title: Knockdown of the epidermal growth factor receptor gene to investigate its therapeutic potential for the treatment of non-small-cell lung cancers.
abstract: BACKGROUND
  Epidermal growth factor receptor (EGFR) is often overexpressed in non-small-cell lung cancer (NSCLC). Anti-EGFR agents, including EGFR-tyrosine kinase inhibitors are considered to be effective when a drug-sensitive EGFR mutation is present. However, inherent and acquired resistances are major problems of EGFR-targeting therapies. In this study, we performed EGFR knockdown by using small interfering RNAs in NSCLC cell lines to examine the significance of targeting EGFR for NSCLC therapy.
  
  
  METHODS
  We treated 13 NSCLC cell lines, including 8 EGFR mutant and 5 EGFR wild type by using gefitinib or small interfering RNAs against EGFR (siEGFR). Three cell lines (PC-9-GR1, RPC-9, and HCC827-ER) were experimentally established with acquired resistance to EGFR-tyrosine kinase inhibitors. The antitumor effect was determined by using an 3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H-tetrazolium, inner salt (MTS) or colony formation assay. The protein expression was evaluated by using Western blotting.
  
  
  RESULTS
  All 13 cell lines expressed EGFR protein, and siEGFR downregulated EGFR protein expression in all. The cell viability was suppressed by siEGFR in 6 of 8 EGFR-mutant cell lines (suppressed 57%-92% of control cells), including PC-9-GR1 and RPC-9. The NCI-H1650 and HCC827-ER harbored EGFR mutations but were not suppressed. Of note, PTEN (phosphatase and tensin homolog) was deleted in NCI-H1650, and c-MET was amplified in HCC827-ER. It was not suppressed in any of the EGFR wild-type cells except in the NCI-H411, in which EGFR is phosphorylated, which indicates its activation.
  
  
  CONCLUSIONS
  Analysis of the results indicated that EGFR can be a therapeutic target in NSCLCs with EGFR activation. In contrast, targeting EGFR is not appropriate for tumors in which EGFR is not activated, even if EGFR is expressed.
authors.affiliation: Department of Cancer and Thoracic Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Shien
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Ueno
authors.forename: Kazunori
authors.initials: K
authors.lastname: Tsukuda
authors.forename: Junichi
authors.initials: J
authors.lastname: Soh
authors.forename: Kenichi
authors.initials: K
authors.lastname: Suda
authors.forename: Takafumi
authors.initials: T
authors.lastname: Kubo
authors.forename: Masashi
authors.initials: M
authors.lastname: Furukawa
authors.forename: Takayuki
authors.initials: T
authors.lastname: Muraoka
authors.forename: Yuho
authors.initials: Y
authors.lastname: Maki
authors.forename: Norimitsu
authors.initials: N
authors.lastname: Tanaka
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Kiura
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Mitsudomi
authors.forename: Shinichi
authors.initials: S
authors.lastname: Toyooka
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Miyoshi
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D066246:ErbB Receptors / Q000235:genetics*; D000077156:Gefitinib; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D058990:Molecular Targeted Therapy; D009154:Mutation; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011799:Quinazolines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000008:administration & dosage
chemical_list: D000970:Antineoplastic Agents; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D034741:RNA, Small Interfering; D066246:ErbB Receptors; D000077156:Gefitinib