%0 Journal Article
%T Quantitative assays for the measurement of HER1-HER2 heterodimerization and phosphorylation in cell lines and breast tumors: applications for diagnostics and targeted drug mechanism of action
%A Lisa DeFazio-Eli
%A Kristi Strommen
%A Trang Dao-Pick
%A Gordon Parry
%A Laurie Goodman
%A John Winslow
%J Breast Cancer Research
%D 2011
%I BioMed Central
%R 10.1186/bcr2866
%X Assays for activated HER1 and HER2 receptors in FFPE and cell lysate formats were developed using VeraTag£¿ technology, which requires the proximity of an antibody pair for light-dependent release of a fluorescently labeled tag, followed by capillary electrophoresis-based quantitation.Ligand-dependent and independent HER1-HER2 heterodimer levels measured by lysate and FFPE VeraTag£¿ assays trended with HER1 and HER2 expression levels in tumor cell lines, which was confirmed by co-immunoprecipitation. The formation of EGF-dependent HER1-HER2 heterodimers were inhibited by the HER2-targeted monoclonal antibody 2C4 and stabilized by the HER1 tyrosine kinase inhibitor (TKI) erlotinib. EGF-dependent HER1 and HER2 phosphorylation was inhibited by lapatinib and erlotinib. Further, we observed that dominant receptor signaling patterns may switch between HER1-HER1 and HER1-HER2, depending on drug mechanism of action and relative levels of HER receptors. In FFPE breast tumors that expressed both HER1 and HER2, HER1-HER2 heterodimers were detected in 25 to 50% of tumors, depending on detection method. The levels of activated phospho-HER1-HER2 heterodimers correlated with HER1 or HER2 levels in an analysis of 43 HER2-positive breast tumors.VeraTag£¿ lysate assays can be used as a tool for understanding the mechanism of action of targeted HER-family inhibitors in the preclinical setting, while VeraTag£¿ FFPE assays of activated HER receptors combined with total HER2 measurements (HERmark£¿) in tumor samples may provide a more accurate prediction of clinical response to both HER1 and HER2 targeted therapies.Both the epidermal growth factor receptor (EGFR/HER1) and HER2 are members of the ErbB family of the type I receptor tyrosine kinases, which also includes HER3 and HER4. These homologous receptors are comprised of an extracellular binding domain (ECD), a transmembrane domain, and an intracellular tyrosine kinase (TK) domain. Binding of ligand to the ECD induces structural reorganiz
%U http://breast-cancer-research.com/content/13/2/R44