title: Correlation of EGFR expression, gene copy number and clinicopathological status in NSCLC.
abstract: BACKGROUND
  Epidermal Growth Factor Receptor (EGFR) targeting therapies are currently of great relevance for the treatment of lung cancer. For this reason, in addition to mutational analysis immunohistochemistry (IHC) of EGFR in lung cancer has been discussed for the decision making of according therapeutic strategies. The aim of this study was to obtain standardization of EGFR-expression methods for the selection of patients who might benefit of EGFR targeting therapies.
  
  
  METHODS
  As a starting point of a broad investigation, aimed at elucidating the expression of EGFR on different biological levels, four EGFR specific antibodies were analyzed concerning potential differences in expression levels by Immunohistochemistry (IHC) and correlated with fluorescence in situ hybridization (FISH) analysis and clinicopathological data. 206 tumor tissues were analyzed in a tissue microarray format employing immunohistochemistry with four different antibodies including Dako PharmDx kit (clone 2-18C9), clone 31G7, clone 2.1E1 and clone SP84 using three different scoring methods. Protein expression was compared to FISH utilizing two different probes.
  
  
  RESULTS
  EGFR protein expression determined by IHC with Dako PharmDx kit, clone 31G7 and clone 2.1E1 (p ≤ 0.05) correlated significantly with both FISH probes independently of the three scoring methods; best correlation is shown for 31G7 using the scoring method that defined EGFR positivity when ≥ 10% of the tumor cells show membranous staining of moderate and severe intensity (p=0.001).
  
  
  CONCLUSIONS
  Overall, our data show differences in EGFR expression determined by IHC, due to the applied antibody. Highest concordance with FISH is shown for antibody clone 31G7, evaluated with score B (p=0.001). On this account, this antibody clone might by utilized for standard evaluation of EGFR expression by IHC.
  The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_165.
authors.forename: Rania
authors.initials: R
authors.lastname: Gaber
authors.forename: Iris
authors.initials: I
authors.lastname: Watermann
authors.forename: Christian
authors.initials: C
authors.lastname: Kugler
authors.forename: Nils
authors.initials: N
authors.lastname: Reinmuth
authors.forename: Rudolf M
authors.initials: RM
authors.lastname: Huber
authors.forename: Philipp A
authors.initials: PA
authors.lastname: Schnabel
authors.forename: Ekkehard
authors.initials: E
authors.lastname: Vollmer
authors.forename: Martin
authors.initials: M
authors.lastname: Reck
authors.forename: Torsten
authors.initials: T
authors.lastname: Goldmann
mesh_terms: D000368:Aged; D000906:Antibodies / Q000276:immunology; D002276:Carcinoid Tumor / Q000175:diagnosis / Q000235:genetics / Q000473:pathology; D018196:Carcinoma, Adenosquamous / Q000175:diagnosis / Q000235:genetics / Q000473:pathology; D018287:Carcinoma, Large Cell / Q000175:diagnosis / Q000235:genetics / Q000473:pathology; D002289:Carcinoma, Non-Small-Cell Lung / Q000175:diagnosis / Q000235:genetics / Q000473:pathology*; D004273:DNA, Neoplasm / Q000235:genetics; D003937:Diagnosis, Differential; D066246:ErbB Receptors / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D005260:Female; D018628:Gene Dosage / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods* / Q000592:standards; D017404:In Situ Hybridization, Fluorescence / Q000379:methods* / Q000592:standards; D008175:Lung Neoplasms / Q000175:diagnosis / Q000235:genetics / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D015203:Reproducibility of Results
chemical_list: D000906:Antibodies; D004273:DNA, Neoplasm; D066246:ErbB Receptors