Overview
Estrogens play important roles in the pathophysiology of breast tumors and are recognized causal factors in the etiology of breast cancer (BC); this central insight has led to many of the available preventive and therapeutic interventions for BC. Endogenous estrogens may also play causal roles in endometrial and ovarian cancers and could also be important in male reproductive cancers, such as male breast cancer, testicular cancer, and prostate cancer. Substantial inter-individual variability has been observed in levels of circulating and excreted estrogens and estrogen metabolites (jointly referred to as EM) among men, postmenopausal women, and premenopausal women. Because EM vary with respect to bioavailability, affinity to estrogen receptors, and mutagenic potential, investigators have hypothesized that variations in estrogen profiles may account for interindividual differences in cancer risks. Until recently, it has been difficult to study this hypothesis in epidemiologic settings. Recent development of a liquid chromatography-tandem mass spectrometry (LC/MS2) method for measurement of estrogens and estrogen metabolites in urine (Xu et al., Anal Chem 2006;78:1553) and serum (Xu et al., Anal Chem 2007;79:7813) represents an important methodologic development because it provides an assay with characteristics that make it feasible for use in epidemiologic studies: high sensitivity, specificity, reliability, and scalability for high-throughput work.
The BREAST Stamp Project
Prior studies of sex-steroid hormones and mammographic density have mainly evaluated older women, providing limited opportunities to assess hormone levels across a broader range of mammographic density. To date, studies have evaluated the effects of only a few estrogens and estrogen metabolites on mammographic density, in large part due to limitations in laboratory assay methods. The BREAST Stamp Project , which has utilized novel, precise, volumetric mammographic density measurements and includes both pre- and postmenopausal women, has the potential to clarify estrogen-mammographic density relationships. Furthermore, the reduction in measurement error with improved density assessment using digital mammography may result in an increased ability to detect even small associations with circulating estrogens and their metabolites. We are examining this relationship using a high-performance liquid chromatography mass spectrometry (LC/MS) method to measure estrogens. The strengths of the BREAST Stamp Project, combined with the precision of the LC/MS techniques, present an exciting opportunity to advance our understanding of the role of estrogens in mammographic density and breast cancer. More information, Gretchen Gierach.
Biomarkers for Breast Cancer Prevention (B4BCP) Study
We are currently conducting a cross-sectional study of urinary estrogen metabolites in association with mammographic density among postmenopausal women. Participants are drawn from the cross-sectional Biomarkers for Breast Cancer Prevention (B4BCP) study, which was designed to explore determinants of mammographic density in a sample of postmenopausal women. Participants were recruited when they sought mammographic evaluations at a radiology clinic near Buffalo, NY in 2005. They included 225 enrolled participants who were aged 45-80, postmenopausal, and reported no history of cancer or current hormone use. They provided first morning urine samples, and completed questionnaires which queried reproductive and medical histories, as well as dietary and lifestyle factors. The present study takes advantage of a well-characterized study sample, an intermediate marker of breast cancer risk, and the sensitive, specific, and reliable LC/MS2 assay developed by Xu and colleagues to test hypotheses about the roles of estrogen metabolism in breast cancer etiology. Investigators are studying associations of urinary estrogen metabolite profiles with mammographic density, dietary and lifestyle factors, and established breast cancer risk factors. More information, Louise Brinton.
Serum Estrogen Metabolites and Postmenopausal Breast Cancer Risk in Columbia, MO Follow-up Study
Using the expanded group of breast cancer cases in the Columbia, MO Serum Bank Follow-up Study, additional biomarker studies have been conducted, including evaluating the role of recently identified adipokines. We are currently analyzing circulating estrogens using the LC/MS2 method that simultaneously measures a panel of 15 estrogens and estrogen metabolites in serum. Although the link between postmenopausal breast cancer risk and pre-diagnostic levels of estrogens is well established, we hope to address several unanswered questions, including whether metabolized forms of estrogen play a role in postmenopausal breast cancer carcinogenesis and whether this new technique provides more discrimination of risk than conventional radioimmunoassays. Having measured the primary estrogens by radioimmunoassay on a subset of the breast cancer cases affords us the unique opportunity to address this question. More information, Louise Brinton.
Serum Sex Steroids and Their Metabolites in Relation to Ovarian and Endometrial Cancer in WHIOS
In collaboration with investigators from the Women’s Health Initiative, we are conducting a nested case-control study of endometrial and ovarian cancers to assess the roles of estrogens, estrogen metabolites, and androgens in the etiologies of these cancers. Cases and shared controls have been drawn from the Women’s Health Initiative Observational Study (WHIOS) cohort. This effort benefits from unique WHIOS resources, including large numbers of cancer cases, prospectively collected serum and baseline data on important cancer risk factors. Assays will relate circulating estrogens and metabolites as measured by LC/MS2 to cancer risk based on approximately 240 ovarian and 430 endometrial cancer cases. More information, Nicolas Wentzensen.
Hormone Levels Related to Testicular Germ Cell Tumors
Testicular germ cell tumors (TGCTs) are cancers that occur, primarily, among young men. TGCTs, as well as several other male reproductive disorders, may have a perinatal etiology that also results in aberrant hormonal levels. To examine this hypothesis, we have been studying hormone levels in men who went on to develop TGCT and men who did not, as part of our STEED TGCT study . Thus far we have examined the gonadotropins, LH and FSH, the steroid hormones, estradiol, testosterone, and sex- androstane-3a,17ß-diol glucuronide (3adiol-G) levels, and sex-hormone binding globulin. To more completely characterize the hormonal milieu that may precede TGCT, we also plan to examine hCG, inhibin, dihydrotestosterone, dehydroepiandrosterone, dehydroepiandrosterone sulfate, and androsterone glucuronide. More information, Katherine McGlynn.
Reproductive Hormone Levels in U.S. Men in the NHANES Survey
In an effort to understand trends in hormone levels that are occurring in the general U.S. population, we measured several sex steroid hormones (testosterone, estradiol, androstanediol glucuronide) and sex hormone-binding globulin in sera from National Health and Nutrition Examination Survey (NHANES) participants. NHANES is a program of studies conducted by the Centers for Disease Control and Prevention (CDC) in order to assess health in the U.S. population. The survey combines interview, physical examination, and laboratory components, and allows for investigator-initiated studies when surplus samples are available. Our most recent study using this data addressed trends in male hormone levels between the 1988-1991 and 1999-2004 survey populations. Future work in this area will involve examining associations between hormone levels and potential risk factors for testicular cancer. More information, Katherine McGlynn.
Serum Estrogen Metabolites and Cancer Risk in the BFIT Study
Although circulating estrogens have been evaluated in prior epidemiological studies of cancer, numerous questions remain with regard to the role of estrogen metabolites in the development of hormone-related cancers. We are currently conducting a case-cohort study to examine circulating estrogens and estrogen metabolites in relation to four specific cancer endpoints within the BFIT study. The BFIT follow-up study includes postmenopausal women (ages 55-80) who volunteered for the Fracture Intervention Trial (FIT) in 1992-1993. Women who were screened for participation in the trial completed a risk factor questionnaire, provided a baseline blood sample and underwent a bone mineral density scan. As part of the B-FIT study, these women were followed (median 10.3 years) to ascertain incident cancer outcomes and incident fractures through the period of 2001-2004. A comprehensive profile of endogenous estrogens, including 15 estrogens and estrogen metabolites, is being measured in pre-diagnostic serum using a Liquid Chromatography-Tandem Mass Spectrometry (LC-MS) assay developed at the SAIC-Frederick Hormone Laboratory. These measures will be examined in relation to breast (n~420), endometrial (n~62), ovarian (n~65), and colorectal (n~178) cancers. In addition to the evaluation of a comprehensive estrogen profile, this study is unique in that we will also be able to examine the interrelationships with measured bone density. Results from this study will further our understanding of endogenous estrogen exposure, bone mineral density, and cancer risk. More information, Louise Brinton.
Urinary Estrogen Metabolites and Accelerometer Measures in the NCI Polish Study
Numerous epidemiological studies suggest that higher levels of physical activity may reduce breast cancer risk among postmenopausal women. Although the mechanisms that account for the protective effect of physical activity are not well understood, it has been hypothesized that physical activity may reduce levels of circulating sex steroid hormones. We are conducting a cross-sectional study of approximately 600 postmenopausal controls in the NCI Polish Breast Study with the overall objective of assessing urinary estrogen metabolites in relation to accelerometer-based measures of active and sedentary behavior. The NCI Polish Breast Cancer Study is a population-based case-control study conducted among women 20-74 years of age, residing in Warsaw and Lódz, Poland from 2000 to 2003. In addition to the collection of questionnaire data and biological specimens, women from the Warsaw, Poland site were also asked to wear an accelerometer (Actigraph 7165) for 7 days. A comprehensive urinary profile of endogenous estrogens, including 15 estrogens and estrogen metabolites, will be measured using a Liquid Chromatography-Tandem Mass Spectrometry (LC-MS) assay developed at the SAIC-Frederick Hormone Laboratory. Findings from this study will extend our biological understanding of the effects of physical activity and sedentary time on estrogen metabolism. More information, Louise Brinton.
Association of Urinary Estrogen Metabolites with Mammographic Density in a Sample of Postmenopausal Women
We are currently conducting a cross-sectional study of urinary estrogen metabolites in association with mammographic density among postmenopausal women. Participants are drawn from the cross-sectional Biomarkers for Breast Cancer Prevention (B4BCP) study, which was designed to explore determinants of mammographic density in a sample of postmenopausal women. Participants were recruited when they sought mammographic evaluations at a radiology clinic near Buffalo, NY in 2005. They included 225 enrolled participants who were aged 45-80, postmenopausal, and reported no history of cancer or current hormone use. They provided first morning urine samples, and completed questionnaires which queried reproductive and medical histories, as well as dietary and lifestyle factors. The present study takes advantage of a well-characterized study sample, an intermediate marker of BC risk, and the sensitive, specific, and reliable assay developed by Xu and colleagues (2005) to test hypotheses about the roles of estrogen metabolism in breast cancer etiology. Investigators will study associations of urinary estrogen metabolite profiles with mammographic density, with dietary and lifestyle factors, and with established breast cancer risk factors. More information, Louise Brinton.
Reproducibility and Validity of Hormone Assays
The branch has been involved in an effort to develop approaches to ensure high quality of biochemical probes in large-scale epidemiologic studies, particularly in the area of hormonal carcinogenesis. An extensive methodologic study designed to assess laboratory reproducibility and validity of a large number of hormone assays has demonstrated that current laboratory assays for most circulating estrogens and some but not all androgens are adequate for large research efforts provided quality control procedures are carefully implemented and monitored. Current assays for urinary estrogens and the 2- and 16 -hydroxyestrone metabolites are also reliable, even in postmenopausal women, where serum estrogen concentrations may be at or below assay sensitivity. For More Information Contact: Roni Falk
In preparation for large-scale epidemiologic studies, we have conducted a number of studies to assess methods for measurement of estrogens and estrogen metabolites. We have conducted formal proofs-of-performance to describe reliability of a recently developed liquid chromatography-tandem mass spectrometry (LC/MS2) method for measurement of 15 estrogens and estrogen metabolites in urine (Falk RT, et al, Cancer Epidemiol Biomarkers Prev 2008, 17:3411), and another to characterize the assay for use in measuring serum EM in unconjugated and total (conjugated + unconjugated) forms (Fuhrman, unpublished). Additional studies have documented the stability of urinary EM under varying conditions of processing and storage (Fuhrman BJ, et al, Int J Biol Markers 2010;25:185) and the comparability of LC/MS2 measures of urinary EM to previously employed immunoassays (Faupel-Badger JM, et al, Cancer Epidemiol Biomarkers Prev 2010;19:292). More information, Gretchen Gierach.
