title: Functional mammary gland development and oncogene-induced tumor formation are not affected by the absence of the retinoblastoma gene.
abstract: Loss of cell cycle regulation in mammary epithelium results in impaired mammary gland development and neoplasia. We investigated the consequences of the absence of pRb in mammary epithelial cells during normal development and in mice that express an oncogene in the mammary epithelium. Since pRb-deficiency results in embryonic lethality, we transplanted pRb-null mammary anlagen into wild hosts. pRb-deficient mammary epithelia were capable of functional differentiation in term animals and they regenerated a differentiated gland even after multiple pregnancies. In serial transplantations no significant differences were found in outgrowth of pRb-deficient and wild type epithelia indicating that the absence of pRb does not lead to transformation. Likewise the effect of a TGFbeta1 transgene was not altered in the absence of pRb. The susceptibility of mammary epithelium to form tumors was assessed in three different models. No differences in tumor incidence were found between wild type and Rb +/- WAP-int3, MMTV-PyMT transgenic and Brcal-/- epithelia. These results demonstrate that the absence of pRb does not affect normal mammary gland development and tumorigenesis in three different mouse models investigated and suggest that loss of more than one member of the pRb pathway is required to induce mammary tumors.
authors.affiliation: Laboratory of Genetics and Physiology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, MD 20892, USA. gertraur@bdg10.niddk.nih.gov
authors.forename: G W
authors.initials: GW
authors.lastname: Robinson
authors.forename: K U
authors.initials: KU
authors.lastname: Wagner
authors.forename: L
authors.initials: L
authors.lastname: Hennighausen
mesh_terms: D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics; D002453:Cell Cycle / Q000235:genetics; D002454:Cell Differentiation; D003433:Crosses, Genetic; D005260:Female; D019398:Genes, BRCA1; D016161:Genes, Retinoblastoma; D008321:Mammary Glands, Animal / Q000196:embryology / Q000254:growth & development* / Q000637:transplantation; D008325:Mammary Neoplasms, Experimental / Q000235:genetics* / Q000473:pathology; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008894:Milk Proteins / Q000235:genetics; D009857:Oncogenes; D011247:Pregnancy; D011518:Proto-Oncogene Proteins / Q000235:genetics; D000074562:Receptor, Notch4; D011956:Receptors, Cell Surface; D051880:Receptors, Notch; D016160:Retinoblastoma Protein / Q000172:deficiency* / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000235:genetics; D053773:Transforming Growth Factor beta1; D019076:Transgenes
chemical_list: D000952:Antigens, Polyomavirus Transforming; D008894:Milk Proteins; D011518:Proto-Oncogene Proteins; D000074562:Receptor, Notch4; D011956:Receptors, Cell Surface; D051880:Receptors, Notch; D016160:Retinoblastoma Protein; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; C024471:whey acidic proteins; C073572:Notch4 protein, mouse