%0 Journal Article
%T Analytical Validation of a Highly Quantitative, Sensitive, Accurate, and Reproducible Assay (HERmarkˋ) for the Measurement of HER2 Total Protein and HER2 Homodimers in FFPE Breast Cancer Tumor Specimens
%A Jeffrey S. Larson
%A Laurie J. Goodman
%A Yuping Tan
%A Lisa Defazio-Eli
%A Agnes C. Paquet
%A Jennifer W. Cook
%A Amber Rivera
%A Kristi Frankson
%A Jolly Bose
%A Lili Chen
%A Judy Cheung
%A Yining Shi
%A Sarah Irwin
%A Linda D. B. Kiss
%A Weidong Huang
%A Shannon Utter
%A Thomas Sherwood
%A Michael Bates
%A Jodi Weidler
%A Gordon Parry
%A John Winslow
%A Christos J. Petropoulos
%A Jeannette M. Whitcomb
%J Pathology Research International
%D 2010
%I Hindawi Publishing Corporation
%R 10.4061/2010/814176
%X We report here the results of the analytical validation of assays that measure HER2 total protein (H2T) and HER2 homodimer (H2D) expression in Formalin Fixed Paraffin Embedded (FFPE) breast cancer tumors as well as cell line controls. The assays are based on the VeraTag technology platform and are commercially available through a central CAP-accredited clinical reference laboratory. The accuracy of H2T measurements spans a broad dynamic range (2-3 logs) as evaluated by comparison with cross-validating technologies. The measurement of H2T expression demonstrates a sensitivity that is approximately 7每10 times greater than conventional immunohistochemistry (IHC) (HercepTest). The HERmark assay is a quantitative assay that sensitively and reproducibly measures continuous H2T and H2D protein expression levels and therefore may have the potential to stratify patients more accurately with respect to response to HER2-targeted therapies than current methods which rely on semiquantitative protein measurements (IHC) or on indirect assessments of gene amplification (FISH). 1. Introduction The human epidermal growth factor receptor 2 (HER2) is a transmembrane protein tyrosine kinase receptor that is important in initiating signal transduction pathways in normal and abnormal cells [1每5]. HER2 is overexpressed/amplified in approximately 15%每30% of human breast tumors and is a biomarker of poor prognosis in patients demonstrating either high protein levels and/or gene amplification on chromosome 17 [4, 6, 7]. For this reason, HER2 testing is recommended for all newly diagnosed breast cancer patients for the selection of individuals that may benefit from treatment with the humanized monoclonal antibody Trastuzumab [8每11]. Despite confirmed overexpression of HER2, the current response rates to Trastuzumab are less than 50% in the metastatic setting and many of the patients that respond initially will eventually develop resistance and subsequent recurrence of their disease [12每14]. Standardization of both IHC and ISH methodologies across laboratories remains a major problem [15]. because of this approximately 20% of HER2 testing performed in the field may be inaccurate [16]. The ability to accurately and reproducibly quantify the level of HER2 protein expression in tumors is critical to the appropriate selection of patients for Trastuzumab and other HER2 targeted therapies. Most laboratories in North America and Europe use IHC to determine HER2 protein status, with equivocal category results confirmed by indirectly measuring HER2 gene amplification by Fluorescence In Situ
%U http://www.hindawi.com/journals/pri/2010/814176/