The estrogen-responsive Agr2 gene regulates mammary epithelial proliferation and facilitates lobuloalveolar development

Abstract Targeted deletion of the bZIP transcription factor, CCAAT/enhancer binding protein-β (C/EBPβ), was shown previously to result in aberrant ductal morphogenesis and decreased lobuloalveolar development, accompanied by an altered pattern of progesterone receptor (PR) expression. Here, similar changes in the level and pattern of prolactin receptor (PrlR) expression were observed while screening for differentially expressed genes in C/EBPβnull mice. PR patterning was also altered in PrlRnull mice, as well as in mammary tissue transplants from both PrlRnull and signal transducer and activator of transcription (Stat) 5a/b-deficient mice, with concomitant defects in hormone-induced proliferation. Down-regulation of PR and activation of Stat5 phosphorylation were seen after estrogen and progesterone treatment in both C/EBPβnull and wild-type mice, indicating that these signaling pathways were functional, despite the failure of steroid hormones to induce proliferation. IGF binding protein-5, IGF-II, and insulin receptor substrate-1 all displayed altered patterns and levels of expression in C/EBPβnull mice, suggestive of a change in the IGF signaling axis. In addition, small proline-rich protein (SPRR2A), a marker of epidermal differentiation, and keratin 6 were misexpressed in the mammary epithelium of C/EBPβnull mice. Together, these data suggest that C/EBPβ is a master regulator of mammary epithelial cell fate and that the correct spatial pattern of PR and PrlR expression is a critical determinant of hormone-regulated cell proliferation.

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Cell interactions in initiation of mammary epithelial proliferation by oestradiol and progesterone in prepubertal heifers

Journal of Endocrinology ◽

10.1677/joe.0.1360149 ◽

1993 ◽

Vol 136 (1) ◽

pp. 149-157 ◽

Cited By ~ 45

Author(s):

T. L. Woodward ◽

W. E. Beal ◽

R. M. Akers

Keyword(s):

Endothelial Cells ◽

Epithelial Cells ◽

Treatment Response ◽

Stromal Cells ◽

Trichloroacetic Acid ◽

Proliferative Response ◽

Mammary Epithelial ◽

Mammary Tissue ◽

Epithelial Proliferation ◽

Cell Type

ABSTRACT The acute temporal effects of exogenous oestradiol (0·1 mg/kg per day), progesterone (0·25 mg/kg per day) or both together on the proliferative response of epithelial cells, fibroblasts, adipocytes and endothelial cells in the mammary tissue of prepubertal cross-bred heifers were determined. Mammary biopsies were taken immediately before, then 24, 48 and 96 h after the initiation of daily administration of hormones to three heifers per treatment group. Incorporation of [3H]thymidine into explants prepared from biopsies was evaluated after a 1-h incubation by measuring trichloroacetic acid (TCA)-insoluble radioactivity in explant homogenates as well as by quantitative histoautoradiography. Incorporation expressed as d.p.m./mg tissue or d.p.m./μg DNA was increased (P ≤ 0·05) approximately 11-fold by 96 h in oestradiol-treated heifers. Progesterone-treated animals were unresponsive and heifers treated with both hormones were intermediate in response compared with oestradiol-treated heifers. Autoradiographic data for ductal or terminal duct epithelial cells showed similar dramatic increases in labelling by 24 h with further increased (P < 0·01) labelling by 96 h (5·1% vs 0·1%) in heifers given oestradiol. As with incorporation, tissue from progesterone-treated heifers showed no time or treatment response compared with pretreatment biopsies and tissue from heifers given both showed intermediate responses, i.e. significantly increased labelling by 96 h compared with pretreatment (P ≤ 0·05) but less labelling (P < 0·05) than oestradiol-treated heifers. A proliferative response of epithelial cells in oestradiol-treated heifers occurred prior to the response of fibroblasts adjacent to epithelial cells (≤ 50 μm). Interestingly, labelling of endothelial cells was also markedly increased by 48 h in oestradiol-treated heifers. Non-adjacent fibroblasts (≥ 100 μm from ductal epithelial cells) and adipocytes showed no time or treatment response. These data demonstrate that exogenous oestradiol markedly and acutely stimulates proliferation of mammary ducts, while progesterone has no effect and may decrease the effectiveness of oestradiol. In contrast to mice, mammary epithelial response to oestradiol in prepubertal heifers is not first exhibited after a proliferative response of stromal cells. This suggests that the cell-type interactions involved in the control of mammogenesis are dissimilar in ruminants and rodents. Journal of Endocrinology (1993) 136, 149–157

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Effects of serum on mammary epithelial proliferation in vitro during mammary gland development.

The Journal of Cell Biology ◽

10.1083/jcb.66.2.243 ◽

1975 ◽

Vol 66 (2) ◽

pp. 243-250 ◽

Cited By ~ 11

Author(s):

H W Hsueh ◽

F E Stockdale

Keyword(s):

Mammary Gland ◽

Proliferative Response ◽

Mammary Epithelial ◽

Serum Factor ◽

Epithelial Proliferation ◽

Hypophysectomized Rats ◽

Gland Development ◽

Proliferation In Vitro

The proliferative response of mammary gland epithelium from nonpregnant, pregnant, and lactating mice to mammary serum factor and insulin was studied in vitro. Mammary gland epiithelium from nonpregnant and lactating animals has a delayed proliferative response to mammary serum factor and insulin when compared to the response of epithelium from pregnant animals. The results show that as the animals go through pregnancy into lactation the mammary gland epithelium becomes less responsive to mammary serum factor while it retains its responsiveness to insulin. The concentration of mammary serum factor in sera from animals at various physiological stages is constant. Sera from hypophysectomized rats, on the other hand, show a 50% drop in mammary serum factor activity. This loss of activity cannot be reversed by injecting prolactin, 17-beta-estradiol, or growth hormone into the hypophysectomized animals. A hypothesis that the mammary gland is composed of two proliferative epithelial populations is developed, and the possible role of prolactin in stimulating DNA synthesis is discussed.

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494 POSTER MMTV-RANK transgenic mice show increased mammary epithelial proliferation and impaired alveolar differentiation during pregnancy and a higher incidence of chemically induced mammary tumors

European Journal of Cancer Supplements ◽

10.1016/s1359-6349(06)70499-2 ◽

2006 ◽

Vol 4 (12) ◽

pp. 150-151

Author(s):

E. Gonzalez Suarez ◽

D. Branstetter ◽

J. Jones ◽

K. Stocking ◽

W. Saxbe ◽

...

Keyword(s):

Transgenic Mice ◽

Mammary Tumors ◽

Mammary Epithelial ◽

Epithelial Proliferation ◽

Chemically Induced

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Respiration of epithelial component of mammary gland slices

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1960.199.6.1067 ◽

1960 ◽

Vol 199 (6) ◽

pp. 1067-1069 ◽

Cited By ~ 2

Author(s):

E. Douglas Rees

Keyword(s):

Mammary Gland ◽

Epithelial Cell ◽

Mammary Epithelial Cell ◽

Mammary Epithelial ◽

Mammary Tissue ◽

Biological Parameters ◽

Hydroxyproline Content ◽

Epithelial Proliferation ◽

Cell Component ◽

Rat Mammary Gland

The respiration of slices from rat mammary gland was accounted for by the independent contributions of each of the three major components of mammary tissue: adipose, epithelial and connective. The contribution of each component was the amount of the component times its characteristic qo2. In the virgin mammary gland the adipose and connective tissue components accounted for the bulk of the observed respiration; but the qo2 increased directly and linearly with epithelial proliferation induced by various means—pregnancy, lactation, or administration of progesterone or estradiol-17ß. An equation containing only biological parameters and relating qo2 to hydroxyproline content of mammary gland was derived. A qo2 value of 14.2 ± 1.8 for the mammary epithelial cell component was obtained.

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Regulation of Mammary Gland Branching Morphogenesis by EphA2 Receptor Tyrosine Kinase

Molecular Biology of the Cell ◽

10.1091/mbc.e08-04-0378 ◽

2009 ◽

Vol 20 (10) ◽

pp. 2572-2581 ◽

Cited By ~ 41

Author(s):

David Vaught ◽

Jin Chen ◽

Dana M. Brantley-Sieders

Keyword(s):

Mammary Gland ◽

Mammary Gland Development ◽

Mammary Epithelium ◽

Branching Morphogenesis ◽

Mammary Epithelial ◽

Mammary Tissue ◽

Wild Type ◽

Epithelial Proliferation ◽

Positive Role ◽

Gland Development

Eph receptor tyrosine kinases, including EphA2, are expressed in the mammary gland. However, their role in mammary gland development remains poorly understood. Using EphA2-deficient animals, we demonstrate for the first time that EphA2 receptor function is required for mammary epithelial growth and branching morphogenesis. Loss of EphA2 decreased penetration of mammary epithelium into fat pad, reduced epithelial proliferation, and inhibited epithelial branching. These defects appear to be intrinsic to loss of EphA2 in epithelium, as transplantation of EphA2-deficient mammary tissue into wild-type recipient stroma recapitulated these defects. In addition, HGF-induced mammary epithelial branching morphogenesis was significantly reduced in EphA2-deficient cells relative to wild-type cells, which correlated with elevated basal RhoA activity. Moreover, inhibition of ROCK kinase activity in EphA2-deficient mammary epithelium rescued branching defects in primary three-dimensional cultures. These results suggest that EphA2 receptor acts as a positive regulator in mammary gland development, functioning downstream of HGF to regulate branching through inhibition of RhoA. Together, these data demonstrate a positive role for EphA2 during normal mammary epithelial proliferation and branching morphogenesis.

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Transcriptional Response of the Murine Mammary Gland to Acute Progesterone Exposure

Endocrinology ◽

10.1210/en.2008-0768 ◽

2008 ◽

Vol 149 (12) ◽

pp. 6236-6250 ◽

Cited By ~ 54

Author(s):

Rodrigo Fernandez-Valdivia ◽

Atish Mukherjee ◽

Chad J. Creighton ◽

Adam C. Buser ◽

Francesco J. DeMayo ◽

...

Keyword(s):

Mammary Gland ◽

Chromatin Immunoprecipitation ◽

Transcriptional Response ◽

Transcriptional Regulators ◽

Mammary Epithelial ◽

Epithelial Proliferation ◽

Chromatin Immunoprecipitation Assay ◽

Mammary Morphogenesis ◽

Effector Pathways ◽

Informational Resource

Our mechanistic understanding of progesterone’s involvement in murine mammary morphogenesis and tumorigenesis is dependent on defining effector pathways responsible for transducing the progesterone signal into a morphogenetic response. Toward this goal, microarray methods were applied to the murine mammary gland to identify novel downstream gene targets of progesterone. Consistent with a tissue undergoing epithelial expansion, mining of the progesterone-responsive transcriptome revealed the up-regulation of functional gene classes involved in epithelial proliferation and survival. Reassuringly, signaling pathways previously reported to be responsive to progesterone were also identified. Mining this informational resource for rapidly induced genes, we identified “inhibitor of differentiation 4” (Id4) as a new molecular target acutely induced by progesterone exposure. Mammary Id4 is transiently induced during early pregnancy and colocalizes with progesterone receptor (PR) expression, suggesting that Id4 mediates the early events of PR-dependent mammary morphogenesis. Chromatin immunoprecipitation assay detecting direct recruitment of ligand occupied PR to the Id4 promoter supports this proposal. Given that Id4 is a member of the Id family of transcriptional regulators that have been linked to the maintenance of proliferative status and tumorigenesis, the establishment of a mechanistic link between PR signaling and Id4 promises to furnish a wider conceptual framework with which to advance our understanding of normal and abnormal mammary epithelial responses to progestins. In sum, the progesterone-responsive transcriptome described herein not only reinforces the importance of progesterone in mammary epithelial expansion but also represents an invaluable information resource with which to identify novel signaling paradigms for mammary PR action.

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