Estimating copy number using next-generation sequencing to determine ERBB2 amplification status

Kohei Nakamura,Koji Okabayashi,Hiroshi Nishihara,Hirohumi Kawakubo,Sadakatsu Ikeda,Hajime Okita,Shigeki Tanishima,Takeru Funakoshi,Tetsu Hayashida,Hiromasa Takaishi,Tomoyuki Hishida,Hideyuki Hayashi,Eriko Aimono,Junna Oba,Tatsuyuki Chiyoda,Takeo Kosaka,Minoru Kitago

doi:10.1007/s12032-021-01482-1

Abstract

Assessing Erb-b2 receptor tyrosine kinase 2 (ERBB2) amplification status in breast and gastric cancer is necessary for deciding the best therapeutic strategy. Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) are currently used for assessing protein levels and gene copy number (CN), respectively. The use of next-generation sequencing (NGS) to measure ERBB2 CN in breast cancer is approved by the United States Federal Drug Administration as a companion diagnostic. However, a CN of less than 8 is evaluated as “equivocal”, which means that some ERBB2 amplification cases diagnosed as “HER2 negative” might be false-negative cases. We reviewed the results of gene profiling targeting 160 cancer-related genes in breast (N = 90) and non-breast (N = 19) cancer tissue, and compared the ERBB2 CN results with the IHC/FISH scores. We obtained an estimated CN from the measured CN by factoring in the histological proportion of tumor cells and found that an ERBB2-estimated CN of 3.2 or higher was concordant with the combined IHC/FISH outcome in 98.4% (88/90) of breast cancer cases, while this was not always evident among non-breast cancer cases. Therefore, NGS-estimated ERBB2 CN could be considered a diagnostic test for anti-HER2 therapy after the completion of adequate prospective clinical trials.

Highlights

Human epidermal growth factor receptor 2 (HER2), the protein encoded by the Erb-b2 receptor tyrosine kinase 2 (ERBB2) gene, is one of the main therapeutic targets in Extended author information available on the last page of the article human cancers [1]
HER2 is a transmembrane receptor tyrosine kinase that belongs to the HER family, and its overexpression leads to homodimerization and heterodimerization with other HER family-member proteins [2], triggering activation of the phosphoinositide-3-kinase/Akt and mitogen-activated protein kinase pathways [3], resulting in tumor proliferation, differentiation, apoptosis regulation, angiogenesis, and invasion [4]
Clinical laboratories stain for HER2 protein by immunohistochemistry (IHC), or detect ERBB2 amplification by fluorescence in situ hybridization (FISH) or chromogenic in situ hybridization

Summary

Introduction

Human epidermal growth factor receptor 2 (HER2), the protein encoded by the Erb-b2 receptor tyrosine kinase 2 (ERBB2) gene, is one of the main therapeutic targets in Extended author information available on the last page of the article human cancers [1]. HER2 overexpression is used as a biomarker in breast and gastric cancers to predict the response to anti-HER2 monoclonal antibody therapies (trastuzumab and pertuzumab) and small-molecule HER2 kinase inhibitors (lapatinib) [5, 6]. Amplification of ERBB2 is a potential therapeutic target in other cancer types, including lung, bladder, endometrial, ovary, colorectal, esophageal, and bile duct cancers [7,8,9,10,11,12,13,14]. There are consensus scoring guidelines for these techniques for breast and gastric cancers [15, 16]; these have not been established for other cancer types

Objectives

Methods

Results

Conclusion