title: Association of cellular and molecular responses in the rat mammary gland to 17β-estradiol with susceptibility to mammary cancer.
abstract: BACKGROUND
  We are using ACI and BN rats, which differ markedly in their susceptibility to 17β-estradiol (E2)-induced mammary cancer, to identify genetic variants and environmental factors that determine mammary cancer susceptibility. The objective of this study was to characterize the cellular and molecular responses to E2 in the mammary glands of ACI and BN rats to identify qualitative and quantitative phenotypes that associate with and/or may confer differences in susceptibility to mammary cancer.
  
  
  METHODS
  Female ACI and BN rats were treated with E2 for 1, 3 or 12 weeks. Mammary gland morphology and histology were examined by whole mount and hematoxylin and eosin (H&E) staining. Cell proliferation and epithelial density were evaluated by quantitative immunohistochemistry. Apoptosis was evaluated by quantitative western blotting and flow cytometry. Mammary gland differentiation was examined by immunohistochemistry. Gene expression was evaluated by microarray, qRT-PCR and quantitative western blotting assays. Extracellular matrix (ECM) associated collagen was evaluated by Picrosirius Red staining and Second Harmonic Generation (SHG) microscopy.
  
  
  RESULTS
  The luminal epithelium of ACI rats exhibited a rapid and sustained proliferative response to E2. By contrast, the proliferative response exhibited by the mammary epithelium of BN rats was restrained and transitory. Moreover, the epithelium of BN rats appeared to undergo differentiation in response to E2, as evidenced by production of milk proteins as well as luminal ectasia and associated changes in the ECM. Marked differences in expression of genes that encode proteins with well-defined roles in mammary gland development (Pgr, Wnt4, Tnfsf11, Prlr, Stat5a, Areg, Gata3), differentiation and milk production (Lcn2, Spp1), regulation of extracellular environment (Mmp7, Mmp9), and cell-cell or cell-ECM interactions (Cd44, Cd24, Cd52) were observed.
  
  
  CONCLUSIONS
  We propose that these cellular and molecular phenotypes are heritable and may underlie, at least in part, the differences in mammary cancer susceptibility exhibited by ACI and BN rats.
authors.forename: Lina
authors.initials: L
authors.lastname: Ding
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhao
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Warren
authors.forename: Ruth
authors.initials: R
authors.lastname: Sullivan
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Eliceiri
authors.affiliation: McArdle Laboratory for Cancer Research, Department of Oncology, School of Medicine and Public Health, University of Wisconsin Madison, 1400 University Avenue, Madison, WI 53706, USA. shull@oncology.wisc.edu.
authors.forename: James D
authors.initials: JD
authors.lastname: Shull
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004198:Disease Susceptibility; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D004958:Estradiol / Q000008:administration & dosage*; D005109:Extracellular Matrix / Q000187:drug effects; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D008321:Mammary Glands, Animal / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D015674:Mammary Neoplasms, Animal / Q000209:etiology / Q000235:genetics* / Q000378:metabolism*; D010641:Phenotype; D051381:Rats; D013045:Species Specificity
chemical_list: D004958:Estradiol