MET gene amplification or EGFR mutation activate MET in lung cancers untreated with EGFR tyrosine kinase inhibitors.
We analyzed MET protein and copy number in NSCLC with or without EGFR mutations untreated with EGFR tyrosine kinase inhibitors (TKIs). MET copy number was examined in 28 NSCLC and 4 human bronchial epithelial cell lines (HBEC) and 100 primary tumors using quantitative real-time PCR. Positive results were confirmed by array comparative genomic hybridization and fluorescence in-situ hybridization. Total and phospho-MET protein expression was determined in 24 NSCLC and 2 HBEC cell lines using Western blot. EGFR mutations were examined for exon 19 deletions, T790M, and L858R. Knockdown of EGFR with siRNA was performed to examine the relation between EGFR and MET activation. High-level MET amplification was observed in 3 of 28 NSCLC cell lines and in 2 of 100 primary lung tumors that had not been treated with EGFR-TKIs. MET protein was highly expressed and phosphorylated in all the 3 cell lines with high MET amplification. In contrast, 6 NSCLC cell lines showed phospho-MET among 21 NSCLC cell lines without MET amplification (p = 0.042). Furthermore, those 6 cell lines harboring phospho-MET expression without MET amplification were all EGFR mutant (p = 0.0039). siRNA-mediated knockdown of EGFR abolished phospho-MET expression in examined 3 EGFR mutant cell lines of which MET gene copy number was not amplified. By contrast, phospho-MET expression in 2 cell lines with amplified MET gene was not down-regulated by knockdown of EGFR. Our results indicated that MET amplification was present in untreated NSCLC and EGFR mutation or MET amplification activated MET protein in NSCLC.
Kubo
Takafumi
T
Department of Cancer and Thoracic Surgery, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
Yamamoto
Hiromasa
H
Lockwood
William W
WW
Valencia
Ilse
I
Soh
Junichi
J
Peyton
Michael
M
Jida
Masaru
M
Otani
Hiroki
H
Fujii
Tetsuya
T
Ouchida
Mamoru
M
Takigawa
Nagio
N
Kiura
Katsuyuki
K
Shimizu
Kenji
K
Date
Hiroshi
H
Minna
John D
JD
Varella-Garcia
Marileila
M
Lam
Wan L
WL
Gazdar
Adi F
AF
Toyooka
Shinichi
S
D000368:Aged; D001980:Bronchi / Q000166:cytology; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004847:Epithelial Cells / Q000166:cytology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics*; D005260:Female; D005784:Gene Amplification; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics* / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics*; D019859:Proto-Oncogene Proteins c-met; D034741:RNA, Small Interfering / Q000378:metabolism; D017978:Receptors, Growth Factor / Q000096:biosynthesis* / Q000235:genetics*
D004791:Enzyme Inhibitors; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D017978:Receptors, Growth Factor; D066246:ErbB Receptors; C491743:MET protein, human; D019859:Proto-Oncogene Proteins c-met