title: Targeting the activator protein 1 transcription factor for the prevention of estrogen receptor-negative mammary tumors.
abstract: The oncogene erbB2 is overexpressed in 20% to 30% human breast cancers and is most commonly overexpressed in estrogen receptor (ER)-negative breast cancers. Transgenic mice expressing erbB2 develop ER-negative mammary tumors, mimicking human breast carcinogenesis. Previously, we have shown that activator protein 1 (AP-1) regulates proliferation of ER-negative breast cancer cells. We hypothesized that blockade of AP-1 in mouse mammary epithelial cells will suppress ER-negative tumorigenesis induced by erbB2. Trigenic erbB2 mice were generated by crossing a bigenic pUHD-Tam67/MMTV-rtTA mouse to a MMTV-erbB2 mouse. The resulting trigenic mice develop tumors and express a doxycycline-inducible c-Jun dominant negative mutant (Tam67) in the mammary glands. In vivo AP-1 blockade by Tam67 expression started delayed mammary tumor formation in MMTV-erbB2 mice by more than 11 weeks. By 52 weeks of age, 100% (18 of 18) of the untreated animals had developed mammary tumors, whereas 56% (9 of 16) of the doxycycline-treated trigenic mice developed tumors. In addition, the tumors that arose in the AP-1-blocked erbB2 mice failed to express Tam67. Twenty-five percent of the doxycycline-treated MMTV-erbB2 mice survived more than 72 weeks of age without developing mammary tumors. Examination of normal-appearing mammary glands from these mice showed that AP-1 blockade by Tam67 also significantly prevents the development of premalignant lesions in these glands. The expression of erbB2 either in normal mammary tissue or in mammary tumors was not altered. Our results show that blocking the AP-1 signaling in mammary cells suppresses erbB2-induced transformation, and show that the AP-1 transcription factor is a critical transducer of erbB2. These results provide a scientific rationale to develop targeted drugs that inhibit AP-1 to prevent the development of ER-negative breast cancer.
authors.affiliation: Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Shen
authors.forename: Ivan P
authors.initials: IP
authors.lastname: Uray
authors.forename: Yuxin
authors.initials: Y
authors.lastname: Li
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jamal
authors.initials: J
authors.lastname: Hill
authors.forename: Xiao-Chun
authors.initials: XC
authors.lastname: Xu
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Young
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Gunther
authors.forename: Susan G
authors.initials: SG
authors.lastname: Hilsenbeck
authors.forename: Nancy H
authors.initials: NH
authors.lastname: Colburn
authors.forename: Lewis A
authors.initials: LA
authors.lastname: Chodosh
authors.forename: Powel H
authors.initials: PH
authors.lastname: Brown
mesh_terms: D000465:Algorithms; D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000453:epidemiology / Q000235:genetics / Q000378:metabolism / Q000517:prevention & control*; D004318:Doxycycline / Q000627:therapeutic use*; D016503:Drug Delivery Systems / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects; D018734:Genes, erbB-2; D015994:Incidence; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D010446:Peptide Fragments / Q000235:genetics; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics; D011960:Receptors, Estrogen / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors* / Q000235:genetics; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D010446:Peptide Fragments; D016755:Proto-Oncogene Proteins c-jun; D011960:Receptors, Estrogen; C439528:TAM67 peptide; D018808:Transcription Factor AP-1; D004318:Doxycycline