title: Delayed involution of the mammary epithelium in BALB/c-p53null mice.
abstract: In mammals, weaning of neonates and subsequent milk stasis initiates removal of the secretory epithelium of the mammary gland by apoptosis. The p53 tumor suppressor gene is induced rapidly following weaning of neonates, but its role in the process of involution has not been defined. Therefore, experiments were performed to identify the cell types in which the p53 gene is expressed during involution and determine the consequences of its absence in BALB/c-p53null mice. Both p53 mRNA and protein were detected in the mammary epithelium within 48 h following weaning and resulted in an eightfold increase in levels of p21WAF1 mRNA. Induction of p21WAF1 mRNA was absent in BALB/c-p53null mice, and therefore, was shown to be p53-dependent. The BALB/c-p53null mice exhibited delayed involution of the mammary epithelium, as measured by 60% greater epithelial area compared to BALB/c-p53(wt) mice through 5 days post-weaning. The delay was transient with no differences being apparent at 7 days post-weaning. Expression of the stromal protease stromelysin-1 was unaffected by the absence of p53 suggesting that stromal responses were intact. These data demonstrate that p53 participates in the first stage of involution initiated by the epithelium itself, but does not affect the second phase during which stromal proteases are induced.
authors.affiliation: Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst 01003, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Jerry
authors.forename: C
authors.initials: C
authors.lastname: Kuperwasser
authors.forename: S R
authors.initials: SR
authors.lastname: Downing
authors.forename: J
authors.initials: J
authors.lastname: Pinkas
authors.forename: C
authors.initials: C
authors.lastname: He
authors.forename: E
authors.initials: E
authors.lastname: Dickinson
authors.forename: S
authors.initials: S
authors.lastname: Marconi
authors.forename: S P
authors.initials: SP
authors.lastname: Naber
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism / Q000502:physiology; D005260:Female; D017403:In Situ Hybridization; D008321:Mammary Glands, Animal / Q000166:cytology* / Q000378:metabolism; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D014886:Weaning
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D019278:Matrix Metalloproteinase 3