title: Increased expression of MDM2, cyclin D1, and p27Kip1 in carcinogen-induced rat mammary tumors.
abstract: It is thought that environmental pollutants, such as polycyclic aromatic hydrocarbons (PAH), contribute to human breast tumorigenesis, yet their roles remain incompletely elucidated. The prototypical PAH 7,12-dimethylbenz(alpha)anthracene (DMBA) specifically and effectively induces mammary tumor formation in rodent models. In an attempt to explore the molecular mechanisms by which PAH initiates and promotes mammary tumorigenesis, we examined the expression of several cell cycle regulators in rat mammary tumors induced by DMBA. Expression of cyclin D1, murine double minute-2 (MDM2), and Akt was up-regulated in tumors in comparison to normal mammary glands, as indicated by RT-PCR, Western blot analysis, and immunohistochemical staining. Expression of p27Kip1 protein was also elevated in the tumors with increased cytoplasmic localization. However, RB protein remained hyperphosphorylated. To directly test the effects of DMBA, the MCF-7 human breast cancer cells were treated. DMBA induced MDM2 expression in a dose- and time-dependent fashion in the MCF-7 cells, and this activation appeared to be p53 dependent. These data suggest that activation of cyclin D1, MDM2, and AKT as well as increased expression and cytoplasmic localization of p27Kip1 may play a role in this model of environmental pollutant-induced mammary tumorigenesis.
authors.affiliation: Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Murray
authors.forename: Shi
authors.initials: S
authors.lastname: Yang
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Demicco
authors.forename: Haoqiang
authors.initials: H
authors.lastname: Ying
authors.forename: David H
authors.initials: DH
authors.lastname: Sherr
authors.forename: Laurie J
authors.initials: LJ
authors.lastname: Hafer
authors.forename: Adrianne E
authors.initials: AE
authors.lastname: Rogers
authors.forename: Gail E
authors.initials: GE
authors.lastname: Sonenshein
authors.forename: Zhi-Xiong Jim
authors.initials: ZX
authors.lastname: Xiao
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity; D000818:Animals; D015153:Blotting, Western; D002273:Carcinogens / Q000633:toxicity; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D019938:Cyclin D1 / Q000235:genetics* / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007124:Immunoenzyme Techniques; D008321:Mammary Glands, Animal; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D051381:Rats; D017207:Rats, Sprague-Dawley; D016160:Retinoblastoma Protein / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D002273:Carcinogens; C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D015127:9,10-Dimethyl-1,2-benzanthracene; C497206:MDM2 protein, human; C497208:Mdm2 protein, rat; D051736:Proto-Oncogene Proteins c-mdm2