title: Discrepancies between FISH and immunohistochemistry for assessment of the ALK status are associated with ALK 'borderline'-positive rearrangements or a high copy number: a potential major issue for anti-ALK therapeutic strategies.
abstract: BACKGROUND
  Patients with advanced lung adenocarcinomas expressing ALK rearrangements are highly responsive to crizotinib, a dual ALK/c-MET inhibitor. Immunohistochemistry (IHC) is an easy clinically and routinely applicable cost-effective assay for ALK, c-MET and ROS1 protein expression for potential treatment with crizotinib. The purpose of this study was to evaluate the percentage and the pattern of ALK-rearranged cells, the variation in the native ALK copy number, as well as ALK, c-MET and ROS1 protein expression, and their significance on outcome of crizotinib-treated lung adenocarcinoma patients.
  
  
  METHODS
  Consecutive lung adenocarcinoma specimens (n = 176) 'double-negative' (wild-type EGFR and KRAS) were tested for ALK rearrangements/copy number alterations and for ALK, c-MET and ROS1 protein expression using automated standardized protocols. Preliminary data on the outcome of crizotinib-treated patients were recorded.
  
  
  RESULTS
  FISH analysis identified 26/176 (15%) cases with ALK rearrangements. Seven cases had discordant results between the ALK FISH and IHC. Five cases with discordant FISH-positive/IHC-negative revealed FISH 'borderline' positivity (15%-20%). Three cases overexpressed c-MET and responded to crizotinib, and two cases with ALK-'borderline' rearranged cells only, not associated with c-MET expression, progressed under crizotinib. Two cases with discordant FISH-negative/IHC-positive revealed ALK gene amplification without associated c-MET or ROS1 protein expression.
  
  
  CONCLUSIONS
  The discrepancies observed between the IHC and FISH data revealed unexpected biological events, rather than technical issues, which potentially can have a strong impact on the therapeutic strategy with crizotinib.
authors.affiliation: Laboratory of Clinical and Experimental Pathology, Pasteur Hospital, Nice; IRCAN Team 3, INSERM U1081/UMR CNRS 7284, Faculty of Medicine of Nice, University of Nice Sophia Antipolis, Nice.
authors.forename: M I
authors.initials: MI
authors.lastname: Ilie
authors.affiliation: Laboratory of Clinical and Experimental Pathology, Pasteur Hospital, Nice.
authors.forename: C
authors.initials: C
authors.lastname: Bence
authors.affiliation: Laboratory of Clinical and Experimental Pathology, Pasteur Hospital, Nice; IRCAN Team 3, INSERM U1081/UMR CNRS 7284, Faculty of Medicine of Nice, University of Nice Sophia Antipolis, Nice; Hospital Integrated Biobank.
authors.forename: V
authors.initials: V
authors.lastname: Hofman
authors.affiliation: Laboratory of Clinical and Experimental Pathology, Pasteur Hospital, Nice; IRCAN Team 3, INSERM U1081/UMR CNRS 7284, Faculty of Medicine of Nice, University of Nice Sophia Antipolis, Nice.
authors.forename: E
authors.initials: E
authors.lastname: Long-Mira
authors.affiliation: Laboratory of Clinical and Experimental Pathology, Pasteur Hospital, Nice.
authors.forename: C
authors.initials: C
authors.lastname: Butori
authors.affiliation: Department of Pneumology.
authors.forename: L
authors.initials: L
authors.lastname: Bouhlel
authors.affiliation: Laboratory of Clinical and Experimental Pathology, Pasteur Hospital, Nice.
authors.forename: S
authors.initials: S
authors.lastname: Lalvée
authors.affiliation: IRCAN Team 3, INSERM U1081/UMR CNRS 7284, Faculty of Medicine of Nice, University of Nice Sophia Antipolis, Nice; Department of Thoracic Surgery, Pasteur Hospital, Nice.
authors.forename: J
authors.initials: J
authors.lastname: Mouroux
authors.affiliation: Department of Pneumology.
authors.forename: M
authors.initials: M
authors.lastname: Poudenx
authors.affiliation: Department of Pneumology, Centre Antoine Lacassagne, Nice, France.
authors.forename: J
authors.initials: J
authors.lastname: Otto
authors.affiliation: IRCAN Team 3, INSERM U1081/UMR CNRS 7284, Faculty of Medicine of Nice, University of Nice Sophia Antipolis, Nice; Department of Pneumology.
authors.forename: C H
authors.initials: CH
authors.lastname: Marquette
authors.affiliation: Laboratory of Clinical and Experimental Pathology, Pasteur Hospital, Nice; IRCAN Team 3, INSERM U1081/UMR CNRS 7284, Faculty of Medicine of Nice, University of Nice Sophia Antipolis, Nice; Hospital Integrated Biobank. Electronic address: hofman.p@chu-nice.fr.
authors.forename: P
authors.initials: P
authors.lastname: Hofman
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000235:genetics* / Q000401:mortality; D000077192:Adenocarcinoma of Lung; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000077548:Anaplastic Lymphoma Kinase; D000077547:Crizotinib; D005260:Female; D005455:Fluorescent Antibody Technique / Q000379:methods*; D018628:Gene Dosage / Q000235:genetics; D015321:Gene Rearrangement; D014644:Genetic Variation / Q000235:genetics; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000401:mortality; D008297:Male; D008875:Middle Aged; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use; D011505:Protein-Tyrosine Kinases / Q000032:analysis; D011518:Proto-Oncogene Proteins / Q000032:analysis; D019859:Proto-Oncogene Proteins c-met / Q000032:analysis / Q000037:antagonists & inhibitors; D011720:Pyrazoles / Q000627:therapeutic use; D011725:Pyridines / Q000627:therapeutic use; D020794:Receptor Protein-Tyrosine Kinases / Q000032:analysis* / Q000037:antagonists & inhibitors* / Q000235:genetics
chemical_list: D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D011720:Pyrazoles; D011725:Pyridines; D000077547:Crizotinib; C000626173:ALK protein, human; D000077548:Anaplastic Lymphoma Kinase; C491743:MET protein, human; D011505:Protein-Tyrosine Kinases; D019859:Proto-Oncogene Proteins c-met; C062333:ROS1 protein, human; D020794:Receptor Protein-Tyrosine Kinases
keywords: ALK; crizotinib; discrepancy; fluorescence in situ hybridization; immunohistochemistry; lung adenocarcinoma