title: ErbB-3 mediates phosphoinositide 3-kinase activity in gefitinib-sensitive non-small cell lung cancer cell lines.
abstract: Therapies that target the EGF receptor (EGFR), such as gefitinib (IRESSA), are effective in a subset of patients with advanced non-small cell lung cancer (NSCLC). The differences in intracellular signaling networks between gefitinib-sensitive and -resistant NSCLCs remain poorly understood. In this study, we observe that gefitinib reduces phospho-Akt levels only in NSCLC cell lines in which it inhibits growth. To elucidate the mechanism underlying this observation, we compared immunoprecipitates of phosphoinositide 3-kinase (PI3K) between gefitinib-sensitive and -resistant NSCLC cell lines. We observe that PI3K associates with ErbB-3 exclusively in gefitinib-sensitive NSCLC cell lines. Gefitinib dissociates this complex, thereby linking EGFR inhibition to decreased Akt activity. In contrast, gefitinib-resistant cells do not use ErbB-3 to activate the PI3K/Akt pathway. In fact, abundant ErbB-3 expression is detected only in gefitinib-sensitive NSCLC cell lines. Two gefitinib-sensitive NSCLC cell lines with endogenous distinct activating EGFR mutations (L858R and Del747-749), frequently observed in NSCLC patients who respond to gefitinib, also use ErbB-3 to couple to PI3K. Down-regulation of ErbB-3 by means of short hairpin RNA leads to decreased phospho-Akt levels in the gefitinib-sensitive NSCLC cell lines, Calu-3 (WT EGFR) and H3255 (L858R EGFR), but has no effect on Akt activation in the gefitinib-resistant cell lines, A549 and H522. We conclude that ErbB-3 is used to couple EGFR to the PI3K/Akt pathway in gefitinib-sensitive NSCLC cell lines harboring WT and mutant EGFRs.
authors.affiliation: Department of Systems Biology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Engelman
authors.forename: Pasi A
authors.initials: PA
authors.lastname: Jänne
authors.forename: Craig
authors.initials: C
authors.lastname: Mermel
authors.forename: Joseph
authors.initials: J
authors.lastname: Pearlberg
authors.forename: Toru
authors.initials: T
authors.lastname: Mukohara
authors.forename: Christina
authors.initials: C
authors.lastname: Fleet
authors.forename: Karen
authors.initials: K
authors.lastname: Cichowski
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Johnson
authors.forename: Lewis C
authors.initials: LC
authors.lastname: Cantley
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D016466:CHO Cells; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000473:pathology; D045744:Cell Line, Tumor; D006224:Cricetinae; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000502:physiology; D000077156:Gefitinib; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D011799:Quinazolines / Q000494:pharmacology*; D020893:Receptor, ErbB-3 / Q000502:physiology*
chemical_list: D000970:Antineoplastic Agents; D066246:ErbB Receptors; D000077156:Gefitinib; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011799:Quinazolines; D020893:Receptor, ErbB-3; C494918:AKT1 protein, human
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