title: Tpl2 is a key mediator of arsenite-induced signal transduction.
abstract: Arsenite is a well-known human carcinogen that especially targets skin. The tumor progression locus 2 (Tpl2) gene encodes a serine/threonine protein kinase that is overexpressed in various cancer cells. However, the relevance of Tpl2 in arsenite-induced carcinogenesis and the underlying mechanisms remain to be explored. We show that arsenite increased Tpl2 kinase activity and its phosphorylation in mouse epidermal JB6 P+ cells in a dose- and time-dependent manner. Exposure to arsenite resulted in a marked induction of cyclooxygenase-2 (COX-2) and prostaglandin E(2) (PGE(2)), important mediators of inflammation and tumor promotion. Treatment with a Tpl2 kinase inhibitor or Tpl2 short hairpin RNA suppressed COX-2 expression and PGE(2) production induced by arsenite treatment, suggesting that Tpl2 is critical in arsenite-induced carcinogenesis. We also found that arsenite-induced phosphorylation of extracellular signal-regulated kinases (ERK) or c-Jun NH(2)-terminal kinases (JNK) was markedly suppressed by Tpl2 kinase inhibitor or Tpl2 short hairpin RNA. Inhibition of arsenite-induced ERK or JNK signaling using a pharmacologic inhibitor of ERK or JNK substantially blocked COX-2 expression. Furthermore, inhibition of Tpl2 reduced the arsenite-induced promoter activity of NF-kappaB and activator protein-1 (AP-1), indicating that NF-kappaB and AP-1 are downstream transducers of arsenite-triggered Tpl2. Our results show that Tpl2 plays a key role in arsenite-induced COX-2 expression and PGE(2) production and further elucidate the role of Tpl2 in arsenite signals that activate ERK/JNK and NF-kappaB/AP-1 in JB6 P+ cells.
authors.affiliation: The Hormel Institute, University of Minnesota, Austin, Minnesota 55912, USA.
authors.forename: Kyung Mi
authors.initials: KM
authors.lastname: Lee
authors.forename: Ki Won
authors.initials: KW
authors.lastname: Lee
authors.forename: Ann M
authors.initials: AM
authors.lastname: Bode
authors.forename: Hyong Joo
authors.initials: HJ
authors.lastname: Lee
authors.forename: Zigang
authors.initials: Z
authors.lastname: Dong
mesh_terms: D000818:Animals; D018053:Arsenites / Q000494:pharmacology*; D015153:Blotting, Western; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000378:metabolism; D000078404:Epidermal Cells; D004817:Epidermis / Q000187:drug effects* / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D047468:Immunoprecipitation; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D013723:Teratogens / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000378:metabolism
chemical_list: D018053:Arsenites; D016328:NF-kappa B; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D013723:Teratogens; D018808:Transcription Factor AP-1; D008156:Luciferases; D051546:Cyclooxygenase 2; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; C489843:Map3k8 protein, mouse; C015001:arsenite