title: Transgenic mice demonstrate AP-1 (activator protein-1) transactivation is required for tumor promotion.
abstract: Activator protein-1 (AP-1) is a transcription factor that consists of either a Jun-Jun homodimer or a Jun-Fos heterodimer. Transactivation of AP-1 is required for tumor promoter-induced transformation in mouse epidermal JB6 cells and for progression in mouse and human keratinocytes. Until now, the question of whether AP-1 transactivation is required for carcinogenesis in vivo has remained unanswered, as has the issue of functionally significant target genes. To address these issues we have generated a transgenic mouse in which transactivation mutant c-jun (TAM67), under the control of the human keratin-14 promoter, is expressed specifically in the basal cells of the epidermis where tumor induction is initiated. The keratin-14-TAM67 transgene was expressed in the epidermis, tongue, and cervix, with no apparent abnormalities in any tissue or organ. TAM67 expression blocked 12-O-tetradecanoylphorbol 13-acetate (TPA, phorbol 12-tetradecanoate 13-acetate) induction of the AP-1-regulated luciferase in AP-1 luciferase/TAM67 mice, but did not inhibit induction of candidate AP-1 target genes, collagenase-1 or stromelysin-3. More interestingly, TAM67 expression did not inhibit TPA-induced hyperproliferation. In two-stage skin carcinogenesis experiments, the transgenic animals showed a dramatic inhibition of papilloma induction. We conclude that transactivation of a subset of AP-1-dependent genes is required for tumor promotion and may be targeted for cancer prevention.
authors.affiliation: Basic Research Laboratory, National Cancer Institute, Frederick, MD 21702, USA. youngm@ncifcrf.gov
authors.forename: M R
authors.initials: MR
authors.lastname: Young
authors.forename: J J
authors.initials: JJ
authors.lastname: Li
authors.forename: M
authors.initials: M
authors.lastname: Rincón
authors.forename: R A
authors.initials: RA
authors.lastname: Flavell
authors.forename: B K
authors.initials: BK
authors.lastname: Sathyanarayana
authors.forename: R
authors.initials: R
authors.lastname: Hunziker
authors.forename: N
authors.initials: N
authors.lastname: Colburn
mesh_terms: D000818:Animals; D002471:Cell Transformation, Neoplastic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D011401:Promoter Regions, Genetic; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis / Q000235:genetics; D012878:Skin Neoplasms / Q000235:genetics*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000502:physiology*; D015533:Transcriptional Activation
chemical_list: D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D013755:Tetradecanoylphorbol Acetate