title: Protease-activated receptor 2 in colon cancer: trypsin-induced MAPK phosphorylation and cell proliferation are mediated by epidermal growth factor receptor transactivation.
abstract: Several lines of evidence suggest that tumor-derived trypsin contributes to the growth and invasion of cancer cells. We have recently shown that trypsin is a potent growth factor for colon cancer cells through activation of the G protein-coupled receptor protease-activated receptor 2 (PAR2). Here, we analyzed the signaling pathways downstream of PAR2 activation that lead to colon cancer cell proliferation in HT-29 cells. Our data are consistent with the following cascade of events upon activation of PAR2 by the serine protease trypsin or the specific PAR2-activating peptide (AP2): (i) a matrix metalloproteinase-dependent release of transforming growth factor (TGF)-alpha, as demonstrated with TGF-alpha-blocking antibodies and measurement of TGF-alpha in culture medium; (ii) TGF-alpha-mediated activation of epidermal growth factor receptor (EGF-R) and subsequent EGF-R phosphorylation; and (iii) activation of ERK1/2 and subsequent cell proliferation. The links between these events are demonstrated by the fact that stimulation of cell proliferation and ERK1/2 upon activation of PAR2 is reversed by the metalloproteinase inhibitor batimastat, TGF-alpha-neutralizing antibodies, EGF-R ligand binding domain-blocking antibodies, and the EGF-R tyrosine kinase inhibitors AG1478 and PD168393. Therefore, transactivation of EGF-R appears to be a major mechanism whereby activation of PAR2 results in colon cancer cell growth. By using the Src tyrosine kinase inhibitor PP2, we further showed that Src plays a permissive role for PAR2-mediated ERK1/2 activation and cell proliferation, probably acting downstream of the EGF-R. These data explain how trypsin exerts robust trophic action on colon cancer cells and underline the critical role of EGF-R transactivation.
authors.affiliation: Neuroendocrinologie et Biologie Cellulaire Digestives, INSERM U410, Faculté de Médecine Xavier Bichat, 75018 Paris, France. darmoul@bichat.inserm.fr
authors.forename: Dalila
authors.initials: D
authors.lastname: Darmoul
authors.forename: Valérie
authors.initials: V
authors.lastname: Gratio
authors.forename: Hélène
authors.initials: H
authors.lastname: Devaud
authors.forename: Marc
authors.initials: M
authors.lastname: Laburthe
mesh_terms: D002455:Cell Division; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000473:pathology; D066246:ErbB Receptors / Q000235:genetics / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors; D011799:Quinazolines; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D044464:Receptor, PAR-2 / Q000378:metabolism*; D015533:Transcriptional Activation; D014357:Trypsin / Q000378:metabolism; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: D011799:Quinazolines; D044464:Receptor, PAR-2; D020032:Tyrphostins; C101044:RTKI cpd; D066246:ErbB Receptors; D020794:Receptor Protein-Tyrosine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D017027:Protein Tyrosine Phosphatases; D014357:Trypsin