title: Epidermal growth factor receptor double activating mutations involving both exons 19 and 21 exist in Chinese non-small cell lung cancer patients.
abstract: OBJECTIVE
  It has been shown that the introduction of a second mutation into the already mutated epidermal growth factor receptor (EGFR) in non-small cell lung cancer (NSCLC) will alter the sensitivity to tyrosine kinase inhibitors (TKIs). EGFR double activating mutations involving both exons 19 and 21 were previously detected in Asian patients, but the sensitivity to TKIs had not yet been characterised. Our objective was to profile the status of EGFR double mutations in Chinese NSCLC patients and to further ascertain the biological properties.
  
  
  METHODS
  In total, 145 NSCLC tumour samples from unselected Chinese NSCLC patients were sequenced to screen mutations in exons 18, 19 and 21 of EGFR. Five patients were detected to harbour the delE746-A750+L858R double activating mutations. Subcloning experiments were carried out, expression vectors inserted with corresponding full-length EGFR were constructed, and in vitro transient transfections were performed in 293T cells. Whole cell lysates were collected to assess the sensitivity to TKIs using immunoblotting.
  
  
  RESULTS
  All five patients had adenocarcinoma. The frequency of double mutations was 3.4% (5/145). Three patients received and responded to gefitinib treatment. Subcloning experiments showed that all the subclones were either wild type or double mutated. At a concentration of TKIs of 0.1 microM, the autophosphorylation of the double mutant was inhibited greater than that of either single mutated EGFR. However, the difference disappeared when the concentration increased to 1 microM.
  
  
  CONCLUSIONS
  delE746-A750+L858R double activating EGFR mutations exist in Chinese NSCLC patients and both locate on the same allele. These patients tend to respond well to TKIs and the sensitivity to TKIs of this double mutated EGFR is enhanced compared with either single mutant. Nonetheless, the alteration in downstream signal transduction of the double mutant remains to be determined.
authors.affiliation: Cancer Center, Sun Yat-Sen University, and Lung Cancer Research Institute, Guangdong Provincial People's Hospital, Dong Chuan Road, Guangzhou 510080, People's Republic of China.
authors.forename: G-C
authors.initials: GC
authors.lastname: Zhang
authors.forename: J-Y
authors.initials: JY
authors.lastname: Lin
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.forename: Q
authors.initials: Q
authors.lastname: Zhou
authors.forename: C-R
authors.initials: CR
authors.lastname: Xu
authors.forename: J-Q
authors.initials: JQ
authors.lastname: Zhu
authors.forename: K
authors.initials: K
authors.lastname: Wang
authors.forename: X-N
authors.initials: XN
authors.lastname: Yang
authors.forename: G
authors.initials: G
authors.lastname: Chen
authors.forename: J-J
authors.initials: JJ
authors.lastname: Yang
authors.forename: Y-J
authors.initials: YJ
authors.lastname: Huang
authors.forename: R-Q
authors.initials: RQ
authors.lastname: Liao
authors.forename: Y-L
authors.initials: YL
authors.lastname: Wu
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics*; D044466:Asian People; D001483:Base Sequence; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics*; D002681:China; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics*; D005091:Exons; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D011505:Protein-Tyrosine Kinases / Q000494:pharmacology
chemical_list: D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases