Abstract
Abstract With the advent of multiple HER-2 targeting agents, the need for a diagnostic test that accurately predicts the levels of HER2 in newly diagnosed breast cancer patients has never been greater. The goal of this study was to develop an immunofluorescence based assay to objectively and reproducibly quantify HER-2 protein level in Formalin-Fixed Paraffin-Embedded (FFPE) specimens using AQUA Technology and to provide a binary readout, thus eliminating reflex testing and enabling quick treatment decisions. Methods: Three well known HER-2 antibody clones, A0485, CB11, and SP3 were evaluated across a three-log dilution series under four different antigen retrieval conditions on a tissue microarray (TMA) containing 80 breast cancer cases with known central HER2 immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) amplification status. The top six immunofluorescence assay combinations out of 108 conditions were quantified by AQUA scoring based on the their ability to accurately separate negative and positive cases using receiver operating characteristic (ROC) analysis. These top six assay conditions were then assessed on an independent TMA containing 94 breast cancer cases and their AQUA scores were compared to HER2 protein levels determined by reverse phase protein microarray (RPMA®), HER2 mRNA levels assessed by RNAscope® as well as to the current “gold standard” IHC and FISH amplification. Results: Top three conditions clearly segregating HER2 positive and HER2 negative breast cancer cases were selected and analyzed on an independent TMA. Conditions associated with both SP3 and A0485 antibodies demonstrated high correlations with both HER2 protein levels determined by RPMA analysis and HER2 mRNA levels assessed by RNAscope (spearman's rho >0.85). Conclusion: Assessment of HER2 status using AQUA Technology was confirmed using two expression platforms, including both protein (RPMA) and RNA (RNAscope) supporting the utilization of the AQUA methodology for diagnostic test development. Citation Format: Jennifer Bordeaux, Krupa Chandrasekaran, Sue Beruti, Mike Nerenberg, Corinne Ramos, David Rimm, Jelveh Lameh, Naveen Dakappagari. Evaluation of HER-2 RNA and protein levels in a large cohort of breast cancer specimens to support development of a diagnostic immunofluorescence assay quantified by AQUA® Technology. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2840. doi:10.1158/1538-7445.AM2014-2840
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