title: Prenatal exposure to BPA alters the epigenome of the rat mammary gland and increases the propensity to neoplastic development.
abstract: Exposure to environmental estrogens (xenoestrogens) may play a causal role in the increased breast cancer incidence which has been observed in Europe and the US over the last 50 years. The xenoestrogen bisphenol A (BPA) leaches from plastic food/beverage containers and dental materials. Fetal exposure to BPA induces preneoplastic and neoplastic lesions in the adult rat mammary gland. Previous results suggest that BPA acts through the estrogen receptors which are detected exclusively in the mesenchyme during the exposure period by directly altering gene expression, leading to alterations of the reciprocal interactions between mesenchyme and epithelium. This initiates a long sequence of altered morphogenetic events leading to neoplastic transformation. Additionally, BPA induces epigenetic changes in some tissues. To explore this mechanism in the mammary gland, Wistar-Furth rats were exposed subcutaneously via osmotic pumps to vehicle or 250 µg BPA/kg BW/day, a dose that induced ductal carcinomas in situ. Females exposed from gestational day 9 to postnatal day (PND) 1 were sacrificed at PND4, PND21 and at first estrus after PND50. Genomic DNA (gDNA) was isolated from the mammary tissue and immuno-precipitated using anti-5-methylcytosine antibodies. Detection and quantification of gDNA methylation status using the Nimblegen ChIP array revealed 7412 differentially methylated gDNA segments (out of 58207 segments), with the majority of changes occurring at PND21. Transcriptomal analysis revealed that the majority of gene expression differences between BPA- and vehicle-treated animals were observed later (PND50). BPA exposure resulted in higher levels of pro-activation histone H3K4 trimethylation at the transcriptional initiation site of the alpha-lactalbumin gene at PND4, concomitantly enhancing mRNA expression of this gene. These results show that fetal BPA exposure triggers changes in the postnatal and adult mammary gland epigenome and alters gene expression patterns. These events may contribute to the development of pre-neoplastic and neoplastic lesions that manifest during adulthood.
authors.affiliation: Department of Anatomy and Cellular Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America.
authors.forename: Eugen
authors.initials: E
authors.lastname: Dhimolea
authors.affiliation: Department of Anatomy and Cellular Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America.
authors.forename: Perinaaz R
authors.initials: PR
authors.lastname: Wadia
authors.affiliation: Department of Anatomy and Cellular Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America.
authors.forename: Tessa J
authors.initials: TJ
authors.lastname: Murray
authors.affiliation: Institute for Bioinformatics and Evolutionary Studies, University of Idaho, Moscow, Idaho, United States of America.
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Settles
authors.affiliation: Department of Anatomy and Cellular Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America.
authors.forename: Jo D
authors.initials: JD
authors.lastname: Treitman
authors.affiliation: Department of Anatomy and Cellular Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America.
authors.forename: Carlos
authors.initials: C
authors.lastname: Sonnenschein
authors.affiliation: MGH Center for Cancer Research, Massachusetts General Hospital, Charlestown, Massachusetts, United States of America.
authors.forename: Toshi
authors.initials: T
authors.lastname: Shioda
authors.affiliation: Department of Anatomy and Cellular Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Soto
mesh_terms: D044503:5-Methylcytosine / Q000276:immunology; D000818:Animals; D000906:Antibodies / Q000276:immunology; D001559:Benzhydryl Compounds / Q000097:blood / Q000633:toxicity*; D063646:Carcinogenesis / Q000187:drug effects; D019175:DNA Methylation / Q000187:drug effects; D044127:Epigenesis, Genetic; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006657:Histones / Q000235:genetics; D007768:Lactalbumin / Q000235:genetics; D008321:Mammary Glands, Animal / Q000187:drug effects* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010636:Phenols / Q000097:blood / Q000633:toxicity*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011401:Promoter Regions, Genetic; D051381:Rats; D017208:Rats, Wistar; D053719:Tandem Mass Spectrometry; D024363:Transcription Initiation Site / Q000187:drug effects; D000098826:Bisphenol A Compounds
chemical_list: D044503:5-Methylcytosine; D000906:Antibodies; D001559:Benzhydryl Compounds; D006657:Histones; D007768:Lactalbumin; D010636:Phenols; C006780:bisphenol A; D000098826:Bisphenol A Compounds