title: In utero exposure to diethylstilbestrol (DES) or bisphenol-A (BPA) increases EZH2 expression in the mammary gland: an epigenetic mechanism linking endocrine disruptors to breast cancer.
abstract: Diethylstilbestrol (DES) and bisphenol-A (BPA) are estrogen-like endocrine-disrupting chemicals that induce persistent epigenetic changes in the developing uterus. However, DES exposure in utero is also associated with an increased risk of breast cancer in adult women. Similarly, fetal exposure to BPA induces neoplastic changes in mammary tissue of mice. We hypothesized that epigenetic alterations would precede the increased risk of breast neoplasia after in utero exposure to endocrine disruptors. Enhancer of Zeste Homolog 2 (EZH2) is a histone methyltransferase that has been linked to breast cancer risk and epigenetic regulation of tumorigenesis. We examined the effect of BPA and DES on EZH2 expression and function in MCF-7 cells and in mammary glands of mice exposed in utero. DES and BPA treatment approximated human exposure. EZH2 functional activity was assessed by measuring histone H3 trimethylation. Treatment of MCF-7 cells with DES or BPA led to a 3- and 2-fold increase in EZH2 mRNA expression, respectively (p < 0.05) as well as increased EZH2 protein expression. Mice exposed to DES in utero showed a >2-fold increase in EZH2 expression in adult mammary tissue compared with controls (p < 0.05). EZH2 protein was elevated in mammary tissue of mice exposed to DES or BPA. Histone H3 trimethylation was increased in MCF-7 cells treated with BPA or DES. Similarly, mice exposed to BPA or DES in utero showed increased mammary histone H3 trimethylation. Developmental programming of EZH2 is a novel mechanism by which in utero exposure to endocrine disruptors leads to epigenetic regulation of the mammary gland.
authors.affiliation: Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, CT 06520, USA.
authors.forename: Leo F
authors.initials: LF
authors.lastname: Doherty
authors.forename: Jason G
authors.initials: JG
authors.lastname: Bromer
authors.forename: Yuping
authors.initials: Y
authors.lastname: Zhou
authors.forename: Tamir S
authors.initials: TS
authors.lastname: Aldad
authors.forename: Hugh S
authors.initials: HS
authors.lastname: Taylor
mesh_terms: D000818:Animals; D001559:Benzhydryl Compounds; D015153:Blotting, Western; D002273:Carcinogens / Q000633:toxicity; D045744:Cell Line, Tumor; D004054:Diethylstilbestrol / Q000633:toxicity*; D052244:Endocrine Disruptors / Q000633:toxicity*; D000071221:Enhancer of Zeste Homolog 2 Protein; D044127:Epigenesis, Genetic / Q000187:drug effects; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D011495:Histone-Lysine N-Methyltransferase / Q000096:biosynthesis*; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000378:metabolism*; D051379:Mice; D010636:Phenols / Q000633:toxicity*; D063151:Polycomb Repressive Complex 2; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000139:chemically induced* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000098826:Bisphenol A Compounds
chemical_list: D001559:Benzhydryl Compounds; D002273:Carcinogens; D004054:Diethylstilbestrol; D052244:Endocrine Disruptors; D000071221:Enhancer of Zeste Homolog 2 Protein; D011495:Histone-Lysine N-Methyltransferase; D010636:Phenols; D063151:Polycomb Repressive Complex 2; C498410:Ezh2 protein, mouse; C006780:bisphenol A; D000098826:Bisphenol A Compounds