title: Dimerization and the signal transduction pathway of a small in-frame deletion in the epidermal growth factor receptor.
abstract: A short, in-frame deletional mutant (E746-A750del) is one of the major mutant forms of epidermal growth factor receptor (EGFR) and has been reported to be a determinant of response to EGFR tyrosine kinase inhibitors such as gefitinib and erlotinib. However, the biological and pharmacological functions of mutational EGFR remain unclear. To clarify these biological functions of deletional EGFR, we examined the cellular response to EGF ligand stimulation. Dimerization and phosphorylation of EGFR were observed without any ligand stimulation in the 293(D) cells transfected with deletional EGFR as compared with those transfected with wild-type EGFR (293(W) cells). When the 293(D) cells were exposed to gefitinib, an immunoblotting analysis revealed remarkable inhibition of AKT phosphorylation but not phospho-p44/42 MAPK. To examine the cellular response in a lung cancer cell line intrinsically expressing deletional EGFR, phospho-EGFR, and downstream reactions were monitored under EGF stimulation with a beads-based mulitiplex assay. EGFR and its downstream proteins were constitutively phosphorylated in the PC-9 cells without any ligand stimulation as compared with A549 lung cancer cells expressing wild-type EGFR. In conclusion, deletional EGFR is constitutively active and phosphorylates p44/42 MAPK and AKT in the cells, although the fact that the EGFR phosphorylation in the PC-9 cells is still modulated by EGF stimulation cannot be ignored. Gefitinib-inhibited phospho-AKT predominantly in deletional EGFR expressing cells.
authors.affiliation: Shien-Lab, Medical Oncology, National Cancer Center Research Institute, Tokyo, Japan.
authors.forename: Kazuko
authors.initials: K
authors.lastname: Sakai
authors.forename: Tokuzo
authors.initials: T
authors.lastname: Arao
authors.forename: Tatsu
authors.initials: T
authors.lastname: Shimoyama
authors.forename: Kimiko
authors.initials: K
authors.lastname: Murofushi
authors.forename: Masaru
authors.initials: M
authors.lastname: Sekijima
authors.forename: Naoko
authors.initials: N
authors.lastname: Kaji
authors.forename: Tomohide
authors.initials: T
authors.lastname: Tamura
authors.forename: Nagahiro
authors.initials: N
authors.lastname: Saijo
authors.forename: Kazuto
authors.initials: K
authors.lastname: Nishio
mesh_terms: D002460:Cell Line; D019281:Dimerization; D066246:ErbB Receptors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000077156:Gefitinib; D005786:Gene Expression Regulation / Q000187:drug effects; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology; D017384:Sequence Deletion / Q000235:genetics*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D048052:Mitogen-Activated Protein Kinase 3; D000077156:Gefitinib