Differential and synergistic effects of epidermal growth factor receptor antibodies on unliganded ErbB dimers and oligomers

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Title: Differential and synergistic effects of epidermal growth factor receptor antibodies on unliganded ErbB dimers and oligomers
Author(s): Kozer, Noga; Kelly, Marcus P.; Orchard, Suzanne; Burgess, Antony W.; Scott, Andrew M.; Clayton, Andrew H. A.
Abstract: Antibodies directed against the epidermal growth factor receptor (EGFR) offer a potentially powerful therapeutic approach against cancers driven by the EGFR pathway. EGFR antibodies are believed to halt cell surface activation by blocking ligand-induced receptor tyrosine kinase activation, i.e., ligand binding, a change in conformation, or the monomer-dimer transition. In this work, we demonstrate that wild-type EGFR and the truncated de2-7-EGFR (tumor-associated mutant) formed unliganded homo-oligomers and examined the effects of two clinically relevant antibodies on the conformation and quaternary state of these ligand-free EGFR oligomers on the surface of cells. The EGFR antibodies were mAb528, a ligand-blocking antibody that binds domain III, and mAb806, a conformationally sensitive antibody that binds near the dimer interface in domain II. We used a model cellular system, BaF/3 cells, with GFP-tagged receptors in the absence of interference from secreted ligands or other erbB receptor members. Different antibody-mediated effects (conformational transition, receptor cross-linking, or receptor dissociation) were distinguished by combining two complementary biophysical techniques: image correlation spectroscopy (submicrometer scale clustering) and homo-Forster resonance energy transfer (association and/or conformation on a 1-10 nm scale). mAb528 cross-linked EGFR into an inactive EGFR dimer of dimers but had no effect when added to de2-7-EGFR oligomers. mAb806 had a minor effect on EGFR dimers as expected from its poor binding to a conformationally shielded epitope on wtEGFR but bound de2-7-EGFR oligomers, causing a conformational change in the intracellular C-terminal GFP-tagged tail. The combination of the two antibodies had synergistic effects, increasing the level of cross-linking of de2-7-EGFR, but did not lead to enhanced cross-linking of EGFR. The results reveal new modes of receptor-antibody interactions for EGFR and de2-7-EGFR.
Publication type: Journal article
Research centre: Swinburne University of Technology. Faculty of Engineering and Industrial Sciences. Centre for Micro-Photonics
Source: Biochemistry, Vol. 50, no. 18 (May 2011), pp. 3581-3590
Publication year: 2011
FOR Code(s): 0601 Biochemistry and Cell Biology; 1101 Medical Biochemistry and Metabolomics
Keyword(s): Antibodies; Cancer research; Dimers; Epidermal growth factor receptor; Oligomers
Publisher: American Chemical Society
ISSN: 0006-2960
Publisher URL: http://dx.doi.org/10.1021/bi101785h
Research Projects: Fluorescence analysis of the EGF receptor signalling network, National Health and Medical Research Council grant number 280918
Signalling dynamics in living cells, National Health and Medical Research Council grant number 433624
Colon cancer: developing new therapies, National Health and Medical Research Council program 280912
Additional information: This work was partially supported by an R. D. Wright Biomedical Career Development Award from the Australian National Health and Medical Research Council (NHMRC).
Peer reviewed