Estrogen plus progestin and breast cancer incidence and mortality in postmenopausal women

Menopause and the hormone controversy: clarification or confusion?

providers. To assist in providing women quality healthcare, recently published new guidelines help provide direction for NPs.

Oral contraceptive use and survival in women with invasive breast cancer

BACKGROUND

Oral contraceptives (OC) are widely used in the United States. Although the relation between OC use and breast cancer incidence has been widely studied, the few studies examining associations between OC use prior to breast cancer diagnosis and survival are inconsistent.

METHODS

Women with invasive breast cancer participating in the Women's Contraceptive and Reproductive Experiences (CARE) Study, a population-based case-control study (4565 women ages 35-64 years), and the California Teachers Study (CTS) cohort (3929 women ages 28-91 years) were followed for vital status. A total of 1,064 women died in the CARE Study (median follow-up, 8.6 years) and 523 died in the CTS (median follow-up, 6.1 years). Cox proportional hazards regression provided hazard rate ratio estimates [(relative risk, RR)] with 95% confidence intervals (CIs) for risk of death from any cause and from breast cancer.

RESULTS

No association was observed for any OC use prior to diagnosis and all-cause mortality [CARE Study: RR = 1.01 (95% CI = 0.86-1.19); CTS: RR = 0.84 (95% CI = 0.67-1.05)]. A decreased risk of all-cause mortality was observed in the CTS among women with more than 10 years of OC use (RR = 0.67, 95% CI = 0.47-0.96); however, no trend of decreasing risk with increasing OC duration was observed (P(trend) = 0.22), and no association was observed in the CARE study. No associations were observed for breast cancer-specific mortality.

CONCLUSIONS

OC use is not associated with all-cause or breast cancer-specific mortality among women with invasive breast cancer.

IMPACT

These 2 independent studies demonstrated no overall association between OC use and survival among women with breast cancer.

Folic acid supplementation improves vascular function in professional dancers with endothelial dysfunction

OBJECTIVE

To determine if folic acid supplementation improves vascular function (brachial artery flow-mediated dilation [FMD]) in professional dancers with known endothelial dysfunction.

DESIGN

Prospective cross-sectional study.

SETTING

Academic institution in the Midwestern United States.

SUBJECTS

Twenty-two professional ballet dancers volunteered for this study.

MAIN OUTCOME MEASURES

Subjects completed a 3-day food record to determine caloric and micronutrient intake. Menstrual status was determined by interview and questionnaire. Endothelial function was determined as flow-induced vasodilation measured by high-frequency ultrasound of the brachial artery. A change in brachial diameter of <5% to hyperemic flow stimulus was defined a priori as endothelial dysfunction. Subjects with abnormal FMD took 10 mg of folic acid daily for 4 weeks, and FMD testing was then repeated. Serum whole blood was measured for folic acid levels before and after supplementation.

RESULTS

Sixty-four percent of dancers (n = 14) had abnormal brachial artery FMD (<5%) (mean ± standard deviation, 2.9% ± 1.5%). After 4 weeks of folic acid supplementation (10 mg/day), FMD improved in all the subjects (7.1% ± 2.3%; P < .0001).

CONCLUSIONS

This study reveals that vascular endothelial function improves in dancers after supplementation with folic acid (10 mg/day) for at least 4 weeks. This finding may have clinically important implications for future cardiovascular disease risk prevention.

Breast cancer after hormone replacement therapy--does prognosis differ in perimenopausal and postmenopausal women?

Hormone replacement therapy (HRT) has been associated with higher incidence of breast cancer in postmenopausal women, but it is unclear if breast cancers developing after HRT use have different prognosis. 1053 women with hormone receptor positive non-metastasized breast cancer were analyzed in a retrospective trial, stratifying by HRT use before diagnosis. Postmenopausal HRT users had significantly more early tumor stages (p<0.001). HRT in postmenopausal patients was associated with longer time to progression (TTP) (HR 0.81, 95%CI 0.55-1.19, p=0.28) and overall survival (OS) (HR 0.68, 95%CI 0.45-1.02, p=0.059). Perimenopausal HRT users showed shorter TTP and OS (HR 1.99, 95%CI 0.57-6.91, p=0.28 and HR 4.59, 95%CI 0.91-23.25, p=0.06 respectively). Higher BMI was significantly associated with poorer prognosis in perimenopausal women only (TTP: HR=1.16; OS: HR=1.31). In this retrospective analysis postmenopausal HRT users seemed to have a better breast cancer prognosis. For perimenopausal HRT users however, a trend towards worse prognosis was found.

Current overview of the management of urogenital atrophy in women with breast cancer

Systemic treatments for women with breast cancer frequently induce urogenital symptoms that can negatively impact a women's quality of life. Urogenital atrophy is frequently undiagnosed and untreated, particularly in breast cancer survivors. Symptoms of urogenital atrophy can usually be relieved with vaginal estrogen preparations, but risk of recurrence and safety is undefined in women with a history of breast cancer. Treatment with nonhormonal modalities including vaginal moisturizers or lubricants and lifestyle modification are the first lines of management. Low-dose vaginal 17 β-estradiol (vaginal estradiol tablets 10 μg or vaginal estradiol ring) can be considered for the treatment of symptomatic urogenital atrophy in women with a history of breast cancer after appropriate disclosure to the patient. While effective in treating the urogenital symptoms, the safety of such therapy remains uncertain. The decision to offer vaginal estrogen therapy needs to be individualized and should be made jointly with the oncologist.

Aging, Angiotensin system and dopaminergic degeneration in the substantia nigra

For years, the renin-angiotensin system (RAS) was described as a circulating humoral system that regulates blood pressure and water homeostasis. Angiotensin II (AII) is the most important effector peptide. However, in addition to the "classical" humoral RAS there exist local RAS in many tissues and locally formed AII activates NADPH-dependent oxidases, which are a major source of superoxide and are upregulated in major aging-related diseases such as hypertension, diabetes and atherosclerosis. Accordingly, disruption of AII receptors promotes longevity in mice. The brain has an independent local RAS, which was also initially associated with the central control of blood pressure. However, more recent studies have involved brain RAS in brain disorders, including neurodegenerative diseases. The interaction between AII and dopamine is particularly interesting. Recent evidence suggests that dopamine and AII systems directly counterregulate each other in renal cells as well as in the striatum and substantia nigra. Dopamine depletion may induce RAS upregulation as a potential compensatory mechanism. However, RAS hyperactivation also exacerbates NADPH-oxidase activity, oxidative stress and the microglial inflammatory response and contribute to progression of dopaminergic neuron loss, as observed in recent studies with animal models of Parkinson's disease (PD). Aging is the most prominent risk factor for PD and other neurodegenerative diseases. Interestingly, we observed increased activation of the NADPH oxidase complex and increased levels of the pro-inflammatory cytokines in the nigra of aged male rats, which was associated with increased RAS activity and was reduced by treatment with AII antagonists. We also observed that the lack of oestrogen may act as an additional factor for increasing RAS activity in the nigra in aged females, which was significantly reduced by treatment with AII antagonists. Manipulation of the brain RAS may constitute an effective neuroprotective strategy against the aging-related risk of dopaminergic degeneration.

The female athlete triad and endothelial dysfunction

A tremendous increase in the number of female athletes of all ages and abilities has occurred in the past 35 years. In general, sports and athletic competition produce healthier and happier women. However, explosion in participation has revealed clear gender-specific injuries and medical conditions unique to the female athlete. This article focuses on the latest advances in our knowledge of the female athlete triad and the relationship between athletic-associated amenorrhea and endothelial dysfunction. Treatment of vascular dysfunction with folic acid is also discussed.

Progesterone receptor action: defining a role in breast cancer

The ovarian steroid hormones, estradiol and progesterone, and their nuclear receptors (estrogen receptor [ER] and progesterone receptor [PR]), are involved in breast cancer development. As ER-positive/PR-positive tumors progress, they are likely to become steroid hormone-resistant/independent, yet often retain expression of their steroid receptors. Notably, up to 40% of women with steroid receptor-positive tumors exhibit de novo resistance or eventually fail on estrogen- or ERα-blocking therapies (acquired resistance). Indeed, most of the research on this topic has centered on mechanisms of ER 'escape' from endocrine therapy and the design of better ER-blocking strategies; signaling pathways that mediate endocrine (i.e., anti-estrogen) resistance are also excellent therapeutic targets. However, serious consideration of PR isoforms as important drivers of early breast cancer progression and ER modulators is timely and significant. Indeed, progress has been hindered by ER-centric experimental approaches. This article will focus on defining a role for PR in breast cancer with hopes of providing a refreshing PR-focused perspective.

An epidemiological overview of the relationship between hormone replacement therapy and breast cancer

Large-scale randomized clinical trials and observational studies have consistently found that use of hormone replacement therapy (HRT) increases the risk of breast cancer. More recently, ecological studies have shown correlations between dramatic reductions in use of HRT in many countries, and declines in the rates of breast cancer in older women. Meta-analyses of data from the trials and observational studies show that the increase in breast cancer risk is greater for combined estrogen-progestin therapies compared with estrogen alone; that for both types of preparation, breast cancer risk increases with duration of use; and that the risks decrease relatively quickly after cessation of use. For both estrogen-only and combined therapies, the risk of breast cancer is higher if therapy is initiated close to the time of the menopause, relative to the risks in women starting HRT later. Most drug regulatory authorities currently recommend that HRT be prescribed only to fully informed women who have moderate-to-severe menopausal symptoms, for the shortest duration possible; and it is recommended that the need for therapy be reviewed at least every 6-12 months.

Apigenin prevents development of medroxyprogesterone acetate-accelerated 7,12-dimethylbenz(a)anthracene-induced mammary tumors in Sprague-Dawley rats

The use of progestins as a component of hormone replacement therapy has been linked to an increase in breast cancer risk in postmenopausal women. We have previously shown that medroxyprogesterone acetate (MPA), a commonly administered synthetic progestin, increases production of the potent angiogenic factor vascular endothelial growth factor (VEGF) by tumor cells, leading to the development of new blood vessels and tumor growth. We sought to identify nontoxic chemicals that would inhibit progestin-induced tumorigenesis. We used a recently developed progestin-dependent mammary cancer model in which tumors are induced in Sprague-Dawley rats by 7,12-dimethylbenz(a)anthracene (DMBA) treatment. The flavonoid apigenin, which we previously found to inhibit progestin-dependent VEGF synthesis in human breast cancer cells in vitro, significantly delayed the development of, and decreased the incidence and multiplicity of, MPA-accelerated DMBA-induced mammary tumors in this animal model. Whereas apigenin decreased the occurrence of such tumors, it did not block MPA-induced intraductal and lobular epithelial cell hyperplasia in the mammary tissue. Apigenin blocked MPA-dependent increases in VEGF, and suppressed VEGF receptor-2 (VEGFR-2) but not VEGFR-1 in regions of hyperplasia. No differences were observed in estrogen or progesterone receptor (ER/PR) levels, or the number of estrogen receptor-positive cells, within the mammary gland of MPA-treated animals administered apigenin, MPA-treated animals, and placebo treated animals. However, the number of progesterone receptor-positive cells was reduced in animals treated with MPA or MPA and apigenin compared with those treated with placebo. These findings suggest that apigenin has important chemopreventive properties for those breast cancers that develop in response to progestins.

Health outcomes after stopping conjugated equine estrogens among postmenopausal women with prior hysterectomy: a randomized controlled trial

CONTEXT

The Women's Health Initiative Estrogen-Alone Trial was stopped early after a mean of 7.1 years of follow-up because of an increased risk of stroke and little likelihood of altering the balance of risk to benefit by the planned trial termination date. Postintervention health outcomes have not been reported.

OBJECTIVE

To examine health outcomes associated with randomization to treatment with conjugated equine estrogens (CEE) among women with prior hysterectomy after a mean of 10.7 years of follow-up through August 2009.

DESIGN, SETTING, AND PARTICIPANTS

The intervention phase was a double-blind, placebo-controlled, randomized clinical trial of 0.625 mg/d of CEE compared with placebo in 10,739 US postmenopausal women aged 50 to 79 years with prior hysterectomy. Follow-up continued after the planned trial completion date among 7645 surviving participants (78%) who provided written consent.

MAIN OUTCOME MEASURES

The primary outcomes were coronary heart disease (CHD) and invasive breast cancer. A global index of risks and benefits included these primary outcomes plus stroke, pulmonary embolism, colorectal cancer, hip fracture, and death.

RESULTS

The postintervention risk (annualized rate) for CHD among women assigned to CEE was 0.64% compared with 0.67% in the placebo group (hazard ratio [HR], 0.97; 95% confidence interval [CI], 0.75-1.25), 0.26% vs 0.34%, respectively, for breast cancer (HR, 0.75; 95% CI, 0.51-1.09), and 1.47% vs 1.48%, respectively, for total mortality (HR, 1.00; 95% CI, 0.84-1.18). The risk of stroke was no longer elevated during the postintervention follow-up period and was 0.36% among women receiving CEE compared with 0.41% in the placebo group (HR, 0.89; 95% CI, 0.64-1.24), the risk of deep vein thrombosis was lower at 0.17% vs 0.27%, respectively (HR, 0.63; 95% CI, 0.41-0.98), and the risk of hip fracture did not differ significantly and was 0.36% vs 0.28%, respectively (HR, 1.27; 95% CI, 0.88-1.82). Over the entire follow-up, lower breast cancer incidence in the CEE group persisted and was 0.27% compared with 0.35% in the placebo group (HR, 0.77; 95% CI, 0.62-0.95). Health outcomes were more favorable for younger compared with older women for CHD (P = .05 for interaction), total myocardial infarction (P = .007 for interaction), colorectal cancer (P = .04 for interaction), total mortality (P = .04 for interaction), and global index of chronic diseases (P = .009 for interaction).

CONCLUSIONS

Among postmenopausal women with prior hysterectomy followed up for 10.7 years, CEE use for a median of 5.9 years was not associated with an increased or decreased risk of CHD, deep vein thrombosis, stroke, hip fracture, colorectal cancer, or total mortality. A decreased risk of breast cancer persisted.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00000611.

An update on hormone replacement therapy: health and medicine for women: a multidisciplinary, evidence-based review of mid-life health concerns

The Department of Obstetrics, Gynecology, and Reproductive Sciences at the Yale School of Medicine hosted a daylong continuing medical education (CME) symposium titled "Health and Medicine for Women: A Multidisciplinary, Evidence-Based Review of Mid-Life Health Concerns" in September 2010. A number of speakers discussed current research on hormone replacement therapy (HRT) and re-evaluated the results of the Women's Health Initiative (WHI), a landmark, randomized, placebo-controlled trial that still sparks debate almost a decade after its conclusion. This article summarizes this discussion and highlights directions for future study.

Promotional tone in reviews of menopausal hormone therapy after the Women's Health Initiative: an analysis of published articles

BACKGROUND

Even after the Women's Health Initiative (WHI) found that the risks of menopausal hormone therapy (hormone therapy) outweighed benefit for asymptomatic women, about half of gynecologists in the United States continued to believe that hormones benefited women's health. The pharmaceutical industry has supported publication of articles in medical journals for marketing purposes. It is unknown whether author relationships with industry affect promotional tone in articles on hormone therapy. The goal of this study was to determine whether promotional tone could be identified in narrative review articles regarding menopausal hormone therapy and whether articles identified as promotional were more likely to have been authored by those with conflicts of interest with manufacturers of menopausal hormone therapy.

METHODS AND FINDINGS

We analyzed tone in opinion pieces on hormone therapy published in the four years after the estrogen-progestin arm of the WHI was stopped. First, we identified the ten authors with four or more MEDLINE-indexed reviews, editorials, comments, or letters on hormone replacement therapy or menopausal hormone therapy published between July 2002 and June 2006. Next, we conducted an additional search using the names of these authors to identify other relevant articles. Finally, after author names and affiliations were removed, 50 articles were evaluated by three readers for scientific accuracy and for tone. Scientific accuracy was assessed based on whether or not the findings of the WHI were accurately reported using two criteria: (1) Acknowledgment or lack of denial of the risk of breast cancer diagnosis associated with hormone therapy, and (2) acknowledgment that hormone therapy did not benefit cardiovascular disease endpoints. Determination of promotional tone was based on the assessment by each reader of whether the article appeared to promote hormone therapy. Analysis of inter-rater consistency found moderate agreement for scientific accuracy (κ=0.57) and substantial agreement for promotional tone (κ=0.65). After discussion, readers found 86% of the articles to be scientifically accurate and 64% to be promotional in tone. Themes that were common in articles considered promotional included attacks on the methodology of the WHI, arguments that clinical trial results should not guide treatment for individuals, and arguments that observational studies are as good as or better than randomized clinical trials for guiding clinical decisions. The promotional articles we identified also implied that the risks associated with hormone therapy have been exaggerated and that the benefits of hormone therapy have been or will be proven. Of the ten authors studied, eight were found to have declared payment for speaking or consulting on behalf of menopausal hormone manufacturers or for research support (seven of these eight were speakers or consultants). Thirty of 32 articles (90%) evaluated as promoting hormone therapy were authored by those with potential financial conflicts of interest, compared to 11 of 18 articles (61%) by those without such conflicts (p=0.0025). Articles promoting the use of menopausal hormone therapy were 2.41 times (95% confidence interval 1.49-4.93) as likely to have been authored by authors with conflicts of interest as by authors without conflicts of interest. In articles from three authors with conflicts of interest some of the same text was repeated word-for-word in different articles.

CONCLUSION

There may be a connection between receiving industry funding for speaking, consulting, or research and the publication of promotional opinion pieces on menopausal hormone therapy.

Breast cancer risk in relation to the interval between menopause and starting hormone therapy

BACKGROUND

Although breast cancer risk is greater in users of estrogen-progestin than estrogen-only formulations of menopausal hormonal therapy, reports on their effects have been somewhat inconsistent. We investigated whether the timing of these therapies affected breast cancer incidence.

METHODS

A total of 1,129,025 postmenopausal UK women provided prospective information on hormonal therapy use and other factors relevant for breast cancer risk. We used Cox regression to estimate adjusted relative risks (RRs) of breast cancer in hormonal therapy users vs never users and calculated standardized incidence rates. All statistical tests were two-sided.

RESULTS

During 4.05 million woman-years of follow-up, 15,759 incident breast cancers occurred, with 7107 in current users of hormonal therapy. Breast cancer incidence was increased in current users of hormonal therapy, returning to that of never users a few years after use had ceased. The relative risks for breast cancer in current users were greater if hormonal therapy was begun before or soon after menopause than after a longer gap (P(heterogeneity) < .001, for both estrogen-only and estrogen-progestin formulations). Among current users of estrogen-only formulations, there was little or no increase in risk if use began 5 years or more after menopause (RR = 1.05, 95% confidence interval [CI] = 0.89 to 1.24), but risk was statistically significantly increased if use began before or less than 5 years after menopause (RR = 1.43, 95% CI = 1.35 to 1.51). A similar pattern was observed among current users of estrogen-progestin formulations (RR = 1.53, 95% CI = 1.38 to 1.70, and RR = 2.04, 95% CI = 1.95 to 2.14, respectively). At 50-59 years of age, annual standardized incidence rates for breast cancer were 0.30% (95% CI = 0.29% to 0.31%) among never users of hormone therapy and 0.43% (95% CI = 0.42% to 0.45%) and 0.61% (95% CI = 0.59% to 0.64%), respectively, among current users of estrogen-only and estrogen-progestin formulations who began use less than 5 years after menopause.

CONCLUSIONS

There was substantial heterogeneity in breast cancer risk among current users of hormonal therapy. Risks were greater among users of estrogen-progestin than estrogen-only formulations and if hormonal therapy started at around the time of menopause than later.

Treatment of osteoporosis and reduction in risk of invasive breast cancer in postmenopausal women with raloxifene

INTRODUCTION

Raloxifene, a non-steroidal selective estrogen receptor modulator (SERM), offers a new dimension for the treatment and prevention of osteoporosis and risk reduction of invasive breast cancer in postmenopausal populations at high risk. Both osteoporosis and breast cancer are important public health issues for postmenopausal women. It is well known that estrogen and estrogen receptors play an important role in the pathogenesis of both diseases. Initially, hormone replacement therapy (HRT) was used for the purpose of preventing and treating postmenopausal osteoporosis. However, HRT significantly contributed to an increase in breast cancer risk. The SERM, raloxifene, is used for the prevention and for the treatment of postmenopausal osteoporosis and reducing the risk of invasive breast cancer in postmenopausal women.

AREAS COVERED

This article reviews the emerging evidence of the efficacy of raloxifene in postmenopausal women, summarizes the results and places in perspective their therapeutic uses for women having either a high risk of osteoporosis or breast cancer. Emerging clinical evidence suggests bisphosphonates, currently used as drugs for the treatment of osteoporosis, may also reduce breast cancer risk. The status of other SERMs and bisphosphonates are included for completeness. A Medline search of raloxifene, osteoporosis, breast cancer and SERMs was used to derive a database of 355 references.

EXPERT OPINION

Readers will understand the value of raloxifene to prevent osteoporosis and breast cancer in postmenopausal women. Although most women do not require pharmacotherapy for menopausal symptoms, many are severely affected by osteoporosis or breast cancer at and beyond menopause and, for such women, pharmacologic intervention is important if they are to retain an acceptable quality of life. It is reasonable to use raloxifene or bisphosphonate as an appropriate drug that targets symptom-free postmenopausal women for treatment and prevention of osteoporosis but raloxifene is proven to reduce the incidence of invasive breast cancer.

Persistent and non-persistent changes in gene expression result from long-term estrogen exposure of MCF-7 breast cancer cells

Life-long estrogen exposure is recognized as a major risk factor for the development of breast cancer. While the initial events in the regulation of gene expression by estrogen have been described in detail, far less is known of the role of estrogen in the long-term regulation of gene expression. In this study, we investigated the effects of long-term exposure of MCF-7 breast cancer cells to 1nM 17β-estradiol on gene expression with the goal of distinguishing between gene expression that is continually reliant on estrogen receptor (ER) function as opposed to secondary and persistent effects that are downstream of ER. To assess the direct involvement of ER in the differential gene expression of long-term estrogen exposed (LTEE) cells in comparison with that of control cells, we exposed cultures to the selective estrogen receptor modulator raloxifene (RAL). cDNA microarray analysis showed that exposure to RAL inhibited expression of numerous characterized estrogen-regulated genes, including PGR, GREB1, and PDZK1. Genes that were increased in expression in LTEE cells yet were unaffected by RAL exposure included the aryl hydrocarbon receptor (AHR) and numerous other genes that were not previously reported to be regulated by estrogen. Epigenetic regulation was evident for the AHR gene; AhR transcript levels remained elevated for several cell passages after the removal of estrogen. Signal transducer and activator of transcription 1 (STAT1); STAT1-regulated genes including ISG15, IFI27, and IFIT1; and MHC class I genes were also up-regulated in LTEE cells and were unaffected by RAL exposure. STAT1 is commonly overexpressed in breast and other cancers, and is associated with increased resistance to radiation and chemotherapy. This is the first study to relate estrogen exposure to increased STAT1 expression in breast cancer cells, an effect that may represent an additional role of estrogen in the pathogenesis of breast cancer.

A local basis for progesterone action during mammary tumorigenesis - no longer RANK and file

Two recent reports provide compelling insights into the role for RANK and its ligand, RANKL, in progestin-dependent mammary tumorigenesis. These findings build upon a considerable body of evidence pointing to the RANK signaling pathway as being a key mediator of progestin action in the mammary glands.

Update on alternative therapies for vulvovaginal atrophy

Although systemic absorption of estrogen with local treatment for vulvovaginal atrophy (VVA) is most likely to be negligible, it is unknown whether this minimal absorption will affect outcomes in women with breast cancer. Use of adjuvant therapy with aromatase inhibitors for breast cancer is associated with high incidence of VVA symptoms. Because of the impact of moderate to severe VVA symptoms on the quality of life in breast cancer survivors, there has been an intense search for alternative therapies. Further, the publicity that followed the publication of data from the Women's Health Initiative Study has led to the suggestion by the medical community to use the lowest dose therapy possible for minimal time duration in order to avoid risks. This article will highlight the progress in alternative therapies for VVA.

How I treat late effects in adults after allogeneic stem cell transplantation

More than 25,000 allogeneic hematopoietic stem cell transplantations (allo-HCTs) are expected to be performed worldwide in 2010, a number that has been increasing yearly. With broadening indications, more options for allo-HCT, and improvement in survival, by 2020 there may be up to half a million long-term survivors after allo-HCT worldwide. These patients have increased risks for various late complications, which can cause morbidity and mortality. Most long-term survivors return to the care of their local hematologists/oncologists or primary care physicians, who may not be familiar with specialized monitoring recommendations for this patient population. The purpose of this article is to describe practical approaches to screening for and managing these late effects, with the goal of reducing preventable morbidity and mortality associated with allo-HCT.

Amphiregulin mediates estrogen, progesterone, and EGFR signaling in the normal rat mammary gland and in hormone-dependent rat mammary cancers

Both estrogen (E) and progesterone (P) are implicated in the etiology of human breast cancer. Defining their mechanisms of action, particularly in vivo, is relevant to the prevention and therapy of breast cancer. We investigated the molecular and cellular mechanisms of E and/or P-induced in vivo proliferation, in the normal rat mammary gland and in hormone-dependent rat mammary cancers which share many characteristics with the normal human breast and hormone-dependent breast cancers. We show that E+P treatment induced significantly greater proliferation in both the normal gland and mammary cancers compared to E alone. In both the normal gland and tumors, E+P-induced proliferation was mediated through the increased production of amphiregulin (Areg), an epidermal growth factor receptor (EGFR) ligand, and the activation of intracellular signaling pathways (Erk, Akt, JNK) downstream of EGFR that regulate proliferation. In vitro experiments using rat primary mammary organoids or T47D breast cancer cells confirmed that Areg and the synthetic progestin, R5020, synergize to promote cell proliferation through EGFR signaling. Iressa, an EGFR inhibitor, effectively blocked this proliferation. These results indicate that mediators of cross talk between E, P, and EGFR pathways may be considered as relevant molecular targets for the therapy of hormone-dependent breast cancers, especially in premenopausal women.