Abstract 1258: High-density protein lysate arrays: an essential tool in assessing antibody specificity for clinical applications

Abstract

Abstract Antibodies for clinical applications require rigorous scrutiny qualifying them for diagnostics or therapeutic use. However, this is a lengthily and complicated process that provides only limited conformation. Protein microarrays are new tools that can determine the specificity and reactivity of Abs and help identifying their target in less than a day. We created a high-density protein array comprised from more than 10,000 over-expressed protein lysates made in human HEK293T cells. We tested more than 15 available antibodies to two cancer targets; the excision repair cross-complementation group 1 (ERCC1) and the receptor tyrosine kinase ERBB2 (Her2/neo). Our results demonstrated the ability of the lysate array in determining the specificity of antibodies with a single fast and easy assay. ERCC1 is a predictor of resistance to platinum based drugs and for poor prognosis in cancer. The commonly used anti ERCC1 antibody, mAb 8F1, is known to give non-specific cytoplasmic staining and to cross-react with an unknown protein of similar size. We tested 10 commercially available Abs to ERCC1 and identified four mono-specific ones (TrueMAb OriGene). Most of these specific Abs gave higher reactivity than clone 8F1. With this test we also identified a cytoplasmic protein of appropriate molecular weight that is cross-reacting with mAb 8F1. The above results were corroborated by WB analysis and IHC assays supporting the validity of this type of assays. We extended our tests to include anti ERBB2 Abs as this important biomarker is indicative for the use and response to the drug Herceptin. Our tests included mono and poly clonal antibodies and clone 4B5, a rabbit mAb currently used for IHC diagnostic. We found clone 4B5 to be reactive with two additional proteins besides ERBB2, one of them is ERBB4. We also tested a rabbit polyclonal anti ERBB2 serum and found it to be reactive with additional proteins unrelated to those recognized by mAb 4B5. Three out of the four mouse mAbs tested (TrueMAb OriGene) were determined to be specific. We submit that the over-expression protein lysate arrays can establish the reactivity and specificity of Abs and identify unknown targets. The speed and convenience of these assays make them an important tool in developing Abs for clinical use. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1258. doi:1538-7445.AM2012-1258