Stimulation of MCF-7 cell proliferation by low concentrations of Chinese domestic polychlorinated biphenyls

Serum levels of environmental pollutants is a risk factor for breast cancer in Inuit: a case control study

BACKGROUND

Environmental Persistent Organic Pollutants (POPs) can alter the hormone homeostasis by mimicking, interfering or blocking the function of hormones; moreover POPs are hypothesized to modify the risk of breast cancer. The association between POPs and breast cancer has been widely studied but the conclusions are inconsistent. The present study examined the associations between serum levels of POPs and breast cancer with focus on the highly exposed Greenlandic Inuit population.

METHODS

The study design was a case-control study of Inuit women from Greenland. The participants were asked to complete a questionnaire with information on reproductive history and lifestyle and to provide a blood sample. The sampling was carried out in two time periods (2000-2003 and 2011-2014). The serum levels were determined of 14 polychlorinated biphenyls (PCBs), 11 organochlorine pesticides (OCPs), 16 perfluoroalkyl acids (PFAAs), 1 polybrominated biphenyl (PBB), and 9 polybrominated diphenyl ethers (PBDEs). Independent samples t-test was used to compare differences between cases and controls and odds ratios (OR) adjusted for identified confounders were obtained using logistic regression.

RESULTS

The study population included 77 breast cancer cases and 84 controls. The majority of the measured compounds declined significantly from 2000 - 2003 to 2011-2014. However, for the perfluorinated carboxylic acids (PFCAs) an increase was observed. The serum levels were significantly higher in cases compared to controls for the majority of the compounds, and after adjusting for age the difference was maintained for ∑OCP, dichlorodiphenyldichloroethylene (p,p'-DDE), ∑PFAA, ∑perfluorinated sulfonic acids (PFSA), perfluorohexane sulfonate (PFHxS), and perfluorooctane sulfonate (PFOS). For the lipophilic POPs, high serum levels (middel/highest vs. lowest tertile) of ∑PCB, ∑estrgoenicPCB, PCB99, PCB138, PCB153, PCB170, PCB170, and PCB183 was associated with breast cancer risk; for the amphiphilic PFAAs, high serum levels of ∑PFAA, ∑PFCA, ∑PFSA, perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), PFHxS, and PFOS were associated with breast cancer risk.

CONCLUSION

Significant, positive associations between breast cancer risk and PCBs and PFAAs were observed. The associations indicate that environmental exposure to POPs can be a factor increasing the risk for breast cancer in Inuit women.

Effect of maternal exposure to endocrine disrupting chemicals on reproduction and mammary gland development in female Sprague-Dawley rats

The aim of the study is to determine whether low doses of "endocrine disrupting chemicals" (EDCs) affect the development and proliferative activity of the mammary glands (MGs). Adult parous/nulliparous female Sprague-Dawley (SD) rats were treated from post-natal day (PND) 1 until PND 180 with diethylphthalate (DEP), methylparaben (MPB), triclosan (TCS) and a mixture at doses comparable to human exposure. The doses (mg/kg b.w./day) were: DEP=0.173; MPB=0.105; TCS=0.05. EDC treatment resulted in mortality rates >20% in pups as early as lactation day 7. Significant morphological/histological changes were observed at the end of lactation in the MGs of EDC-treated dams. The total transcriptome profile as well as lactation-related genes in MGs also corroborate the morphological findings as more profound gene expression changes are present only at the weaning period. The study highlights the heightened sensitivity of the MGs during critical windows of exposure, particularly pregnancy and lactation, with an impact on pups' survival.

Endocrine disruption of the epigenome: a breast cancer link

The heritable component of breast cancer accounts for only a small proportion of total incidences. Environmental and lifestyle factors are therefore considered to among the major influencing components increasing breast cancer risk. Endocrine-disrupting chemicals (EDCs) are ubiquitous in the environment. The estrogenic property of EDCs has thus shown many associations between ongoing exposures and the development of endocrine-related diseases, including breast cancer. The environment consists of a heterogenous population of EDCs and despite many identified modes of action, including that of altering the epigenome, drawing definitive correlations regarding breast cancer has been a point of much discussion. In this review, we describe in detail well-characterized EDCs and their actions in the environment, their ability to disrupt mammary gland formation in animal and human experimental models and their associations with exposure and breast cancer risk. We also highlight the susceptibility of early-life exposure to each EDC to mediate epigenetic alterations, and where possible describe how these epigenome changes influence breast cancer risk.

Catalase ameliorates polychlorinated biphenyl-induced cytotoxicity in nonmalignant human breast epithelial cells

Polychlorinated biphenyls (PCBs) are environmental chemical contaminants believed to adversely affect cellular processes. We investigated the hypothesis that PCB-induced changes in the levels of cellular reactive oxygen species (ROS) induce DNA damage resulting in cytotoxicity. Exponentially growing cultures of human nonmalignant breast epithelial cells (MCF10A) were incubated with PCBs for 3 days and assayed for cell number, ROS levels, DNA damage, and cytotoxicity. Exposure to 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153) or 2-(4-chlorophenyl)benzo-1,4-quinone (4-Cl-BQ), a metabolite of 4-chlorobiphenyl (PCB3), significantly decreased cell number and MTS reduction and increased the percentage of cells with sub-G1 DNA content. Results from electron paramagnetic resonance (EPR) spectroscopy showed a 4-fold increase in the steady-state levels of ROS, which was suppressed in cells pretreated with catalase. EPR measurements in cells treated with 4-Cl-BQ detected the presence of a semiquinone radical, suggesting that the increased levels of ROS could be due to the redox cycling of 4-Cl-BQ. A dose-dependent increase in micronuclei frequency was observed in PCB-treated cells, consistent with an increase in histone 2AX phosphorylation. Treatment of cells with catalase blunted the PCB-induced increase in micronuclei frequency and H2AX phosphorylation that was consistent with an increase in cell survival. Our results demonstrate a PCB-induced increase in cellular levels of ROS causing DNA damage, resulting in cell killing.

Physiologically based pharmacokinetic modeling of persistent organic pollutants for lifetime exposure assessment: a new tool in breast cancer epidemiologic studies

BACKGROUND

Despite experimental evidence, most epidemiologic studies to date have not supported an association between exposure to persistent organic pollutants (POP) and breast cancer incidence in humans. This may be attributable to difficulties in estimating blood/tissue POP concentration at critical time periods of carcinogenesis.

OBJECTIVES

In this work we aimed to develop a tool to estimate lifetime POP blood/tissue exposure and levels during any hypothesized time window of susceptibility in breast cancer development.

METHODS

We developed a physiologically based pharmacokinetic (PBPK) model that can account for any given physiologic lifetime history. Using data on pregnancies, height, weight, and age, the model estimates the values of physiologic parameters (e.g., organ volume, composition, and blood flow) throughout a woman's entire life. We assessed the lifetime toxicokinetic profile (LTP) for various exposure scenarios and physiologic factors (i.e., breast-feeding, growth, pregnancy, lactation, and weight changes).

RESULTS

Simulations for three POPs [hexachlorobenzene, polychlorinated biphenyl (PCB)-153, PCB-180] using different lifetime physiologic profiles showed that the same blood concentration at 55 years of age can be reached despite totally different LTP. Aside from exposure levels, lactation periods and weight profile history were shown to be the factors that had the greatest impact on the LTP.

CONCLUSIONS

This new lifetime PBPK model, which showed the limitations of using a single sample value obtained around the time of diagnosis for lifetime exposure assessment, will enable researchers conducting environmental epidemiology studies to reduce uncertainty linked to past POP exposure estimation and to consider exposure during time windows that are hypothesized to be mechanistically critical in carcinogenesis.

Effect of mono-ortho and di-ortho substituted polychlorinated biphenyl (PCB) congeners on leopard frog survival and sexual development

We tested the effect of mono-ortho and di-ortho PCB congeners on northern leopard frog (Rana pipiens) hatching success, survival and sexual development. Embryos and tadpoles were exposed to two levels (0.5 and 50 microg/l) of two PCBs. PCBs 101 and 70 were selected because they were present in amphibians collected in the Fox River-Green Bay ecosystem and they have the theoretical structural requirements to be able to bind to the estrogen receptor and mediate estrogenic responses. The exposure of leopard frog embryos and tadpoles to PCB 70 and 101 did not significantly affect hatchability, survival, deformities or growth. There were significant departures from the expected 50:50 sex ratio in tadpoles/froglets exposed to PCB 101 and PCB 70. In all the cases of significant departure, the bias was towards higher number of females. Decrease in the proportion of male gonads and increase in the proportion of intersex gonads were observed with increasing PCB tissue concentrations. The effects of PCB congeners on sexual differentiation occur at concentrations higher than observed in frogs in the Fox River/Green Bay ecosystem.

Induction of cytochromes P-450 1A1 and 1B1 by motorcycle exhaust particulate in human breast cancer MCF-7 cells

The effects of motorcycle exhaust particulate (MEP) on cytochrome P-450-dependent monooxygenases were determined using MCF-7 human breast cancer cells treated with organic extracts of MEP. Treatment with MEP extract produced concentration- and time-dependent increases of monooxygenase activity in S9 fractions. Treatment with 50 microg/ml MEP extract for 24 h increased benzo[a]pyrene hydroxylase and 7-ethoxycoumarin, 7-ethoxyresorufin, and methoxyresorufin O-dealkylases activities in S9. Treatments with 1 and 10 microg/ml MEP extract for 24 h markedly enhanced catabolism of 17beta-estradiol in MCF-7 cells. Cotreatment of the cells with 2 microM alpha-naphthoflavone, a cytochrome P-450 inhibitor and arylhydrocarbon receptor antagonist, blocked the increase of benzo[a]pyrene hydroxylase activity induced by treatment with MEP extract alone. Immunoblot analyses of S9 proteins using a mouse monoclonal antibody 1-12-3 against rat cytochrome P-450 1A1 and a rabbit polyclonal antibody against human cytochrome P-450 1B1 revealed that MEP extract induced proteins immunorelated to cytochromes P-450 1A1 and 1B1. RNA blot analysis of total RNA using human cytochrome P-450 (CYP)1A1 3'-end and human CYP1B1 RT-PCR product cDNA probes showed that MEP extract increased the levels of cytochromes P-450 1A1 and 1B1 mRNA hybridizable to the respective cDNA probes. Treatment with 10 micro M benzo[a]pyrene, a component of MEP extract, for 24 h induced catalytic activity, protein, and mRNA of cytochromes P-450 1A1 and 1B1 in MCF-7 cells. Treatment with MEP extract increased cytochromes P-450 1A1 and 1B1 proteins and mRNA levels in NCI-H322 human lung carcinoma and CL5 human lung adenocarcinoma cells. The extract also increased cytochrome P-450 1A1, but not cytochrome P-450 1B1, protein, and mRNA, in HepG2 human hepatoma cells. The present findings demonstrate that MEP extract has the ability to induce cytochromes P-450 1A1 and 1B1 in the estrogen-responsive MCF-7 cells. Induction of the carcinogen- and estrogen-metabolizing cytochromes P-450 1A1 and 1B1 may be an important factor to consider in assessing the potential health effects associated with human exposure to MEP.