Endocrine-disrupting compounds and mammary gland development: early exposure and later life consequences

Grouping of endocrine disrupting chemicals for mixture risk assessment - Evidence from a rat study

Exposure to mixtures of endocrine disrupting chemicals may contribute to the rising incidence of hormone-related diseases in humans. Real-life mixtures are complex, comprised of chemicals with mixed modes of action, and essential knowledge is often lacking on how to group such chemicals into cumulative assessment groups, which is an essential prerequisite to conduct a chemical mixture risk assessment. We investigated if mixtures of chemicals with diverse endocrine modes of action can cause mixture effects on hormone sensitive endpoints in developing and adult rat offspring after perinatal exposure. Wistar rats were exposed during pregnancy and lactation simultaneously to either bisphenol A and butylparaben (Emix), diethylhexyl phthalate and procymidone (Amix), or a mixture of all four substances (Totalmix). In male offspring, the anogenital distance was significantly reduced and nipple retention increased in animals exposed to Amix and Totalmix, and the mixture effects were well approximated by the dose addition model. The combination of Amix and Emix responded with more marked changes on these and other endocrine-sensitive endpoints than each binary mixture on its own. Sperm counts were reduced by all exposures. These experimental outcomes suggest that the grouping of chemicals for mixture risk assessment should be based on common health outcomes rather than only similar modes or mechanisms of action. Mechanistic-based approaches such as the concept of Adverse Outcome Pathway (AOP) can provide important guidance if both the information on shared target tissues and the information on shared mode/mechanism of action are taken into account.

Investigation of the adolescent female breast transcriptome and the impact of obesity

Background

Early life environmental exposures affect breast development and breast cancer risk in adulthood. The breast is particularly vulnerable during puberty when mammary epithelial cells proliferate exponentially. In overweight/obese (OB) women, inflammation increases breast aromatase expression and estrogen synthesis and promotes estrogen-receptor (ER)-positive breast cancer. In contrast, recent epidemiological studies suggest that obesity during childhood decreases future breast cancer risk. Studies on environmental exposures and breast cancer risk have thus far been limited to animal models. Here, we present the first interrogation of the human adolescent breast at the molecular level and investigate how obesity affects the immature breast.

Methods

We performed RNA-seq in 62 breast tissue samples from adolescent girls/young women (ADOL; mean age 17.8 years) who underwent reduction mammoplasty. Thirty-one subjects were non-overweight/obese (NOB; mean BMI 23.4 kg/m²) and 31 were overweight/obese (OB; BMI 32.1 kg/m²). We also compared our data to published mammary transcriptome datasets from women (mean age 39 years) and young adult mice, rats, and macaques.

Results

The ADOL breast transcriptome showed limited (30%) overlap with other species, but 88% overlap with adult women for the 500 most highly expressed genes in each dataset; only 43 genes were shared by all groups. In ADOL, there were 120 differentially expressed genes (DEG) in OB compared with NOB samples (p_adj < 0.05). Based on these DEG, Ingenuity Pathway Analysis (IPA) identified the cytokines CSF1 and IL-10 and the chemokine receptor CCR2 as among the most highly activated upstream regulators, suggesting increased inflammation in the OB breast. Classical ER targets (e.g., PR, AREG) were not differentially expressed, yet IPA identified the ER and PR and growth factors/receptors (VEGF, HGF, HER3) and kinases (AKT1) involved in hormone-independent ER activation as activated upstream regulators in OB breast tissue.

Conclusions

These studies represent the first investigation of the human breast transcriptome during late puberty/young adulthood and demonstrate that obesity is associated with a transcriptional signature of inflammation which may augment estrogen action in the immature breast microenvironment. We anticipate that these studies will prompt more comprehensive cellular and molecular investigations of obesity and its effect on the breast during this critical developmental window.

Epigenetics in Inflammatory Breast Cancer: Biological Features and Therapeutic Perspectives

Evidence has emerged implicating epigenetic alterations in inflammatory breast cancer (IBC) origin and progression. IBC is a rare and rapidly progressing disease, considered the most aggressive type of breast cancer (BC). At clinical presentation, IBC is characterized by diffuse erythema, skin ridging, dermal lymphatic invasion, and peau d'orange aspect. The widespread distribution of the tumor as emboli throughout the breast and intra- and intertumor heterogeneity is associated with its poor prognosis. In this review, we highlighted studies documenting the essential roles of epigenetic mechanisms in remodeling chromatin and modulating gene expression during mammary gland differentiation and the development of IBC. Compiling evidence has emerged implicating epigenetic changes as a common denominator linking the main risk factors (socioeconomic status, environmental exposure to endocrine disruptors, racial disparities, and obesity) with IBC development. DNA methylation changes and their impact on the diagnosis, prognosis, and treatment of IBC are also described. Recent studies are focusing on the use of histone deacetylase inhibitors as promising epigenetic drugs for treating IBC. All efforts must be undertaken to unravel the epigenetic marks that drive this disease and how this knowledge could impact strategies to reduce the risk of IBC development and progression.

A modern look at the molecular-biological mechanisms of breast tumours in dogs

High morbidity and increase in the number of registrations of breast tumours in dogs, their wide application as biological models, discussion of numerous questions of oncogenesis, and the lack of a uniform/unified methodological approach to the study of molecular and biological mechanisms of treatment of cancer determine the relevance of the problem of cancer both in humans and in our domestic companions. The analysis of publications allowed us to establish the following patterns of carcinogenesis. The peculiarities of the biological behaviour of breast tumours depend on their pathomorphological structure. Genetic predisposition to breast cancer is characteristic only in the single breed aspect. Environmental factors are of critical relevance to carcinogenesis : chemical pollutants initiate oncogenesis indirectly – by altering the expression of several receptors, impaired endocrine balance and direct mutagenic effects. Reproductive status plays a key role in the initiation and progression of breast tumours by reducing the expression of estrogen, progesterone and prolactin receptor genes. The inflammatory response that accompanies the neoplasia process is characterized by increased production of cytokines, cyclooxygenase-2, interleukins (IL-1, IL-6, IL-8), vascular endothelial growth receptors, and impaired hemostatic status (oxidative stress), which promotes progression of disease. In breast cancer in dogs, genomic instability leads to genomic aberrations, and subsequently, mutations that support the proliferation, survival and dissemination of neoplastic cells. The initiation and progression of mammary gland tumours is provided by cancer stem cells by disrupting the regulation of precursor cell self-renewal, which also predispose to resistance to chemotherapeutic agents, radiation, and hormonal cancer therapy. The analysis of the publications revealed the major markers of carcinogenesis that could potentially be used as biological targets for the design of modern diagnostic strategies and high-performance therapeutic protocols.

Heightened susceptibility: A review of how pregnancy and chemical exposures influence maternal health

Pregnancy is a unique period when biological changes can increase sensitivity to chemical exposures. Pregnant women are exposed to multiple environmental chemicals via air, food, water, and consumer products, including flame retardants, plasticizers, and pesticides. Lead exposure increases risk of pregnancy-induced hypertensive disorders, although women's health risks are poorly characterized for most chemicals. Research on prenatal exposures has focused on fetal outcomes and less on maternal outcomes. We reviewed epidemiologic literature on chemical exposures during pregnancy and three maternal outcomes: preeclampsia, gestational diabetes, and breast cancer. We found that pregnancy can heighten susceptibility to environmental chemicals and women's health risks, although variations in study design and exposure assessment limited study comparability. Future research should include pregnancy as a critical period for women's health. Incorporating biomarkers of exposure and effect, deliberate timing and method of measurement, and consistent adjustment of potential confounders would strengthen research on the exposome and women's health.

Glyphosate-based herbicide induces hyperplastic ducts in the mammary gland of aging Wistar rats

Glyphosate-based herbicide (GBH) exposure is known to have adverse effects on endocrine-related tissues. Here, we aimed to determine whether early postnatal exposure to a GBH induces long-term effects on the rat mammary gland. Thus, female Wistar pups were injected with saline solution (Control) or GBH (2 mg glyphosate/kg/day) on postnatal days (PND) 1, 3, 5 and 7. At 20 months of age, mammary gland samples were collected to determine histomorphological features, proliferation index and the expression of steroid hormone receptors expression, by immunohistochemistry, and serum samples were collected to assess 17β-estradiol (E2) and progesterone (P4) levels. GBH exposure induced morphological changes evidenced by a higher percentage of hyperplastic ducts and a fibroblastic-like stroma in the mammary gland. GBH-treated rats also showed a high expression of steroid hormone receptors in hyperplastic ducts. The results indicate that early postnatal exposure to GBH induces long-term alterations in the mammary gland morphology of aging female rats.

Perturbation of Nuclear Hormone Receptors by Endocrine Disrupting Chemicals: Mechanisms and Pathological Consequences of Exposure

Much of the early work on Nuclear Hormone Receptors (NHRs) focused on their essential roles as mediators of sex steroid hormone signaling in reproductive development and function, and thyroid hormone-dependent formation of the central nervous system. However, as NHRs display tissue-specific distributions and activities, it is not surprising that they are involved and vital in numerous aspects of human development and essential for homeostasis of all organ systems. Much attention has recently been focused on the role of NHRs in energy balance, metabolism, and lipid homeostasis. Dysregulation of NHR function has been implicated in numerous pathologies including cancers, metabolic obesity and syndrome, Type II diabetes mellitus, cardiovascular disease, hyperlipidemia, male and female infertility and other reproductive disorders. This review will discuss the dysregulation of NHR function by environmental endocrine disrupting chemicals (EDCs), and the associated pathological consequences of exposure in numerous tissues and organ systems, as revealed by experimental, clinical, and epidemiological studies.

NAMS 2018 Utian Translational Science Symposium, October 2018, San Diego, California New therapies for leiomyomas: when surgery may not be the best option

The North American Menopause Society (NAMS) held the 2018 Utian Translational Science Symposium on October 2, 2018, in San Diego, California, to discuss new therapeutic approaches to uterine leiomyomas when surgery is not the optimal choice.Uterine leiomyomas arise from a single clonal cell and are the most common gynecologic disorder affecting reproductive and perimenopausal women worldwide. The prevalence of this disorder is approximately 40% to 70% in white women and 60% to 80% in black women. Recent research suggests that both estrogen and progesterone modulate the growth of leiomyomas, with progesterone being a major stimulator of leiomyoma growth.Women with symptomatic uterine leiomyomas experience heavy uterine bleeding, bulk symptoms, miscarriages, and pregnancy complications. Surgical therapies such as myomectomy or hysterectomy are highly effective; however, medical therapy with progestin-predominant contraceptives or gonadotropin-releasing hormone (GnRH) agonists are in many ways inadequate to address the unmet need for better, noninvasive, and cost-effective treatments.Recent advances in medical treatment, such as selective progesterone receptor modulators, new oral GnRH analogs, and clinical trials that provide new therapeutic approaches, were presented by speakers at the symposium. Research on why there is a prevalence of leiomyomas in black women, the racial and genetic effects on leiomyoma growth, and potential molecular mechanisms also were discussed.

Exposure to low doses of oxybenzone during perinatal development alters mammary gland morphology in male and female mice

Oxybenzone (benzophenone-3) is an ultraviolet radiation filter commonly used in personal care products including sunscreens, textiles and inks, and food and beverage containers, among others. Due to its widespread use, human exposures to oxybenzone are widespread. Oxybenzone is considered an endocrine disrupting chemical due to its antiestrogenic and antiandrogenic properties. We evaluated the effects of oral exposures to oxybenzone on the growth and morphology of the mammary gland, body weight and anogenital distance in BALB/c mice exposed to 30, 212 or 3000 μg/kg/day in utero and during lactation. Developmental exposures to oxybenzone reduced the size and growth of mammary gland in males prior to and during puberty. In exposed females, oxybenzone reduced mammary cell proliferation, decreased the number of cells expressing estrogen receptor α, and altered mammary gland morphology in adulthood. These results suggest that even low doses of oxybenzone can disrupt hormone sensitive organs during critical windows of development.

Levels of phthalate acid esters and sex hormones and their possible sources in traffic-patrol policemen in Chongqing

To investigate the correlation between the air phthalate acid ester (PAE) exposure and serum PAE concentration and the effects of PAE exposure on reproductive health among Chongqing traffic-patrol policemen. In 2013, 32 traffic-patrol policemen working in an area with poor air quality in Chongqing and 28 traffic-patrol policemen working in an area with good air quality were selected. Their blood levels of 14 PAEs and six reproductive hormones were determined. Air samples were collected from four traffic-patrol platforms. The concentrations of 14 PAEs in the air samples were evaluated. All 14 PAEs were detected in the blood samples. The concentrations of seven PAEs in the total suspended particulate, namely, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, bis (2-ethox-yethyl) phthalate, dihexyl phthalate, benzyl butyl phthalate, and bis (2-n-butoxyethyl) phthalate, were positively and significantly associated with the blood levels of these PAEs in the participants. All the sex hormone levels measured here were significantly different between the participants from the two areas. The PAE concentrations in the blood samples were correlated with the reproductive hormone levels in the participants. Air PAE pollution may be a major source of PAE exposure in the traffic-patrol policemen of Chongqing.

The tributyltin leads to obesogenic mammary gland abnormalities in adult female rats

Tributyltin chloride (TBT) is an obesogen associated with several complications. However, few investigations have evaluated TBT effects on adult mammary glands (MG). In this investigation, we assessed whether TBT's obesogenic effects resulted in abnormal MG fat pad expansion and other irregularities. TBT was administered to female rats (100 ng/kg/day for 15 days via gavage), and their MG morphophysiological development was assessed. We further assessed the MG fat pad for PPARγ, ERα, and aromatase protein expression, as well as inflammation, oxidative stress (OS), apoptosis and fibrosis. Irregular MG morphological development such as lower TEB number, alveolar (AB), lobule and differentiation (DF) score were observed in TBT rats. TBT rats had abnormal MG fat accumulation as evidenced by increased numbers of hypertrophic adipocytes, triglyceride (TG) levels and PPARγ expression. A strong negative correlation between the MG obesogenic makers and TEB number, AB and DF score were observed in TBT rats. MG inflammation was observed in TBT rats. A positive correlation between the MG obesogenic markers and inflammation were observed. High ERα and aromatase expression were observed in MG of TBT rats. MG OS, apoptosis and fibrosis were present in the TBT rats. Additionally, a positive correlation between the MG obesogenic markers and OS were observed in TBT rats. Thus, these data suggest that obesogenic TBT effects led to MG irregularities in the adult female rats.

Male mammary gland development and methylation status of estrogen receptor alpha in Wistar rats are modified by the developmental exposure to a glyphosate-based herbicide

Postnatal treatment with glyphosate-based herbicides (GBHs) induces endocrine-disrupting effects on the male rat mammary gland. In this study, the effects of developmental exposure to GBH on mammary gland growth and development, and the possible molecular mechanisms involved, were evaluated in pre- and post-pubertal male rats. To this end, pregnant rats were orally exposed through the food to 0, 3.5 or 350 mg GBH/kg bw/day from gestational day 9 until weaning. Mammary gland development and estradiol (E2) and testosterone (T) serum levels of male offspring were evaluated on postnatal day (PND)21 and PND60. Besides, prolactin (PRL) serum levels, proliferation index, androgen (AR) and estrogen receptor alpha (ESR1) expression, ESR1 alternative transcript mRNA levels, and DNA methylation status of ESR1 promoters were assessed on PND60. No differences between groups were observed in mammary gland development at PND21 or in E2 and T levels on both PNDs studied. On PND60, GBH3.5-exposed animals presented similar mammary gland histology but higher AR protein expression than controls, whereas GBH350-exposed males presented a less developed mammary gland, accompanied by a lower proliferation index, similar AR levels, and slightly increased PRL serum levels than controls. In both exposed groups, ESR1 expression was lower than in control rats, being lower in GBH350-exposed rats. GBH also altered the abundance of ESR1 transcript variants by hypermethylation of ESR1 promoters. GHB3.5 decreased only ESR1-OS expression, whereas GBH350 affected ESR1-O, OT and E1 expression. Our results show that developmental exposure to GBH induces epigenetic changes in ESR1, which could be responsible for the altered male mammary gland development observed in GBH350-exposed animals.

Breast Cancer and Exposure to Organochlorines in the CECILE Study: Associations with Plasma Levels Measured at the Time of Diagnosis and Estimated during Adolescence

Exposure to environmental chemicals with hormonal effects, such as organochlorine compounds (OCs), during developmental periods of breast cells may have an impact on the incidence of breast cancer later in life. However, the assessment of exposure to these chemicals that occurred in early life at the time of breast cancer development in adult women is a difficult challenge in epidemiological studies. Plasma levels of the OCs p,p'-dichlorodiphenyl dichloroethene (DDE) and polychlorinated biphenyl congener 153 (PCB153) were measured in 695 cases and 1055 controls of a population-based case-control study conducted in France (CECILE study). Based on these values, we used a physiologically-based pharmacokinetic (PBPK) model to estimate PCB153 levels at age 11⁻20 years when the women were adolescents. Overall, there was no clear association between breast cancer risk and measured levels of DDE and PCB153 at the time of diagnosis, but there was a trend of decreasing odds ratios of breast cancer with increasing DDE and PCB153 levels in women aged 50 years and over. The PBPK model revealed that PCB153 concentrations estimated during adolescence were highest in the youngest women born after 1960 who reached adolescence at a time when environmental contamination was maximum, and very low in the oldest women who attained adolescence before the contamination peak. Negative associations between breast cancer and PCB153 estimates during adolescence were also found. The negative associations between DDE and PCB153 levels measured at the time of diagnosis or estimated during adolescence in our study were unexplained. Further investigations are needed to clarify whether this finding is real or related to study artifacts. However, this study suggests that using PBPK models in epidemiological studies to back-estimate OC exposures during early life stages may be useful to address critical questions on cancer development.

Concerns related to ED-mediated effects of Bisphenol A and their regulatory consideration

The extensive database on BPA provides strong evidence of its adverse effects on reproductive, neurobehavioural, metabolic functions and mammary gland. Disruption of estrogenic pathway is central in the mediation of these effects although other modes of action may be involved. BPA has a weak affinity for ERα/β but interaction with extranuclearly located pathways activated by estrogens such as ERRγ and GPER reveals how BPA can act at low doses. The effects are observed later in life after developmental exposure and are associated with pathologies of major societal concern in terms of severity, incidence, impact on quality of life, burden on public health system. The complexity of the dose response raise uncertainties on the possibility to establish safe levels and the scope of ED-mediated effects of BPA may be wider. These concerns fulfill the requirements for ED identification under REACH regulation.

Alteration of mammary gland development by bisphenol a and evidence of a mode of action mediated through endocrine disruption

The development and function of the mammary gland are endocrine-dependent processes, depending on the stage of development. Foetal and/or postnatal exposure to low doses of BPA alters tissue organisation through epithelial proliferation and stroma-epithelial interactions. BPA also alters the expression of E2-dependent epithelial and stroma transcriptomes. Several signalling pathways are consistent with the observed phenotype: proliferation and apoptosis, a focal adhesion pathway indicating changes in biomechanical properties of the extracellular matrix, and immune function. Some of BPA's effects are reversed by oestrogen and/or GPER inhibitors. BPA also alters the expression of epigenetic marks (EZH2, HOTAIR), which would explain the delayed effect of foetal BPA exposure. In conclusion, experimental evidence shows that pre- or postnatal BPA exposure consistently causes endocrine modifications in the mammary tissue of different animal species, disrupting stromal-epithelial interactions and ultimately increasing its susceptibility to carcinogens. An interspecies comparison highlights why and how these effects apply to humans.

From the Cover: Exposure to an Environmentally Relevant Mixture of Brominated Flame Retardants Decreased p-β-Cateninser675 Expression and Its Interaction With E-Cadherin in the Mammary Glands of Lactating Rats

Proper mammary gland development and function require precise hormonal regulation and bidirectional cross talk between cells provided by means of paracrine factors as well as intercellular junctions; exposure to environmental endocrine disruptors can disturb these processes. Exposure to one such family of chemicals, the brominated flame retardants (BFRs), is ubiquitous. Here, we tested the hypothesis that BFR exposures disrupt signaling pathways and intercellular junctions that control mammary gland development. Before mating, during pregnancy and throughout lactation, female Sprague-Dawley rats were fed diets containing that BFR mixture based on house dust, delivering nominal exposures of BFR of 0 (control), 0.06, 20, or 60 mg/kg/d. Dams were euthanized and mammary glands collected on postnatal day 21. BFR exposure had no significant effects on mammary gland/body weight ratios or the levels of proteins involved in milk synthesis, epithelial-mesenchymal transition, cell-cell interactions, or hormone signalling. However, BFR exposure (0.06 mg/kg/d) down-regulated phospho-ser675 β-catenin (p-β-catSer675) levels in the absence of any effect on total β-catenin levels. Levels of p-CREB were also down-regulated, suggesting that PKA inhibition plays a role. p-β-catSer675 co-localized with β-catenin at the mammary epithelial cell membrane, and its expression was decreased in animals from the 0.06 and 20 mg/kg/d BFR treatment groups. Although β-Catenin signaling was not affected by BFR exposure, the interaction between p-β-catSer675 and E-cadherin was significantly reduced. Together, our results demonstrate that exposure to an environmentally relevant mixture of BFR during pregnancy and lactation decreases p-β-catser675 at cell adhesion sites, likely in a PKA-dependant manner, altering mammary gland signaling.

Metabolomics Reveals Aryl Hydrocarbon Receptor Activation Induces Liver and Mammary Gland Metabolic Dysfunction in Lactating Mice

The liver and the mammary gland have complementary metabolic roles during lactation. Substrates synthesized by the liver are released into the circulation and are taken up by the mammary gland for milk production. The aryl hydrocarbon receptor (AHR) has been identified as a lactation regulator in mice, and its activation has been associated with myriad morphological, molecular, and functional defects such as stunted gland development, decreased milk production, and changes in gene expression. In this study, we identified adverse metabolic changes in the lactation network (mammary, liver, and serum) associated with AHR activation using 1H nuclear magnetic resonance (NMR)-based metabolomics. Pregnant mice expressing Ahr d (low affinity) or Ahr b (high affinity) were fed diets containing beta naphthoflavone (BNF), a potent AHR agonist. Mammary, serum, and liver metabolomics analysis identified significant changes in lipid and TCA cycle intermediates in the Ahr b mice. We observed decreased amino acid and glucose levels in the mammary gland extracts of Ahr b mice fed BNF. The serum of BNF fed Ahr b mice had significant changes in LDL/VLDL (increased) and HDL, PC, and GPC (decreased). Quantitative PCR analysis revealed ∼50% reduction in the expression of key lactogenesis mammary genes including whey acid protein, α-lactalbumin, and β-casein. We also observed morphologic and developmental disruptions in the mammary gland that are consistent with previous reports. Our observations support that AHR activity contributes to metabolism regulation in the lactation network.

Low dose bisphenol S or ethinyl estradiol exposures during the perinatal period alter female mouse mammary gland development

Throughout life, mammary tissue is strongly influenced by hormones. Scientists have hypothesized that synthetic chemicals with hormonal activities could disrupt mammary gland development and contribute to breast diseases and dysfunction. Bisphenol S (BPS) is an estrogenic compound used in many consumer products. In this study, CD-1 mice were exposed to BPS (2 or 200 μg/kg/day) during pregnancy and lactation. Mice exposed to 0.01 or 1 μg/kg/day ethinyl estradiol (EE2), a pharmaceutical estrogen, were also evaluated. Mammary glands from female offspring were collected prior to the onset of puberty, during puberty, and in early adulthood. Growth parameters, histopathology, cell proliferation and expression of hormone receptors were quantified. Our evaluations revealed age- and dose-specific effects of BPS that were different from the effects of EE2, and distinct from the effects of BPA that have been reported previously. These assessments suggest that individual xenoestrogens may have unique effects on this sensitive tissue.

The molecular mechanisms of action of the endocrine disrupting chemical bisphenol A in the development of cancer

The endocrine disrupting chemical (EDC) is an exogenous substance or mixture that alters the function of the endocrine system and consequently causes adverse effects in intact organisms. Bisphenol A (BPA), one of the most common endocrine disrupting chemicals is a carbon-based synthetic compound used in the production of water bottles, cans, and teeth suture materials. It is known to be a xenoestrogen as it interacts with estrogen receptors and acts as agonist or antagonist via estrogen receptor-dependent signaling pathways. BPA has been associated with serious health effects in humans and wildlife. It elicits several endocrine disorders and plays a role in the pathogenesis of several hormone-dependent tumors such as breast, ovarian, prostate cancer and others. More complicate to this picture, its effects rely on several and diverse molecular and epigenetic mechanisms that converge upon endocrine and reproductive systems. The present review gives an overview of general hazards of BPA, its epigenetic modifications and the molecular mechanisms of BPA action in different types of cancers as the increase in information about responses and action mechanisms of BPA may bring a better understanding of the risks of BPA exposure in humans and provide an important platform on which human health can be improved.

Left-right analysis of mammary gland development in retinoid X receptor-α+/- mice

Left-right (L-R) differences in mammographic parenchymal patterns are an early predictor of breast cancer risk; however, the basis for this asymmetry is unknown. Here, we use retinoid X receptor alpha heterozygous null (RXRα^+/-) mice to propose a developmental origin: perturbation of coordinated anterior-posterior (A-P) and L-R axial body patterning. We hypothesized that by analogy to somitogenesis-in which retinoic acid (RA) attenuation causes anterior somite pairs to develop L-R asynchronously-that RA pathway perturbation would likewise result in asymmetric mammary development. To test this, mammary glands of RXRα^+/- mice were quantitatively assessed to compare left- versus right-side ductal epithelial networks. Unlike wild-type controls, half of the RXRα^+/- thoracic mammary gland (TMG) pairs exhibited significant L-R asymmetry, with left-side reduction in network size. In RXRα^+/- TMGs in which symmetry was maintained, networks had bilaterally increased size, with left networks showing greater variability in area and pattern. Reminiscent of posterior somites, whose bilateral symmetry is refractory to RA attenuation, inguinal mammary glands (IMGs) also had bilaterally increased network size, but no loss of symmetry. Together, these results demonstrate that mammary glands exhibit differential A-P sensitivity to RXRα heterozygosity, with ductal network symmetry markedly compromised in anterior but not posterior glands. As TMGs more closely model human breast development than IMGs, these findings raise the possibility that for some women, breast cancer risk may initiate with subtle axial patterning defects that result in L-R asymmetric growth and pattern of the mammary ductal epithelium.This article is part of the themed issue 'Provocative questions in left-right asymmetry'.

Association of Bisphenol A Exposure with Breastfeeding and Perceived Insufficient Milk Supply in Mexican Women

Introduction Estrogen inhibits lactation and bisphenol A (BPA) is a high production environmental estrogen. We hypothesize an inhibitory effect of BPA on lactation and aim to analyze the association between third trimester pregnancy urinary BPA and breastfeeding rates 1 month postpartum. Methods Odds ratios (OR) and 95 % confidence intervals (95 % CI) of breastfeeding and perceived insufficient milk supply (PIM) in relation to maternal peripartum urinary BPA concentrations were calculated in 216 mothers. Results 97.2 % of mothers in the lowest BPA tertile were breastfeeding at 1 month postpartum, compared to 89.9 % in highest (p = 0.01). Adjusted ORs (95 % CI) for not breastfeeding at 1 month were 1.9 (0.3, 10.7) and 4.3 (0.8, 21.6) for second and third BPA tertiles, respectively, compared to the lowest (p = 0.06, trend). 4.2 % reported PIM in the lowest BPA tertile, compared to 8.7 % in the highest (p = 0.03). Adjusted ORs (95 % CI) for PIM were 1.8 (0.4, 7.7) and 2.2 (0.5, 9.5), for the second and third BPA tertiles, respectively, compared to the lowest (p = 0.29, trend). Discussion These results suggest an association between maternal BPA exposure and decreased breastfeeding.

John PM, Burd CJ. Varying Susceptibility of the Female Mammary Gland to In Utero Windows of BPA Exposure

In utero exposure to the endocrine disrupting compound bisphenol A (BPA) is known to disrupt mammary gland development and increase tumor susceptibility in rodents. It is unclear whether different periods of in utero development might be more susceptible to BPA exposure. We exposed pregnant CD-1 mice to BPA at different times during gestation that correspond to specific milestones of in utero mammary gland development. The mammary glands of early-life and adult female mice, exposed in utero to BPA, were morphologically and molecularly (estrogen receptor-α and Ki67) evaluated for developmental abnormalities. We found that BPA treatment occurring before mammary bud invasion into the mesenchyme [embryonic day (E)12.5] incompletely resulted in the measured phenotypes of mammary gland defects. Exposing mice up to the point at which the epithelium extends into the precursor fat pad (E16.5) resulted in a nearly complete BPA phenotype and exposure during epithelial extension (E15.5 to E18.5) resulted in a partial phenotype. Furthermore, the relative differences in phenotypes between exposure windows highlight the substantial correlations between early-life molecular changes (estrogen receptor-α and Ki67) in the stroma and the epithelial elongation defects in mammary development. These data further implicate BPA action in the stroma as a critical mediator of epithelial phenotypes.

Bisphenol S Alters the Lactating Mammary Gland and Nursing Behaviors in Mice Exposed During Pregnancy and Lactation

High doses of estrogenic pharmaceuticals were once prescribed to women to halt lactation. Yet, the effects of low-level xenoestrogens on lactation remain poorly studied. We investigated the effects of bisphenol S (BPS), an estrogen receptor (ER) agonist, on the lactating mammary gland; the arcuate nucleus, a region of the hypothalamus important for neuroendocrine control of lactational behaviors; and nursing behavior in CD-1 mice. Female mice were exposed to vehicle, 2 or 200 µg BPS/kg/d from pregnancy day 9 until lactational day (LD) 20, and tissues were collected on LD21. Tissues were also collected from a second group at LD2. BPS exposure significantly reduced the fraction of the mammary gland comprised of lobules, the milk-producing units, on LD21, but not LD2. BPS also altered expression of Esr1 and ERα in the mammary gland at LD21, consistent with early involution. In the arcuate nucleus, no changes were observed in expression of signal transducer and activator of transcription 5, a marker of prolactin signaling, or ERα, suggesting that BPS may act directly on the mammary gland. However, observations of nursing behavior collected during the lactational period revealed stage-specific effects on both pup and maternal nursing behaviors; BPS-treated dams spent significantly more time nursing later in the lactational period, and BPS-treated pups were less likely to initiate nursing. Pup growth and development were also stunted. These data indicate that low doses of BPS can alter lactational behaviors and the maternal mammary gland. Together, they support the hypothesis that pregnancy and lactation are sensitive to low-dose xenoestrogen exposures.

A single neonatal administration of Bisphenol A induces higher tumour weight associated to changes in tumour microenvironment in the adulthood

BPA is an oestrogenic endocrine disrupting chemical compound. Exposure to BPA in as early as pregnancy leads to lifelong effects. Since endocrine and immune systems interact in a bidirectional manner, endocrine disruption may cause permanent alterations of the immune system, affecting a future anti-tumoral response. Neonate (PND 3) female syngeneic BALB/c mice were exposed to a single dose of 250 µg/kg BPA. Once sexual maturity was reached, a mammary tumour was induced injecting 4T1 cells in situ, these cells are derived from a spontaneous adenocarcinoma in a BALB/c mouse and therefore allows for an immunocompetent recipient. After 25 days of injection, showing no major endocrine alterations, BPA-exposed mice developed larger tumours. Tumour leukocytic infiltrate analysis revealed a higher proportion of regulatory T lymphocytes in the BPA-exposed group. RT-PCR analysis of tumour samples showed a decreased expression of TNF-α and IFN-γ, as well as the M2 macrophage marker Fizz-1 in the BPA-exposed group. Flow cytometry analysis revealed differences in ERα expression by T lymphocytes, macrophages and NK cells, both associated to BPA exposure and tumour development. These findings show a new aspect whereby early life BPA exposure can contribute to breast cancer development and progression by modulating the anti-tumoral immune response.

The endocrine disrupting alkylphenols and 4,4'-DDT interfere with estrogen conversion and clearance by mouse liver cytosol

Endocrine disrupting chemicals (EDCs) are ubiquitous compounds known for negative impacts on reproductive functions and for increasing cancer risk. EDCs are believed to cause the harmful effects in part through their inappropriate low-affinity binding to steroid receptors and other possible non-receptor mediated paradigms, however there is a need to further elucidate other mechanisms involving the direct and indirect impact of EDCs on reproductive functions. We examined the metabolism of 17β-estradiol (E2) and estrone (E1) by cell-free hepatic cytosol in the presence of alkylphenols (nonylphenol/NP and 4-tert-octylphenol/tOP), Dichlorodiphenyltrichloroethane (4,4'-DDT) and other EDCs. Tandem liquid chromatography mass spectrometry was utilized to quantitatively assess the impact of each EDC on estrogen clearance, inter-conversions and downstream metabolism by mouse liver cytosol. The results revealed that NP and tOP (0.1-3μg/mL) significantly reduced the hepatic cytosol clearance and biotransformation of estrogens with inclination for accumulating E2, the stronger estrogen form, than E1. Alkylphenols also caused up to a 34-fold increase in the E2/E1 ratio possibly by suppressing the hepatic E2→E1 conversion by 17β-hydroxysteroid dehydrogenase (17βHSD) types 2, 4 while displaying a weaker inhibition of E1→E2 conversion by type 1, 17βHSD. On the other hand, the pesticide 4,4'-DDT was a weaker inhibitor of clearance of estrogens by the cytosol preparations when compared to alkylphenols, whereas chemicals such as phthalates and atrazine were ineffective. Our data suggest that exposure to NP, tOP and DDT can indirectly increase the estrogenic load by suppressing the hepatic clearance of estrogens and by elevating the E2/1 ratio and could therefore increase the risk of reproductive lesions.

Temperature Impacts on Soil Microbial Communities and Potential Implications for the Biodegradation of Turfgrass Pesticides

Maintaining healthy turfgrass often results in the use of pesticides to manage weed, insect, and disease pests. To identify and understand potential nontarget impacts of pesticide usage while still maintaining attractive and functional turfgrass sites, it is important to improve our understanding of how pesticides degrade in various environments throughout the growing season. Temperature heavily influences microbial community composition and activity, and the microbial community often heavily influences pesticide degradation in soil ecosystems. Pesticide transformation products generated through the action of soil microbial degradation networks can vary in their toxicity, with the potential result that a pesticide applied in the spring at 10°C could produce different transformation products with different toxicological impacts than the sample pesticide applied to the same site at 22°C. The objective of this review is to examine past research surrounding soil microbial activity related to pesticide degradation and provide a foundation for how the soil microbiome interacts with pesticides and how seasonal temperature variations may influence those interactions.

Endocrine disruption by dietary phyto-oestrogens: impact on dimorphic sexual systems and behaviours

A wide range of health benefits have been ascribed to soya intake including a lowered risk of osteoporosis, heart disease, breast cancer, and menopausal symptoms. Because it is a hormonally active diet, however, soya can also be endocrine disrupting, suggesting that intake has the potential to cause adverse health effects in certain circumstances, particularly when exposure occurs during development. Consequently, the question of whether or not soya phyto-oestrogens are beneficial or harmful to human health is neither straightforward nor universally applicable to all groups. Possible benefits and risks depend on age, health status, and even the presence or absence of specific gut microflora. As global consumption increases, greater awareness and consideration of the endocrine-disrupting properties of soya by nutrition specialists and other health practitioners is needed. Consumption by infants and small children is of particular concern because their hormone-sensitive organs, including the brain and reproductive system, are still undergoing sexual differentiation and maturation. Thus, their susceptibility to the endocrine-disrupting activities of soya phyto-oestrogens may be especially high. As oestrogen receptor partial agonists with molecular and cellular properties similar to anthropogenic endocrine disruptors such as bisphenol A, the soya phyto-oestrogens provide an interesting model for how attitudes about what is 'synthetic' v. what is 'natural,' shapes understanding and perception of what it means for a compound to be endocrine disrupting and/or potentially harmful. This review describes the endocrine-disrupting properties of soya phyto-oestrogens with a focus on neuroendocrine development and behaviour.

Simvastatin down-regulates differential genetic profiles produced by organochlorine mixtures in primary breast cell (HMEC)

Women all over the world are exposed to an unavoidable contamination by organochlorine pesticides and other chemical pollutants. Many of them are considered as xenoestrogens and have been associated with the development and progression of breast cancer. We have demonstrated that the most prevalent pesticide mixtures found in healthy women and in women diagnosed with breast cancer modulates the gene expression in human epithelial mammary cells. Statins are well-known cholesterol-depleting agents acting as inhibitors of cholesterol synthesis. Since the early 1990s, it has been known that statins could be successfully used in cancer therapy, including breast cancer, but the exact mechanism behind anti-tumor activity of the statins remains unclear. In the present study we evaluated the effect of simvastatin in the gene expression pattern induced by realistic organochlorine mixtures found in breast cancer patients. The gene expression of 94 genes related with the cell signaling pathways were assessed. Our results indicate that simvastatin exerts a global down regulating effect on successfully determined genes (78.7%), thus attenuating the effects induced by organochlorine mixtures on the gene profile of human mammary epithelial cells. This effect was more evident on genes whose function is the ATP-binding process (that also were particularly up-regulated by pesticide mixtures). We also found that MERTK (a proto-oncogene which is overexpressed in several malignancies) and PDGFRB (a member of the platelet-derived growth factor family whose expression is high in breast-cancer cells that have become resistant to endocrine therapy) were among the genes with a higher differential regulation by simvastatin. Since resistance to treatment with tyrosine kinase inhibitors is closely related to MERKT, our findings would enhance the possible utility of statins in breast cancer treatment, i.e. improving therapeutic results combining statins with tyrosine Kinase inhibitors.

CtBP1 associates metabolic syndrome and breast carcinogenesis targeting multiple miRNAs

Metabolic syndrome (MeS) has been identified as a risk factor for breast cancer. C-terminal binding protein 1 (CtBP1) is a co-repressor of tumor suppressor genes that is activated by low NAD+/NADH ratio. High fat diet (HFD) increases intracellular NADH. We investigated the effect of CtBP1 hyperactivation by HFD intake on mouse breast carcinogenesis. We generated a MeS-like disease in female mice by chronically feeding animals with HFD. MeS increased postnatal mammary gland development and generated prominent duct patterns with markedly increased CtBP1 and Cyclin D1 expression. CtBP1 induced breast cancer cells proliferation. Serum from animals with MeS enriched the stem-like/progenitor cell population from breast cancer cells. CtBP1 increased breast tumor growth in MeS mice modulating multiple genes and miRNA expression implicated in cell proliferation, progenitor cells phenotype, epithelial to mesenchymal transition, mammary development and cell communication in the xenografts. These results define a novel function for CtBP1 in breast carcinogenesis.

Review on crosstalk and common mechanisms of endocrine disruptors: Scaffolding to improve PBPK/PD model of EDC mixture

Endocrine disruptor compounds (EDCs) are environment chemicals that cause harmful effects through multiple mechanisms, interfering with hormone system resulting in alteration of homeostasis, reproduction and developmental effect. Many of these EDCs have concurrent exposure with crosstalk and common mechanisms which may lead to dynamic interactions. To carry out risk assessment of EDCs' mixture, it is important to know the detailed toxic pathway, crosstalk of receptor and other factors like critical window of exposure. In this review, we summarize the major mechanism of actions of EDCs with the different/same target organs interfering with the same/different class of hormone by altering their synthesis, metabolism, binding and cellular action. To show the impact of EDCs on life stage development, a case study on female fertility affecting germ cell is illustrated. Based on this summarized discussion, major groups of EDCs are classified based on their target organ, mode of action and potential risk. Finally, a conceptual model of pharmacodynamic interaction is proposed to integrate the crosstalk and common mechanisms that modulate estrogen into the predictive mixture dosimetry model with dynamic interaction of mixture. This review will provide new insight for EDCs' risk assessment and can be used to develop next generation PBPK/PD models for EDCs' mixture analysis.

New insights into fetal mammary gland morphogenesis: differential effects of natural and environmental estrogens

An increased breast cancer risk during adulthood has been linked to estrogen exposure during fetal life. However, the impossibility of removing estrogens from the feto-maternal unit has hindered the testing of estrogen’s direct effect on mammary gland organogenesis. To overcome this limitation, we developed an ex vivo culture method of the mammary gland where the direct action of estrogens can be tested during embryonic days (E)14 to 19. Mouse mammary buds dissected at E14 and cultured for 5 days showed that estrogens directly altered fetal mammary gland development. Exposure to 0.1 pM, 10 pM, and 1 nM 17 β-estradiol (E2) resulted in monotonic inhibition of mammary buds ductal growth. In contrast, Bisphenol-A (BPA) elicited a non-monotonic response. At environmentally relevant doses (1 nM), BPA significantly increased ductal growth, as previously observed in vivo, while 1 μM BPA significantly inhibited ductal growth. Ductal branching followed the same pattern. This effect of BPA was blocked by Fulvestrant, a full estrogen antagonist, while the effect of estradiol was not. This method may be used to study the hormonal regulation of mammary gland development, and to test newly synthesized chemicals that are released into the environment without proper assessment of their hormonal action on critical targets like the mammary gland.

Childhood and Adolescent Pesticide Exposure and Breast Cancer Risk

BACKGROUND

To date, epidemiologic studies have not strongly supported an association between pesticide exposure and breast cancer. However, few previous studies had the ability to assess specific time periods of exposure. Studies that relied on adult serum levels of metabolites of organochlorine pesticides may not accurately reflect exposure during developmental periods. Furthermore, exposure assessment often occurred after diagnosis and key tumor characteristics, such as hormone receptor status, have rarely been available to evaluate tumor subtype-specific associations. We examined the association between pesticide exposure during childhood and adolescence and breast cancer risk in the prospective Sister Study cohort (N = 50,884 women) to assess this relation by tumor subtype.

METHODS

During an average 5-year follow-up, 2,134 incident invasive and in situ breast cancer diagnoses were identified. Residential and farm exposure to pesticides were self-reported at study enrollment during standardized interviews. Multivariable hazard ratios and 95% confidence intervals for breast cancer risk were calculated with Cox proportional hazards regression.

RESULTS

HRs were near null for the association between childhood/adolescent pesticide exposure and breast cancer risk overall or among ER+/PR+ invasive tumors. However, among women who were ages 0-18 before the ban of dichlordiphenyltrichloroethane in the US, exposure to fogger trucks or planes was associated with a hazard ratio = 1.3 for premenopausal breast cancer (95% confidence interval: 0.92, 1.7).

CONCLUSION

These findings do not support an overall association between childhood and adolescent pesticide exposure and breast cancer risk. However, modest increases in breast cancer risk were associated with acute events in a subgroup of young women.

Inhibition of peripubertal sheep mammary gland development by cysteamine through reducing progesterone and growth factor production

Cysteamine has been used for treating cystinosis for many years, and furthermore it has also been used as a therapeutic agent for different diseases including Huntington's disease, Parkinson's disease (PD), nonalcoholic fatty liver disease, malaria, cancer, and others. Although cysteamine has many potential applications, its use may also be problematic. The effects of low doses of cysteamine on the reproductive system, especially the mammary glands are currently unknown. In the current investigation, low dose (10 mg/kg BW/day) of cysteamine did not affect sheep body weight gain or organ index of the liver, spleen, or heart; it did, however, increase the levels of blood lymphocytes, monocytes, and platelets. Most interestingly, it inhibited mammary gland development after 2 or 5 months of treatment by reducing the organ index and the number of mammary gland ducts. Plasma growth hormone and estradiol remained unchanged; however, plasma progesterone levels and the protein level of HSD3β1 in sheep ovaries were decreased by cysteamine. In addition to steroid hormones, growth factors produced in the mammary glands also play crucial roles in mammary gland development. Results showed that protein levels of HGF, GHR, and IGF1R were decreased after 5 months of cysteamine treatment. These findings together suggest that progesterone and local growth factors in mammary glands might be involved in cysteamine initiated inhibition of pubertal ovine mammary gland development. Furthermore, it may lead to a reduction in fertility. Therefore, cysteamine should be used with great caution until its actions have been further investigated and its limitations overcome.

Mammary Gland Evaluation in Juvenile Toxicity Studies: Temporal Developmental Patterns in the Male and Female Harlan Sprague-Dawley Rat

There are currently no reports describing mammary gland development in the Harlan Sprague-Dawley (HSD) rat, the current strain of choice for National Toxicology Program (NTP) testing. Our goals were to empower the NTP, contract labs, and other researchers in understanding and interpreting chemical effects in this rat strain. To delineate similarities/differences between the female and male mammary gland, data were compiled starting on embryonic day 15.5 through postnatal day 70. Mammary gland whole mounts, histology sections, and immunohistochemically stained tissues for estrogen, progesterone, and androgen receptors were evaluated in both sexes; qualitative and quantitative differences are highlighted using a comprehensive visual timeline. Research on endocrine disrupting chemicals in animal models has highlighted chemically induced mammary gland anomalies that may potentially impact human health. In order to investigate these effects within the HSD strain, 2,3,7,8-tetrachlorodibenzo-p-dioxin, diethylstilbestrol, or vehicle control was gavage dosed on gestation day 15 and 18 to demonstrate delayed, accelerated, and control mammary gland growth in offspring, respectively. We provide illustrations of normal and chemically altered mammary gland development in HSD male and female rats to help inform researchers unfamiliar with the tissue and may facilitate enhanced evaluation of both male and female mammary glands in juvenile toxicity studies.

Differences in the Rate of in Situ Mammary Gland Development and Other Developmental Endpoints in Three Strains of Female Rat Commonly Used in Mammary Carcinogenesis Studies: Implications for Timing of Carcinogen Exposure

The potential of chemicals to alter susceptibility to mammary tumor formation is often assessed using a carcinogen-induced study design in various rat strains. The rate of mammary gland (MG) development must be considered so that the timing of carcinogen administration is impactful. In this study, in situ MG development was assessed in females of the Harlan Sprague-Dawley (Hsd:SD), Charles River Sprague-Dawley (Crl:SD), and Charles River Long-Evans (Crl:LE) rat strains at postnatal days 25, 33, and 45. Development was evaluated by physical assessment of growth parameters, developmental scoring, and quantitative morphometric analysis. Although body weight (BW) was consistently lower and day of vaginal opening (VO) occurred latest in female Hsd:SD rats, they exhibited accelerated pre- and peripubertal MG development compared to other strains. Glands of Crl:SD and Crl:LE rats exhibited significantly more terminal end buds (TEBs) and TEB/mm than Hsd:SD rats around the time of VO. These data suggest a considerable difference in the rate of MG development across commonly used strains, which is independent of BW and timing of VO. In mammary tumor induction studies employing these strains, administration of the carcinogen should be timed appropriately, based on strain, to specifically target the peak of TEB occurrence.

Urine and serum biomonitoring of exposure to environmental estrogens II: Soy isoflavones and zearalenone in pregnant women

Urine and serum biomonitoring was used to measure internal exposure to selected dietary estrogens in a cohort of 30 pregnant women. Exposure was measured over a period comprising one-half day in the field (6 h) and one day in a clinic (24 h). Biomonitoring of the dietary phytoestrogens genistein (GEN), daidzein (DDZ) and equol (EQ), as well as the mycoestrogen, zearalenone (ZEN) and its congeners, was conducted using UPLC-MS/MS. Biomonitoring revealed evidence of internal exposure to naturally occurring dietary estrogens during pregnancy. Urinary concentrations of total GEN, DDZ and EQ were similar to levels reported for general adult U.S.

POPULATION

Measurable concentrations of total (parent and metabolites) GEN, DDZ and EQ were present in 240, 207 and 2 of 270 serum samples, respectively. Six out of 30 subjects had measurable concentrations of unconjugated GEN and/or DDZ in serum between 0.6 and 7.1 nM. Urine to serum total isoflavone ratios for GEN, DDZ and EQ were 13, 47, and 180, respectively. ZEN and its reductive metabolite, α-zearalenol (α-ZEL), were present in pregnant women (11 out of 30 subjects) as conjugates at levels near the limit of quantification. The average total urinary concentration was 0.10 μg/L for ZEN and 0.11 μg/L for α-ZEL.

Neonatal overfeeding induces early decline of the ovarian reserve: Implications for the role of leptin

Early life nutrition is crucial for reproduction. Overweight and obese girls are more likely to experience early menarche, increasing the risk of adult disease. We have previously demonstrated neonatal overfeeding in the rat leads to accelerated growth, early puberty and increased circulating levels of leptin, an adipocyte-derived hormone that regulates puberty. However, the long-term consequences of accelerated puberty and metabolic dysfunction on ovarian reserve are unknown. Here we show that neonatal overfeeding reduced the number of ovarian follicles in adult rats; specifically, the primordial follicle pool was reduced compared to controls. The reduction of ovarian reserve coincided with a diminished release of pituitary gonadotropins at ovulation and altered expression of ovarian markers important for follicular recruitment and survival. These changes were associated with increased levels of ovarian leptin and its receptor. Postnatal administration of leptin antagonist did not reverse the weight gain induced by early life overfeeding, but rescued the decline in the primordial follicle pool and abolished the differences in circulating leptin and gonadotropins. Our findings suggest that the acute effects of elevated circulating leptin may be responsible for the long-term reproductive outcomes after neonatal overfeeding, leading to premature ovarian ageing and changes in reproductive efficiency.

Bisphenol A (BPA) Exposure In Utero Leads to Immunoregulatory Cytokine Dysregulation in the Mouse Mammary Gland: A Potential Mechanism Programming Breast Cancer Risk

Bisphenol-A (BPA) is a ubiquitous estrogen-like endocrine disrupting compound (EDC). BPA exposure in utero has been linked to breast cancer and abnormal mammary gland development in mice. The recent rise in incidence of human breast cancer and decreased age of first detection suggests a possible environmental etiology. We hypothesized that developmental programming of carcinogenesis may involve an aberrant immune response. Both innate and adaptive immunity play a role in tumor suppression through cytolytic CD8, NK, and Th1 T-cells. We hypothesized that BPA exposure in utero would lead to dysregulation of both innate and adaptive immunity in the mammary gland. CD1 mice were exposed to BPA in utero during gestation (days 9-21) via osmotic minipump. At 6 weeks, the female offspring were ovariectomized and estradiol was given at 8 weeks. RNA and protein were extracted from the posterior mammary glands, and the mRNA and protein levels were measured by PCR array, qRT-PCR, and western blot. In mouse mammary tissue, BPA exposure in utero significantly decreased the expression of members of the chemokine CXC family (Cxcl2, Cxcl4, Cxcl14, and Ccl20), interleukin 1 (Il1) gene family (Il1β and Il1rn), interleukin 2 gene family (Il7 receptor), and interferon gene family (interferon regulatory factor 9 (Irf9), as well as immune response gene 1 (Irg1). Additionally, BPA exposure in utero decreased Esr1 receptor gene expression and increased Esr2 receptor gene expression. In utero exposure of BPA resulted in significant changes to inflammatory modulators within mammary tissue. We suggest that dysregulation of inflammatory cytokines, both pro-inflammatory and anti-inflammatory, leads to a microenvironment that may promote disordered cell growth through inhibition of the immune response that targets cancer cells.

Biological underpinnings of breastfeeding challenges: the role of genetics, diet, and environment on lactation physiology

Lactation is a dynamic process that has evolved to produce a complex biological fluid that provides nutritive and nonnutritive factors to the nursing offspring. It has long been assumed that once lactation is successfully initiated, the primary factor regulating milk production is infant demand. Thus, most interventions have focused on improving breastfeeding education and early lactation support. However, in addition to infant demand, increasing evidence from studies conducted in experimental animal models, production animals, and breastfeeding women suggests that a diverse array of maternal factors may also affect milk production and composition. In this review, we provide an overview of our current understanding of the role of maternal genetics and modifiable factors, such as diet and environmental exposures, on reproductive endocrinology, lactation physiology, and the ability to successfully produce milk. To identify factors that may affect lactation in women, we highlight some information gleaned from studies in experimental animal models and production animals. Finally, we highlight the gaps in current knowledge and provide commentary on future research opportunities aimed at improving lactation outcomes in breastfeeding women to improve the health of mothers and their infants.

Effects of Neonatally Administered Diethylstilbestrol on Induction of Mammary Carcinomas Induced by 7, 12-Dimethylbenz[A]Anthracene in Female Rats

Various doses of diethylstilbestrol (DES) were administered to rats once at birth. Thereafter, at 50 days after birth, the rats in all groups were given 10 mg 7, 12-dimethylbenz[a]anthracene (DMBA) and undergone necropsy at 300 days after birth. The incidence of mammary carcinomas (MCs) were 50, 54, 91, 39, 19% at 175 days after birth, and 77, 87, 100, 85, 75% at necropsy in the 0, 0.1, 1, 10, 100 μg groups, respectively. The incidence of rats without corpus luteum were 0, 0, 0, 30, 100% at 50 days after birth, and 0, 40, 53, 93, 100% at necropsy in the 0, 0.1, 1, 10, 100 μg groups, respectively. Observation of the whole mount specimens showed a higher number of terminal end buds (TEBs) in the 1 μg group and a lower number in the 100 μg group compared with the control at 50 days after birth. It suggested that the administration of a relatively low dose (1 μg) of DES during neonatal period may increase TEBs, thus resulting in a stimulatory effect on the initiation of MCs.

Occupational exposure and risk of breast cancer

Breast cancer is a multifactorial disease and the most commonly diagnosed cancer in women. Traditional risk factors for breast cancer include reproductive status, genetic mutations, family history and lifestyle. However, increasing evidence has identified an association between breast cancer and occupational factors, including environmental stimuli. Epidemiological and experimental studies demonstrated that ionizing and non-ionizing radiation exposure, night-shift work, pesticides, polycyclic aromatic hydrocarbons and metals are defined environmental factors for breast cancer, particularly at young ages. However, the mechanisms by which occupational factors can promote breast cancer initiation and progression remains to be elucidated. Furthermore, the evaluation of occupational factors for breast cancer, particularly in the workplace, also remains to be explained. The present review summarizes the occupational risk factors and the associated mechanisms involved in breast cancer development, in order to highlight new environmental exposures that could be correlated to breast cancer and to provide new insights for breast cancer prevention in the occupational settings. Furthermore, this review suggests that there is a requirement to include, through multidisciplinary approaches, different occupational exposure risks among those associated with breast cancer development. Finally, the design of new epigenetic biomarkers may be useful to identify the workers that are more susceptible to develop breast cancer.

[Night work, shift work: Breast cancer risk factor?]

OBJECTIVE

The aim of this review was to determine the link between night/shift work and breast cancer.

METHODS

The analysed articles were taken from the PUBMED database between 1996 and 2015. The keywords used were "breast cancer risk", "night work" and "shift work". In total, 25 articles were selected.

RESULTS

Night/shift workers are more at risk to develop a breast cancer (relative risk (RR) between 1.09; 95% CI: 1.02-1.20 and 1.48; 95% CI: 1.36-1.61 in the meta-analyses). However, this risk is not found by some cohort and case-control studies. The circadian rhythm disruption, responsible of disorderliness of melatonin secretion, could be one of the mechanisms involved in the increase of that risk. Hormonal status of night/shift workers, their geographic origin, their lifestyle and their vitamin D deficiency appear as other mechanisms potentially responsible for increased risk of cancer in this professional population. Moreover, a dose-effect connection may exist, with an increase of the risk with the number of years of night/shift work.

CONCLUSION

Night/shift work is associated with a moderate increased risk of breast cancer, especially among women who worked over 20 years. Recommendations concerning the breast monitoring in this population could be diffused. The benefit of melatonin supplementation remains to be assessed.