title: Up-regulation of Rac1 by epidermal growth factor mediates COX-2 expression in recurrent respiratory papillomas.
abstract: Recurrent respiratory papillomas are epithelial tumors of the airway caused by human papillomaviruses. We previously reported that the epidermal growth factor receptor (EGFR) is overexpressed in papilloma cells, that cyclooxygenase-2 (COX-2) is induced, and that COX-2 expression in primary papilloma cells requires activation of the EGFR but not Erk. Rac1, a member of the Rho family of GTPases, is a key signaling element that is known to control multiple pathways downstream of the EGFR. Here we report that Rac1 is overexpressed in papilloma cells compared with normal laryngeal epithelial cells and that the increased levels of Rac1 are mediated by EGFR activation. Transfecting cells with Rac1-specific siRNA suppressed COX-2 expression. Surprisingly, Rac1 mediated phosphorylation of p38 mitogen-activated kinase in papilloma cells but not normal cells, and inhibition of p38 with the specific inhibitor SB202190 suppressed COX-2 expression in papilloma cells but had no effect on low-level COX-2 expression in normal cells. Thus, the signaling cascades that regulate COX-2 expression are different in HPV-infected papilloma cells, with a significant contribution by the EGFR-- Rac1-->p38 pathway.
authors.affiliation: The Feinstein Institute for Medical Research, North Shore-LIJ Health System, New Hyde Park, and Department of Otorhinolaryngology-Head and Neck Surgery, Albert Einstein College of Medicine, Bronx, New York, USA.
authors.forename: Rong
authors.initials: R
authors.lastname: Wu
authors.forename: Salvatore J
authors.initials: SJ
authors.lastname: Coniglio
authors.forename: Amanda
authors.initials: A
authors.lastname: Chan
authors.forename: Marc H
authors.initials: MH
authors.lastname: Symons
authors.forename: Bettie M
authors.initials: BM
authors.lastname: Steinberg
mesh_terms: D051546:Cyclooxygenase 2 / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D009364:Neoplasm Recurrence, Local / Q000201:enzymology* / Q000821:virology; D027383:Papillomaviridae / Q000302:isolation & purification; D012142:Respiratory Tract Neoplasms / Q000201:enzymology* / Q000821:virology; D015854:Up-Regulation; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D066246:ErbB Receptors; D020830:rac1 GTP-Binding Protein