Validation of chromogenic in situ hybridization for detection of EGFR copy number amplification in nonsmall cell lung carcinoma.
Epidermal growth factor receptor (EGFR) gene copy number correlates with response to tyrosine kinase inhibitors in patients with nonsmall cell lung carcinoma. Fluorescence in situ hybridization (FISH), a standard methodology to detect EGFR copy number abnormalities in nonsmall cell lung carcinoma, is limited by instrumentation and cost. Chromogenic in situ hybridization (CISH) is an emerging alternative detection technique using light microscopy, but its utility in assessing EGFR copy number in lung cancer is not established. To address the utility of CISH, we studied paraffin-embedded nonsmall cell lung carcinoma specimens from 77 Taiwanese nonsmoking women treated by surgery alone. We recorded the number of signals per tumor cell nucleus, correlated EGFR copy number by CISH with FISH results, and used receiver operating characteristics to identify cut-off points for the CISH results. Tumors were classified as adenocarcinoma (n=28), mixed adenocarcinoma with bronchioloalveolar features (n=25), bronchioloalveolar carcinoma (n=2), squamous cell carcinoma (n=15), and adenosquamous carcinoma (n=7). By FISH, 29% of cases had no amplification, 18% had low polysomy, 35% had high polysomy, and 12% had gene amplification. EGFR copy number detected by CISH highly correlated with FISH (Spearman r=0.81, P<0.0001). We determined the optimal EGFR CISH cut-off points that discriminate between no amplification and low polysomy (2.8 signals, P=0.09); no amplification plus low polysomy and high polysomy plus gene amplification (4.5 signals, P<0.0001); and high polysomy and gene amplification (7.1 signals, P=0.0003). CISH is an alternative assay to FISH in determining EGFR copy number status that may contribute to stratification of patients with nonsmall cell lung carcinoma for clinical trials and identify a subset of patients that should be treated with tyrosine kinase inhibitors.
Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Lynette M
LM
Sholl
A
A
John Iafrate
Yi-Ping
YP
Chou
Ming-Tsang
MT
Wu
Yih-Gang
YG
Goan
Li
L
Su
Yen-Tsung
YT
Huang
David C
DC
Christiani
Lucian R
LR
Chirieac
D014408:Biomarkers, Tumor / Q000378:metabolism; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology; D002863:Chromogenic Compounds / Q000737:chemistry; D016002:Discriminant Analysis; D066246:ErbB Receptors / Q000378:metabolism*; D005260:Female; D005784:Gene Amplification; D018628:Gene Dosage; D018773:Genes, erbB-1; D006801:Humans; D017403:In Situ Hybridization / Q000379:methods*; D017404:In Situ Hybridization, Fluorescence / Q000379:methods; D008175:Lung Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D012680:Sensitivity and Specificity
D014408:Biomarkers, Tumor; D002863:Chromogenic Compounds; C512478:EGFR protein, human; D066246:ErbB Receptors