title: Gefitinib targets EGFR dimerization and ERK1/2 phosphorylation to inhibit pleural mesothelioma cell proliferation.
abstract: Altered EGFR activity is a causal factor for human tumor development, including malignant pleural mesotheliomas. The aim of the present study was the evaluation of the effects of Gefitinib on EGF-induced mesothelioma cell proliferation and the intracellular mechanisms involved. Cell proliferation, DNA synthesis and apoptosis were measured by MTT, thymidine incorporation and FACS analysis; EGFR, ERK1/2 and Akt expression and phosphorylation by Western blot, whereas receptor sites were analyzed by binding studies. Gefitinib inhibited EGF-induced proliferation in two mesothelioma cell lines, derived from pleural effusion (IST-Mes2) or tumor biopsy (ZL55). The treatment with Gefitinib induced cell cycle arrest in both cell lines, while apoptosis was observed only for high concentrations and prolonged drug exposure. EGF-dependent mesothelioma cell proliferation was mediated by EGFR and ERK1/2 phosphorylation, while Akt was not affected. Gefitinib inhibited both EGFR and ERK1/2 activation, being maximal at drug concentrations that induce cytostatic effects, suggesting that the proapoptotic activity of Gefitinib is independent from EGFR inhibition. Gefitinib treatment increased EGFR Bmax, possibly through membrane stabilization of inactive receptor dimers that we show to be induced by the drug also in the absence of EGF. EGFR activation of ERK1/2 represents a key pathway for pleural mesothelioma cell proliferation. Low concentrations of Gefitinib cause mesothelioma cell cycle arrest through the blockade of EGFR activity while high concentrations induce apoptosis. Finally, we propose that the formation of inactive EGFR dimers may contribute to the antitumoral activity of Gefitinib.
authors.affiliation: Department of Oncologia Traslazionale, Lab. Trasferimento Genico, Istituto Nazionale per la Ricerca sul Cancro (IST-Nord, B3, Rm18), Largo Rosanna Benzi, 10-16132 Genova, Italy. roberto.favoni@istge.it
authors.forename: Roberto E
authors.initials: RE
authors.lastname: Favoni
authors.forename: Alessandra
authors.initials: A
authors.lastname: Pattarozzi
authors.forename: Michele
authors.initials: M
authors.lastname: Lo Casto
authors.forename: Federica
authors.initials: F
authors.lastname: Barbieri
authors.forename: Monica
authors.initials: M
authors.lastname: Gatti
authors.forename: Laura
authors.initials: L
authors.lastname: Paleari
authors.forename: Adriana
authors.initials: A
authors.lastname: Bajetto
authors.forename: Carola
authors.initials: C
authors.lastname: Porcile
authors.forename: Giovanni
authors.initials: G
authors.lastname: Gaudino
authors.forename: Luciano
authors.initials: L
authors.lastname: Mutti
authors.forename: Giorgio
authors.initials: G
authors.lastname: Corte
authors.forename: Tullio
authors.initials: T
authors.lastname: Florio
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D003432:Cross-Linking Reagents / Q000494:pharmacology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D000077156:Gefitinib; D006801:Humans; D008654:Mesothelioma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010997:Pleural Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D055503:Protein Multimerization / Q000187:drug effects*; D011799:Quinazolines / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D003432:Cross-Linking Reagents; D011799:Quinazolines; C512478:EGFR protein, human; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D000077156:Gefitinib