Do urinary oestrogen metabolites predict breast cancer? Guernsey III cohort follow-up

Associations of established breast cancer risk factors with urinary estrogens in postmenopausal women

PURPOSE

Circulating estrogens are an established risk factor for postmenopausal breast cancer (BCa). We describe the distribution of urinary estrogens, their metabolites, and relevant metabolic pathway ratios among healthy postmenopausal women and examine associations of several known BCa factors with these estrogen measures.

METHODS

Eligible postmenopausal women (n = 167) had no history of hormone use (previous 6 months) and cancer/metabolic disorders and had a body mass index (BMI) ≤ 35 kg/m². Estrogens were quantified in spot urine samples with liquid chromatography-high-resolution mass spectrometry and corrected for creatinine. We assessed overall distributions of estrogens and associations of age, BMI, race/ethnicity, parity/age at first birth, age at menarche, alcohol, and smoking with log-transformed estrogen measures using multivariate regression.

RESULTS

BMI was positively associated with estrone (β per unit = 0.04, 95% Confidence Interval [CI] 0.00; 0.07), combined parent estrogens (β = 0.04, 95% CI 0.01; 0.07), and E2:total estrogens (β = 0.04, 95% CI 0.02; 0.06), and inversely associated with 4-MeOE1 (β = - 0.17, 95% CI - 0.33; - 0.02), E3:parent estrogens (β = - 0.04, 95% CI - 0.07; - 0.00), and 16-pathway:parent (β = - 0.04, 95% CI - 0.07; - 0.01). Being African American vs. white was associated with higher levels of 4-MeOE1 (β = 3.41, 95% CI 0.74; 6.08), 17-epiE3 (β = 1.19, 95% CI 0.07; 2.31), 2-pathway:parent (β = 0.54, 95% CI 0.04; 1.04), and lower levels of E2:total estrogens (β = - 0.48, 95% CI - 0.83; - 0.13). Having < 7 alcohol drinks/week vs. none was associated with higher levels of 16-ketoE2 (β = 1.32, 95% CI 0.36; 2.27), 16-epiE3 (β = 1.02, 95% CI 0.24; 1.79), and 17-epiE3 (β = 0.55, 95% CI 0.02; 1.08). Smoking was positively associated with E3:parent (β = 0.29, 95% CI 0.01; 0.57), 16-pathway:parent (β = 0.25, 95% CI 0.01; 0.49), and inversely associated with estradiol (β = - 0.52, 95% CI - 0.93; - 0.10). As compared to nulliparous, parous women with age at first birth ≥ 25 years had lower levels of estrone, combined parent estrogens, 2-OHE1, and 2-OHE2.

CONCLUSION

Our findings suggest that BMI, race/ethnicity, and some reproductive and lifestyle factors may contribute to postmenopausal BCa through their effects on circulating estrogens.

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.

Cytochrome P450: Implications for human breast cancer

The treatment options for breast cancer include endocrine therapy, targeted therapy and chemotherapy. However, some patients with triple-negative breast cancer cannot benefit from these methods. Therefore, novel therapeutic targets should be developed. The cytochrome P450 enzyme (CYP) is a crucial metabolic oxidase, which is involved in the metabolism of endogenous and exogenous substances in the human body. Some products undergoing the metabolic pathway of the CYP enzyme, such as hydroxylated polychlorinated biphenyls and 4-chlorobiphenyl, are toxic to humans and are considered to be potential carcinogens. As a class of multi-gene superfamily enzymes, the subtypes of CYPs are selectively expressed in breast cancer tissues, especially in the basal-like type. In addition, CYPs are essential for the activation or inactivation of anticancer drugs. The association between CYP expression and cancer risk, tumorigenesis, progression, metastasis and prognosis has been widely reported in basic and clinical studies. The present review describes the current findings regarding the importance of exploring metabolic pathways of CYPs and gene polymorphisms for the development of vital therapeutic targets for breast cancer.

Markers of Local and Systemic Estrogen Metabolism in Endometriosis

Estrogen metabolites (EMs) can work independently from their parent hormones. We hypothesize that in endometriosis, estrogen is metabolized preferentially along hormonally active pathways. We recruited 62 women with endometriosis (proven laparoscopically and histologically) and 52 control women (normal findings with laparoscopy) among patients undergoing surgery for pelvic pain and/or infertility during the proliferative phase of the menstrual cycle. Urinary samples were collected preoperatively. Biopsies from eutopic endometrium of control women and women with endometriosis were collected during surgery. EMs in urine and endometrial tissues were extracted and determined using Liquid Chromatography-Electrospray Ionization Tandem Mass Spectrometry (LC-ESI-MS/MS). These included: 2-hydroxyestrone (2OHE1), 16-α hydroxyestrone (16α-OHE1), 2OHE1/16α-OHE1 ratio, 4-hydroxyestrone (4OHE1), 2-hydroxyestradiol (2OHE2), and 4-hydroxyestradiol (4OHE2). Eutopic endometrium of endometriosis patients, as compared to control endometrium, contained significantly higher level of 4OHE1 (0.03 (IQR: 0.03-0.265) versus 0.03 (IQR: 0.03-0.03) μg/g, respectively, P = 0.005), 2-OHE2 (0.241 (IQR: 0.1-0.960) versus 0.1 (IQR: 0.1-0.1) μg/g, respectively, P < 0.001), and 4-OHE2 (0.225 (IQR: 0.22-1.29) versus 0.0.2 (IQR: 0.2-0.2) μg/g, respectively, P < 0.001). Only 2OHE1 showed higher concentration in urine of women with endometriosis than controls (9.9 (IQR: 3.64-14.88) versus 4.5 (IQR: 1.37-17.00) μg/mg creatinine, respectively, P = 0.042). Eutopic endometrium of women with endometriosis metabolizes estrogen preferentially to the biologically active 2OHE2, and potentially genotoxic 4OHE1 and 4OHE2 metabolites. This contributes to further understanding of endometriosis etiology, its link to ovarian cancer, and could help identifying an endometrial biomarker of the disease.

The Steroid Metabolome and Breast Cancer Risk in Women with a Family History of Breast Cancer: The Novel Role of Adrenal Androgens and Glucocorticoids

BACKGROUND

No study has comprehensively examined how the steroid metabolome is associated with breast cancer risk in women with familial risk.

METHODS

We examined 36 steroid metabolites across the spectrum of familial risk (5-year risk ranged from 0.14% to 23.8%) in pre- and postmenopausal women participating in the New York site of the Breast Cancer Family Registry (BCFR). We conducted a nested case-control study with 62 cases/124 controls individually matched on menopausal status, age, and race. We measured metabolites using GC-MS in urine samples collected at baseline before the onset of prospectively ascertained cases. We used conditional logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI) per doubling in hormone levels.

RESULTS

The average proportion of total steroid metabolites in the study sample were glucocorticoids (61%), androgens (26%), progestogens (11%), and estrogens (2%). A doubling in glucocorticoids (aOR = 2.7; 95% CI = 1.3-5.3) and androgens (aOR = 1.6; 95% CI = 1.0-2.7) was associated with increased breast cancer risk. Specific glucocorticoids (THE, THF αTHF, 6β-OH-F, THA, and α-THB) were associated with 49% to 161% increased risk. Two androgen metabolites (AN and 11-OH-AN) were associated with 70% (aOR = 1.7; 95% CI = 1.1-2.7) and 90% (aOR = 1.9; 95% CI = 1.2-3.1) increased risk, respectively. One intermediate metabolite of a cortisol precursor (THS) was associated with 65% (OR = 1.65; 95% CI = 1.0-2.7) increased risk. E1 and E2 estrogens were associated with 20% and 27% decreased risk, respectively.

CONCLUSIONS

Results suggest that glucocorticoids and 11-oxygenated androgens are positively associated with breast cancer risk across the familial risk spectrum.

IMPACT

If replicated, our findings suggest great potential of including steroids into existing breast cancer risk assessment tools.

LC-HRMS of derivatized urinary estrogens and estrogen metabolites in postmenopausal women

In order to undertake an epidemiologic study relating levels of parent estrogens (estrone and estradiol) and estrogen metabolites (EMs) to other breast cancer risk factors, we have optimized methods for EM quantification with ultra high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS). A two-step approach was adopted; the first step comprised method development and evaluation of the method performance. The second step consisted of applying this method to quantify estrogens in postmenopausal women and determine if the observed patterns are consistent with the existing literature and prior knowledge of estrogen metabolism. First, 1-methylimidazole-2-sulfonyl chloride (MIS) was used to derivatize endogenous estrogens and estrogen metabolites in urine from study participants. Since C18 reversed phase columns have not been able to separate all the structurally related EMs, we used a C18-pentafluorophenyl (PFP) column. The parent estrogens and EMs were baseline resolved with distinct retention times on this C18-PFP column using a 30 min gradient. This method was used to quantify the parent estrogens and 13 EMs in urine samples collected in an initial pilot study involving males as well as pre- and peri-menopausal females to assess a range of EM levels in urine samples and enable comparison to the previous literature for assay evaluation. Detection limits ranged from 1 - 20 pg/mL depending on the EM. We evaluated matrix effects and interference as well as the intra- and inter-batch reproducibility including hydrolysis, extraction, derivatization and LC-MS analysis using charcoal-stripped human urine as a matrix. Methods were then applied to the measurement of estrogens in urine samples from 169 postmenopausal women enrolled in an epidemiological study to examine relationships between breast cancer risk, the intestinal microbiome, and urinary EMs. The results from our cohort are comparable to previous reports on urinary EMs in postmenopausal women and enabled thorough evaluation of the method.

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.

Toward a holistic view of multiscale breast cancer molecular biomarkers

Powered by rapid technology developments, biomarkers become increasingly diverse, including those detected at genomic, transcriptomic, proteomic, metabolomic and cellular levels. While diverse sets of biomarkers have been utilized in breast cancer predisposition, diagnosis, prognosis, treatment and management, recent additions derived from lincRNA, circular RNA, circulating DNA together with its methylated and hydroxymethylated forms and immune signatures are likely to further transform clinical practice. Here, we take breast cancer as an example of heterogeneous diseases that require many informed decisions from treatment to care to review the huge variety of biomarkers. By assessing the advantages and limitations of modern biomarkers in diverse use scenarios, this article outlines the prospects and challenges of releasing complimentary advantages by augmentation of multiscale molecular biomarkers.

4-Hydroxy estrogen metabolite, causing genomic instability by attenuating the function of spindle-assembly checkpoint, can serve as a biomarker for breast cancer

Sex hormone metabolism is altered during mammary gland tumorigenesis, and different metabolites may have different effects on mammary epithelial cells. This study aimed to evaluate associations between urinary sexual metabolite levels and breast cancer risk among premenopausal women of Mainland China. The molecular metabolism of the cancer-related metabolites was also explored based on the clinical data. The sex hormone metabolites in the urine samples of patients with breast cancer versus normal healthy women were analyzed comprehensively. Among many alterations of sex hormone metabolisms, 4-hydroxy estrogen (4-OH-E) metabolite was found to be significantly increased in the urine samples of patients with breast cancer compared with the normal healthy controls. This was the most important risk factor for breast cancer. Several experiments were conducted in vitro and in vivo to probe this mechanism. 4-Hydroxyestradiol (4-OH-E₂) was found to induce malignant transformation of breast cells and tumorigenesis in nude mice. At the molecular level, 4-OH-E₂ compromised the function of spindle-assembly checkpoint and rendered resistance to the anti-microtubule drug. Further, transgenic mice with high expression of CYP1B1, a key enzyme of 4-hydroxy metabolites, were established and stimulated with estrogen. Cancerous tissue was found to appear in the mammary gland of transgenic mice.

Endogenous Estrogens, Estrogen Metabolites, and Breast Cancer Risk in Postmenopausal Chinese Women

BACKGROUND

The role of estrogen metabolism in determining breast cancer risk and differences in breast cancer rates between high-incidence and low-incidence nations is poorly understood.

METHODS

We measured urinary concentrations of estradiol and estrone (parent estrogens) and 13 estrogen metabolites formed by irreversible hydroxylation at the C-2, C-4, or C-16 positions of the steroid ring in a nested case-control study of 399 postmenopausal invasive breast cancer case participants and 399 matched control participants from the population-based Shanghai Women's Health Study cohort. Odds ratios (ORs) and 95% confidence intervals (CIs) of breast cancer by quartiles of metabolic pathway groups, pathway ratios, and individual estrogens/estrogen metabolites were estimated by multivariable conditional logistic regression. Urinary estrogen/estrogen metabolite measures were compared with those of postmenopausal non-hormone-using Asian Americans, a population with three-fold higher breast cancer incidence rates. All statistical tests were two-sided.

RESULTS

Urinary concentrations of parent estrogens were strongly associated with breast cancer risk (ORQ4vsQ1 = 1.94, 95% CI = 1.21 to 3.12, Ptrend = .01). Of the pathway ratios, the 2-pathway:total estrogens/estrogen metabolites and 2-pathway:parent estrogens were inversely associated with risk (ORQ4vsQ1 = 0.57, 95% CI = 0.35 to 0.91, Ptrend = .03, and ORQ4vsQ1 = 0.61, 95% CI = 0.37 to 0.99, Ptrend = .04, respectively). After adjusting for parent estrogens, these associations remained clearly inverse but lost statistical significance (ORQ4vsQ1 = 0.65, 95% CI = 0.39 to 1.06, Ptrend = .12 and ORQ4vsQ1 = 0.76, 95% CI = 0.44 to 1.32, Ptrend = .28). The urinary concentration of all estrogens/estrogen metabolites combined in Asian American women was triple that in Shanghai women.

CONCLUSIONS

Lower urinary parent estrogen concentrations and more extensive 2-hydroxylation were each associated with reduced postmenopausal breast cancer risk in a low-risk nation. Markedly higher total estrogen/estrogen metabolite concentrations in postmenopausal United States women (Asian Americans) than in Shanghai women may partly explain higher breast cancer rates in the United States.

The effect of oral 3,3'-diindolylmethane supplementation on the 2:16α-OHE ratio in BRCA1 mutation carriers

Hormonal exposures are known to influence breast cancer risk among women with a BRCA1 mutation. Thus, dietary factors that increase the 2-hydroxyestrone (OHE):16α-OHE ratio, a biomarker inversely related to breast cancer development, may also influence cancer risk. We conducted a dietary intervention study to evaluate the ability of 300 mg/day of 3,3'-diindolylmethane (DIM) to increase the urinary 2:16α-OHE ratio in 20 women with a BRCA1 mutation. BRCA1 mutation carriers (n = 15) were assigned to receive 300 mg/day of Rx Balance BioREsponse DIM for 4-6 weeks (intervention group) and five BRCA1 mutation carriers did not take DIM (control group). The urinary 2:16α-OHE ratio was assessed at baseline and after 4-6 weeks by immunoassay. There was no significant effect of DIM on the 2:16α-OHE ratio (2.4 at baseline vs. 3.0 after the intervention, P = 0.35). A short dietary intervention with DIM did not significantly increase the 2:16α-OHE ratio in female BRCA1 mutation carriers. Larger studies investigating the effect of dietary or lifestyle interventions on circulating hormone levels in these high-risk women are warranted.

Epidemiologic studies of estrogen metabolism and breast cancer

Early epidemiologic studies of estrogen metabolism measured only 2-hydroxyestrone and 16α-hydroxyestrone and relied on direct enzyme immunoassays without purification steps. Eight breast cancer studies have used these assays with prospectively collected blood or urine samples. Results were inconsistent, and generally not statistically significant; but the assays had limited specificity, especially at the low concentrations characteristic of postmenopausal women. To facilitate continued testing in population-based studies of the multiple laboratory-based hypotheses about the roles of estrogen metabolites, a novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay was developed to measure concurrently all 15 estrogens and estrogen metabolites in human serum and urine, as unconjugated and total (glucuronidated+sulfated+unconjugated) concentrations. The assay has high sensitivity (lower limit of quantitation ∼1-2 pmol/L), reproducibility (coefficients of variation generally ⩽5%), and accuracy. Three prospective studies utilizing this comprehensive assay have demonstrated that enhanced 2-hydroxylation of parent estrogens (estrone+estradiol) is associated with reduced risk of postmenopausal breast cancer. In the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) cohort, the serum ratio of 2-hydroxylation pathway metabolites to parent estrogens was associated with a 28% reduction in breast cancer risk across extreme deciles (p-trend=.05), after adjusting for unconjugated estradiol and breast cancer risk factors. Incorporating this ratio into a risk prediction model already including unconjugated estradiol improved absolute risk estimates substantially (by ⩾14%) in 36% of the women, an encouraging result that needs replication. Additional epidemiologic studies of the role of estrogen metabolism in the etiology of hormone-related diseases and continued improvement of estrogen metabolism assays are justified.

4,4'-Methylenedianiline Alters Serotonergic Transport in a Novel, Sex-Specific Model of Pulmonary Arterial Hypertension in Rats

Pulmonary arterial hypertension (PAH) is a cardiovascular disorder characterized by elevated pulmonary artery pressure as a result of arterial wall thickening. Patients are 3-4 times more likely to be women than men. This gender discrepancy demonstrates a need for an animal model with similar sex differences. 4,4'-Methylenedianiline (DAPM) is an aromatic amine used industrially in the synthesis of polyurethanes. Chronic, intermittent treatment of male and female rats with DAPM resulted in medial hyperplasia of pulmonary arterioles, exclusively in females, coupled to increases in pulmonary arterial pressures. Significant increases in plasma levels of endothelin-1 (ET-1) and serotonin, but decreases in nitrite [Formula: see text], were observed in females treated with DAPM. A decrease was observed in the serum ratio of the estrogen metabolites 2-hydroxyestradiol (2-OHE1)/16α-hydroxyestrogen (16α-OHE1). In females, ET-1,[Formula: see text] , and 2-OHE1/16α-OHE1 were significantly correlated with peak pressure gradient, an indirect measure of pulmonary arterial pressure. Expression of the serotonin transport protein (SERT) was significantly higher in the arteries of DAPM-treated females. In vitro, DAPM induced human pulmonary vascular smooth muscle cell proliferation and serotonin uptake, both of which were inhibited by treatment with the estrogen receptor antagonist ICI 182,780 or the selective serotonin reuptake inhibitor fluoxetine. DAPM also induced the release of serotonin from human pulmonary endothelial cells in culture, which is blocked by ICI 182,780. Taken together, this suggests that DAPM-mediated dysregulation of serotonin transport is estrogen-receptor dependent. Thus, DAPM-induced PAH pathology may be a new tool to clarify the sex selectivity of PAH disease pathogenesis.

The ratio of the estradiol metabolites 2-hydroxyestrone (2-OHE1) and 16α-hydroxyestrone (16-OHE1) may predict breast cancer risk in postmenopausal but not in premenopausal women: two case-control studies

PURPOSE

Two main estradiol metabolites have different biological behavior with tumorigenic features of 16-OHE1 and antiproliferative characteristics of 2-OHE1. We investigated the ratio of these estradiol metabolites in pre- and postmenopausal patients with breast cancer (BC) within two case-control studies.

METHODS

From 41 premenopausal patients with (cases) and without (controls N = 211) BC and 207 postmenopausal patients with and without BC (N = 206), urine samples were collected. Urine samples were collected prior to surgery and stored at -20 °C until measurement by ELISA. The multiple linear regression test with two interactions was performed to evaluate the influence of different factors on the metabolic ratio.

RESULTS

In premenopausal patients, log ratio of 2-OHE1/16-OHE1 was 0.25 (CI 0.20;0.29) and 0.21 (CI 0.11;0.31) for controls and cases without significant difference. In postmenopausal patients, log ratio was 0.22 (CI 0.17;0.26) and 0.11 (CI 0.07;0.15) in controls and cases, respectively, and was statistically significantly lower (p = 0.0002). Log ratio was significantly influenced by BMI, but only in postmenopausal patients, an increased BMI resulted in a significantly (p < 0.042) decreased ratio.

CONCLUSIONS

Our case control studies suggest that in postmenopausal women a different metabolism of estrogens may play a role in the tumorigenesis of breast cancer. This genetically determined metabolism could be influenced by the exogenic factor BMI. In premenopausal women different hormone levels at different time points of the menstrual cycle may be an explanation that why we could not find an influence of estrogen metabolism.

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.

Estrogen metabolism and breast cancer risk among postmenopausal women: a case-cohort study within B~FIT

Although elevated circulating estrogens are associated with increased postmenopausal breast cancer risk, less is known regarding the role of estrogen metabolism in breast carcinogenesis. We conducted a case-cohort study within the Breast and Bone Follow-up to the Fracture Intervention Trial to assess serum estrogens and estrogen metabolites (EMs) in 407 incident breast cancer cases diagnosed during follow-up and a subcohort of 496 women. In 1992-93, women completed a baseline questionnaire and provided blood samples. Hazard ratios (HRs) and 95% confidence intervals (CIs), adjusted for geography and trial participation status, were estimated using Cox proportional hazard regression. Serum concentrations of EMs were measured by liquid chromatography-tandem mass spectrometry. EMs (quintiles, Q) were analyzed individually, as metabolic pathways (C-2, -4 or -16) and as ratios. Elevated circulating estradiol was associated with increased breast cancer risk (HRQ5vsQ1 = 1.86; 95% CI: 1.19-2.90; P trend = 0.04). An elevated ratio of the 2-hydroxylation pathway (HRQ5vsQ1 = 0.69; 95% CI: 0.46-1.05; P trend = 0.01) and 4-hydroxylation pathway (HRQ5vsQ1 = 0.61; 95% CI: 0.40-0.93; P trend = 0.004) to parent estrogens (estradiol and estrone) was inversely associated with risk. A higher ratio of the 2/16-hydroxylation pathways was associated with reduced risk (HRQ5vsQ1 = 0.60; 95% CI: 0.40-0.90; P trend = 0.002). Increased 2- or 4-hydroxylation of parent estrogens may lower risk of postmenopausal breast cancer. Analyses of metabolic pathways may help elucidate the role of estrogen metabolism in breast carcinogenesis.

The effects of aerobic exercise on estrogen metabolism in healthy premenopausal women

BACKGROUND

It is well accepted that exercise can decrease breast cancer risk. Limited clinical evidence suggests that this risk could be mediated through changes in estrogen metabolism in premenopausal women. Our objective was to investigate the effects of exercise on premenopausal estrogen metabolism pertinent to breast cancer risk.

METHODS

Sedentary, healthy, young eumenorrheic women were randomized into an intervention of 30 minutes of moderate-to-vigorous aerobic exercise five times a week for approximately 16 weeks (n = 212), or into a usual-lifestyle sedentary control group (n = 179). Urinary levels of estrogens [estrone [E1], estradiol, and estriol] and nine estrogen metabolites were measured at baseline and at study end by liquid chromatography/tandem mass spectrometry. The ratios of 2-hydroxyestrone to 16α-hydroxyestrone (2-OHE1/16α-OHE1) and 2-OHE1 to 4-hydroxyestrone (2- OHE1/4-OHE1) were also calculated.

RESULTS

The exercise intervention resulted in significant increases in aerobic fitness and lean body mass and a significant decrease in percent body fat. For exercisers who completed the study (n = 165), 2-OHE1/16α-OHE1 increased significantly (P = 0.043), whereas E1 decreased significantly (P = 0.030) in control participants (n = 153). The change from baseline in 2-OHE1/16α-OHE1 was significantly different between groups (P = 0.045), even after adjustment for baseline values.

CONCLUSIONS

The exercise intervention resulted in a significant increase in the 2-OHE1/16α-OHE1 ratio but no differences in other estrogen metabolites or ratios.

IMPACT

Our results suggest that changes in premenopausal estrogen metabolism may be a mechanism by which increased physical activity lowers breast cancer risk.

Endogenous sex steroids in premenopausal women and risk of breast cancer: the ORDET cohort

INTRODUCTION

Previous studies showed that higher testosterone levels are associated with greater risk of breast cancer in premenopausal women, but the literature is scant and inconsistent.

METHODS

In a prospective nested case-control study of 104 premenopausal women with incident breast cancer and 225 matched controls, all characterized by regular menstrual cycles throughout their lifetime, we measured the concentration of estradiol, total and free testosterone (FT), progesterone, sex hormone-binding globulin (SHBG), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) in blood samples collected on days 20 through 24 of their cycles.

RESULTS

In logistic regression models, the multivariate odds ratios (ORs) of invasive breast cancer for women in the highest tertile of circulating FT compared with the lowest was 2.43 (95% confidence interval (95% CI), 1.15 to 5.10; Ptrend = 0.03), whereas for total testosterone, the association had the same direction but was not statistically significant (OR, 1.27; 95% CI, 0.62 to 2.61; Ptrend = 0.51). Endogenous progesterone was not statistically associated with breast cancer (OR, 1.16; 95% CI, 0.60 to 2.27; Ptrend = 0.75), nor were the other considered hormones.

CONCLUSIONS

Consistent with previous prospective studies in premenopausal women and our own earlier investigation, we observed that higher levels of FT are positively associated with breast cancer risk in women with regular menstrual cycles throughout their lifetimes. No evidence of risk was found associated with the other endogenous sex steroids.

Urinary estrogen metabolites and breast cancer: a combined analysis of individual level data

BACKGROUND

Circulating estrogens are associated with increased breast cancer risk, yet the role of estrogen metabolites in breast carcinogenesis remains unclear. This combined analysis of 5 published studies evaluates urinary 2-hydroxyestrone (2-OHE1), 16α-hydroxyestrone (16α-OHE1), and their ratio (2:16α-OHE1) in relation to breast cancer risk.

METHODS

Primary data on 726 premenopausal women (183 invasive breast cancer cases and 543 controls) and 1,108 postmenopausal women (385 invasive breast cancer cases and 723 controls) were analyzed. Urinary estrogen metabolites were measured using enzyme linked immunosorbent assays. Study-specific and combined multivariable adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated based on tertiles of estrogen metabolites. Multinomial logistic regression models were fit according to hormone receptor status.


RESULTS

Higher premenopausal 2:16α-OHE1 was suggestive of reduced breast cancer risk overall (study-adjusted ORIIIvsI=0.80; 95% CI: 0.49-1.32) and for estrogen receptor negative (ER-) subtype (ORIIIvsI=0.33; 95% CI: 0.13-0.84). Among postmenopausal women, 2:16α-OHE1 was unrelated to breast cancer risk (study-adjusted ORIIIvsI=0.93; 95% CI: 0.65-1.33); however, the association between 2-OHE1 and risk varied by body mass index (p-interaction=0.003).

CONCLUSIONS

Premenopausal urinary 2:16α-OHE1 may play a role in breast carcinogenesis; however, larger studies are needed. Our findings do not support reduced breast cancer risk with higher postmenopausal 2:16α-OHE1 overall, although obesity may modify associations with 2-OHE1.

Role of CYP1A2 polymorphisms in breast cancer risk in women

Cytochrome P4501A2 (CYP1A2) is a key enzyme in the etiology of breast cancer (BC). It is involved in breast carcinogen activation [aromatic (AAs) and heterocyclic amines (HAs), polycyclic aromatic hydrocarbons (PAHs)], in the production of beneficial oestrogen [2-hydroxyestrone (2-OHE1)] and in converting arachidonic acid (AAc) to epoxyeicosatrienoic acids (EETs), which have anti-inflammatory properties. Within a hospital-based case-control study, the effect of functional CYP1A2 variants [-3860G/A (rs2069514), -2467T/delT (rs3569413), -163C/A (rs762551)] and their interactions with environmental factors in BC risk was investigated. The study population included 125 BC cases and 43 non-cancer controls. Genotyping was performed in RT-PCR using Taqman assays. The gene-environment interaction was appraised using a case-only study design. We found that the -3860A variant, independently from environmental factors, as well as by interacting with fried foods (p=0.025) and indoor exposure to pollutants (p=0.050), reduced the risk of BC (p=0.025), whereas its interaction with coffee (p=0.045) increased the BC risk. This is the first study indicating that the -3860A variant, by decreasing CYP1A2 activity, modifies BC risk by interacting with environmental factors, thereby supporting the hypothesis that reduced CYP1A2 activity contributes to BC risk in different ways, for example, it may be protective by reducing the activation of pro-carcinogens such as AAs, HAs and PAHs, but would increase risk by reducing the beneficial formation of 2-OHE1 and EETs.

Hormone therapy, estrogen metabolism, and risk of breast cancer in the Women's Health Initiative Hormone Therapy Trial

BACKGROUND

In the Women's Health Initiative Hormone Trials (WHI-HT), breast cancer risk was increased with estrogen plus progestin (E+P) but not with unopposed estrogen (E-alone). We hypothesized that E+P would preferentially metabolize to 16α-hydroxyestrone (16α-OHE1) rather than 2-hydroxyestrone (2-OHE1), and that breast cancer risk would be associated with baseline and 1 year changes in estrogen metabolites: positively for 16α-OHE1 levels and negatively for levels of 2-OHE-1 and the 2:16 ratio.

METHODS

In a prospective case-control study nested in the WHI-HT, 845 confirmed breast cancer cases were matched to 1,690 controls by age and ethnicity. Using stored serum, 2-OHE1 and 16α-OHE1 levels were measured by enzyme immunoassay at baseline, and for those randomized to active treatment (n = 1,259), at 1 year.

RESULTS

The 1-year increase in 16α-OHE1 was greater with E+P than E-alone (median 55.5 pg/mL vs. 43.5 pg/mL, P < 0.001), but both increased 2-OHE1 by ∼300 pg/mL. Breast cancer risk was modestly associated with higher baseline levels of 2-OHE1 and the 2:16 ratio, and for estrogen receptor+/progesterone+ cases only, higher baseline 16α-OHE1 levels. For those randomized to active treatment, breast cancer risk was associated with greater increase in 2-OHE-1 and the 2:16 ratio, but associations were not significant.

CONCLUSIONS

Although E+P modestly increased 16α-OHE1 more than E-alone, increase in 16α-OHE1 was not associated with breast cancer.

IMPACT

Study results do not explain differences between the WHI E+P and WHI E-alone breast cancer results but metabolism of oral HT, which may explain smaller than expected increase in breast cancer compared with endogenous estrogens.

Association between reproductive factors and urinary estrogens and estrogen metabolites in premenopausal women

BACKGROUND

Little is known about relationships among reproductive factors, estrogens and estrogen metabolites (jointly referred to as EM), and estrogen metabolism patterns.

METHODS

In a cross-sectional analysis, we examined the associations of age at menarche, menstrual cycle length and regularity, parity, age at first and last birth, breastfeeding, and duration of and time since use of oral contraceptives with mid-luteal phase urinary EM in a sample of 603 premenopausal women, ages 33 to 51 years, within the Nurses' Health Study II (NHSII). Fifteen individual urinary EMs were measured with liquid chromatography/tandem mass spectrometry (LC/MS-MS) and analyzed both individually and in metabolic pathways.

RESULTS

Compared with women with extremely regular cycles, those with irregular cycles had lower levels of total EM (percent difference = 24%; P(trend) = 0.01), estradiol (23%; P(trend) = 0.02), and 16-hydroxylation pathway EM (32%; P(trend) < 0.01). Longer menstrual cycles were associated with higher levels of estrone (percent difference ≥32 vs. <26 days: 25%; P(trend) = 0.03), estradiol (24%; P(trend) = 0.01), and 16-hydroxylation pathway EM (22%; P(trend) = 0.02). Among parous women, older age at first birth was associated with lower 16-hydroxylation pathway EM (percent difference age at first birth >35 vs. ≤25 years: 20%; P(trend) = 0.02). The other reproductive factors were not statistically significantly associated with individual urinary EM or EM pathways.

CONCLUSIONS AND IMPACT

These data, based on a LC/MS-MS assay with high specificity and precision, provide an initial, comprehensive evaluation of the associations between reproductive factors and estrogen metabolism patterns.

Microbiome and malignancy

Current knowledge is insufficient to explain why only a proportion of individuals exposed to environmental carcinogens or carrying a genetic predisposition to cancer develop disease. Clearly, other factors must be important, and one such element that has recently received attention is the human microbiome, the residential microbes including Bacteria, Archaea, Eukaryotes, and viruses that colonize humans. Here, we review principles and paradigms of microbiome-related malignancy, as illustrated by three specific microbial-host interactions. We review the effects of the microbiota on local and adjacent neoplasia, present the estrobolome model of distant effects, and discuss the complex interactions with a latent virus leading to malignancy. These are separate facets of a complex biology interfacing all the microbial species we harbor from birth onward toward early reproductive success and eventual senescence.

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.

Urinary estrogen metabolites during a randomized soy trial

One of the hypothesized protective mechanisms of soy against breast cancer involves changes in estrogen metabolism to 2-hydroxy (OH) and 16α-OH estrogens. The current analysis examined the effect of soy foods on the 2:16α-OH E(1) ratio among premenopausal women during a randomized, crossover intervention study; women were stratified by equol producer status, a characteristic thought to enhance the protective effects of soy isoflavones. The study consisted of a high-soy diet with 2 soy food servings/day and a low-soy diet with <3 servings of soy/wk for 6 mo each; estrogen metabolites were measured in 3 overnight urines (baseline and at the end of the low- and high-soy diet) using gas chromatography mass spectrometry for the 82 women who completed the study. Urinary isoflavonoids were assessed by liquid chromatography mass spectrometry. When applying mixed models, the 2:16α-OH E(1) ratio increased (P = 0.05) because of a nonsignificant decrease in 16α-OH E(1) (P = 0.21) at the end of the high-soy diet. Similar nonsignificant increases in the 2:16α-OH E(1) ratio were observed in equol producers (P = 0.13) and nonproducers (P = 0.23). These findings suggest a beneficial influence of soy foods on estrogen metabolism regardless of equol producer status.

Estrogen metabolism and risk of breast cancer in postmenopausal women

BACKGROUND

Estrogens are recognized causal factors in breast cancer. Interindividual variation in estrogen metabolism may also influence the risk of breast cancer and could provide clues to mechanisms of breast carcinogenesis. Long-standing hypotheses about how estrogen metabolism might influence breast cancer have not been adequately evaluated in epidemiological studies because of the lack of accurate, reproducible, and high-throughput assays for estrogen metabolites.

METHODS

We conducted a prospective case-control study nested within the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO). Participants included 277 women who developed invasive breast cancer (case subjects) and 423 matched control subjects; at PLCO baseline, all subjects were aged 55-74 years, postmenopausal and not using hormone therapy, and provided a blood sample. Liquid chromatography-tandem mass spectrometry was used to measure serum concentrations of 15 estrogens and estrogen metabolites, in unconjugated and conjugated forms, including the parent estrogens, estrone and estradiol, and estrogen metabolites in pathways defined by irreversible hydroxylation at the C-2, C-4, or C-16 positions of the steroid ring. We calculated hazard ratios (HRs) approximating risk in highest vs lowest deciles of individual estrogens and estrogen metabolites, estrogens and estrogen metabolites grouped by metabolic pathways, and metabolic pathway ratios using multivariable Cox proportional hazards models. All statistical tests were two-sided.

RESULTS

Nearly all estrogens, estrogen metabolites, and metabolic pathway groups were associated with an increased risk of breast cancer; the serum concentration of unconjugated estradiol was strongly associated with the risk of breast cancer (HR = 2.07, 95% confidence interval [CI] = 1.19 to 3.62). No estrogen, estrogen metabolite, or metabolic pathway group remained statistically significantly associated with the risk of breast cancer after adjusting for unconjugated estradiol. The ratio of the 2-hydroxylation pathway to parent estrogens (HR = 0.66, 95% CI = 0.51 to 0.87) and the ratio of 4-hydroxylation pathway catechols to 4-hydroxylation pathway methylated catechols (HR = 1.34, 95% CI = 1.04 to 1.72) were statistically significantly associated with the risk of breast cancer and remained so after adjustment for unconjugated estradiol.

CONCLUSIONS

More extensive 2-hydroxylation of parent estrogens is associated with lower risk, and less extensive methylation of potentially genotoxic 4-hydroxylation pathway catechols is associated with higher risk of postmenopausal breast cancer.

Estrogen activity as a preventive and therapeutic target in thyroid cancer

Thyroid cancer is the most common endocrine-related cancer with increasing incidences during the last five years. Interestingly, according to the American Thyroid Association, the incidences of thyroid proliferative diseases occur four to five times more in women than in men with the risk of developing thyroid disorders being one in every eight females. Several epidemiological studies have suggested a possible correlation between incidences of thyroid malignancies and hormones but the precise contribution of estrogen in thyroid proliferative disease initiation, and progression is not well understood. This review is an attempt to define the phenotypic and genotypic modulatory effects of estrogen on thyroid proliferative diseases. The significance and relevance of expression of estrogen receptors, α and β, in normal and malignant thyroid tissues and their effects on different molecular pathways involved in growth and function of the thyroid gland are discussed. These novel findings open up areas of developing alternative therapeutic treatments and preventive approaches which employ the use of antiestrogen to treat thyroid malignancies.

Analysis of multiplex endogenous estrogen metabolites in human urine using ultra-fast liquid chromatography-tandem mass spectrometry: a case study for breast cancer

A rapid, sensitive, specific and accurate analytical method of ultra-fast liquid chromatography combined with tandem mass spectrometry (UFLC-MS/MS) was established for simultaneous quantitative analysis of 16 distinct endogenous estrogens and their metabolites (EMs) in postmenopausal female urine. The quantitative method utilized a hydrolysis/extraction/derivatization step and a UFLC system to achieve separation in 16 min. The lower limit of quantitation for each estrogen metabolite was 2 pg mL(-1) with the percent recovery of a known added amount of estrogen at 93.2-109.3%. The intra-batch accuracy and precision for all analytes were 87.5-107.7% and 0.6-11.7%, respectively, while inter-batch accuracy and precision were 87.0-105.8% and 1.2-10.2%, respectively. Using this developed and validated method, the comprehensive metabolic profiling of 16 EMs in urine samples of 86 postmenopausal female breast cancer patients and 36 healthy controls was investigated by systematic statistical analysis. As a result, the circulating levels of 6 EMs were found to be different by a comparison of patients and healthy controls. The parent estrogens, estrone (E1) and 17β-estradiol (E2), as well as 2-hydroxyestradiol (2-OHE2) and 4-hydroxyestradiol (4-OHE2) were produced in higher abundance, whereas 16α-hydroxyestrone (16α-OHE1) and 2-methoxyestradiol (2-MeOE2) were decreased in the breast cancer group. 2-OHE2 and 4-OHE2 in particular showed significant elevation in patients, which are consistent with the carcinogenic mechanism hypothesis that catechol estrogens can react with DNA via quinones, resulting in mutations to induce breast cancer. Thus, 2,4-hydroxylation may be the dominant metabolic pathway for parent estrogens rather than 16α-hydroxylation. The lower level of 2-MeOE2 in the breast cancer group was believed to correlate with its protective effect against tumor formation. This study could provide valuable information on the association of the EM metabolic pathway with carcinogenesis as well as identify potential biomarkers for estrogen-induced breast cancer risk.

Postmenopausal circulating levels of 2- and 16α-hydroxyestrone and risk of endometrial cancer

Background:

It has been suggested that the relative importance of oestrogen-metabolising pathways may affect the risk of oestrogen-dependent tumours including endometrial cancer. One hypothesis is that the 2-hydroxy pathway is protective, whereas the 16α-hydroxy pathway is harmful.

Methods:

We conducted a case–control study nested within three prospective cohorts to assess whether the circulating 2-hydroxyestrone : 16α-hydroxyestrone (2-OHE1 : 16α-OHE1) ratio is inversely associated with endometrial cancer risk in postmenopausal women. A total of 179 cases and 336 controls, matching cases on cohort, age and date of blood donation, were included. Levels of 2-OHE1 and 16α-OHE1 were measured using a monoclonal antibody-based enzyme assay.

Results:

Endometrial cancer risk increased with increasing levels of both metabolites, with odds ratios in the top tertiles of 2.4 (95% CI=1.3, 4.6; P_trend=0.007) for 2-OHE1 and 1.9 (95% CI=1.1, 3.5; P_trend=0.03) for 16α-OHE1 in analyses adjusting for endometrial cancer risk factors. These associations were attenuated and no longer statistically significant after further adjustment for oestrone or oestradiol levels. No significant association was observed for the 2-OHE1 : 16α-OHE1 ratio.

Conclusion:

Our results do not support the hypothesis that greater metabolism of oestrogen via the 2-OH pathway, relative to the 16α-OH pathway, protects against endometrial cancer.

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.

A preliminary study of the effectiveness of chinese therapeutic food on regulating female reproductive hormones

This study investigated the effectiveness of Chinese therapeutic food on female reproductive hormones in a double-blind, placebo-controlled clinical trial. Chinese kiwi fruit extract (Hong En No. 1) was provided for Australian peri-menopausal women for one month. Chinese medical assessment and urinary 2-hydroxyestrone (2-OHE) and 16alpha-hydroxyestrone (16alpha-OHE) tests were conducted. Twenty-six urinary samples (pre and post-trial) which met the requirement of testing were analysed, the ratio 2-OHE:16alpha-OHE of pre-trial (1.18 ± 0.34) and post-trial (0.97 ± 0.29) in the control group (n = 6) decreased but showed no significant change, this ratio of pre-trial (1.44 ± 0.16) and post-trial (1.65 ± 0.21) in the treatment group (n = 7) indicated an improvement (P = 0.066), which results in beneficial hormone regulation. The Chinese medicine assessment indicated that the patterns of disharmony mainly include Liver Qi stagnation and Liver-Kidney Yin deficiency patterns. No significant change observed in the control group, significant score reduction of the patterns of disharmony was achieved at post-trial in the treatment group, which indicates an improvement of general health condition.

3,3'-diindolylmethane modulates estrogen metabolism in patients with thyroid proliferative disease: a pilot study

BACKGROUND

The incidence of thyroid cancer is four to five times higher in women than in men, suggesting a role for estrogen (E₂) in the pathogenesis of thyroid proliferative disease (TPD) that comprises cancer and goiter. The objective of this study was to investigate the antiestrogenic activity of 3,3'-diindolylmethane (DIM), a bioactive compound derived from cruciferous vegetables, in patients with TPD.

METHODS

In this limited phase I clinical trial study, patients found to have TPD were administered 300 mg of DIM per day for 14 days. Patients subsequently underwent a total or partial thyroidectomy, and tissue, urine, and serum samples were collected. Pre- and post-DIM serum and urine samples were analyzed for DIM levels as well as estrogen metabolites. DIM levels were also determined in thyroid tissue samples.

RESULTS

DIM was detectable in thyroid tissue, serum, and urine of patients after 14 days of supplementation. Urine analyses revealed that DIM modulated estrogen metabolism in patients with TPD. There was an increase in the ratio of 2-hydroxyestrones (C-2) to 16α-hydroxyestrone (C-16), consistent with antiestrogenic activity that results in more of C-2 product compared with C-16.

CONCLUSION

Our data suggest that DIM enhances estrogen metabolism in TPD patients and can potentially serve as an antiestrogenic dietary supplement to help reduce the risk of developing TPD. The fact that DIM is detected in thyroid tissue implicates that it can manifest its antiestrogenic activity in situ to modulate TPD.

Estrogen metabolite ratio: Is the 2-hydroxyestrone to 16α-hydroxyestrone ratio predictive for breast cancer?

Experimental studies have shown that two main estrogen metabolites hydroxylated by CYP1A1 and CYP1B1 in the breast differentially affect breast cell proliferation and carcinogenesis. Although 16α-hydroxyestrone (16αOHE1) exerts estrogenic activity through covalent estrogen receptor (ER) binding, 2-hydroxyestrone (2OHE1) presumably has antiestrogenic capabilities. The ratio of 2OHE1 to 16αOHE1 represents the relative dominance of one pathway over the other and is believed to be modifiable by diet. It was hypothesized that women with or at high risk of breast cancer have a lower estrogen metabolite ratio (EMR) compared with women without breast cancer. We conducted a systematic review on the EMR as a predictor for breast cancer. A total of nine studies (six prospective and three retrospective) matched our inclusion criteria, comprising 682 premenopausal cases (1027 controls) and 1189 postmenopausal cases (1888 controls). For the highest compared with the lowest quantile of urinary EMR, nonsignificant associations suggested at best a weak protective effect in premenopausal but not in postmenopausal breast cancer (range of odds ratios: 0.50-0.75 for premenopausal and 0.71-1.31 for postmenopausal). Circulating serum/plasma EMR was not associated with breast cancer risk. Associations were inconclusive for receptor subtypes of breast cancer. Uncontrolled factors known to be involved in breast carcinogenesis, such as 4-hydroxyestrone (4OHE1) concentration, may have confounded results for EMR. Results of the prospective studies do not support the hypothesis that EMR can be used as a predictive marker for breast cancer risk. Future research should concentrate on profiles of estrogen metabolites, including 4OHE1, to gain a more complete picture of the relative importance of single metabolites for breast cancer.

Urinary 2/16 estrogen metabolite ratio levels in healthy women: a review of the literature

This is a summary of the published literature on the urinary 2/16 estrogen metabolite ratio in human populations, and a report the observed range of normal values in healthy women. Original research studies that included the measurement of urinary estrogen metabolites in human subjects were identified through an extensive Medline search; 43 distinct studies were identified, including a total of 6802 healthy women. The range of mean values of the 2/16 ratio measured with the ELISA method varied from 0.98 to 1.74; in studies of pre-menopausal women the range of mean values was 1.5-2.74, in studies of post-menopausal women mean values ranged from 1.15 to 2.25. The heterogeneity across studies was highly significant (p-value Q-test: <0.0001). In multivariable analyses, only race confirmed its role as an independent predictor of 2/16 ratio (F-value: 7.95; p-value: 0.009), after adjustment for age and menopausal status. There appears to be a large body of data on the 2/16 urinary ratio in healthy women. However, summary estimates are difficult to perform due to the high variability of the published study-specific values. The data suggests that race may be a contributor to 2/16 urinary ratio levels.

Comparison of estrogens and estrogen metabolites in human breast tissue and urine

BACKGROUND

An important aspect of the link between estrogen and breast cancer is whether urinary estrogen levels are representative of the intra-tissue levels of bioavailable estrogens.

METHODS

This study compares 15 estrogen and estrogen metabolite levels in breast tissue and urine of 9 women with primary breast cancer using a quantitative liquid chromatography-mass spectrometry method.

RESULTS

The average levels of estrogens (estrone, 17 beta-estradiol) were significantly higher in breast tissue than in urine. Both the 2 and the 16-hydroxylation pathways were less represented in breast tissue than urine; no components of the 4-hydroxypathway were detected in breast tissue, while 4-hydroxyestrone was measured in urine. However, the 2/16 ratio was similar in urine and breast tissue. Women carrying the variant CYP1B1 genotype (Leu/Val and Val/Val) showed significantly lower overall estrogen metabolite, estrogen, and 16-hydroxylation pathway levels in breast tissue in comparison to women carrying the wild type genotype. No effect of the CYP1B1 polymorphism was observed in urinary metabolites.

CONCLUSIONS

The urinary 2/16 ratio seems a good approximation of the ratio observed in breast tissue. Metabolic genes may have an important role in the estrogen metabolism locally in tissues where the gene is expressed, a role that is not readily observable when urinary measurements are performed.

The assessment of efficacy of Diascorea alata for menopausal symptom treatment in Taiwanese women

OBJECTIVE

The aim of this study was to assess the efficacy and safety of Diascorea alata for treatment of menopausal symptoms.

MATERIALS AND METHODS

Two-center, randomized, double-blind, placebo-controlled clinical investigation on 50 menopausal women randomly assigned to two groups, treated for 12 months with either placebo or two sachets daily of Diascorea extracts containing 12 mg/sachet. Primary outcome measures were changes in the Greene Climacteric Scale caused by Diascorea compared with placebo; secondary outcomes were changes in plasma hormone profiles. One-way ANCOVA test was performed to investigate the significance.

RESULTS

At 6 months and at the end of treatment, those women who received Diascorea showed general improvement in almost all the clinical symptoms investigated. A significant reduction was noted in the total Greene scores in the Diascorea group assessed at the end of 12 months' treatment (p < 0.01). This phenomenon was more significant for the psychological parameters of anxiety than for other parameters. Apparent improvements were noted in the parameters 'feeling tense or nervous' (p = 0.007), 'insomnia' (p = 0.004), 'excitable' (p = 0.047) and 'musculoskeletal pain' (p = 0.019) among those receiving Diascorea. Diascorea consumption also resulted in positive effects on blood hormone profiles.

CONCLUSIONS

Compared with placebo, Diascorea alata improves symptoms, particularly the psychological parameters in menopausal women. Safety monitoring indicated that standardized extracts of Diascorea alata were safe during daily administration over a period of 12 months.

Comparison of liquid chromatography-tandem mass spectrometry, RIA, and ELISA methods for measurement of urinary estrogens

Absolute and relative concentrations of estrogens and estrogen metabolites are important for clinical decisions as well as for epidemiologic, experimental, and clinical research on hormonal carcinogenesis. RIA and ELISA are routinely used for measuring estrogen metabolites in blood and urine due to efficiency and low cost. Here, we compare absolute and ranked concentrations of estrone, estradiol, and estriol measured by indirect RIA and of 2-hydroxyestrone and 16alpha-hydroxyestrone measured by ELISA to the concentrations obtained using a novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, which measures 15 estrogen metabolites concurrently. We used overnight urine samples collected from control women (362 premenopausal and 168 postmenopausal) participating in a population-based case-control study of breast cancer among Asian American women ages 20 to 55 years. When comparing RIA or ELISA levels to LC-MS/MS, absolute concentrations for the five estrogen metabolites ranged from 1.6 to 2.9 and 1.4 to 11.8 times higher in premenopausal and postmenopausal women, respectively (all P < 0.0001). However, LC-MS/MS measurements were highly correlated [Spearman r (r(s)) = 0.8-0.9] with RIA and ELISA measurements in premenopausal women and moderately correlated (r(s) = 0.4-0.8) in postmenopausal women. Measurements of the 2-hydroxyestrone:16alpha-hydroxyestrone ratio, a putative biomarker of breast cancer risk, were moderately correlated in premenopausal women (r(s) = 0.6-0.7) but only weakly correlated in postmenopausal women (r(s) = 0.2). LC-MS/MS had higher intraclass correlation coefficients (> or =99.6%) and lower coefficients of variation (< or =9.4%) than ELISA (> or =97.2% and < or =14.2%) and RIA (> or =95.2% and < or =17.8%). Comparison with the LC-MS/MS method suggests that the widely used RIA and ELISA estrogen metabolite measures may be problematic, especially at low estrogen metabolite levels characteristic of postmenopausal women.

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.

Are estradiol metabolites involved in gynaecological carcinogenesis?

Certain estradiol metabolites are biologically active, sometimes several times more potent than their parent substance. Highly sophisticated laboratory methods allow us to understand oestrogenic effects as a net effect of the corresponding metabolite pattern. Currently, research is focused on the anticancerogenic effects of 2-hydroxyestrone and particularly 2-methoxyestradiol, as well as the possible carcinogenic properties of 4-hydroxyoestrogens and 16α-hydroxyestrone. The clinical relevance of these activities, demonstrated in in-vitro and animal experiments, remains unclear - it is proven, however, that the metabolite production can be altered in certain malignancies such as endometrial-, breast- and cervical carcinoma. Clinical studies, including our studies, have demonstrated a negative correlation between the ratio of 2-hydroxyestrone to 16α-hydroxyestrone and breast cancer risk. However, the design and interpretation of such studies should consider factors influencing metabolic pattern such as diet, physical activity, smoking, as well as internal diseases and certain drugs.

Diet, physical activity and energy balance and their impact on breast and prostate cancers

Obesity, physical activity status and circulating levels of sex steroid hormones and growth factor proteins are intrinsically linked to energy balance. Epidemiological studies have previously reported associations between these factors and the risk of hormone-related cancers such as prostate and breast cancer in men and postmenopausal women. An increasing number of intervention studies in 'at-risk' populations and cancer survivors are now investigating the effects of lifestyle interventions that promote negative energy balance on circulating levels of sex hormones and growth factor proteins as surrogate markers of cancer risk. Evidence from these studies suggests that lifestyle interventions can improve insulin sensitivity, alter the balance of circulating sex steroid hormones and insulin-like growth factor (IGF) axis proteins (including IGF-1 and the IGF binding proteins 1 and 3) and change the functioning of immune cells in peripheral blood. Such changes could influence the risk of developing hormone-related cancers, as well as having the potential to improve disease-free survival in patients recovering from cancer treatment. However, despite promising results, the methodological quality of most intervention studies has been limited due to small subject numbers, lack of adequate control groups or non-randomised designs and the absence of long-term follow-up measures. More intervention studies with randomised controlled designs, higher numbers of subjects and longer-term follow-up measures are needed to establish which combination of specific dietary and physical activity interventions work best for reducing risk in 'at-risk' populations and survivors, optimal dose-response relationships and the magnitude of change in surrogate markers of cancer risk that is required to induce a protective effect.

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.

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.

Urinary estrogen metabolites and prostate cancer: a case-control study and meta-analysis

OBJECTIVE

To investigate prostate cancer (Pca) risk in relation to estrogen metabolism, expressed as urinary 2-hydroxyestrone (2-OHE1), 16alpha-hydroxyestrone (16alpha-OHE1) and 2-OHE1 to 16alpha-OHE1 ratio.

METHODS

We conducted a case-control study within the Western New York Health Cohort Study (WNYHCS) from 1996 to 2001. From January 2003 through September 2004, we completed the re-call and follow-up of 1092 cohort participants. Cases (n = 26) and controls (n = 110) were matched on age, race and recruitment period according to a 1:4 ratio. We used the unconditional logistic regression to compute crude and adjusted odds ratios (OR) and 95% confident interval (CI) of Pca in relation to 2-OHE1, 16alphaOHE1 and 2-OHE1 to 16alpha-OHE1 by tertiles of urine concentrations (stored in a biorepository for an average of 4 years). We identified age, race, education and body mass index as covariates. We also conducted a systematic review of the literature which revealed no additional studies, but we pooled the results from this study with those from a previously conducted case-control study using the DerSimonian-Laird random effects method.

RESULTS

We observed a non-significant risk reduction in the highest tertile of 2-OHE1 (OR 0.72, 95% CI 0.25-2.10). Conversely, the odds in the highest tertile of 16alpha-OHE1 showed a non-significant risk increase (OR 1.76 95% CI 0.62-4.98). There was a suggestion of reduced Pca risk for men in the highest tertile of 2-OHE1 to 16alpha-OHE1 ratio (OR 0.56, 95% CI 0.19-1.68). The pooled estimates confirmed the association between an increased Pca risk and higher urinary levels of 16alpha-OHE1 (third vs. first tertile: OR 1.82, 95% CI 1.09-3.05) and the protective effect of a higher 2-OHE 1 to 16alpha-OHE1 ratio (third vs. first tertile: OR 0.53, 95% CI 0.31-0.90).

CONCLUSION

Our study and the pooled results provide evidence for a differential role of the estrogen hydroxylation pathway in Pca development and encourage further study.

Ethnicity, body size, and estrogen levels in postmenopausal Hispanic and non-Hispanic white women

BACKGROUND

Hispanic women are at lower risk for incident breast cancer, but the reasons for this lower risk are unknown. Among postmenopausal women, breast cancer risk is inversely associated with circulating levels of 2-hydroxyestrone but directly associated with levels of 16alpha-hydroxyestrone, according to most studies. Likewise, according to most research, the ratio of 2-hydroxyestrone/16alpha-hydroxyestrone is, therefore, inversely associated with breast cancer risk.

METHODS

We measured levels of these two circulating estrones as well as estradiol in 40 Hispanic women and 40 non-Hispanic white women who were all postmenopausal and not taking hormones.

RESULTS

Compared with non-Hispanic white women, Hispanic women had 69% higher circulating levels of 2-hydroxyestrone (p = 0.04), and 10% lower levels of 16alpha-hydroxyestrone (p = 0.09). Consequentially, Hispanic women had more favorable estrogen profiles than non-Hispanic white women, with an 89% higher 2:16 ratio (p = 0.01). This finding was not substantially affected by adjustment for other breast cancer risk factors, including matching on body mass index (BMI).

CONCLUSIONS

This ethnic difference in estrogen profile requires further research to establish whether there is a causal relationship to breast cancer risk that may, at least partially, explain why postmenopausal Hispanic women have a lower incidence of breast cancer.

Urinary estrogen metabolites in women at high risk for breast cancer

OBJECTIVE

This study explored whether average urinary estrogen metabolites in breast cancer high-risk women can be used to identify a subgroup of women at particularly high risk to develop breast cancer, to which prevention strategies should be addressed.

METHODS

The population consisted of 77 high-risk women, 30 breast cancer patients and 41 controls. All subjects answered a standardized questionnaire; height and weight and spot urine samples were also obtained. Urine hydroxyestrogen metabolites were measured in triplicate by enzyme immunoassay, and the estrogen metabolite ratios for each individual were calculated.

RESULTS

The 2:16 OHE ratio (2-hydroxyestrone/16-alpha-hydroxyestrone) in women at high risk for breast cancer was similar to that observed in the breast cancer group (1.76 +/- 2.33 versus 1.29 +/- 0.80) and lower than in controls (2.47 +/- 1.14; P = 0.00). At the multivariate linear regression model, the 2:16 OHE ratio was significantly associated with diagnosis (P = 0.000 for both the high risk and breast cancer group versus the controls) and body mass index (P = 0.005), but not with age (P = 0.604), or smoking history (P = 0.478).

CONCLUSIONS

This study suggests that lower urinary 2:16 OHE ratios are predictors of breast cancer risk. Profiling estrogen metabolites may identify women who are more probably to develop breast cancer within a population of women with known risk factors and may help to further elucidate the clinical relevance of urinary 2:16 OHE ratios as clinical markers and prognostic indicators in this population.