would depend on the specific tissue expression of the enzymes. These enzymes are all known to be genetically variant in the human population, and additional studies to assess the role CYP1A2, CYP2C19, and CYP3A5 in breast cancer risk are indicated.

Catechol-O-methyltransferase polymorphism is associated with increased uterine leiomyoma risk in different ethnic groups

OBJECTIVES

Uterine leiomyomas (ULMs) are estrogen-dependent tumors that are more common in African American women. The etiology for such ethnic disparity is currently unknown. Catechol-O-methyltransferase (COMT) is an essential enzyme in estrogen metabolism. In the current study, we investigated the association of the functional COMT Val158Met polymorphism with ULM in different ethnic groups. We also studied the biologic role of COMT in tumor formation in human and rat leiomyoma cell lines and the potential therapeutic utility of COMT inhibitors.

METHODS

The genotype frequencies of the functional COMT Val158Met polymorphism among participants with (186 women) or without (142 women) ULMs were compared, as was the differential ethnic distribution of that polymorphism using polymerase chain reaction (PCR) and restriction-fragment linkage polymorphism. Proliferation, Western blot, and reporter transactivation analyses were applied to myometrial and leiomyoma cells representative of different COMT genotypes.

RESULTS

Women with the high-activity COMT Val/Val genotype are 2.5 times more likely to develop ULMs than women with other genotypes (confidence interval, 1.017 to 6.151; P <.001). The prevalence of this genotype was significantly higher in African American women (47%) compared with white (19%) or Hispanic (30%) women (P = .003). Myometrial cell lines expressing the Val/Val genotype exhibited significantly enhanced responses to estrogen in proliferation and in estrogen-responsive element reporter assays. COMT-specific inhibitors reversed such a response and induced apoptosis. Myometrial specimens from Val/Val women demonstrated distinct estrogen-regulated gene expression that was consistent with enhanced proliferation and decreased apoptosis.

CONCLUSIONS

The high-activity COMT Val/Val genotype is associated with increased risk of ULM. Our results provide a possible explanation for the higher prevalence of ULMs among African American women and offer a potential new target for nonsurgical treatment using COMT inhibitors.

Effects of Testosterone, 17beta-Estradiol, and Downstream Estrogens on Cytokine Secretion from Human Leukocytes in the Presence and Absence of Cortisol

Estrogens at physiological concentrations are thought to play an immune-stimulating role, whereas androgens have an anti-inflammatory impact. However, their role on cytokine secretion in the presence or absence of cortisol has not been investigated. Furthermore, the role of hydroxylated estrogens downstream of 17beta-estradiol (E2) on secretion of tumor necrosis factor (TNF) is not known. In this study on peripheral blood leukocytes of healthy male subjects, we scrutinized the influence of prior sex hormones (for 24 h) with and without later addition of cortisol (for another 24 h) on stimulated secretion of TNF, IL-2, IL-4, IL-6, IL-10, and interferon-gamma (IFN-gamma). E2 stabilized or increased immune stimuli-induced secretion of TNF, IL-2, IL-4, IL-6, IL-10, and IFNgamma in relation to testosterone. Testosterone, in contrast, inhibited (IL-2, IL-4, IL-10) or tended to inhibit stimulated secretion of these cytokines (TNF, IFNgamma). This effect of E2 was pronounced at a concentration of 10(-10) M (testosterone: 10(-7) M) in the presence of cortisol. E2 (10(-8) M, 10(-10) M) and testosterone (10(-7) M) did not change glucocorticoid receptor expression. The downstream estrogens 2OH-estradiol(one), 4OH-estradiol(one), and 16OH-estradiol(one) did not stimulate TNF secretion at 10(-10) M, but even inhibited its secretion at 10(-11) M. However, the combination of 16OH-estradiol(one) on one side and 2OH-estradiol(one) or 4OH-estradiol(one) on the other side markedly stimulated TNF secretion that was only observable in the presence of cortisol. In conclusion, at physiological concentrations, E2 and a combination of downstream estrogens stabilized or increased immune stimuli-induced TNF secretion. These effects are dependent on the presence of physiological concentrations of cortisol. This study underlines the proinflammatory role of E2, which is probably dependent on conversion to a proinflammatory cocktail of downstream estrogens and the presence of cortisol.

Hormonal regulation of catechol-O-methyl transferase activity in women with uterine leiomyomas

Catechol-O-methyl transferase (COMT) expression is higher in leiomyomas compared with paired normal myometrium. The expression of COMT in leiomyoma cells is hormonally regulated-estrogen down-regulates, whereas P and dexamethasone up-regulate, COMT expression.

Obesity, hormone therapy, estrogen metabolism and risk of postmenopausal breast cancer

Hormone therapy (HT) and body mass index (BMI) have been associated with postmenopausal breast cancer. Because estrogen metabolism may affect breast cancer risk and can be altered by weight and HT, it might play a role in the HT-BMI-breast cancer associations. We undertook a nested case-control study within the Observational Study of the Women's Health Initiative. Baseline levels of 2- and 16alpha-hydroxy estrone (2-OHE1 and 16alpha-OHE1) were measured in 200 women who developed breast cancer during follow-up and 200 healthy controls matched to cases by ethnicity, enrollment date, clinic site, type of HT and years since menopause. Wilcoxon nonparametric tests were used to compare estrogen metabolite levels between cases and controls. Conditional logistic regression was used to assess the relationship between BMI, estrogen metabolites and breast cancer risk. 16alpha-OHE1 levels were modestly but significantly higher in HT users among cases (median 356 pg/ml vs. 315 pg/ml) and controls (354 pg/ml vs. 298 pg/ml). 2-OHE1 levels were substantially and significantly higher in HT users among cases (369 pg/ml vs. 125 pg/ml) and controls (347 pg/ml vs. 134 pg/ml). For non-HT users only, greater BMI and higher 16alpha-OHE1 levels were individually and jointly associated with increased breast cancer risk (OR for women with high BMI and high 16alpha-OHE1 compared to those with low BMI and low 16alpha-OHE1 = 3.51, 95% CI = 1.34-9.16). No associations between BMI, estrogen metabolism and breast cancer risk were found for HT users. Estrogen metabolism differs according to both BMI and HT use, potentially explaining the interaction between BMI and HT in relation to breast cancer risk.

Urinary hydroxyestrogens and breast cancer risk among postmenopausal women: a prospective study

BACKGROUND

It has been suggested that a low level of the 2-hydroxyestrogen metabolites (2-OHE) and a high level of 16alpha-hydroxyestrone (16alpha-OHE1) are associated with an enhanced risk of breast cancer. We examined the association between the metabolite levels and breast cancer in a nested case-control study, which also addressed hormone replacement therapy (HRT) and estrogen receptor status of the tumors.

METHODS

24,697 postmenopausal Danish women were enrolled in the "Diet, Cancer and Health" cohort. During follow-up, 426 breast cancer cases were identified and controls were matched by age at diagnosis, baseline age, and HRT use. The concentrations of 2-OHE and 16alpha-OHE1 in spot urine were measured by an enzyme immunoassay. Incidence rate ratios (IRR) and 95% confidence intervals (95% CI) were estimated for total and estrogen receptor-specific breast cancer and were stratified according to HRT use.

RESULTS

A higher incidence of estrogen receptor-positive breast cancer with an enhanced 2-OHE level was observed among current HRT users, IRR per doubling = 1.30 (95% CI, 1.02-1.66), whereas no association was seen among nonusers of HRT, IRR per doubling = 1.00 (95% CI, 0.69-1.45). The association between estrogen receptor-positive breast cancer and the 16alpha-OHE1 metabolite level was in the opposite direction but slightly weaker and statistically insignificant. For estrogen receptor-negative breast cancer, no significant associations were seen.

CONCLUSIONS

The risk of breast cancer, in particular the estrogen receptor-positive type, was enhanced among postmenopausal women using estradiol-based HRT and among those who had a high 2-OHE concentration.

Urinary Estrogen Metabolites and Their Ratio among Asian American Women

Controversy persists regarding the role of a low ratio of 2-hydroxyestone (2-OHE1)/16α-hydroxyestrone (16α-OHE1) as a potential estrogen metabolism marker of increased risk for breast cancer. Most of the evidence has been provided by case-control studies, where tumor effects on hormone metabolism are not known. Studies in populations at various risk of breast cancer are not consistent, with some suggesting that levels of the ratio may be altered by changes in diet and exercise. We studied Asian American women participating as controls in a case-control study of breast cancer in which migration history—a composite of the subject's place of birth, type of residence in Asia (urban or rural), length of time living in the West, and grandparents' place of birth—was associated with a 6-fold risk gradient that paralleled the historical differences in incidence rates between the United States and Asian countries. This population offered the possibility to address whether the ratio of 2-OHE1:16α-OHE1 differs according to recognized breast cancer risk factors, including migration history. Overnight 12-hour urines were obtained from 368 premenopausal and 143 naturally postmenopausal women of Chinese, Japanese, or Filipino descent who donated urines between 1985 and 1988. The estrogen metabolites 2-OHE1 and 16α-OHE1 were measured with an ELISA kit and adjusted for creatinine levels. In each ethnic group, the ratio of 2-OHE1:16α-OHE1 was consistently lower in women born in the West than in those who had migrated from Asia. For premenopausal women, the ratio declined 20% due to lower levels of 2-OHE1. Among postmenopausal women, the ratio was 23% lower in those born in the West, but no consistent patterns based on place of birth were observed for either 2-OHE1 or 16α-OHE1. The ratio did not vary with most recognized breast cancer risk factors, except for lower metabolite ratios in women with a younger age at first birth and more children, which runs contrary to the hypothesis, because both characteristics reduce breast cancer risk. Our study suggests that the ratio of 2-OHE1:16α-OHE1 may be a marker for lifestyle influences on estrogen metabolism associated with westernization.

Systemic lupus erythematosus in a multiethnic US cohort (LUMINA): XXI. Disease activity, damage accrual, and vascular events in pre- and postmenopausal women

OBJECTIVE

To determine the differences in clinical manifestations, disease activity, damage accrual, and medication use in systemic lupus erythematosus (SLE) patients as a function of menopausal status at disease onset.

METHODS

Women with SLE as per the criteria of the American College of Rheumatology, with disease duration of </=5 years and of Hispanic (Texas and Puerto Rico ancestries), African American, and Caucasian ethnicity, from LUMINA (LUpus in MInorities, NAture versus nurture), a multiethnic, longitudinal cohort, were studied. Menopause at the time of disease onset was defined as self-report of climacteric symptoms, and/or amenorrhea lasting >6 months, and/or oophorectomy, and/or increased follicle-stimulating hormone values for reproductive-age women, and/or treatment with hormone replacement therapy. Patients were divided into premenopausal and postmenopausal categories. Socioeconomic status, cumulative clinical manifestations, disease activity (at study entry or time 0, last visit, and over time), as measured by the Systemic Lupus Activity Measure, and damage accrual, as measured by the Systemic Lupus International Collaborating Clinics/American College of Rheumatology damage index (at time 0 and at last visit) were compared between the 2 groups of women. Multivariable models were then examined making adjustments for all possible known confounders. Dependent variables in the models were renal involvement, damage accrual, arterial vascular events, and venous thrombosis.

RESULTS

Five hundred eighteen women from the LUMINA cohort were included; 436 (84.2%) were premenopausal and 82 (15.8%) were postmenopausal. Disease onset after menopause was more common among Caucasians. Renal involvement was more common in premenopausal women, whereas vascular arterial events were more frequent in postmenopausal women. All other disease manifestations, as well as disease activity, were comparable between both groups. The presence of damage accrual at time 0 and study end was more frequent in postmenopausal women. Age, rather than menopausal status, independently contributed to damage accrual, renal involvement, and vascular arterial events in these women.

CONCLUSION

A hypoestrogenemic state secondary to menopause appears not to be protective against disease activity and damage accrual. Age rather than menopausal status is a strong independent predictor of damage accrual and of vascular events in women with lupus.

A Potential Role for the Estrogen-metabolizing Cytochrome P450 Enzymes in Human Breast Carcinogenesis

PURPOSE

The cytochrome P450 (CYP) enzymes play a critical role in the oxidative metabolism of a variety of endogenous and exogenous compounds, including drugs. Although intermediate CYP metabolites are believed to play a role in carcinogenesis, little is known about tissue-specific CYP expression and the role of local activation in breast carcinogenesis. The goals of this study are to identify CYPs expressed in breast tissue by measuring mRNA levels and to determine whether there are differences in mRNA levels between breast tumors and histologically-normal adjacent breast tissue.

EXPERIMENTAL DESIGN

Quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) analysis was used to quantitate mRNA expression levels of 11 CYPs in 29 human breast tumor and non-tumor adjacent tissue pairs. The CYPs examined included: CYP1A1, CYP1A2, CYPB1, CYP2C8, CYP2C9, CYP2C18, CYP2C19, CYP2D6, CYP2E1, CYP3A4, and CYP3A5.

RESULTS

Only four CYPs were detected in breast tumor or adjacent tissue: CYP1A1, CYPB1, CYP2C9, CYP3A4. Each of these CYPs was expressed in at least 75% of the samples. Three of these CYPs are involved in estradiol hydroxylation (CYP1A1, 2-OH; CYP1B1, 4-OH; CYP3A4, 2- and 16-OH). CYP2C9 is involved in the conversion of estrone sulfate to the 16-hydroxy sulfate metabolite. Higher levels of CYP1B1 and 3A4 were found more often in non-tumor tissue than in tumor tissue (P < 0.04). CYP1A1 was elevated in non-tumor tissue only among pairs in which the tumor expressed the estrogen receptor (ER+, P < 0.03). All of these results were independent of recorded clinical-pathological covariates.

CONCLUSIONS

CYPs involved in estrogen metabolism are expressed in both tumor and non-tumor breast tissue. Local activation of estrogen to potentially reactive metabolites by the CYPs in breast tissue may play a role in initiating and promoting the carcinogenic process.

Relationship between urinary profile of the endogenous steroids and postmenopausal women with stress urinary incontinence

AIMS

The aims of this study were to investigate whether endogenous steroid hormones are (1) related to pathogenesis of stress urinary incontinence after menopause, (2) are related to severity of stress urinary incontinence, and (3) are related to prognostic parameters of stress urinary incontinence.

METHODS

Twenty post-partum women with clinically diagnosed stress urinary incontinence and 20 age-matched postmenopausal women without stress urinary incontinence (control group) were evaluated. We compared urinary profile of the endogenous steroid hormones patients with stress urinary incontinence and controls, and between grade I and grade II of stress urinary incontinence. We also investigated the relationship between urinary profile of the endogenous steroid hormones and prognostic parameters of stress urinary incontinence (maximal urethral closure pressure, functional urethral length, Valsalva leak point pressure, cough leak point pressure, posterior urethrovesical angle, bladder neck descent, and stress urethral axis). The ages of the patients and those in the control group were 64.3 +/- 5.6 and 57.5 +/- 3.8 years old and the body mass indexes were 24.96 +/- 3.14 and 22.11 +/- 2.73 kg/m2 in patients and in normal subjects, respectively. Nine patients were grade I and 11 were grade II. Estrone and 17beta-estradiol only were detected in all subjects, regardless of control or patient group. It is noteworthy that there were no significant differences (P > 0.05) in the levels of estrone and 17beta-estradiol in the urine of postmenopausal normal subjects compared with in the urine of postmenopausal patients with urinary incontinence. E2/E1 ratio was not different between the two groups (P > 0.05). Among the objective steroids, DHEA, Delta4-dione, Delta5-diol, Te, DHT, 16alpha-DHT, 11-keto An, THDOC, and THB were not detected either in the urine of normal subjects and nor in the urine of the patients. After comparing androgen levels between normal subjects and patients, no significant differences (P>0.05) were detected, except for 5alpha-THB and 5alpha-THF. Neither 5alpha-THB or 5alpha-THF were detected in the patients' urine. Et/An (11beta-OH Et/11beta-OH An) concentration ratios were not significantly different between the two groups, either (P > 0.05). There were not significant differences of concentrations (micromol/g creatinine) of urinary steroids between grade I and grade II of stress urinary incontinence. Pregnanediol was significantly related to bladder neck descent in supine and sitting positions (R = 0.79, P = 0.01, and R = 0.73, P = 0.03, respectively), and pregnanetriol was significantly related to maximal urethral closure pressure and functional urethral length (R = 0.68, P = 0.04, and R = -0.79, P = 0.01, respectively). Androsterone was significantly related to bladder neck descent in supine and sitting positions (R = 0.68, P = 0.04, and R = 0.78, P = 0.01, respectively). 5-AT was significantly related to bladder neck descent in sitting position and stress urethral axis (R = 0.72, P = 0.03, and R = -0.71, P = 0.03). 11-keto Et was significantly related to bladder neck descent in supine and sitting positions and related to stress urethral axis (R = 0.82, P = 0.01, and R = 0.81, P = 0.01, R = -0.67, P = 0.04, respectively). THS was significantly related to bladder neck descent in supine and sitting positions and related to stress urethral axis (R = 0.76, P = 0.02, and R = 0.74, P = 0.02, R = -0.68, P = 0.04, respectively). THE was significantly related to bladder neck descent in sitting position (R = 0.67, P = 0.04).beta-Tetrahydrocortisol/alpha-tetrahydrocortisol (beta-THF/alpha-THF) and alpha-cortol were significantly related to maximal urethral closure pressure and functional urethral length (R = 0.74, P = 0.02, and R = -0.92, P = 0.01; R = 0.71, P = 0.36, and R = -0.87, P = 0.000, respectively). 17beta-estradiol (E2) was significantly related to bladder neck descent in supine position (R = -0.62, P = 0.04) and 17beta-estradiol/estrone (E2/E1) was significantly related to cough leak point pressure (R = 0.79, P = 0.01). In conclusion, the urinary concentrations of endogenous steroid metabolites in postmenopausal patients with stress urinary incontinence were not significantly different from normal patients and were not significantly different between grade I and grade II patients with stress urinary incontinence. Some endogenous steroid metabolites were positively or negatively significantly related to prognostic parameters of stress urinary incontinence.

Benzo(a)pyrene exposure induces CYP1A1 activity and expression in human endometrial cells

Estrogen is a major risk factor for endometrial cancer and it has been well-established that smokers have a significantly reduced risk of endometrial cancer. Localized levels of estrogen within the uterus may determine the estrogenic response. The objective of this research was to investigate effects of cigarette smoke related hydrocarbons (benzo(a)pyrene, BP) on uterine CYP1A1/2 and 1B1, enzymes involved in estrogen metabolism. Human endometrium epithelial cells (RL95-2) were incubated with various concentrations (0.05, 0.1, 0.5, 1, and 10mM) of BP for 48h. CYP1 catalytic activity, protein and mRNA levels were determined. Selective chemical and immuno-inhibitors were used to determine the contribution of individual CYP1 isoenzymes. Cells expressing CYP1A1, CYP1A2 and CYP1B1 were used for comparisons. CYP1A1/2 protein and mRNA levels were significantly elevated by BP. Low level of constitutive CYP1 activity was observed in RL95-2 cells, which was significantly induced by BP exposure (12-fold at 1mM). CYP1 activity in BP-induced cells was significantly inhibited by specific anti-CYP1A1 and high concentration of alpha-naphthoflavone (ANF, 100nM), but not by selective CYP1A2 (furafylline) and CYP1B1 (homoeriodictoyl) inhibitors and low concentration of ANF (5nM). These studies suggest that CYP1A2 and CYP1B1 are not induced by BP in the endometrial cells. It also appears that CYP1A1 is one of the major CYP450 enzymes induced by BP.

High metabolization of catecholestrogens by type 1 estrogen sulfotransferase (hEST1)

Recently, two types of estrogen sulfotransferase, chronologically named types 1 and 2 estrogen sulfotransferase (hEST1 and hEST2), have been described. Since hEST2 selectively catalyzes the sulfonation of ethinyl estradiol as well as that of estrone (E1) and estradiol (E2), but poorly the sulfonation of catecholestrogens, we wanted to assess the ability of hEST1 to metabolize these compounds. We overexpressed hEST1 in Escherichia coli in fusion with GST, then purified the enzyme using a glutathione affinity column, and obtained GST-free enzyme by digestion with thrombin. Using [35S]-phosphosadenosine phosphosulfate (PAPS) as cofactor, we showed that hEST1 efficiently metabolizes the transformation of 2-OH-E2 and 2-OH-E1. However, the transformation of 4-OH-E1 and 4-OH-E2 is much less efficient. Our results also show that hEST1 metabolizes more efficiently E2 than E1. Since hEST1 mRNA is produced from the same gene as MPST using different alternative promoters and since it is expressed in most breast cancer cells (MCF-7, ZR-75-1, T47-D, MDA-231, and MDA-418), studies of the expression and activity of hEST1 will be most important to have a better knowledge about its involvement in the control of the genotoxicity of estrogens and catecholestrogens.

The oxidative metabolism of estradiol conditions postmenopausal bone density and bone loss

Because lifelong exposure to estrogen is a strong determinant of bone mass, we asked whether metabolic conversion of estrogen to either inactive or active metabolites would reflect postmenopausal bone mineral density (BMD) and rate of bone loss. Biochemical markers of inactive estrogen metabolites, urinary 2-hydroxyestrogen (2OHE1) and 2-methoxyestrogen (2MeOE1), and active metabolites, urinary 16alpha-hydroxyestrone (16alphaOHE1), estradiol (E2), and estriol (E3), were determined in 71 untreated, healthy postmenopausal women (age, 47-59 years) followed prospectively for 1 year. Urinary 2MeOE1 was correlated negatively with baseline vertebral (anteroposterior [AP] projection, r = -0.23 andp < 0.05; lateral view, r = -0.27 and p < 0.05) and proximal femur bone density measured by dual-energy X-ray absorptiometry (DXA; total, r = -0.38 and p < 0.01; neck, r = -0.28 and p = 0.02; trochanter, r = -0.44 and p < 0.01). BMDs of women in the lowest quartile of urinary 2MeOE1 (< 15 ng/g) were significantly higher than those in the highest quartile at all skeletal sites (p < 0.05). Likewise, women in the lowest quartile of urinary 2OHE1/16alphaOHE1 ratio (< 1.6) did not experience bone loss after 1 year, in contrast to women in the higher quartiles. We propose that the rate of inactivation of estrogens through 2-hydroxylation may contribute to postmenopausal osteoporosis.

Estrogens and women's health: interrelation of coronary heart disease, breast cancer and osteoporosis

The determinants of blood levels of estrogen, estrogen metabolites, and relation to receptors and post-transitional effects are the likely primary cause of breast cancer. Very high risk women for breast cancer can now be identified by measuring bone mineral density and hormone levels. These high risk women have rates of breast cancer similar to risk of myocardial infarction. They are candidates for SERM therapies to reduce risk of breast cancer. The completion of the Women's Health Initiative and other such trials will likely provide a definite association of risk and benefit of both estrogen alone and estrogen-progesterone therapy, coronary heart disease, osteoporotic fracture, and breast cancer. The potential intervention of hormone replacement therapy, obesity, or weight gain and increased atherogenic lipoproteinemia may be of concern and confound the results of clinical trials. Estrogens, clearly, are important in the risk of bone loss and osteoporotic fracture. Obesity is the primary determinant of postmenopausal estrogen levels and reduced risk of fracture. Weight reduction may increase rates of bone loss and fracture. Clinical trials that evaluate weight loss should monitor effects on bone. The beneficial addition of increased physical activity, higher dose of calcium or vitamin D, or use of bone reabsorption drugs in coordination with weight loss should be evaluated. Any therapy that raises blood estrogen or metabolite activity and decreases bone loss may increase risk of breast cancer. Future clinical trials must evaluate multiple endpoints such as CHD, osteoporosis, and breast cancer within the study. The use of surrogate markers such as bone mineral density, coronary calcium, carotid intimal medial thickness and plaque, endothelial function, breast density, hormone levels and metabolites could enhance the evaluation of risk factors, genetic-environmental intervention, and new therapies.

Direct action of naturally occurring estrogen metabolites on human osteoblastic cells

This article describes experiments that were performed to examine the direct action of estrogen metabolites on cultured human osteoblast cells. The human fetal osteoblastic cell line, hFOB/ER9, which expresses high levels of the estrogen receptor (ER) alpha, was used to examine the direct effects of 16alpha-hydroxyestrone (16alpha-OHE1) and 2-hydroxyestrone (2-OHE1) on osteoblast differentiation. The 16alpha-OHE1 caused a decrease in osteocalcin (OC) secretion to a maximum of 40% of control values (vehicle-treated cells) at 10(-7) M. Alkaline phosphatase (AP) activity was significantly induced at 10(-7) M 16alpha-OHE1 with greater than 500% of control at 10(-6) M 16alpha-OHE1. Finally, AP steady-state messenger RNA (mRNA) levels were increased within 24 h of 16alpha-OHE1 treatment. In contrast to 16alpha-OHE1, 2-OHE1 had no effects on the secretion of OC, AP activity, or AP gene expression. The 2-OHE1 also did not display any antiestrogen activity because treatment in combination with 17beta-estradiol (E2) and 16alpha-OHE1 had no significant effect on the reduction in OC secretion or induction of AP activity. Similar to E2, 16alpha-OHE1 stimulated the expression of an early response gene, a TGF-beta inducible early gene, designated TIEG, as early as 60 minutes after treatment, whereas treatment with 2-OHE1 displayed no effect. Support that the 16alpha-OHE1 regulation of these osteoblasts (OB) markers was mediated through the ER is shown by the fact that the estrogen antagonist ICI 182,780 abrogated these effects. These data suggest that is a potent estrogen agonist on human osteoblastic hOB/ER9 cells. In contrast, 2-OHE1 displayed no estrogenic or antiestrogenic activity in this human osteoblast cell model.

Soluble and membrane-bound catechol-O-methyltransferase in normal and malignant mammary gland

The levels of 26 kDa-soluble (S) and 30 kDa-membrane-bound (MB) catechol-O-methyltransferase (COMT) polypeptides were determined in paired samples from normal and neoplastic breast tissue of 32 patients with breast cancer. Immunohistochemical staining showed that the COMT reaction in normal mammary tissue was restricted to the epithelial cells in the ducti and lobuli, whereas in the tumors a strong reaction was also seen in the malignant cells. The amounts of COMT proteins in tumors could not be correlated with various clinical or pathological parameters. Quantitative immunoblotting analysis revealed that the total amount of COMT proteins in tumors was more than 50% higher than in respective normal samples in 26 out of 32 patients. Five cases showed less than a 50% difference and in one case less COMT was detected in the tumor. In most cases the amount of both S- and MB-COMT forms was increased. The average amount of total COMT was 178 +/- 57 pg/microg total protein in normal tissue and 566 +/- 94 pg/microg total protein in tumor. Respective values for S-COMT were 137 +/- 52 pg/microg total protein in normal tissue and 369 +/- 62 pg/microg total protein in tumor and for MB-COMT 41 +/- 10 and 197 +/- 41 pg/microg total protein, respectively. Analysis of COMT-specific transcripts suggested that the COMT enzyme level in tumors is determined in some cases by transcriptional and in some cases by post-transcriptional mechanisms.

Endogenous hormones and the risk of hip and vertebral fractures among older women. Study of Osteoporotic Fractures Research Group

BACKGROUND AND METHODS

In postmenopausal women, the serum concentrations of endogenous sex hormones and vitamin D might influence the risk of hip and vertebral fractures. In a study of a cohort of women 65 years of age or older, we compared the serum hormone concentrations at base line in 133 women who subsequently had hip fractures and 138 women who subsequently had vertebral fractures with those in randomly selected control women from the same cohort. Women who were taking estrogen were excluded. The results were adjusted for age and weight.

RESULTS

The women with undetectable serum estradiol concentrations (<5 pg per milliliter [18 pmol per liter]) had a relative risk of 2.5 for subsequent hip fracture (95 percent confidence interval, 1.4 to 4.6) and subsequent vertebral fracture (95 percent confidence interval, 1.4 to 4.2), as compared with the women with detectable serum estradiol concentrations. Serum concentrations of sex hormone-binding globulin that were 1.0 microg per deciliter (34.7 nmol per liter) or higher were associated with a relative risk of 2.0 for hip fracture (95 percent confidence interval, 1.1 to 3.9) and 2.3 for vertebral fracture (95 percent confidence interval, 1.2 to 4.4). Women with both undetectable serum estradiol concentrations and serum sex hormone-binding globulin concentrations of 1 microg per deciliter or more had a relative risk of 6.9 for hip fracture (95 percent confidence interval, 1.5 to 32.0) and 7.9 for vertebral fracture (95 percent confidence interval, 2.2 to 28.0). For those with low serum 1,25-dihydroxyvitamin D concentrations (< or =23 pg per milliliter [55 pmol per liter]), the risk of hip fracture increased by a factor of 2.1 (95 percent confidence interval, 1.2 to 3.5).

CONCLUSIONS

Postmenopausal women with undetectable serum estradiol concentrations and high serum concentrations of sex hormone-binding globulin have an increased risk of hip and vertebral fracture.

Serum estrogen levels, cognitive performance, and risk of cognitive decline in older community women

OBJECTIVE

To determine the association between serum estrogen levels, cognitive performance, and risk of cognitive decline in older women.

DESIGN

Prospective cohort study with an average follow-up of 5 years.

SETTING

Clinical centers in Baltimore, MD, Minneapolis, MN, Portland, OR, and the Monongahela Valley in Pennsylvania.

PARTICIPANTS

532 women aged 65 years or older who were the controls from two nested case-control studies in the ongoing Study of Osteoporotic Fractures.

OUTCOME MEASURES

Three cognitive tests--a modified Mini-Mental Status Exam, Digit Symbol, and Trails B--were administered at study initiation and were then repeated approximately 5 years later. Estrone and estradiol levels were determined by radioimmunoassay at two laboratories from baseline stored serum.

RESULTS

The characteristics of the women in the four serum estrogen quartiles did not differ except that body weight and change in weight since age 50 increased directly with higher quartile of serum estrogen (P < .001, for both estrone and estradiol). Initial cognitive performance on all three tests did not differ consistently by quartile of estradiol or by the estradiol to estrone ratio. Women in the higher estrone quartiles had 15% lower (worse) scores on Digit Symbol compared with the lower quartiles (P=.004) but there was no difference by quartile on the modified MMSE or on Trails B. Cognitive function test scores declined over the 5 years of follow-up. There was no difference in amount of change by quartile of estradiol, but women in the higher estrone quartiles had greater reduction of scores on Trails B compared with those in the lower quartiles (P=.012), even after adjusting for age, education, depression, stroke history, weight, and change in weight since age 50. The age-adjusted odds of cognitive decline (defined as tenth percentile of women with the largest decline in cognitive performance) did not vary across quartile of estrone or estradiol.

CONCLUSIONS

Endogenous estrogens are not associated consistently with cognitive performance or risk of cognitive decline on a selected battery of cognitive tests in older community-dwelling women. Worse performance on two cognitive tests among women with higher estrone levels was surprising and warrants further investigation.

Differential effects of estrogen metabolites on bone and reproductive tissues of ovariectomized rats

The effects of 17 beta-estradiol and the important estrogen metabolites, 2-hydroxyestrone (2-OHE1) and 16 alpha-hydroxyestrone (16 alpha-OHE1) on bone, mammary gland, and uterine histology, and on blood cholesterol were investigated in ovariectomized growing rats. Rats were treated with 200 micrograms/kg of body weight/day of each of the test compounds for 3 weeks. Ovariectomy resulted in uterine and mammary gland atrophy, increased body weight, bone turnover and tibia growth, and hypercholesterolemia. 17 beta-estradiol treatment prevented these changes, with the exception that this high dose of estrogen did not prevent hypercholesterolemia. 2-OHE1 had no effect on any of the measurements. 16 alpha-OHE1 resulted in bone measurements that did not differ from the 17 beta-estradiol-treated rats and prevented the increase in serum cholesterol. In contrast, 16 alpha-OHE1 resulted in increases in uterine weight, uterine epithelial cell height, and mammary gland cell proliferation that were significantly less than the 17 beta-estradiol treatment. These findings demonstrate that 16 alpha-hydroxylation of estrone results in tissue-selective estrogen agonistic activity, whereas 2-hydroxylation resulted in no measured activity. Furthermore, they suggest that factors that modulate the synthesis of these metabolites could selectively influence estrogen target tissues.

Changes in levels of urinary estrogen metabolites after oral indole-3-carbinol treatment in humans

BACKGROUND

The oxidative metabolism of estrogens in humans is mediated primarily by cytochrome P450, many isoenzymes of which are inducible by dietary and pharmacologic agents. One major pathway, 2-hydroxylation, is induced by dietary indole-3-carbinol (I3C), which is present in cruciferous vegetables (e.g., cabbage and broccoli).

PURPOSE

Because the pool of available estrogen substrates for all pathways is limited, we hypothesized that increased 2-hydroxylation of estrogens would lead to decreased activity in competing metabolic pathways.

METHODS

Urine samples were collected from subjects before and after oral ingestion of I3C (6-7 mg/kg per day). In the first study, seven men received I3C for 1 week; in the second study, 10 women received I3C for 2 months. A profile of 13 estrogens was measured in each sample by gas chromatography-mass spectrometry.

RESULTS

In both men and women, I3C significantly increased the urinary excretion of C-2 estrogens. The urinary concentrations of nearly all other estrogen metabolites, including levels of estradiol, estrone, estriol, and 16alpha-hydroxyestrone, were lower after I3C treatment.

CONCLUSIONS

These findings support the hypothesis that I3C-induced estrogen 2-hydroxylation results in decreased concentrations of several metabolites known to activate the estrogen receptor. This effect may lower estrogenic stimulation in women.

IMPLICATIONS

I3C may have chemopreventive activity against breast cancer in humans, although the long-term effects of higher catechol estrogen levels in women require further investigation.

Equine cytochrome P450 aromatase exhibits an estrogen 2-hydroxylase activity in vitro

Aromatase (estrogen synthetase) is a steroidogenic enzyme complex which catalyzes the conversion of androgens to estrogens (termed aromatization). This enzyme was purified from adult equine testis to homogeneity by five chromatographic steps. The ability of purified and reconstituted equine aromatase to exhibit an estrogen 2-hydroxylase activity was tested and compared to testosterone aromatization. Enzymatic activities were assessed by tritiated water release from labelled estradiol and testosterone. Kinetic analysis of estradiol 2-hydroxylation showed an apparent K(m) of 23 microM and a V(max) of 18 nmol/min/mg, whereas the values for testosterone aromatization were a K(m) of 15.7 nM and a V(max) of 34.6 pmol/min/mg. A specific antiserum raised against purified testicular equine P450arom and known to inhibit aromatase activity [1] was also found to inhibit the estrogen hydroxylase activity of equine placental microsomes in a dose-dependent manner with an IC50 value of 15 microl serum: 0.5 ml incubate. The estrogen hydroxylase activity was inhibited in a dose-dependent manner by two classes of aromatase inhibitors, i.e. steroidal-- (4-hydroxyandrostenedione and 7alpha-([4-aminophenyl]thio)-androst-4-ene-3, 17-dione)--and non-steroidal--(fadrozole and miconazole). The IC50 values were approximately 300 and 890 nM for 4-hydroxyandrostenedione and 7alpha-([4-aminophenyl]thio)-androst-4-ene-3, 17-dione, and 92 and 285 nM, for fadrozole and miconazole, respectively. Furthermore, 4-hydroxyandrostenedione caused a time-dependent inactivation of estrogen hydroxylase activity. We conclude that equine aromatase is able to use estradiol as a substrate, and converts it to catechol estradiol in vitro, possibly using the active site of aromatization. This is the first demonstration that equine aromatase functions as an estrogen 2-hydroxylase, in addition to transforming androgens into estrogen.

Experimental down-regulation of intermediate biomarkers of carcinogenesis in mouse mammary epithelial cells

The polycyclic aromatic hydrocarbon 7,12-dimethylbenz(a)anthracene (DMBA) is a metabolism-dependent procarcinogen whose tumorigenicity is modified by dietary and endocrine manipulations in vivo. DMBA initiates molecular and cellular alterations in the mammary tissue, while dietary components and estrogens affect the post-initiational phase of tumorigenic transformation. The mechanism(s) responsible for modulation of tumorigenic transformation remain unclear. This study examines the effects of selected tumor suppressing agents and estradiol (E2) metabolites on in vitro DMBA carcinogenesis utilizing a newly established mouse mammary epithelial cell line C57/MG. Alteration in DNA repair synthesis, metabolism of E2 via the C2- and C16 alpha-hydroxylation pathways, and acquisition of anchorage-independent growth were utilized as molecular, endocrine, and cellular biomarkers to quantitate the cellular transformation by DMBA and its modulation by tumor suppressing agents and E2 metabolites. A single 24 hr exposure of 0.78 microM DMBA to C57/MG cells resulted in a 193.9% increase in DNA repair synthesis and a 73.1% decrease in C2/C16 alpha hydroxylation of E2. The DMBA treated C57/MG cells also exhibited increased anchorage-independence in vitro prior to tumorigenesis in vivo. A simultaneous treatment of cells with DMBA and with the highest noncytotoxic doses of the tumor suppressing agents 5 microM N-(4-hydroxyphenyl) retinamide (HPR), 50 microM indole-3-carbinol (I3C), or 1 microM tamoxifen (TAM) resulted in a 35.6% to 63.9% decrease in DNA repair synthesis, a 23.8% to 1347.6% increase in C2/C16 alpha hydroxylation of E2, and a 53.8% to 72.4% decrease in anchorage-independent growth. The E2 metabolites at the highest non-cytotoxic doses of 0.76 microM estrone (E1), 0.69 microM 2-hydroxyestrone (2-OHE1), and 0.66 microM 2-methoxyestrone (2-MeOHE1) suppressed DMBA-induced DNA repair synthesis by 56.0% to 68.8%. These tumor suppressing agents and E2 metabolites also effectively suppressed post-initiational, anchorage-independent growth by 24.9% to 72.4%. These results indicate that DMBA induces cellular transformation in part by causing DNA damage, altering C2/C16 alpha hydroxylation in favor of C16 alpha-hydroxylation, and inducing anchorage-independent growth prior to tumor development. Effective downregulation of these genotoxic, endocrine and proliferative end points by prototypic tumor suppressing agents and by E2 metabolites generated via the C2-hydroxylation pathway suggest that these agents may influence mammary tumorigenesis by inhibiting early occurring initiational and/or post initiational events.

Gas chromatography/mass spectrometry of catechol estrogens

Catecholestrogens (CCEs), namely 2- or 4-hydroxyestradiol and hydroxyestrone, are highly polar, reactive, and extremely labile estrogen metabolites in many experimental conditions. For these reasons, indirect assay methods mainly have been used. Some experimental evidence suggests that CCEs are synthesized and biologically active mostly in target cells. At this level, unfortunately, the indirect assays cannot be used. We present a method of gas chromatographic/mass spectral (GC/MS) analysis for the identification of individual CCEs; the major fragmentation ions of authentic estrogen standards as trimethylsilylether derivatives, and the MS patterns of the major CCEs, namely, 2-hydroxyestradiol and hydroxyestrone, are included. Few examples of CCEs detected in human breast cancer tissues and in breast cyst fluids are reported. Sample extracts were submitted to reversed-phase, high-performance liquid chromatography (RP-HPLC) and were quantified by "on line" electrochemical (EC) detection; thereafter, either crude extracts or single eluted peaks were submitted to GC/MS, by which detection limits of less than 5 pmol were attained. As expected, the molecular ion was the most relevant molecule in all but one case. On the contrary, the other relative intensities of major fragmentation ions M -15, M -30, M -90, and M -15 + (-90) were unevenly distributed, although represented in the majority of cases. In all cases, the GC/MS of peak fractions, purified by RP-HPLC and UV detection, confirmed the results of liquid chromatographic analysis combined with EC detection. In contrast, GC/MS of crude extracts was not equally satisfactory. Comparison of a liquid chromatography system with EC detection and the GC/MS approach revealed some inconsistency in quantitation of individual CCEs.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell-type specific responses in prostaglandin secretion by glandular and stromal cells from pig endometrium treated with catecholestrogens, methoxyestrogens and progesterone

The pig conceptus and endometrium possess the ability to convert estrogens into catecholestrogens and catecholestrogens into methoxyestrogens. Experiments were carried out to evaluate the effect of catecholestrogens, methoxyestrogens and progesterone on the secretion of prostaglandin (PG) E and F2 alpha by porcine endometrial glandular and stromal cells in vitro. Both 2-hydroxyestradiol (2-OH-E2, 0-20 microM) and 4-hydroxyestradiol (4-OH-E2, 0-20 microM) increased (P less than .05) PGE and PGF2 alpha secretion by stromal cells in a dose response manner. Two-hydroxyestradiol tended (P less than .1) to decrease PGF2 alpha production by glandular cells. Two-methoxyestradiol (20 microM) suppressed (P less than .05) PGF2 alpha secretion by glandular and stromal cells. Four-methoxyestradiol (20 microM) stimulated (P less than .05) PGE production and PGE:PGF2 alpha ratio. Progesterone (.1 microM) suppressed (P less than .05) PG secretion in both cell types. We conclude that catecholestrogens, methoxyestrogens, and progesterone may participate in the establishment of pregnancy by modulating PG production in the endometrium.

Enzymatic regulation of estradiol-17 beta concentrations in human breast cancer cells

Estradiol-17 beta is known to be involved in both the etiology and maintenance of growth of breast cancer. However, blood levels of the hormone do not reflect those found within the cells due to a number of transformations catalysed by enzymes which may be under metabolite and/or hormonal regulation. Recognition of the importance of the hormone microenvironment within the cell focuses attention on these enzymes and provides the subject for this review. An interplay between the sex hormones, estrogen and progestin, can control estradiol-17 beta concentrations in breast cancer cells at the level of key transforming enzymes. In addition, some enzymes catalyse production of biologically inert derivatives which are rapidly eliminated from the cell. Other enzymes catalyse the formation of derivatives which are exclusively intracellular and can act as reserve forms of the hormone. Yet others lead to estradiol-17 beta metabolites which are cytotoxic. An improved understanding of the enzymes and the role of the related metabolites can provide the opportunity for the development of new therapeutic agents.