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Title: Identification of the epitope for the epidermal growth factor receptor-specific monoclonal antibody 806 reveals that it preferentially recognizes an untethered form of the receptor.
Austin Authors: Johns, Terrance G;Adams, Timothy E;Cochran, Jennifer R;Hall, Nathan E;Hoyne, Peter A;Olsen, Mark J;Kim, Yong-Sung;Rothacker, Julie;Nice, Edouard C;Walker, Francesca;Ritter, Gerd;Jungbluth, Achim A;Old, Lloyd J;Ward, Colin W;Burgess, Antony W;Wittrup, K Dane;Scott, Andrew M 
Affiliation: Tumour Targeting Program, Ludwig Institute for Cancer Research, Austin Hospital, Heidelberg 3084, Australia
Issue Date: 9-Apr-2004
Publication information: The Journal of Biological Chemistry 2004; 279(29): 30375-84
Abstract: The epidermal growth factor receptor (EGFR) is overexpressed in many epithelial cancers, an observation often correlated with poor clinical outcome. Overexpression of the EGFR is commonly caused by EGFR gene amplification and is sometimes associated with expression of a variant EGFR (de2-7 EGFR or EGFRvIII) bearing an internal deletion in its extracellular domain. Monoclonal antibody (mAb) 806 is a novel EGFR antibody with significant antitumor activity that recognizes both the de2-7 EGFR and a subset of the wild type (wt) EGFR when overexpressed but does not bind the wt EGFR expressed in normal tissues. Despite only binding to a low proportion of the wt EGFR expressed in A431 tumor cells (approximately 10%), mAb 806 displays robust antitumor activity against A431 xenografts grown in nude mice. To elucidate the mechanism leading to its unique specificity and mode of antitumor activity, we have determined the EGFR binding epitope of mAb 806. Analysis of mAb 806 binding to EGFR fragments expressed either on the surface of yeast or in an immunoblot format identified a disulfide-bonded loop (amino acids 287-302) that contains the mAb 806 epitope. Indeed, mAb 806 binds with apparent high affinity (approximately 30 nm) to a synthetic EGFR peptide corresponding to these amino acids. Analysis of EGFR structures indicates that the epitope is fully exposed only in the transitional form of the receptor that occurs because EGFR changes from the inactive tethered conformation to a ligand-bound active form. It would seem that mAb 806 binds this small proportion of transient receptors, preventing their activation, which in turn generates a strong antitumor effect. Finally, our observations suggest that the generation of antibodies to transitional forms of growth factor receptors may represent a novel way of reducing normal tissue targeting yet retaining antitumor activity.
Gov't Doc #: 15075331
DOI: 10.1074/jbc.M401218200
Type: Journal Article
Subjects: Amino Acid Sequence
Antibodies, Monoclonal.chemistry
Antineoplastic Agents.pharmacology
Blotting, Western
Cell Line
Cell Line, Tumor
Cell Membrane.metabolism
Dose-Response Relationship, Drug
Enzyme-Linked Immunosorbent Assay
Flow Cytometry
Gene Deletion
Genetic Variation
Genetic Vectors
Models, Molecular
Molecular Sequence Data
Protein Binding
Protein Conformation
Protein Structure, Tertiary
Receptor, Epidermal Growth Factor.chemistry.immunology
Signal Transduction
Surface Plasmon Resonance
Time Factors
Appears in Collections:Journal articles

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