title: CRKL amplification is rare as a mechanism for acquired resistance to kinase inhibitors in lung cancers with epidermal growth factor receptor mutation.
abstract: OBJECTIVE
  Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) often provide dramatic responses in lung cancer patients with somatic EGFR mutation. However, acquired resistance to the drugs usually emerges within a few years. EGFR T790M secondary mutation, MET gene amplification, and transformation to small cell lung cancer are well-validated mechanisms that underlie acquisition of resistance to EGFR-TKIs. In addition, many molecular aberrations have been reported as candidates for mechanisms of acquired resistance to EGFR-TKIs. Amplification of the CRKL gene was reportedly observed in 1 of 11 lung cancer patients with EGFR mutations who acquired resistance to EGFR-TKI. This study is the first report, to our knowledge, that validated the role of CRKL gene amplification as a mechanism for acquisition of resistance to EGFR-TKIs.
  
  
  METHODS
  We analyzed CRKL gene copy numbers, using a quantitative real-time PCR method, in 2 in vitro acquired-resistance cell-line models: 11 clinical samples from patients who developed acquired resistance to EGFR-TKIs, and 39 tumor specimens obtained from 7 autopsy patients whose cancers acquired resistance to EGFR-TKIs. Mutational status of EGFR codon 790 and copy numbers for the MET gene were also determined.
  
  
  CONCLUSIONS
  In analysis for in vitro models, CRKL gene copy numbers were identical between EGFR-TKI-sensitive parental cells and their acquired resistant descendant cells. In addition, we found no clinical tumor specimens with acquired EGFR-TKI resistance to harbor amplified CRKL genes. These results indicate that CRKL gene amplification is rare in acquisition of resistance to EGFR-TKIs in lung cancer patients with EGFR mutations.
authors.affiliation: Division of Thoracic Surgery, Department of Surgery, Kinki University Faculty of Medicine, 377-2 Ohno-higashi, Osaka-Sayama, Japan. Electronic address: ascaris@surg2.med.kyushu-u.ac.jp.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Suda
authors.affiliation: Division of Thoracic Surgery, Department of Surgery, Kinki University Faculty of Medicine, 377-2 Ohno-higashi, Osaka-Sayama, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Mizuuchi
authors.affiliation: Department of Respiratory Medicine, Higashi-Hiroshima Medical Center, 513 Jike, Saijo-Cho, Higashi-Hiroshima, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Murakami
authors.affiliation: Second Department of Surgery, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahata-nishi-ku, Kitakyushu, Japan.
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Uramoto
authors.affiliation: Second Department of Surgery, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahata-nishi-ku, Kitakyushu, Japan.
authors.forename: Fumihiro
authors.initials: F
authors.lastname: Tanaka
authors.affiliation: Division of Thoracic Surgery, Department of Surgery, Kinki University Faculty of Medicine, 377-2 Ohno-higashi, Osaka-Sayama, Japan.
authors.forename: Katsuaki
authors.initials: K
authors.lastname: Sato
authors.affiliation: Division of Thoracic Surgery, Department of Surgery, Kinki University Faculty of Medicine, 377-2 Ohno-higashi, Osaka-Sayama, Japan.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Takemoto
authors.affiliation: Division of Thoracic Surgery, Department of Surgery, Kinki University Faculty of Medicine, 377-2 Ohno-higashi, Osaka-Sayama, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Iwasaki
authors.affiliation: Division of Molecular Oncology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Sekido
authors.affiliation: Department of Pathology and Molecular Diagnostics, Aichi Cancer Center Hospital, 1-1 Kanokoden, Chikusa-ku, Nagoya, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Yatabe
authors.affiliation: Division of Thoracic Surgery, Department of Surgery, Kinki University Faculty of Medicine, 377-2 Ohno-higashi, Osaka-Sayama, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Mitsudomi
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D000368:Aged; D000369:Aged, 80 and over; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D066246:ErbB Receptors / Q000235:genetics*; D005260:Female; D005784:Gene Amplification; D018628:Gene Dosage; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009367:Neoplasm Staging; D009687:Nuclear Proteins / Q000235:genetics*; D011379:Prognosis; D047428:Protein Kinase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D019859:Proto-Oncogene Proteins c-met / Q000235:genetics; D012307:Risk Factors
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C082869:CRKL protein; D009687:Nuclear Proteins; D047428:Protein Kinase Inhibitors; D066246:ErbB Receptors; D019859:Proto-Oncogene Proteins c-met
keywords: Acquired resistance; EGFR mutation; Erlotinib; Gefitinib; MET gene amplification; Molecular target therapy; T790M mutation