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Determination of True ERBB2 Gene Amplification in Breast Cancer by Quantitative PCR Using a Reference and a Novel Control Gene

Determination of True ERBB2 Gene Amplification in Breast Cancer by Quantitative PCR Using a... Human epidermal growth factor receptor 2 ( ERBB2 / HER2 ) is amplified and overexpressed in 20% to 25% of breast carcinomas, correlates with poor outcome, and is an indication for treatment with trastuzumab. Accurate assessment of ERBB2 status is crucial for proper prognosis and to offer appropriate treatment for patients. ERBB2 status is generally determined by immunohistochemistry or fluorescence in situ hybridization (FISH), and sporadically by quantitative real-time polymerase chain reaction (PCR). We developed a new algorithm, termed quantitative PCR algorithm ( QPA ) score, and compared its performance with the gold standard FISH assay. The QPA is a computation of the relative number of copies of the ERBB2 gene with respect to a nonstandard, short-arm centromeric sequence on chromosome 17, and referenced to a single-copy gene, RPP30 . This provides a more reliable determination of ERBB2 amplification, reducing the false polysomy 17 error. A total of 69 breast carcinoma samples were tested for quantitative real-time PCR and FISH, and the degree of concordance was analyzed. Sixty-two cases were in agreement between the 2 methods, and the contingency study assigned a κ value of 0.729 for their correlation. A receiver operating characteristic analysis was used to determine the optimal cut-off point for ERBB2 amplification, which was estimated at a QPA =1.53 (sensitivity=0.863; specificity=0.944). Our data conclude that the QPA is able to determine ERBB2 gene status with high accuracy, while also overcoming the limitations of conventional techniques and providing better cost-effectiveness. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Applied Immunohistochemistry & Molecular Morphology Wolters Kluwer Health

Determination of True ERBB2 Gene Amplification in Breast Cancer by Quantitative PCR Using a Reference and a Novel Control Gene

Determination of True ERBB2 Gene Amplification in Breast Cancer by Quantitative PCR Using a Reference and a Novel Control Gene


Breast cancer (BC) accounts for 23% of total cancer cases and 14% of cancer mortality around the world. 1 ERBB2 oncogene amplification and ERBB2 protein overexpression have been largely used to define a clinically challenging subgroup of BC with variable prognosis and response to therapy. 2 The ERBB2 oncogene (also known as HER2 or neu ) is localized on the long arm of chromosome 17 and belongs to the epidermal growth factor receptor family. 3 It encodes a 185 kDa transmembrane glycoprotein (p185c-erbB2) with intrinsic tyrosine kinase activity. ERBB2 gene amplification has been reported in 10% to 35% of invasive breast carcinomas, and it is associated with an aggressive disease course, increased disease recurrence, and decreased disease-free and overall survival in lymph node–positive patients. 4,5 The overexpression of the ERBB2 gene has been also traditionally associated with chromosome 17 polysomy. However, polysomy 17 might not reflect a true ERBB2-positive case, and recent studies have indicated that polysomy 17 is a rare event in BC. 6–8 In the present study, we aimed to clarify this issue. The discovery that ERBB2 gene overexpression in BC tissues is associated with a more aggressive clinical behavior has generated diagnostic interest, subsequently reinforced by the demonstration that ERBB2 gene expression is also a predictive marker of treatment response to trastuzumab 9,10 —a humanized monoclonal antibody directed against the ERBB2 receptor. Consequently, by the determination of the ERBB2 status in BC, the pathologist nowadays causes to reach a decision with ethical goal, not only to select ERBB2-positive patients for a therapy, but also to efficiently exclude ERBB2-negative patients from an ERBB2 targeted therapy. In addition, targeting therapies such as trastuzumab do have side effects, and an expensive cost. Different techniques are currently available to assess the ERBB2 status from tissue sections: immunohistochemistry (IHC), in...
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Publisher
Wolters Kluwer Health
Copyright
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Subject
Research Articles
ISSN
1541-2016
eISSN
1533-4058
DOI
10.1097/PAI.0000000000000160
pmid
25789534
Publisher site
See Article on Publisher Site

Abstract

Human epidermal growth factor receptor 2 ( ERBB2 / HER2 ) is amplified and overexpressed in 20% to 25% of breast carcinomas, correlates with poor outcome, and is an indication for treatment with trastuzumab. Accurate assessment of ERBB2 status is crucial for proper prognosis and to offer appropriate treatment for patients. ERBB2 status is generally determined by immunohistochemistry or fluorescence in situ hybridization (FISH), and sporadically by quantitative real-time polymerase chain reaction (PCR). We developed a new algorithm, termed quantitative PCR algorithm ( QPA ) score, and compared its performance with the gold standard FISH assay. The QPA is a computation of the relative number of copies of the ERBB2 gene with respect to a nonstandard, short-arm centromeric sequence on chromosome 17, and referenced to a single-copy gene, RPP30 . This provides a more reliable determination of ERBB2 amplification, reducing the false polysomy 17 error. A total of 69 breast carcinoma samples were tested for quantitative real-time PCR and FISH, and the degree of concordance was analyzed. Sixty-two cases were in agreement between the 2 methods, and the contingency study assigned a κ value of 0.729 for their correlation. A receiver operating characteristic analysis was used to determine the optimal cut-off point for ERBB2 amplification, which was estimated at a QPA =1.53 (sensitivity=0.863; specificity=0.944). Our data conclude that the QPA is able to determine ERBB2 gene status with high accuracy, while also overcoming the limitations of conventional techniques and providing better cost-effectiveness.

Journal

Applied Immunohistochemistry & Molecular MorphologyWolters Kluwer Health

Published: Mar 1, 2016

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