Estrogen Suppression Research Articles

Impact of aromatase inhibitors on bone health in breast cancer patients

Following the implementation of the third generation aromatase inhibitors in the treatment algorithms for early breast cancer, special attention has been given to the influence of these drugs on bone health. Due to their potent estrogen suppression, the aromatase inhibitors anastrozole and letrozole, as well as the aromatase inactivator exemestane, enhance bone loss in postmenopausal women reflected in decreasing levels of bone mineral density. Moreover, all major phase III trials involving aromatase inhibitors in the adjuvant setting have reported increased fracture rates. All in all, there is no hard evidence to suggest major differences between the individual compounds concerning their side-effects on bone. The consequences of AI therapy on bone are in addition modified by a variety of factors like the BMD level prior to therapy, time since menopause, and vitamin D status. Strategies to avoid bone loss during AI therapy have shown promising results. Thus, bisphosphonates have been shown to prohibit bone loss during AI therapy if used upfront. Novel treatment strategies, like antibodies against RANKL have been developed and promising preliminary results have been published from early trials. Standardized guidelines to avoid or minimize bone loss during AI therapy have been developed, in most countries involving calcium and vitamin D supplementation, as well as BMD measurements to identify patient subgroups demanding bisphosphonate therapy.

Evaluation of plasma and tissue estrogen suppression with third-generation aromatase inhibitors: Of relevance to clinical understanding?

Development of aromatase inhibition and aromatase inhibitors as a therapeutic strategy was initiated through two different pathways. The one pathway went through systematic exploration of aromatase substrate analogues for enzyme inhibitions, subsequently leading to the development of steroidal agents for clinical use. The second involved clinical observation with an unsuccessful anti-epileptic compound named aminoglutethimide, attempting to achieve a “medical adrenalectomy”. Endocrine studies on patients treated with aminoglutethimide lead to direct assessment of in vivo aromatase inhibition in patients on treatment, thus identifying a novel therapeutic strategy. As such, both research programs represent different examples of pioneering translational work leading towards a successful therapeutic strategy. Subsequent studies with respect to total aromatase inhibition have led to successful development of more potent strategies. Most importantly, these studies have revealed a correlation between aromatase inhibition and clinical outcome. Ongoing studies exploring tissue estrogen levels as well as gene expression profiles on therapy may further improve this important therapeutic area.

Colorectal Cancer Risk in Patients with Breast Cancer Survivors: Evidence from a Comprehensive Cancer Center

Purpose: Previous epidemiological and observational studies have yielded conflicting results about incidence of colorectal cancer in patients with breast cancer. With increasing effectiveness of treatment regimens and increasing patient survivability, there is a paucity of data about the necessary frequency of high risk screening measures in this patient subpopulation. Methods: We conducted a retrospective cohort study among long term survivors (breast cancer free patients) on regular surveillance. The medical records of the patients was systematically reviewed by two independent physicians to collect relevant information including results of their index colonoscopy. Incidence rate ratios (RR) and 95% confidence intervals (95% CI) were calculated. Results: Our study included 303 patients with a follow up over 2232 person years. One patient was diagnosed with colonic adenocarcinoma. The RR of villous adenoma in patients over 50 years of age was 1.80 (95% CI 0.10- 32.06). RR of Tubular adenoma in patients more than and less than 50 years of age was 1.48 (95% CI 0.55-3.96) and 0.67 (95% CI 0.25-1.78) respectively. In patients with a family history of colorectal cancer the RR of development of villous adenoma was 3.37 (95% CI 0.57-19.67) and of tubular adenoma was 0.70 (95% CI 0.29- 1.70). Among patients on an estrogen antagonist, the RR of development of villous adenoma was 1.91 (95% CI 0.21-16.88) while that of tubular adenoma was 0.92 (95% CI 0.50-1.67). Conclusion: The results of our study indicate that age, family history of colon cancer and use of estrogen inhibitors are not a risk factor for development of advanced adenomas in this patient population. It is inferred that long term survivors of breast cancer are not an increased risk of premalignant and malignant lesions of colon in comparison with general population.FigureTable: Incidence of neoplastic lesions in breast cancer survivors

Dehydroepiandrosterone Reverses Systemic Vascular Remodeling Through the Inhibition of the Akt/GSK3-β/NFAT Axis

The remodeled vessel wall in many vascular diseases such as restenosis after injury is characterized by proliferative and apoptosis-resistant vascular smooth muscle cells. There is evidence that proproliferative and antiapoptotic states are characterized by a metabolic (glycolytic phenotype and hyperpolarized mitochondria) and electric (downregulation and inhibition of plasmalemmal K(+) channels) remodeling that involves activation of the Akt pathway. Dehydroepiandrosterone (DHEA) is a naturally occurring and clinically used steroid known to inhibit the Akt axis in cancer. We hypothesized that DHEA will prevent and reverse the remodeling that follows vascular injury. We used cultured human carotid vascular smooth muscle cell and saphenous vein grafts in tissue culture, stimulated by platelet-derived growth factor to induce proliferation in vitro and the rat carotid injury model in vivo. DHEA decreased proliferation and increased vascular smooth muscle cell apoptosis in vitro and in vivo, reducing vascular remodeling while sparing healthy tissues after oral intake. Using pharmacological (agonists and antagonists of Akt and its downstream target glycogen-synthase-kinase-3beta [GSK-3beta]) and molecular (forced expression of constitutively active Akt1) approaches, we showed that the effects of DHEA were mediated by inhibition of Akt and subsequent activation of GSK-3beta, leading to mitochondrial depolarization, increased reactive oxygen species, activation of redox-sensitive plasmalemmal voltage-gated K(+) channels, and decreased [Ca(2+)](i). These functional changes were accompanied by sustained molecular effects toward the same direction; by decreasing [Ca(2+)](i) and inhibiting GSK-3beta, DHEA inhibited the nuclear factor of activated T cells transcription factor, thus increasing expression of Kv channels (Kv1.5) and contributing to sustained mitochondrial depolarization. These results were independent of any steroid-related effects because they were not altered by androgen and estrogen inhibitors but involved a membrane G protein-coupled receptor. We suggest that the orally available DHEA might be an attractive candidate for the treatment of systemic vascular remodeling, including restenosis, and we propose a novel mechanism of action for this important hormone and drug.

Aromatase Inhibitor–Induced Carpal Tunnel Syndrome: Results From the ATAC Trial

Carpal tunnel syndrome (CTS) is a condition in which the median nerve is compressed, leading to pain and muscle weakness in the fingers and hand. Aromatase inhibitors lead to profound estrogen suppression and may be expected to increase the risk of CTS in postmenopausal women receiving adjuvant therapy for early breast cancer. The current analyses were based on the 100-month median follow-up data in postmenopausal women in the two monotherapy arms (anastrozole, n = 3,092; tamoxifen, n = 3,094). Here, we investigate the natural history of patients who presented with CTS during adjuvant treatment for breast cancer and the relative importance of a range of known risk factors for CTS. After 100 months of follow-up, 80 cases (2.6%) of CTS were reported in the anastrozole arm, compared with 23 cases (0.7%) in the tamoxifen arm (P < .0001). The majority of CTS cases were reported as mild to moderate intensity and occurred early. None of the women stopped treatment medication as a result of CTS. CTS was significantly increased for women who used prior hormone replacement therapy (P = .007) or received prior chemotherapy (P = .01). Those who were 60 years of age or older at entry were at lower risk of CTS compared with their counterparts (P = .002). Although the use of anastrozole is associated with a greater incidence of CTS, it is rare, and most cases were of mild to moderate intensity and short duration. CTS has little impact on the overall risk-to-benefit ratio for the use of anastrozole in postmenopausal women with early breast cancer.

Long-term efficacy and safety of letrozole for the adjuvant treatment of early breast cancer in postmenopausal women: a review.

Aromatase inhibitors (AIs) are becoming more widely used than tamoxifen as adjuvant hormonal therapy for postmenopausal women (PMW) with early breast cancer (EBC). It is clear that these drugs offer important efficacy benefits over tamoxifen and differ from tamoxifen in their safety profile. The accepted strategies for adjuvant AI therapy include initial adjuvant treatment following surgery, switching and/or sequencing from prior tamoxifen, and extended adjuvant therapy following the full 5 years of tamoxifen treatment. Among the available AIs, letrozole has been evaluated in large, well-controlled, double-blind clinical trials in the initial adjuvant, extended adjuvant, and more recently, the sequential adjuvant settings. Letrozole is the most potent of the AIs and provides near complete suppression of plasma estrogens in PMW. Letrozole also significantly reduces the occurrence of early distant metastases, the most lethal type of recurrence event, which can lead to improved survival. Clinical comparisons of letrozole with both tamoxifen and placebo have also provided important long-term safety data on the use of AIs as adjuvant therapy in PMW with EBC. The weight of clinical evidence indicates that letrozole is a safe and effective option for adjuvant hormonal therapy across all three AI treatment settings.

Estrogen Replacement in Female Lung Cancer During Gefitinib Therapy

Estrogen receptor (ER) has been detected in some specimens of lung cancer. Estrogen has an effect on the growth of lung cancer cell lines. An inverse relationship between ER and epithelial growth factor receptor (EGFR) was reported in pre-clinical data. A 70-year-old female with lung adenocarcinoma, who achieved a partial response by gefitinib, underwent estrogen replacement for menopause-associated symptoms during gefinitib therapy. Lung nodules enlarged with 1-month estrogen use and regressed 6 weeks after the end of estrogen therapy. To our knowledge, this is the first case report regarding the interaction between estrogen and EGFR inhibitors.

An economic analysis of arthralgia/myalgia (A/M) versus recurrence in women with hormone receptor-positive (HR+) breast cancer (BC) on aromatase inhibitors (AIs)

e11601 Background: The symptoms of A/M are associated with estrogen suppression and are more common with AIs relative to tamoxifen (TAM). AIs have demonstrated superior efficacy when compared with TAM. In BIG 1–98, letrozole (LET) treatment provides a significant reduction in the risk of distant metastasis (DM); the updated 76 month BIG 1–98 analysis now suggests that early reduction in DM ultimately leads to overall survival (OS) benefit, 40 fewer deaths with LET compared with TAM. [Mouridsen, 2008] It has been reported that women reporting new joint symptoms at 3 months after initiating an AI have a significantly lower risk for recurrence compared with women not reporting these symptoms [Cuzick, 2008]. Methods: Data from the Henry Ford Health System (1995–2005) were used to identify postmenopausal HR+ early BC patients with at least 1 year of AI therapy follow-up after surgery. Total health care costs of managing A/M associated with hormone therapy as well as BC recurrences were estimated from charges incurred during health care encounters for these conditions. Results: In the 834 patients eligible, the treated A/M incidence was 21% and the total health care cost ∼ $429 per symptomatic patient/yr. The average annual cost of any BC recurrence was previously reported at ∼$131,000/yr, with greatest cost seen with DM at ∼ $265,783/yr [Weiderkehr, 2008]. Conclusions: The economic costs of treating A/M are nominal, particularly in light of the superior efficacy of AIs and the economic burden of BC recurrences. DM is the most costly of the recurrences, and in BIG 1–98, reducing early DM appears to impact OS. Discontinuation of AIs, or switching to less effective therapies in an effort to manage A/M, should be weighed against the benefit of AI therapy in reducing BC recurrences, particularly DM, as well as the high costs associated the managing these recurrences. No significant financial relationships to disclose.

Skeletal sequelae of cancer and cancer treatment

Survivors of cancer may experience lingering adverse skeletal effects such as osteoporosis and osteomalacia. Skeletal disorders are often associated with advancing age, but these effects can be exacerbated by exposure to cancer and its treatment. This review will explore the cancer and cancer treatment-related causes of skeletal disorders. We performed a comprehensive search, using various Internet-based medical search engines such as PubMed, Medline Plus, Scopus, and Google Scholar, for published articles on the skeletal effects of cancer and cancer therapies. One-hundred-forty-two publications, including journal articles, books, and book chapters, met the inclusion criteria. They included case reports, literature reviews, systematic analyses, and cohort reports. Skeletal effects resulting from cancer and cancer therapies, including hypogonadism, androgen deprivation therapy, estrogen suppression, glucocorticoids/corticosteroids, methotrexate, megestrol acetate, platinum compounds, cyclophosphamide, doxorubicin, interferon-alpha, valproic acid, cyclosporine, vitamin A, NSAIDS, estramustine, ifosfamide, radiotherapy, and combined chemotherapeutic regimens, were identified and described. Skeletal effects of hyperparathyroidism, vitamin D deficiency, gastrectomy, hypophosphatemia, and hyperprolactinemia resulting from cancer therapies were also described. The publications researched during this review both highlight and emphasize the association between cancer therapies, including chemotherapy and radiotherapy, and skeletal dysfunction. These studies confirm that cancer survivors experience a more rapid acceleration of bone loss than their age-matched peers who were never diagnosed with cancer. Further studies are needed to better address the skeletal needs of cancer survivors.

CBF changes in relation to the phase of ovarian cycle in guinea pig Fallopian tube: effects of estrogen and progesterone

Ciliary beat frequency (CBF) of Fallopian tube of guinea pig was measured using a light microscope connecting a high‐speed camera (500 Hz), CBFs ranged from 10 to 15 Hz in the phases of ovarian cycle. In follicular phase, CBF increased transiently; an increase at the beginning of estradiol (E2) rise (14 Hz) followed by a rapid decrease at the peak of E2 rise (10 Hz). In ovulatory and luteal phase (high progesterone), CBF was maintained 12 Hz. β‐Estradiol‐benzoate (βE2‐benz) and medroxy‐progesterone (m‐prog) dissolved in a steroid solution were administered subcutaneously for 1.5 ‐ 4 days. A high concentration of βE2‐benz administered (20 mg/day) decreased CBF (11 Hz), while a low concentration (2 mg/day) increased it (14.5 Hz), and these βE2‐benz actions were inhibited by an estrogen inhibitor (ICI 182,780, 2 mg/day). m‐Prog administered (2‐20 mg/day) maintained CBF approximately 12.5 Hz, which was abolished by a progesterone inhibitor (mifepristone, 50 mg/day). Ciliary cells of Fallopian tube were immuno‐positively stained for estrogen and progesterone receptors. The present study demonstrated that βE2‐benz accelerates CBF at a low concentration and suppresses it at a high concentration, and that progesterone maintains CBF around 12 Hz. CBF in Fallopian tube is regulated by estrogen and progesterone in relation to the ovarian cycle.

Immoderate inhibition of estrogen by anastrozole enhances the severity of experimental polyarthritis

Aromatase inhibitors have become the standard of care for the adjuvant treatment of postmenopausal, hormone-sensitive breast cancer. Meanwhile, more and more breast cancer patients who are treated with aromatase inhibitors as adjuvant therapies often experience arthralgias and musculoskeletal aching, in some cases, have necessitated discontinuation of treatment. We therefore use a rat model of human RA to test the hypothesis that anastrozole, an aromatase inhibitor, could enhance arthritis. The parameters used for analyzing the disease severity included paw volume, radiology, histopathological examination, markers for cytokine profile, immunophenotypic assays, and immune response to type II collagen. Administration of anastrozole significantly increased the severity of arthritis. Anastrozole induced the increased levels of proinflammatory cytokines, IFN-gamma, IL-12, and the decreased levels of IL-4, IL-10 secretion. We further found that anastrozole suppressed the differentiation of naive T cells to Treg cells, and it blocked the balance of IgG2a/IgG1 in peripheral blood. Meanwhile, estradiol concentration was the lowest in the anastrozole group. In a well-established model of postmenopausal RA, anastrozole potently promote the progression of arthritis and the associated development of osteoporosis. This potential problem should alert the oncologists and other health professionals.

A Delay in Pubertal Onset Affects the Covariation of Body Weight, Estradiol, and Bone Size

The skeletal system functions as a locomotive organ and a mineral reservoir and combinations of genetic and environmental factors affect the skeletal system. Although delayed puberty is associated with compromised bone mass, suppression of estrogen should be beneficial to cortical strength. The purpose was to employ path analysis to study bone strength and delayed puberty. Forty-five female rats were randomly assigned to a control group (n = 15) and an experimental group (n = 30) that received injections of gonadotropin releasing hormone antagonist (GnRH-a). Causal models were constructed by specifying directed paths between bone traits. The first model tested the hypothesis that the functional relationships between bone traits and body weight were altered by a delay in pubertal onset. GnRH-a injections during puberty altered the covariation between body weight and bone size. The second model was constructed to test the hypothesis that variability in stiffness was causally related to variability in body weight. The model also tested the relationship between the periosteal and endocortical surfaces and their relationship to stiffness. There was no change in the relationship between the surfaces in the GnRH-a group. The third model determined the effect of estradiol on both total area and relative cortical area in both groups. The relationship between periosteal surface and serum estradiol levels was only significant during estrogen suppression. These data suggest that increases in body weight during or prior to puberty may not be protective of bone strength.

The anti-inflammatory activities of Tanshinone IIA, an active component of TCM, are mediated by estrogen receptor activation and inhibition of iNOS

Tanshinone IIA (Tan IIA) is a major compound extracted from a traditional herbal medicine Salvia miltiorrhiza BUNGE, which is used to treat cardiovascular diseases, cerebrovascular diseases and postmenopausal syndrome. It has also been shown to possess anti-inflammatory activity. Since Tan IIA has a similar structure to that of 17β-estradiol (E 2), the present study was undertaken to characterize the estrogenic activity of Tan IIA and to demonstrate a functional role of this activity in RAW 264.7 cells. In transient transfection assay, Tan IIA (10 μM) increases ERE-luciferase activity in an estrogen receptor (ER) subtype-dependent manner when either ERα or ERβ were co-expressed in Hela cells. In LPS-induced RAW 264.7 cells, Tan IIA exerts anti-inflammatory effects by inhibition of iNOS gene expression and NO production, as well as inhibition of inflammatory cytokine (IL-1β, IL-6, and TNF-α) expression via ER-dependent pathway. Therefore, it could serve as a potential selective estrogen receptor modulator (SERM) to treat inflammation-associated neurodegenerative and cardiovascular diseases without increasing the risk of breast cancer.

Characteristics of carpal-tunnel syndrome in the ATAC trial.

Abstract Abstract #5085 Introduction: Carpal-tunnel syndrome (CTS) is a condition in which the median nerve is compressed leading to pain and muscle weakness in fingers and the hand. Oestrogen depletion has been shown to induce CTS, whereas the use of hormone replacement therapy is associated with a resolution of the symptom. Aromatase inhibitors lead to profound oestrogen suppression and therefore might induce CTS in postmenopausal women.&amp;#x2028; Methods: The Arimidex Tamoxifen Alone or in Combination (ATAC) trial randomised 9,366 postmenopausal women to anastrozole (1mg/day), tamoxifen (20mg/day) or the combination. Analyses were based on the 100 month median follow-up data in women in the two monotherapy arms who started their allocated treatment (anastrozole=3,092; tamoxifen=3,094). Here, we retrospectively investigate the influence of anastrozole on CTS, clinical outcomes, the relative importance of a range of risk factors for CTS, and examine whether they act differently in the presence of anastrozole treatment.&amp;#x2028; Results: During the entire active treatment period, 80 (2.6%) cases of CTS were reported in the anastrozole arm compared with 23 (0.7%) in the tamoxifen arm (OR=3.55 (2.22-5.65), P&amp;lt;0.001). In both treatment arms, the majority of CTS were reported as of mild or moderate severity. Most reports of CTS in the anastrozole arm occurred within 18 months of treatment initiation, but incidence remained elevated compared to the tamoxifen arm for the entire treatment period. Median time to resolution of CTS was 8.4 months and none of the women stopped treatment medication due to this adverse event. 13 women underwent carpal-tunnel release surgery (11 anastrozole (1 in 300) vs. 2 tamoxifen (1 in 1500)). Reports of CTS were significantly increased for women who used prior hormone replacement therapy (HRT) (2.3% vs. 1.3%, OR=1.72 (1.16-2.54), P=0.007) or prior chemotherapy (2.5% vs. 1.4%, OR=1.73 (1.14-2.62)). Furthermore, women who were aged 60 years or younger at entry were at greater risk of CTS compared with those aged 61 years or older (2.5% vs. 1.2%, OR=0.48 (0.30-0.76), P=0.002). Body mass index (BMI), hormone receptor status, smoking status, and prior radiotherapy were not found to be risk factors for the development of CTS. When analyses were restricted to only women receiving anastrozole, the same risk factors were identified.&amp;#x2028; Conclusions: Although the use of anastrozole is clearly associated with a greater incidence of CTS, it is rare and most cases were of mild severity and short duration and did not lead to treatment discontinuation or surgical intervention. Thus, while CTS can be quite debilitating for the few patients who have severe symptoms, this side effect has minimal impact on the overall risk-benefit ratio for the use of anastrozole in postmenopausal women. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5085.

Proteomics analysis of tissue samples obtained before and during letrozole treatment in postmenopausal patients with locally advanced breast cancer.

Abstract Abstract #3030 Introduction&amp;#x2028; We report on the analysis of protein expression in the tumor tissue of postmenopausal patients before and after 4 months of letrozole treatment in the neoadjuvant setting. All patients had ER and/or PGR positive breast cancer and were enrolled in the “FAST-study”. Letrozole was given orally as 2.5 mg once daily. Tumor tissue was obtained by large, open biopsies prior to treatment and during final surgery (in general: mastectomy).&amp;#x2028; Methods&amp;#x2028; We used paired samples from 13 postmenopausal breast cancer patients. Breast cancer tissue and plasma samples were obtained prior to treatment and after 4 months of therapy with letrozole in the neoadjuvant setting. Thus, all in all 26 tumor samples were used from 13 individual patients. Proteins were extracted from 20-50 mg of breast cancer tissue, labeled with fluorescent dyes and separated using 2-dimensional difference gel electrophoresis (2-D DIGE). After image analysis, differentially expressed proteins (p&amp;lt;0.01, paired T- and Wilcoxon tests) were identified using MALDI tandem mass spectrometry.&amp;#x2028; Results and discussion&amp;#x2028; The 2-D DIGE based method allowed monitoring of 2000-2500 protein species in each sample. After alignment of all these patterns, around 25 cellular proteins were found to be differentially expressed in the pairwise pre-/post-treatment comparison, along with several plasma proteins. Among these cellular proteins were several reported tumor markers such as stathmin and NDPKA, chaperones such as HSP-60, and members of the annexin family. We are currently investigating the correlation between these proteins and the clinical parameters.&amp;#x2028; To our knowledge this is the first report on proteomics analysis comparing samples obtained before and during treatment with a third-generation aromatase inhibitor. The study demonstrates the feasibility of performing a high-resolution proteomics analysis on tumor material derived from needle biopsies and yielded a number of potential markers, which will require further confirmation in a larger population. The results might be useful to elucidate adaptive mechanisms to estrogen suppression in vivo. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3030.

Buthionine sulfoximine sensitizes antihormone-resistant human breast cancer cells to estrogen-induced apoptosis

IntroductionEstrogen deprivation using aromatase inhibitors is one of the standard treatments for postmenopausal women with estrogen receptor (ER)-positive breast cancer. However, one of the consequences of prolonged estrogen suppression is acquired drug resistance. Our group is interested in studying antihormone resistance and has previously reported the development of an estrogen deprived human breast cancer cell line, MCF-7:5C, which undergoes apoptosis in the presence of estradiol. In contrast, another estrogen deprived cell line, MCF-7:2A, appears to have elevated levels of glutathione (GSH) and is resistant to estradiol-induced apoptosis. In the present study, we evaluated whether buthionine sulfoximine (BSO), a potent inhibitor of glutathione (GSH) synthesis, is capable of sensitizing antihormone resistant MCF-7:2A cells to estradiol-induced apoptosis.MethodsEstrogen deprived MCF-7:2A cells were treated with 1 nM 17β-estradiol (E2), 100 μM BSO, or 1 nM E2 + 100 μM BSO combination in vitro, and the effects of these agents on cell growth and apoptosis were evaluated by DNA quantitation assay and annexin V and terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) staining. The in vitro results of the MCF-7:2A cell line were further confirmed in vivo in a mouse xenograft model.ResultsExposure of MCF-7:2A cells to 1 nM E2 plus 100 μM BSO combination for 48 to 96 h produced a sevenfold increase in apoptosis whereas the individual treatments had no significant effect on growth. Induction of apoptosis by the combination treatment of E2 plus BSO was evidenced by changes in Bcl-2 and Bax expression. The combination treatment also markedly increased phosphorylated c-Jun N-terminal kinase (JNK) levels in MCF-7:2A cells and blockade of the JNK pathway attenuated the apoptotic effect of E2 plus BSO. Our in vitro findings corroborated in vivo data from a mouse xenograft model in which daily administration of BSO either as a single agent or in combination with E2 significantly reduced tumor growth of MCF-7:2A cells.ConclusionsOur data indicates that GSH participates in retarding apoptosis in antihormone-resistant human breast cancer cells and that depletion of this molecule by BSO may be critical in predisposing resistant cells to E2-induced apoptotic cell death. We suggest that these data may form the basis of improving therapeutic strategies for the treatment of antihormone resistant ER-positive breast cancer.

Methodology for Profiling the Steroid Metabolome in Animal Tissues Using Ultraperformance Liquid Chromatography−Electrospray-Time-of-Flight Mass Spectrometry

The advent of mass spectrometry-based metabolite profiling techniques should allow investigations into the behavior and regulation of many of the low abundant signaling molecules present in the animal metabolome such as hormones and so aid investigations into the mechanisms of endocrine system function and disorders. Examples of their potential applications include endocrine-related diseases such as some cancers, as well as endocrine disruption in wildlife and humans caused by some environmental contaminants. In the present study, a method was developed to profile a variety of vertebrate steroids and their conjugates in fish tissues using solid phase extraction (SPE) prior to ultraperformance liquid chromatography linked to electrospray-time-of-flight mass spectrometry (UPLC-TOF MS). Analysis of tissue extracts spiked with steroids revealed that most analytes could be detected at subnanogram per gram concentrations in liver or testes, but ovarian extracts caused ion suppression of estrogens. A comparison of the steroid metabolome of the ovaries and testes using partial least-squares discrimination analysis (PLS-DA) revealed that the androgens 11-ketotestosterone, 11-hydroxyandrostenedione, androstenedione, and two unidentified cortisol-type glucocorticoids were discriminatory steroid markers in testes extracts. In contrast, cortisol was the predominant glucocorticoid marker in ovary extracts, and cortisone was abundant in extracts of both testes and ovaries. A number of other unidentified nonsteroidal metabolites were also differentially expressed between the testes and ovarian tissues. These studies reveal that metabolite profiling using UPLC-TOF MS is a promising approach to investigate steroid homeostasis in animal tissues.

Involvement of estradiol-17β and its membrane receptor, G protein coupled receptor 30 (GPR30) in regulation of oocyte maturation in zebrafish, Danio rario

The orphan G protein coupled receptor, GPR30, has the characteristics of a high affinity, specific estrogen membrane receptor on Atlantic croaker oocytes and mediates estrogen inhibition of oocyte maturation in this perciform fish. In order to determine the broad applicability of these findings to other teleosts, similar experiments were conducted in a cyprinid fish, zebrafish, in the present study. GPR30 mRNA expression was detected in zebrafish oocytes but not in the ovarian follicular cells. Both spontaneous and 17, 20β-dihyroxy-4-pregnen-3-one (DHP)-induced maturation of follicle-enclosed zebrafish oocytes was significantly decreased when they were incubated with either estradiol-17β, or the GPR30 agonists, ICI 182 780 and tamoxifen, or with the GPR30 specific agonist G-1. On the other hand spontaneous oocyte maturation increased two-fold when zebrafish ovarian follicles were incubated with an aromatase inhibitor, ATD. Moreover, the stimulatory effects of ATD on germinal vesicle breakdown (GVBD) were partially reversed by co-treatment with 100 nM of E2 or G-1. These results suggest that endogenous estrogens acting through GPR30 are involved in maintaining meiotic arrest of zebrafish oocytes.

Letrozole is Superior to Anastrozole in Suppressing Breast Cancer Tissue and Plasma Estrogen Levels

To evaluate the influence of the third-generation aromatase inhibitor letrozole (Femara) on breast cancer tissue levels of estrone (E(1)), estradiol (E(2)), and estrone sulfate (E(1)S) in postmenopausal women undergoing primary treatment for locally advanced estrogen receptor/progesterone receptor-positive breast cancers. Breast cancer tissue samples were collected before and following 4 months of neoadjuvant therapy with letrozole (2.5 mg o.d.), and tissue estrogen levels measured using a highly sensitive RIA after high-pressure liquid chromatography purification. Letrozole suppressed pretreatment tumor levels of E(2), E(1), and E(1)S by 97.6%, 90.7%, and 90.1%, respectively. These data reveal that letrozole suppresses tissue estrogen levels significantly below what has previously been recorded with anastrozole (89.0%, 83.4%, and 72.9% suppression, respectively) using the same methods. To confirm the differential effect of letrozole and anastrozole on each plasma estrogen fraction, we re-analyzed plasma samples obtained from a previous intrapatient cross-over study comparing letrozole and anastrozole using an improved RIA (detection limits of 0.67, 1.14, and 0.55 pmol/L for E(2), E(1), and E(1)S, respectively). Letrozole consistently suppressed each plasma estrogen fraction below the levels recorded for anastrozole: E(2) (average suppression by 95.2% versus 92.8%; P = 0.018), E(1) (98.8% suppression versus 96.3%; P = 0.003), and E(1)S (98.9% suppression versus 95.3%; P = 0.003). Our data reveals that letrozole (2.5 mg o.d.) is more effective compared with anastrozole (1.0 mg o.d.) with respect to tissue as well as plasma estrogen suppression in patients with postmenopausal breast cancer.

Endocrine Therapy and Bone Loss in Breast Cancer: Time to Close in the RANK(L)?

Endocrine Therapy and Bone Loss in Breast Cancer: Time to Close in the RANK(L)?