Targeting obesity-related dysfunction in hormonally driven cancers.

Obesity is a risk factor for at least 13 different types of cancer, many of which are hormonally driven, and is associated with increased cancer incidence and morbidity. Adult obesity rates are steadily increasing and a subsequent increase in cancer burden is anticipated. Obesity-related dysfunction can contribute to cancer pathogenesis and treatment resistance through various mechanisms, including those mediated by insulin, leptin, adipokine, and aromatase signalling pathways, particularly in women. Furthermore, adiposity-related changes can influence tumour vascularity and inflammation in the tumour microenvironment, which can support tumour development and growth. Trials investigating non-pharmacological approaches to target the mechanisms driving obesity-mediated cancer pathogenesis are emerging and are necessary to better appreciate the interplay between malignancy, adiposity, diet and exercise. Diet, exercise and bariatric surgery are potential strategies to reverse the cancer-promoting effects of obesity; trials of these interventions should be conducted in a scientifically rigorous manner with dose escalation and appropriate selection of tumour phenotypes and have cancer-related clinical and mechanistic endpoints. We are only beginning to understand the mechanisms by which obesity effects cell signalling and systemic factors that contribute to oncogenesis. As the rates of obesity and cancer increase, we must promote the development of non-pharmacological lifestyle trials for the treatment and prevention of malignancy.

Hormone-Dependent Tumors and Sexuality in the Neuro-Oncology of Women (N.O.W.): Women's Brain Tumors, Gaps in Sexuality Considerations, and a Need for Evidence-Based Guidelines.

PURPOSE OF REVIEW: While females make up almost 60% of all brain and spinal cord tumors in adults, guidelines that address women's issues in neuro-oncology are lacking. This review sheds light on two common women's issues in neuro-oncology. RECENT FINDINGS: Neuro-oncology providers are often faced with patient questions about fertility and pregnancy maintenance or prevention and typically respond with generic cancer chemotherapy recommendations, based on the paucity of evidence on the use of common neuro-oncology chemotherapies and pregnancy. While these remain important gap issues, there are several other poorly researched issues in the Neuro-Oncology of Women (N.O.W.) including recommendations around endogenous and iatrogenic hormone exposure and female sexuality in cancer. As a significant percentage of cancers are hormone-dependent, it is important to understand how changes in hormone levels impact tumor biology over the course of a woman's lifespan. Furthermore, greater attention should be given to the impact of tumors and tumor treatments on female sexuality. This article is intended to serve as an introduction to these two specific subjects within the vast expanse of N.O.W. subject matter.

Gender-affirming hormone therapy and the risk of sex hormone-dependent tumours in transgender individuals-A systematic review.

BACKGROUND: Cancers are a leading cause of death worldwide, and transgender individuals are no exception. The effects of gender-affirming hormone therapy (GAHT) on sex hormone-dependent tumours are unclear. Therefore, this review seeks to determine whether tumour risk in transgender individuals differs from the general population, to guide clinical screening recommendations. METHODS: We performed a systematic review based on the PRISMA guidelines. MEDLINE, Embase and PsycINFO databases were searched for studies examining tumour incidence, prevalence or cancer-related mortality in transgender individuals. All English peer-reviewed publications were included if histological type and temporal relation to GAHT were reported. Case reports were included if there were ≥2 cases of the same histological type. RESULTS: The search strategy identified 307 studies. Excluding those that did not meet inclusion criteria, 43 studies (7 cohort studies, 2 cross-sectional studies and 34 case reports) were reviewed. Retrospective cohort studies suggest no increase in risk of tumour development in transgender individuals receiving GAHT compared to the general population. Notably, the mean ages of cohorts were young and were treated with GAHT for insufficient durations to assess tumour risk. Case reports raise potential associations between high-dose oestradiol and anti-androgen therapy with prolactinoma and meningioma, respectively. CONCLUSIONS: Further longitudinal studies are required to assess the risk of GAHT and hormone-dependent tumour development. Until further evidence is available, tumour screening should be based on guidelines for the general population and the presence of organs in transgender individuals rather than gender identity or hormonal therapy status.

Obesity surgery and risk of cancer.

BACKGROUND: Obesity increases the risk of several types of cancer. Whether bariatric surgery influences the risk of obesity-related cancer is not clear. This study aimed to uncover the risk of hormone-related (breast, endometrial and prostate), colorectal and oesophageal cancers following obesity surgery. METHODS: This national population-based cohort study used data from the Hospital Episode Statistics database in England collected between 1997 and 2012. Propensity matching on sex, age, co-morbidity and duration of follow-up was used to compare cancer risk among obese individuals undergoing bariatric surgery (gastric bypass, gastric banding or sleeve gastrectomy) and obese individuals not undergoing such surgery. Conditional logistic regression provided odds ratios (ORs) with 95 per cent confidence intervals. RESULTS: In the study period, from a cohort of 716 960 patients diagnosed with obesity, 8794 patients who underwent bariatric surgery were matched exactly with 8794 obese patients who did not have surgery. Compared with the no-surgery group, patients who had bariatric surgery exhibited a decreased risk of hormone-related cancers (OR 0·23, 95 per cent c.i. 0·18 to 0·30). This decrease was consistent for breast (OR 0·25, 0·19 to 0·33), endometrium (OR 0·21, 0·13 to 0·35) and prostate (OR 0·37, 0·17 to 0·76) cancer. Gastric bypass resulted in the largest risk reduction for hormone-related cancers (OR 0·16, 0·11 to 0·24). Gastric bypass, but not gastric banding or sleeve gastrectomy, was associated with an increased risk of colorectal cancer (OR 2·63, 1·17 to 5·95). Longer follow-up after bariatric surgery strengthened these diverging associations. CONCLUSION: Bariatric surgery is associated with decreased risk of hormone-related cancers, whereas gastric bypass might increase the risk of colorectal cancer.

[Endocrinology of cancer and age: early and late stages of ontogenesis].

Processes important for hormone-mediated carcinogenesis are present on different, even very early, ontogenesis stages. Early shifts in hormone-metabolic status often display opposite correlations with the risk of most common age-associated non-communicable pathologies (namely, hormone-dependent cancers and cardiovascular diseases). Additional known contradiction is the raise of reproductive system tumors incidence in the age associated with lower production of mitogenic hormones. Consequently, one should take into account production of steroids in target tissues themselves, recognize the importance of progenotoxic effect, which, apart from mitogenic function, is characteristic for estrogens and their derivatives, as well as the role of endocrine-genotoxic switchings forming so called basic triad, which is born under the influence of age-associated endocrine shifts and environmental factors. Aside from steroids-related system of increased cancer risk, attention should be paid to non-steroid ones (in particular insulin resistance- and inflammatory cytokines-associated), with their close connection to immune system functional state, low-grade chronic inflammation, obesity phenotype, and pro-/anti-inflammatory lipid factors ratio. In total, it confirms and importance of timely preventive interventions on both ontogenesis stages, early and late ones, which are often separated by several decades.

Stromal epigenetic dysregulation is sufficient to initiate mouse prostate cancer via paracrine Wnt signaling.

Carcinomas most often result from the stepwise acquisition of genetic alterations within the epithelial compartment. The surrounding stroma can also play an important role in cancer initiation and progression. Given the rare frequencies of genetic events identified in cancer-associated stroma, it is likely that epigenetic changes in the tumor microenvironment could contribute to its tumor-promoting activity. We use Hmga2 (High-mobility group AT-hook 2) an epigenetic regulator, to modify prostate stromal cells, and demonstrate that perturbation of the microenvironment by stromal-specific overexpression of this chromatin remodeling protein alone is sufficient to induce dramatic hyperplasia and multifocal prostatic intraepithelial neoplasia lesions from adjacent naïve epithelial cells. Importantly, we find that this effect is predominantly mediated by increased Wnt/ß-catenin signaling. Enhancement of Hmga2-induced paracrine signaling by overexpression of androgen receptor in the stroma drives frank murine prostate adenocarcinoma in the adjacent epithelial tissues. Our findings provide compelling evidence for the critical contribution of epigenetic changes in stromal cells to multifocal tumorigenesis.

[MALIGNANT MELANOMA--THE INFLUENCE OF HORMONAL FACTORS ON THE PROGRESSION AND PROGNOSIS. COMPARATIVE ANALYSIS BASED ON TWO CLINICAL CASES].

Malignant melanoma is the most aggressive form of skin cancer showing extremely high metastatic rate and leading to high levels of lethality. The continually growing incidence of malignant melanoma in the world and his difficult early diagnosis are the occasion for numerous studies. The individual risk for malignant transformation of melanocytes is determined by a number of etiologic factors--endogenous and exogenous. Ultraviolet radiation has a leading role in the group of exogenous factors. Within the group of endogenous factors, besides the well-known photo type skin, as well as genes mutations, are added and the sex hormones, with their significant prognostic importance. The differences, which are observed in the progression and prognosis of malignant melanoma in pre- and postmenopausal women, and men, have defined this cutaneous neoplasma as hormone-dependent tumor. We present two seemingly similar clinical cases of 52 year old woman and 53-year-old man diagnosed with malignant melanomas, developed on the basis of pigmented lesions located on the upper back, as we attempt a comparative analysis on etiopathogenetic factors led to radically different course and prognosis of the disease in these two patients.

Role of autonomous androgen receptor signaling in prostate cancer initiation is dichotomous and depends on the oncogenic signal.

The steroid hormone signaling axis is thought to play a central role in initiation and progression of many hormonally regulated epithelial tumors. It is unclear whether all cancer-initiating signals depend on an intact hormone receptor signaling machinery. To ascertain whether cell autonomous androgen receptor (AR) is essential for initiation of prostate intraepithelial neoplasia (PIN), the response of AR-null prostate epithelia to paracrine and cell autonomous oncogenic signals was assessed in vivo by using the prostate regeneration model system. Epithelial-specific loss of AR blocked paracrine FGF10-induced PIN, whereas the add back of exogenous AR restored this response. In contrast, PIN initiated by cell-autonomous, chronic-activated AKT developed independent of epithelial AR signaling. Our findings demonstrate a selective role for AR in the initiation of PIN, dependent on the signaling pathways driving tumor formation. Insights into the role of hormone receptor signaling in the initiation of epithelial tumors may help define this axis as a target for chemoprevention of carcinomas.

Defining molecular sensors to assess long-term effects of pesticides on carcinogenesis.

The abundance of dioxins and dioxin-like pollutants has massively increased in the environment due to human activity. These chemicals are particularly persistent and accumulate in the food chain, which raises major concerns regarding long-term exposure to human health. Most dioxin-like pollutants activate the aryl hydrocarbon receptor (AhR) transcription factor, which regulates xenobiotic metabolism enzymes that belong to the cytochrome P450 1A family (that includes CYP1A1 and CYP1B1). Importantly, a crosstalk exists between estrogen receptor α (ERα) and AhR. More specifically, ERα represses the expression of the CYP1A1 gene, which encodes an enzyme that converts 17ß-estradiol into 2-hydroxyestradiol. However, (ERα) does not repress the CYP1B1 gene, which encodes an enzyme that converts 17ß-estradiol into 4-hydroxyestradiol, one of the most genotoxic estrogen metabolites. In this review, we discuss how chronic exposure to xenobiotic chemicals, such as pesticides, might affect the expression of genes regulated by the AhR-ERα crosstalk. Here, we focus on recent advances in the understanding of molecular mechanisms that mediate this crosstalk repression, and particularly on how ERα represses the AhR target gene CYP1A1, and could subsequently promote breast cancer. Finally, we propose that genes implicated in this crosstalk could constitute important biomarkers to assess long-term effects of pesticides on human health.

An unusual case of a borderline Brenner tumor associated with bilateral serous cystadenoma and endometrial carcinoma.

Brenner tumor accounts for 1.5 to 2.5% of ovarian tumors. Nearly all are benign and 1% malignant. Less than twenty-five cases of borderline Brenner tumor have been reported worldwide. Our case is the first one related to a bilateral ovarian serous cystadenofibroma and endometrioid adenocarcinoma. This unusual case increases the limited data for borderline Brenner tumors.

Is polycystic ovary syndrome, a state of relative estrogen excess, a real risk factor for estrogen-dependant malignancies?

Polycystic ovary syndrome (PCOS) is a common endocrinopathy affecting women of fertile age. It is associated with several risk factors and long-term health consequences. Chronic anovulation combined with relative estrogen excess and consequent prolonged stimulatory effect on the endometrium can lead to the pathogenesis of hormonal dependant carcinoma. PCOS is thus traditionally reported to be associated with increased risk of endometrial, as well as breast and ovarian cancers. This article provides a critical literature review of the relationship between PCOS and the incidence of estrogen-dependant gynecological tumours, and it then discusses whether the commonly cited risk factor association can be substantiated by high quality studies which comply with the requirements of "evidence-based medicine."

Local estrogen therapy and risk of breast cancer recurrence among hormone-treated patients: a nested case-control study.

Women with estrogen-positive breast cancers receive endocrine treatment such as tamoxifen and aromatase inhibitors (AI) for 5-10 years. An important side effect of these drugs is vaginal dryness for which local hormonal therapy (LHT) represents the most effective treatment but is theoretically contraindicated. This study aimed to assess whether the use of LHT increases the risk of breast cancer recurrence among women receiving endocrine treatment. We conducted a cohort study with nested case-control analysis using the United Kingdom General Practice Research Database (GPRD). The cohort included female patients at least 18 years of age, newly diagnosed with breast cancer who received at least one AI or tamoxifen prescription between January 1, 1998 and June 30, 2008. Cases, who were patients experiencing a breast cancer recurrence during follow-up, were each matched with up to 10 controls based on age, date of cohort entry, type of endocrine treatment received, and duration of follow-up. Conditional logistic regression was used to estimate rate ratios (RR), and 95 % confidence intervals. A total of 13,479 women were included in the study, of which 2,673 received AIs, 10,806 received tamoxifen, and 271 received LHT. Mean (SD) age at cohort entry was 63.7 (14.1) years, and mean follow-up was 3.5 (2.6) years. The crude recurrence rate 25.9 per 1,000 per year. Overall, the use of LHT was not associated with an increased risk of recurrence (RR: 0.78, 95 % CI 0.48-1.25) compared with non-use. In stratified analyses, LHT did not increase the risk of recurrence among tamoxifen-treated patients (RR: 0.83, 95 % CI 0.51-1.34), while the risk was not estimable among AI-treated patients since no patients receiving LHT experienced a recurrence. The use of LHT is not associated with an increase in breast cancer recurrence among women receiving a hormone therapy.

Endometrial carcinoma tumorigenesis and pharmacotherapy research.

Endometrial carcinoma is the common malignant tumor of the female genital tract, and its incidence is increasing. Two different clinicopathological subtypes are recognized based on epidemiology, genetic carcinogenesis and clinical behavior. Understanding and identifying molecular biology and genetics is essential to the development of novel therapies. This article reviews the current understanding of its risk factors, recent conceptions on its tumorigenesis and advances on its drug therapies.

Alcohol consumption and the risk of breast cancer.

Epidemiologic studies addressing the association of alcohol consumption with breast cancer consistently suggest a modest association and a dose-response relationship. The epidemiologic evidence does not point to a single mechanism to explain the association, and several mechanisms have been proposed. Alcohol consumption is shown to increase levels of endogenous estrogens, known risk factors for breast cancer. This hypothesis is further supported by data showing that the alcohol-breast cancer association is limited to women with estrogen-receptor positive tumors. Products of alcohol metabolism are known to be toxic and are hypothesized to cause DNA modifications that lead to cancer. Recent research has focused on genes that influence the rate of alcohol metabolism, with genes that raise blood concentrations of acetaldehyde hypothesized to heighten breast cancer risk. Mounting evidence suggests that antioxidant intake(e.g.folate)mayreducealcohol-associatedbreast cancer risk, because it neutralizes reactive oxygen species, a second-stage product of alcohol metabolism. Diets lacking sufficient antioxidant intake, as a result, may further elevate the risk of breast cancer among alcohol consumers. Given that alcohol consumption is increasing worldwide and especially among women in countries of rapid economic growth, a greater understanding of the mechanisms underlying the known alcohol-breast cancer association is warranted. Avoiding overconsumption of alcohol is recommended, especially for women with known risk factors for breast cancer.

[Cancer risk in women: a possible connection with geographic and certain economic and social factors].

The paper deals with mulivariate regression analysis of effects of latitude, economic environment and electricity consumption on breast cancer morbidity in 35 countries (1985-2007). Our data are compared with the influence of the same factors on incidence rates for ovarian carcinoma, endometrial and cervical cancer as well as those of the stomach, liver, colon and lung. It was found that rates of morbidity for breast, endometrial, colonic and lung cancer tend to increase north of the equator while cervical, gastric and hepatic cancer incidence is relatively higher in circumequatorial populations. In 1985, geographic factors made a dramatic contribution to hormone-dependent tumors incidence while economic ones--to that of gastrointestinal neoplasms. In the 2000-ies, climate-related risks of hormone-dependent tumors have gradually slumped down while those of economic and social factors have increased.

Regulation of mitochondrial respiratory chain biogenesis by estrogens/estrogen receptors and physiological, pathological and pharmacological implications.

There has been increasing evidence pointing to the mitochondrial respiratory chain (MRC) as a novel and important target for the actions of 17beta-estradiol (E(2)) and estrogen receptors (ER) in a number of cell types and tissues that have high demands for mitochondrial energy metabolism. This novel E(2)-mediated mitochondrial pathway involves the cooperation of both nuclear and mitochondrial ERalpha and ERbeta and their co-activators on the coordinate regulation of both nuclear DNA- and mitochondrial DNA-encoded genes for MRC proteins. In this paper, we have: 1) comprehensively reviewed studies that reveal a novel role of estrogens and ERs in the regulation of MRC biogenesis; 2) discussed their physiological, pathological and pharmacological implications in the control of cell proliferation and apoptosis in relation to estrogen-mediated carcinogenesis, anti-cancer drug resistance in human breast cancer cells, neuroprotection for Alzheimer's disease and Parkinson's disease in brain, cardiovascular protection in human heart and their beneficial effects in lens physiology related to cataract in the eye; and 3) pointed out new research directions to address the key questions in this important and newly emerging area. We also suggest a novel conceptual approach that will contribute to innovative regimens for the prevention or treatment of a wide variety of medical complications based on E(2)/ER-mediated MRC biogenesis pathway.

Association between phthalate exposure and glutathione S-transferase M1 polymorphism in adenomyosis, leiomyoma and endometriosis.

BACKGROUND: Phthalates are known to have estrogenic effects in cell models and experimental animals. However, the evidence regarding the effects of phthalates on human reproduction is still limited. We conducted a case-control study to determine whether estrogen-dependent diseases are associated with phthalate exposure and how the glutathione S-transferase M1 (GSTM1; a major detoxification enzyme) genotype modulates the risk. METHODS: We recruited subjects who underwent laparotomy and had pathologic confirmation of endometriosis (EN) (n = 28), adenomyosis (AD) (n = 16) and leiomyoma (LEI) (n = 36) from the Department of Obstetrics and Gynecology at a medical center in Taiwan between 2005 and 2007. Controls (n = 29) were patients without any of the three aforementioned gynecologic conditions. Urine samples were collected before surgery and analyzed for seven phthalate metabolites using liquid chromatography-tandem mass spectrometry. Peripheral lymphocytes were used for GSTM1 genotype determination. RESULTS: Patients with LEIs had significantly higher levels of total urinary mono-ethylhexyl phthalate (SigmaMEHP; 52.1 versus 18.9 microg/g creatinine, P < 0.05) than the controls, whereas patients with EN had an increased level of urinary mono-n-butyl phthalate (94.1 versus 58.0 microg/g creatinine, P < 0.05). Subjects with GSTM1 null genotype had significantly increased odds for AD relative to those with GSTM1 wild genotype [odds ratio (OR) = 5.30; 95% CI, 1.22-23.1], even after adjustment for age and phthalate exposure. Subjects who carried the GSTM1 null genotype and had a high urinary level of SigmaMEHP showed a significantly increased risk for AD (OR = 10.4; 95% CI, 1.26-85.0) and LEIs (OR = 5.93; 95% CI, 1.10-31.9) after adjustment for age, compared with those with GSTM1 wild-type and low urinary level of SigmaMEHP. CONCLUSIONS: These results suggest that both GSTM1 null and phthalate exposure are associated with AD and LEI. Larger studies are warranted to investigate potential interaction between GSTM1 null and phthalate exposure in the etiology of estrogen-dependent gynecologic conditions.

[Carcinogenesis theory based on estrogen deficiency]. / Az ösztrogénhiányon alapuló rákelmélet.

Earlier, estrogens were considered simply the most important hormones involved in female physiology and reproduction. Nowadays it has become familiar that they have pivotal roles in gene regulation of cell differentiation and proliferation. There are many contradictions concerning the associations of female sexual steroids and cancer. Cancers of the highly estrogen dependent organs are in the forefront of tumors as they are regarded as hormone associated ones. However, re-evaluation of earlier results supporting the carcinogenic capacity of estrogen exhibited many shortcomings and controversies. Recently, the clinical studies on hormone replacement therapy in postmenopausal women justified beneficial anticancer effects in several organs even in the female breast. The newly revealed association between estrogen deficiency and oral cancer risk also means a contradiction of the traditional concept of estrogen-induced cancer. Distinction between cancers of moderately and highly estrogen dependent tumors can be based on their different epidemiological features. The vast majority of the so-called smoking associated malignancies of the moderately estrogen dependent organs occur typically in the late postmenopausal life of women when the ovarian estrogen production is fairly decreased. However cancers of the highly estrogen dependent organs such as breast, endometrium and ovary exhibit both premenopausal and postmenopausal occurrence. In spite of the different epidemiological data of these two groups of cancers the mechanism of gene regulation disorder in the background of tumor initiation cannot act through quite opposite pathways. This suggests that in moderately estrogen sensitive organs a serious, in the highly estrogen dependent sites even a mild estrogen deficiency is enough to provoke gene regulation disorders. The new findings both on smoking associated and hormone related cancers might lead to the same conversion; not estrogen but rather its deficiency may provoke cancer initiation.

Heparanase Accelerates Obesity-Associated Breast Cancer Progression.

Obese women have higher risk of bearing breast tumors that are highly aggressive and resistant to therapies. Tumor-promoting effects of obesity occur locally via adipose inflammation and related alterations to the extracellular matrix (ECM) as well as systemically via circulating metabolic mediators (e.g., free fatty acids, FFA) associated with excess adiposity and implicated in toll-like receptor-mediated activation of macrophages-key cellular players in obesity-related cancer progression. Although the contribution of macrophages to proneoplastic effects of obesity is well documented, the role of ECM components and their enzymatic degradation is less appreciated. We show that heparanase, the sole mammalian endoglucuronidase that cleaves heparan sulfate in ECM, is preferentially expressed in clinical/experimental obesity-associated breast tumors. Heparanase deficiency abolished obesity-accelerated tumor progression in vivo. Heparanase orchestrated a complex molecular program that occurred concurrently in adipose and tumor tissue and sustained the cancer-promoting action of obesity. Heparanase was required for adipose tissue macrophages to produce inflammatory mediators responsible for local induction of aromatase, a rate-limiting enzyme in estrogen biosynthesis. Estrogen upregulated heparanase in hormone-responsive breast tumors. In subsequent stages, elevated levels of heparanase induced acquisition of procancerous phenotype by tumor-associated macrophages, resulting in activation of tumor-promoting signaling and acceleration of breast tumor growth under obese conditions. As techniques to screen for heparanase expression in tumors become available, these findings provide rational and a mechanistic basis for designing antiheparanase approaches to uncouple obesity and breast cancer in a rapidly growing population of obese patients. SIGNIFICANCE: This study reveals the role of heparanase in promoting obesity-associated breast cancer and provides a mechanistically informed approach to uncouple obesity and breast cancer in a rapidly growing population of obese patients.

Alcohol intake and risk of breast cancer defined by estrogen and progesterone receptor status--a meta-analysis of epidemiological studies.

The association between alcohol consumption and an increased risk of breast cancer has been established. It is still unclear however, whether this relationship differs across the estrogen receptor (ER) and progesterone receptor (PR) tumors subtypes. To provide a quantitative assessment of the association between alcohol intake and the risk of ER-/PR-defined breast cancer, we conducted a meta-analysis of cohort and case-control studies. Studies were identified by a literature search of PubMed through April 20, 2007 and by searching the reference lists of relevant articles. Summarized risk estimates (REs) with 95% confidence intervals (CIs) were calculated using random-effects models. The summarized results of the meta-analysis comparing the highest versus the lowest consumption categories showed statistically significant higher risks of developing all ER+ (27%), all ER- (14%), ER+PR+ (22%) and ER+PR- (28%), but not ER-PR- tumors. The dose-response meta-analysis showed that an increase in alcohol consumption of 10 g of ethanol per day was associated with statistically significant increased risks for all ER+ (12%), all ER- (7%), ER+PR+ (11%) and ER+PR- (15%), but not ER-PR-. A statistically significant heterogeneity of the REs across all ER+ versus ER-PR- was observed (p(heterogeneity) = 0.02). The summarized results from studies with adjustment for postmenopausal hormone use, body mass index and family history of breast cancer were higher and statistically significantly different from those without. The observed positive associations with alcohol for ER+PR+ and ER+PR- tumors cannot be explained by estrogen-dependent pathway only. Further studies need to clarify the biological mechanisms.