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Effect of pubertal BPA exposure on mammary stem cells

ABSTRACT: Perinatal exposure to bisphenol A (BPA) has been shown to cause aberrant mammary gland morphogenesis and mammary neoplastic transformation. Yet, the underlying mechanism is poorly understood. We tested the hypothesis that mammary glands exposed to BPA during a susceptible window may lead to its susceptibility to tumorigenesis through a stem-cell mediated mechanism. We exposed 21-day-old Balb/c mice to BPA by gavage (25 µg/kg/day) during puberty for 3 weeks, and a subset of animals were further challenged with one oral dose (30 mg/kg) of 7,12-dimethylbenz[a]anthracene (DMBA) at 2 months of age. Primary mammary cells were isolated at 6 weeks, and 2 and 4 months of age for mammary stem cell (MaSC) quantification and function analysis. Pubertal exposure to the low-dose BPA increased lateral branches and hyperplasia in adult mammary glands and caused an acute increase of MaSC in 6-week-old glands and a delayed increase of luminal progenitors in 4-month-old adult gland. Most importantly, pubertal BPA exposure altered the function of MaSC from different age groups, causing pre-neoplastic lesions in their regenerated glands similar to those induced by DMBA exposure, which indicates that MaSCs are susceptible to BPA-induced transformation. Deep sequencing analysis on MaSC-enriched mammospheres identified a set of aberrantly expressed genes associated with pre-neoplastic lesions in human breast cancer patients. Thus, our study for the first time shows that pubertal BPA exposure altered MaSC gene expression and function such that they induced early neoplastic transformation.

ORGANISM(S): Mus musculus

PROVIDER: GSE46815 | GEO | 2016/04/26

SECONDARY ACCESSION(S): PRJNA202390

REPOSITORIES: GEO

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Project description:The present experiments were performed to determine the roles of estrogen receptors M-NM-1 and M-NM-2 (ERM-NM-1 and ERM-NM-2) in normal and neoplastic development in the mouse mammary gland. In wild-type mice, in vivo administration of estradiol (E) + progesterone (P) stimulated mammary ductal growth and alveolar differentiation. Mammary glands from mice in which the ERM-NM-2 gene has been deleted (M-NM-2ERKO mice) demonstrated normal ductal growth and differentiation in response to E + P. By contrast, mammary glands from mice in which the ERM-NM-1 gene has been deleted (M-NM-1ERKO mice) demonstrated only rudimentary ductal structures that did not differentiate in response to E + P. EGF demonstrates estrogen-like activity in the mammary glands of M-NM-1ERKO mice: treatment of M-NM-1ERKO mice with EGF + P (without E) supported normal mammary gland development, induced expression of progesterone receptor (PR), and increased levels of G- protein-coupled receptor (GPR30) protein. Mammary gland development in M-NM-2ERKO mice treated with EGF + P was comparable to that of wild-type mice receiving EGF + P; EGF had no statistically significant effects on the induction of PR or expression of GPR30 in mammary glands harvested from either wild-type mice or M-NM-2ERKO mice. In vitro exposure of mammary glands to 7,12-dimethylbenz[a]anthracene (DMBA) induced preneoplastic mammary alveolar lesions (MAL) in glands from wild-type mice and M-NM-2ERKO mice, but failed to induce MAL in mammary glands from M-NM-1ERKO mice. Microarray analysis of DMBA-treated mammary glands identified 28 functional pathways whose expression was significantly different in M-NM-1ERKO mice versus both M-NM-2ERKO and wild-type mice; key functions that were differentially expressed in M-NM-1ERKO mice included cell division, cell proliferation, and apoptosis. The data demonstrate distinct roles for ERM-NM-1 and ERM-NM-2 in normal and neoplastic development in the mouse mammary gland, and suggest that EGF can mimic the ERM-NM-1-mediated effects of E in this organ. Gene expression of mammary gland organ culture and DMBA-induced lesions from 4 mouse strains.

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Effect of pubertal BPA exposure on mammary stem cells

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