Combinatory effects of PBDEs and 17β-estradiol on MCF-7 cell proliferation and apoptosis

Update of the risk assessment of polybrominated diphenyl ethers (PBDEs) in food

The European Commission asked EFSA to update its 2011 risk assessment on polybrominated diphenyl ethers (PBDEs) in food, focusing on 10 congeners: BDE-28, -47, -49, -99, -100, -138, -153, -154, -183 and ‑209. The CONTAM Panel concluded that the neurodevelopmental effects on behaviour and reproductive/developmental effects are the critical effects in rodent studies. For four congeners (BDE-47, -99, -153, -209) the Panel derived Reference Points, i.e. benchmark doses and corresponding lower 95% confidence limits (BMDLs), for endpoint-specific benchmark responses. Since repeated exposure to PBDEs results in accumulation of these chemicals in the body, the Panel estimated the body burden at the BMDL in rodents, and the chronic intake that would lead to the same body burden in humans. For the remaining six congeners no studies were available to identify Reference Points. The Panel concluded that there is scientific basis for inclusion of all 10 congeners in a common assessment group and performed a combined risk assessment. The Panel concluded that the combined margin of exposure (MOET) approach was the most appropriate risk metric and applied a tiered approach to the risk characterisation. Over 84,000 analytical results for the 10 congeners in food were used to estimate the exposure across dietary surveys and age groups of the European population. The most important contributors to the chronic dietary Lower Bound exposure to PBDEs were meat and meat products and fish and seafood. Taking into account the uncertainties affecting the assessment, the Panel concluded that it is likely that current dietary exposure to PBDEs in the European population raises a health concern.

Polybrominated Diphenyl Ethers (PBDEs) and Human Health: Effects on Metabolism, Diabetes and Cancer

There is increasing evidence of the role of endocrine disruptors (EDs) derived from commonly employed compounds for manufacturing and processing in altering hormonal signaling and function. Due to their prolonged half-life and persistence, EDs can usually be found not only in industrial products but also in households and in the environment, creating the premises for long-lasting exposure. Polybrominated diphenyl ethers (PBDEs) are common EDs used in industrial products such as flame retardants, and recent studies are increasingly showing that they may interfere with both metabolic and oncogenic pathways. In this article, a multidisciplinary panel of experts of the Italian Association of Medical Diabetologists (AMD), the Italian Society of Diabetology (SID), the Italian Association of Medical Oncology (AIOM), the Italian Society of Endocrinology (SIE) and the Italian Society of Pharmacology (SIF) provides a review on the potential role of PBDEs in human health and disease, exploring both molecular and clinical aspects and focusing on metabolic and oncogenic pathways.

Adipose tissue levels of polybrominated diphenyl ethers in relation to prognostic biomarkers and progression-free survival time of breast cancer patients in eastern area of southern China: A hospital-based study

Evidence indicates that individual or groups of polybrominated diphenyl ethers (PBDEs) are associated with risk of breast cancer (BC). Epidemiological studies of PBDEs and BC progression are scarce. This study aimed to investigate the relationships between PBDE burdens in adipose tissues and prognostic biomarkers of BC as well as progression-free survival (PFS) of patients for the first time. The concentrations of 14 PBDE congeners in breast adipose tissues of 183 cases from the eastern area of southern China were analyzed by gas chromatography-mass spectrometry (GC-MS). Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by logistic regression models for the associations between PBDE levels and prognostic biomarkers. Kaplan-Meier and Cox regression analyses were conducted to identify the correlations between PBDEs and PFS. The results showed that BDE-99 and 190 levels were positively associated with clinical stage and N stage respectively (OR = 2.61 [1.26-5.40], OR = 2.78 [1.04-7.46]). Concentrations of BDE-28 and BDE-183 were negatively associated with the expression of estrogen receptor (ER) (OR = 0.30 [0.11-0.81]; 0.39 [0.15-0.99]) and progesterone receptor (PR) (OR = 0.36 [0.14-0.92]; 0.37 [0.15-0.91]), and increased BDE-47 was associated with lower human epidermal growth factor receptor 2 (HER2) expression (OR = 0.44 [0.23-0.86]). Adipose levels of BDE-71, 99, 138, 153, 154 and total PBDEs were positively associated with p53 expression (all P < 0.05). Finally, BDE-47, 99 and 183 were considered as independent prognostic factors for shorter PFS in the Cox models (adjusted hazard ratios = 3.14 [1.26-7.82]; 2.25 [1.03-4.94]; 2.60 [1.08-6.25], respectively). The recurrence risk and prognosis of BC may be closely bound to the body burdens of certain PBDE congeners. Further epidemiological and experimental studies are needed for confirmation.

The role of polybrominated diphenyl ethers in the induction of cancer: a systematic review of insight into their mechanisms

Environmental pollution caused by persistent organic pollutants (POPs) has increased the challenge for the scientific communities. Polybrominated diphenyl ethers (PBDEs), classified as POPs, are widely applied in various materials as brominated flame retardants (BFRs). Because of the nature of these chemical compounds including toxicity, stability, and capability to bioaccumulate and biomagnify, PBDEs have posed a great challenge and risk to human health and wildlife. Therefore, the side effects of exposure to PBDEs as ubiquitous pollutants in the environment on cancer progression were investigated using a systematic review (SR) survey. To achieve this goal, forty studies were considered after defining the search terms and inclusion criteria, and/or exclusion criteria; the eligible records were collected from the international bibliographic databases. Based on the findings of the reviewed records, environmental exposure to the BFRs including PBDEs has a positive association with different mechanisms that induce cancer progression. However, the findings of the reviewed studies were not totally consistent with the mode of action and side effects are yet to be fully elucidated. Several articles have reported that BFRs can be carcinogenic and induce epithelial to mesenchymal transition via different mechanisms. The main mode of action involved in the environmental exposure to BFRs and the risk of cancer progression is endoplasmic reticulum and oxidative stress (OS). Generally, the imbalance of antioxidant mechanisms, reactive nitrogen species (RNSs) and reactive oxygen species (ROSs), during damage in cells, and stress caused OS, which increases tumorigenesis via multiple mechanisms, such as DNA damage, inflammation, and angiogenesis.

Analysis of Estrogenic Activity in Maryland Coastal Bays Using the MCF-7 Cell Proliferation Assay

Contaminants of Emerging Concern (CECs) with estrogenic or estrogenic-like activity have been increasingly detected in aquatic environments and have been an issue of global concern due to their potential negative effects on wildlife and human health. This study used the MCF-7 cell proliferation assay (E-Screen) to assess the estrogenic activity profiles in Maryland Coastal Bays (MCBs), a eutrophic system of estuaries impacted by human activities. Estrogenic activity was observed in all study sites tested. Water samples from MCBs increased MCF-7 cell proliferation above the negative control from 2.1-fold at site 8, located in Sinepuxent Bay close to the Ocean City Inlet, to 6.3-fold at site 6, located in Newport Bay. The proliferative effects of the sediment samples over the negative control ranged from 1.9-fold at the Assateague Island National Seashore site to 7.7-fold at the Public Landing site. Moreover, elevated cell proliferation (p < 0.05) was observed when cells were co-exposed with 17ß-Estradiol (E2), while reduction in cell proliferation was observed when cells were co-exposed with the antagonist ICI 182, 780 suggesting that cell proliferative effects were primarily mediated by the estrogen receptor (ER). These results suggest the occurrence of some estrogenic or hormonal-like compounds in the MCBs and are consistent with our previous findings based on vitellogenin analyses.

Metabolomics and lipidomics study unveils the impact of polybrominated diphenyl ether-47 on breast cancer mice

Polybrominated diphenyl ether-47 (BDE-47) is a congener of polybrominated diphenyl ethers (PBDEs) and relates to different health risks. However, in vivo study of the association between BDE-47 and breast cancer was scarce. In this study, we performed in vivo exposure of BDE-47 to breast cancer nude mice and conducted mass spectrometry-based metabolomics and lipidomics analysis to investigate the metabolic changes in mice. Results showed that the tumor sizes were positively associated with the dosage of BDE-47. Metabolomics and lipidomics profiling analysis indicated that BDE-47 induced significant alterations of metabolic pathways in livers, including glutathione metabolism, ascorbate and aldarate metabolism, and lipids metabolism, etc. The upregulations of phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs) suggested the membrane remodeling, and the downregulations of Lyso-PCs and Lyso-PEs might be associated with the tumor growth. Targeted metabolomics analysis revealed that BDE-47 inhibited fatty acid β-oxidation (FAO) and induced incomplete FAO. The inhibition of FAO and downregulation of PPARγ would contribute to inflammation, which could promote tumor growth. In addition, BDE-47 elevated the expression of the cytokines TNFRSF12A, TNF-α, IL-1β and IL-6, and lowered the cytokines SOCS3 and the nuclear receptor PPARα. The changes of cytokines and receptor may contribute to the tumor growth of mice.

Gestational and Lactational Exposure to an Environmentally-relevant Mixture of Brominated Flame Retardants Down-regulates Junctional Proteins, Thyroid Hormone Receptor α1 Expression and the Proliferation-Apoptosis Balance in Mammary Glands Post Puberty

Mammary gland development requires hormonal regulation during puberty, pregnancy and lactation. Brominated flame retardants (BFRs) are endocrine disruptors; they are added to consumer products to satisfy flammability standards. Previously, we showed that gestational and lactational exposure to an environmentally-relevant mixture of BFRs disrupts proteins of the adherens junctions in rat dam mammary glands at weaning. Here, we hypothesize that perinatal exposure to the same BFR mixture also disrupts junctional proteins and signaling pathways controlling mammary gland development in pups. Dams were exposed through diet to a BFR mixture based on the substances in house dust; doses of the mixture used were 0, 0.06, 20 or 60 mg/kg/day. Dams were exposed continuously beginning prior to mating until pups' weaning; female offspring were euthanized on postnatal day (PND) 21, 46 and 208. The lowest dose of BFRs significantly down-regulated adherens junction proteins, E-cadherin and β-catenin, and the gap junction protein p-Cx43, as well as thyroid hormone receptor alpha1 protein at PND 46. No effects were observed on estrogen or progesterone receptors. The low dose also resulted in a decrease in cleaved-caspase 3, a downward trend in PARP levels, proteins involved in apoptosis, and an upward trend in PCNA, a marker of proliferation. No effects were observed on ductal elongation or on the numbers of terminal end buds. Together, our results indicate that gestational and lactational exposure to an environmentally-relevant mixture of BFRs disrupts cell-cell interactions, thyroid hormone homeostasis and the proliferation-apoptosis balance at PND 46, a critical stage for mammary gland development.

A breast cancer case-control study of polybrominated diphenyl ether (PBDE) serum levels among California women

PURPOSE

Polybrominated diphenyl ethers (PBDEs) are among the most persistent and pervasive global environmental contaminants. Their toxic and endocrine-disrupting properties have made them a focus of concern for breast cancer. Our objective was to evaluate the risk of breast cancer associated with serum PBDE levels in a case-control study nested within the California Teachers Study.

METHODS

Participants were 902 women with invasive breast cancer (cases) and 936 with no such diagnosis (controls) who provided 10 mL of blood and were interviewed between 2011 and 2015. Blood samples were collected from cases an average of 35 months after diagnosis. PBDEs were measured in serum using automated solid phase extraction and gas chromatography/high resolution mass spectrometry. Statistical analyses were restricted to the three congeners with detection frequencies ≥75%: 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), 2,2',4,4',6-pentabromodiphenyl ether (BDE-100), and 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE-153). Unconditional logistic regression was used to estimate multivariable-adjusted odds ratios (ORs) and their 95% confidence intervals (CI) for each BDE congener, adjusting for serum lipids and other potential confounders.

RESULTS

The OR for each of the three BDE congeners was close to unity with a CI that included one. Analyses stratified by menopausal status, tumor hormone responsiveness, BMI, and changes in body weight yielded similarly null results.

CONCLUSIONS

Our findings provide no evidence that serum levels of BDE-47, BDE-100 or BDE-153 are associated with breast cancer risk. These results should be interpreted in the context of study limitations which include the reliance on PBDE measurements that may not represent pre-diagnostic, early-life or chronic exposures and a lack of information on genetic polymorphisms and other factors which may affect endogenous estrogen levels.

Adipose tissue levels of polybrominated diphenyl ethers and breast cancer risk in Chinese women: A case-control study

Polybrominated diphenyl ethers (PBDEs) are suspected to be associated with breast cancer risk because of their estrogenic potencies. Epidemiological studies of PBDEs and breast cancer are scarce. Our study aimed to estimate the association between adipose-tissue PBDE concentrations and breast cancer risk. A total of 209 breast cancer cases and 165 controls were recruited from hospitals between January 2014 and May 2016 in Shantou, Chaoshan area, China. Concentrations of 14 PBDE congeners were measured in adipose tissues obtained from the breast for cases and the abdomen/breast for controls during surgery. Demographic and clinicopathologic characteristics were obtained from medical records. Breast cancer risk as well as clinicopathologic characteristics were evaluated by adipose-tissue PBDE level. Odds ratios (ORs) and 95% confidence intervals (95% CIs) for breast cancer risk associated with levels of PBDE congeners were estimated from logistic regression models for all cases and stratified by estrogen receptor (ER) status. Level of total PBDEs (∑PBDE) and most individual PBDE congeners were higher in breast cancer cases than controls (median ∑PBDE, 94.99 vs 73.72 ng/g lipid). In the adjusted univariate model for all cases, breast cancer risk was increased with both 2nd and 3rd tertiles versus the 1st tertile of BDE-47 level (OR 2.05 [95% CI 1.08-3.92]; 5.47 [2.96-10.11]) and BDE-209 level (2.48 [1.30-4.73]; 4.72 [2.52-8.83]) with trend (both P < 0.001) and with the 3rd tertile of BDE-28 level (2.83 [1.63-4.92]), BDE-99 (3.22 [1.85-5.60]), BDE-100 (5.45 [2.90-10.23]), BDE-138 (2.40 [1.37-4.20]), BDE-153 (1.74 [1.02-2.97]), BDE-154 (1.84 [1.05-3.22]), and ∑PBDE levels (1.83 [1.07-3.14]) but decreased with the 3rd tertile of BDE-71 level (0.38 [0.22-0.65]) with trend (all P < 0.01). After stratifying by ER-positive or -negative status, the adjusted results were similar for ER-positive patients except for BDE-153 and BDE-154, with no statistical significance. In the multivariate model for all cases, age, menarche age, BDE-47, 71, 99, 100, 183 and 209 were independent factors associated with breast-cancer risk. ∑PBDE and most individual PBDE congeners investigated were positively associated with breast cancer risk in women from the Chaoshan area, China. PBDE may play a role in the occurrence and development of breast cancer.

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.

State of the evidence 2017: an update on the connection between breast cancer and the environment

BACKGROUND

In this review, we examine the continually expanding and increasingly compelling data linking radiation and various chemicals in our environment to the current high incidence of breast cancer. Singly and in combination, these toxicants may have contributed significantly to the increasing rates of breast cancer observed over the past several decades. Exposures early in development from gestation through adolescence and early adulthood are particularly of concern as they re-shape the program of genetic, epigenetic and physiological processes in the developing mammary system, leading to an increased risk for developing breast cancer. In the 8 years since we last published a comprehensive review of the relevant literature, hundreds of new papers have appeared supporting this link, and in this update, the evidence on this topic is more extensive and of better quality than that previously available.

CONCLUSION

Increasing evidence from epidemiological studies, as well as a better understanding of mechanisms linking toxicants with development of breast cancer, all reinforce the conclusion that exposures to these substances - many of which are found in common, everyday products and byproducts - may lead to increased risk of developing breast cancer. Moving forward, attention to methodological limitations, especially in relevant epidemiological and animal models, will need to be addressed to allow clearer and more direct connections to be evaluated.

Impact of low concentrations of phthalates on the effects of 17β-estradiol in MCF-7 breast cancer cells

OBJECTIVE

To explore whether lower concentrations of phthalates interfere with the effects of 17β-estradiol on the growth of MCF-7 breast cancer cells.

MATERIALS AND METHODS

MCF-7 cells were treated with 17β-estradiol (E₂), phthalates, including butyl benzyl phthalate (BBP), di(n-butyl) phthalate (DBP), and di(20ethylhexyl) phthalate (DEHP), or with both E₂ and phthalates, all at 10nM. After incubation for 48 hours, the cells were harvested and extracted for MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. The proteins involving proliferative and apoptotic pathway were then evaluated using Western blot analysis.

RESULTS

In MCF-7 cell cultures, the MTT assay revealed a significant increase in cell viability with E₂ and these three phthalates, and significantly more cell proliferation with the combination of E₂ and phthalates. Proliferating cell nuclear antigen, as well as phosphatidylinositide 3-kinase (PI3K) and p-Akt, were all substantially increased in cultures with E₂, phthalates, and the two combined. An additive effect of phthalates on the obvious increase of Bcl-2 and ER α expression was also noted in the presence of E₂.

CONCLUSION

The present study demonstrates that even at a very low concentration, BBP, DBP, and DEHP were not only still capable of displaying estrogenic activity, but also of inducing an additive proliferative effect through the PI3K/Akt signaling pathway and preventing apoptosis in the presence of E₂. Therefore, the effects of current reference doses for phthalates defined by the government, especially for premenopausal women, should be further considered.

Differences in the mechanisms of action of BDE-47 and its metabolites on OVCAR-3 and MCF-7 cell apoptosis

Data concerning possible carcinogenic action of polybrominated diphenyl ethers (PBDEs) in hormone-dependent tissues are limited. Our earlier studies showed that 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) stimulated OVCAR-3 and MCF-7 cell proliferation, while its hydroxylated metabolites (5-OH-BDE-47 and 6-OH-BDE-47) increased estrogen receptors protein expression and extracellular signal-regulated kinase 1/2 and protein kinase Cα phosphorylation in these cell lines. In addition to cell proliferative disorder, a failure in the regulation of apoptosis can also lead to the formation and development of tumors. Therefore, in the present study, we investigated the effect of BDE-47 and its metabolites (2.5-50 ng ml^-1 ) on the expression of apoptosis regulatory genes and proteins, caspase-8 and -9 activity and DNA fragmentation induced by extracellular signal-regulated kinase inhibitor (PD098059) and protein kinase Cα inhibitor (Gӧ 6976) in ovarian (OVCAR-3) and breast (MCF-7) cancer cells. In OVCAR-3 cells, BDE-47 upregulated expression of most of the investigated genes and increased protein expression of tumor necrosis factor (TNF)-α, TNF receptor 1, caspase-6, Bcl-xl and caspase-8 activity. Whereas in MCF-7 cells, BDE-47 resulted in the downregulation of most of the investigated genes, and decreased caspase-8 and -9 activity. In both OVCAR-3 and MCF-7 cells, the expression of most of the investigated genes were downregulated by metabolites. Exposure of OVCAR-3 cells to 5-OH-BDE-47 corresponded with a decrease in the protein expression of caspase-6, caspase-9 and Bcl-xl and treatment with 6-OH-BDE-47 decreased Bcl-xl and TNF receptor 1 expression in OVCAR-3 cells and caspase-9 expression in MCF-7 cells. Hydroxylated metabolites of BDE-47 have strong inhibitory effects on apoptosis in ovarian and breast tumor cells and thus should be considered potential carcinogens in hormone-dependent cancers. Copyright © 2016 John Wiley & Sons, Ltd.

Environmental immune disruptors, inflammation and cancer risk

An emerging area in environmental toxicology is the role that chemicals and chemical mixtures have on the cells of the human immune system. This is an important area of research that has been most widely pursued in relation to autoimmune diseases and allergy/asthma as opposed to cancer causation. This is despite the well-recognized role that innate and adaptive immunity play as essential factors in tumorigenesis. Here, we review the role that the innate immune cells of inflammatory responses play in tumorigenesis. Focus is placed on the molecules and pathways that have been mechanistically linked with tumor-associated inflammation. Within the context of chemically induced disturbances in immune function as co-factors in carcinogenesis, the evidence linking environmental toxicant exposures with perturbation in the balance between pro- and anti-inflammatory responses is reviewed. Reported effects of bisphenol A, atrazine, phthalates and other common toxicants on molecular and cellular targets involved in tumor-associated inflammation (e.g. cyclooxygenase/prostaglandin E2, nuclear factor kappa B, nitric oxide synthesis, cytokines and chemokines) are presented as example chemically mediated target molecule perturbations relevant to cancer. Commentary on areas of additional research including the need for innovation and integration of systems biology approaches to the study of environmental exposures and cancer causation are presented.

Endocrine-Disrupting Chemicals: Some Actions of POPs on Female Reproduction

Persistent organic pollutants (POPs), such as polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and polybrominated ethers (PBDEs), chloronaftalens (PCNs), and bisphenol A (BPA), are stable, lipophilic pollutants that affect fertility and cause serious reproductive problems, including ovotoxic action, lack of ovulation, premature ovarian failure (POF), or polycystic ovarian syndrome (PCOS). Most of the representatives of POPs influence the activation of transcription factors, not only activation of aromatic hydrocarbon receptor (AhR), but also the steroid hormone receptors. This minireview will focus on a variety of PAH activities in oocyte, ovary, placenta, and mammary gland. The complexity and diversity of factors belonging to POPs and disorders of the reproductive function of women indicate that the impact of environmental pollution as an important determinant factor in fertility should not be minimize.