title: Expression profiling of rat mammary epithelial cells reveals candidate signaling pathways in dietary protection from mammary tumors.
abstract: The role of diet in the prevention of breast cancer is widely accepted, yet little is known about how its biological effects mitigate susceptibility to this disease. Soy consumption is associated with reduced breast cancer risk in women, an effect largely attributed to the soy isoflavone genistein (Gen). We previously showed reduced incidence of chemically induced mammary tumors in young adult rats with lifetime dietary intake of soy protein isolate (SPI) than in those fed the control diet containing casein (Cas). To gain insight into signaling pathways underlying dietary tumor protection, we performed genome-wide expression profiling of mammary epithelial cells from young adult rats lifetime fed Cas, SPI, or Cas supplemented with Gen. We identified mammary epithelial genes regulated by SPI (79 total) and Gen (96 total) using Affymetrix rat 230A GeneChip arrays and found minimal overlap in gene expression patterns. We showed that the regulated transcripts functionally clustered in biochemical pathways involving metabolism, immune response, signal transduction, and ion transport. We confirmed the differential expression of Wnt (Wnt5a, Sfrp2) and Notch (Notch2, Hes1) signaling components by SPI and/or Gen using quantitative real-time PCR. Wnt pathway inhibition by Gen was supported by reduced cyclin D1 immunoreactivity in mammary ductal epithelium of Gen relative to Cas and SPI groups, despite comparable levels of membrane-localized E-cadherin and beta-catenin. Identification of distinct Gen and SPI responsive genes in mammary epithelial cells may define early events contributing to tumor protection by diet relevant to the prevention of breast and other types of cancer.
authors.affiliation: Department of Physiology & Biophysics, University of Arkansas for Medical Sciences, and Arkansas Children's Nutrition Center, Little Rock, Arkansas 72202, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Su
authors.forename: Frank A
authors.initials: FA
authors.lastname: Simmen
authors.forename: Rijin
authors.initials: R
authors.lastname: Xiao
authors.forename: Rosalia C M
authors.initials: RC
authors.lastname: Simmen
mesh_terms: D000818:Animals; D002364:Caseins / Q000008:administration & dosage / Q000494:pharmacology; D002478:Cells, Cultured; D016000:Cluster Analysis; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods*; D005786:Gene Expression Regulation / Q000187:drug effects; D019833:Genistein / Q000008:administration & dosage / Q000494:pharmacology; D007150:Immunohistochemistry; D008297:Male; D008321:Mammary Glands, Animal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008770:Methylnitrosourea / Q000008:administration & dosage / Q000494:pharmacology; D020411:Oligonucleotide Array Sequence Analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D051883:Receptor, Notch2 / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D030262:Soybean Proteins / Q000008:administration & dosage / Q000494:pharmacology; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D000071818:Wnt-5a Protein
chemical_list: D002364:Caseins; C497766:Notch2 protein, rat; D051883:Receptor, Notch2; D030262:Soybean Proteins; D051153:Wnt Proteins; D000071818:Wnt-5a Protein; C491837:Wnt5a protein, rat; D008770:Methylnitrosourea; D019833:Genistein