title: Dominant-negative c-Jun (TAM67) target genes: HMGA1 is required for tumor promoter-induced transformation.
abstract: Activation of the transcription factor AP-1 (activator protein-1) is required for tumor promotion and maintenance of malignant phenotype. A number of AP-1-regulated genes that play a role in tumor progression have been identified. However, AP-1-regulated genes driving tumor induction are yet to be defined. Previous studies have established that expression of a dominant-negative c-Jun (TAM67) inhibits phorbol 12-tetradecanoyl-13-acetate (TPA)-induced AP-1 transactivation as well as transformation in mouse epidermal JB6/P+ cells and tumor promotion in mouse skin carcinogenesis. In this study, we utilized the tumor promotion-sensitive JB6/P+ cells to identify AP-1-regulated TAM67 target genes and to establish causal significance in transformation for one target gene. A 2700 cDNA microarray was queried with RNA from TPA-treated P+ cells with or without TAM67 expression. Under conditions in which TAM expression inhibited TPA-induced transformation, microarray analysis identified a subset of six genes induced by TPA and suppressed by TAM67. One of the identified genes, the high-mobility group protein A1 (Hmga1) is induced by TPA in P+, but not in transformation-resistant P cells. We show that TPA induction of the architectural transcription factor HMGA1 is inhibited by TAM67, is extracellular-signal-regulated kinase (ERK)-activation dependent, and is mediated by AP-1. HMGA1 antisense construct transfected into P+ cells blocked HMGA1 protein expression and inhibited TPA-induced transformation indicating that HMGA1 is required for transformation. HMGA1 is not however sufficient as HMGA1a or HMGA1b overexpression did not confer transformation sensitivity on P- cells. Although HMGA1 expression is ERK dependent, it is not the only ERK-dependent event required for transformation because it does not suffice to rescue ERK-deficient P- cells. Our study shows (a) TAM 67 when it inhibits AP-1 and transformation, targets a relatively small number of genes; (b) HMGA1, a TAM67 target gene, is causally related to transformation and therefore a potentially important target for cancer prevention.
authors.affiliation: Gene Regulation Section, Laboratory of Cancer Prevention, NCI at Frederick, Frederick, MD 21702-1201, USA. adhar@ncifcrf.gov
authors.forename: Arindam
authors.initials: A
authors.lastname: Dhar
authors.forename: Jing
authors.initials: J
authors.lastname: Hu
authors.forename: Raymond
authors.initials: R
authors.lastname: Reeves
authors.forename: Linda M S
authors.initials: LM
authors.lastname: Resar
authors.forename: Nancy H
authors.initials: NH
authors.lastname: Colburn
mesh_terms: D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002460:Cell Line / Q000187:drug effects / Q000378:metabolism; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000235:genetics*; D002999:Clone Cells / Q000187:drug effects / Q000378:metabolism; D019938:Cyclin D1 / Q000096:biosynthesis / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004198:Disease Susceptibility; D000078404:Epidermal Cells; D004817:Epidermis / Q000187:drug effects / Q000378:metabolism; D020869:Gene Expression Profiling; D016758:Genes, jun / Q000235:genetics*; D025741:HMGA1a Protein / Q000502:physiology*; D025742:HMGA1b Protein / Q000502:physiology*; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors; D020935:MAP Kinase Signaling System; D051379:Mice; D008822:Mice, Transgenic; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D009570:Nitriles / Q000494:pharmacology; D020411:Oligonucleotide Array Sequence Analysis; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D053495:Osteopontin; D016755:Proto-Oncogene Proteins c-jun / Q000172:deficiency / Q000502:physiology*; D012795:Sialoglycoproteins / Q000096:biosynthesis / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000633:toxicity; D018808:Transcription Factor AP-1 / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics*
chemical_list: D002070:Butadienes; D018076:DNA, Complementary; D009570:Nitriles; D016376:Oligonucleotides, Antisense; D016755:Proto-Oncogene Proteins c-jun; D012795:Sialoglycoproteins; C506896:Spp1 protein, mouse; D018808:Transcription Factor AP-1; C113580:U 0126; D053495:Osteopontin; D025742:HMGA1b Protein; D025741:HMGA1a Protein; D019938:Cyclin D1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases; C482578:Map3k1 protein, mouse; D013755:Tetradecanoylphorbol Acetate