title: Antibodies specifically targeting a locally misfolded region of tumor associated EGFR.
abstract: Epidermal Growth Factor Receptor (EGFR) is involved in stimulating the growth of many human tumors, but the success of therapeutic agents has been limited in part by interference from the EGFR on normal tissues. Previously, we reported an antibody (mab806) against a truncated form of EGFR found commonly in gliomas. Remarkably, it also recognizes full-length EGFR on tumor cells but not on normal cells. However, the mechanism for this activity was unclear. Crystallographic structures for Fab:EGFR(287-302) complexes of mAb806 (and a second, related antibody, mAb175) show that this peptide epitope adopts conformations similar to those found in the wtEGFR. However, in both conformations observed for wtEGFR, tethered and untethered, antibody binding would be prohibited by significant steric clashes with the CR1 domain. Thus, these antibodies must recognize a cryptic epitope in EGFR. Structurally, it appeared that breaking the disulfide bond preceding the epitope might allow the CR1 domain to open up sufficiently for antibody binding. The EGFR(C271A/C283A) mutant not only binds mAb806, but binds with 1:1 stoichiometry, which is significantly greater than wtEGFR binding. Although mAb806 and mAb175 decrease tumor growth in xenografts displaying mutant, overexpressed, or autocrine stimulated EGFR, neither antibody inhibits the in vitro growth of cells expressing wtEGFR. In contrast, mAb806 completely inhibits the ligand-associated stimulation of cells expressing EGFR(C271A/C283A). Clearly, the binding of mAb806 and mAb175 to the wtEGFR requires the epitope to be exposed either during receptor activation, mutation, or overexpression. This mechanism suggests the possibility of generating antibodies to target other wild-type receptors on tumor cells.
authors.affiliation: Walter and Eliza Hall Institute of Medical Research, Parkville 3050, Australia.
authors.forename: Thomas P J
authors.initials: TP
authors.lastname: Garrett
authors.forename: Antony W
authors.initials: AW
authors.lastname: Burgess
authors.forename: Hui K
authors.initials: HK
authors.lastname: Gan
authors.forename: Rod B
authors.initials: RB
authors.lastname: Luwor
authors.forename: Glenn
authors.initials: G
authors.lastname: Cartwright
authors.forename: Francesca
authors.initials: F
authors.lastname: Walker
authors.forename: Suzanne G
authors.initials: SG
authors.lastname: Orchard
authors.forename: Andrew H A
authors.initials: AH
authors.lastname: Clayton
authors.forename: Edouard C
authors.initials: EC
authors.lastname: Nice
authors.forename: Julie
authors.initials: J
authors.lastname: Rothacker
authors.forename: Bruno
authors.initials: B
authors.lastname: Catimel
authors.forename: Webster K
authors.initials: WK
authors.lastname: Cavenee
authors.forename: Lloyd J
authors.initials: LJ
authors.lastname: Old
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Stockert
authors.forename: Gerd
authors.initials: G
authors.lastname: Ritter
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Adams
authors.forename: Peter A
authors.initials: PA
authors.lastname: Hoyne
authors.forename: Dane
authors.initials: D
authors.lastname: Wittrup
authors.forename: Ginger
authors.initials: G
authors.lastname: Chao
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Cochran
authors.forename: Cindy
authors.initials: C
authors.lastname: Luo
authors.forename: Mezhen
authors.initials: M
authors.lastname: Lou
authors.forename: Trevor
authors.initials: T
authors.lastname: Huyton
authors.forename: Yibin
authors.initials: Y
authors.lastname: Xu
authors.forename: W Douglas
authors.initials: WD
authors.lastname: Fairlie
authors.forename: Shenggen
authors.initials: S
authors.lastname: Yao
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Scott
authors.forename: Terrance G
authors.initials: TG
authors.lastname: Johns
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000627:therapeutic use; D000912:Antibodies, Neoplasm / Q000276:immunology* / Q000627:therapeutic use; D000936:Antigen-Antibody Complex / Q000737:chemistry; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D018360:Crystallography, X-Ray; D000939:Epitopes; D066246:ErbB Receptors / Q000276:immunology*; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009363:Neoplasm Proteins / Q000276:immunology*; D011487:Protein Conformation; D011489:Protein Denaturation / Q000276:immunology; D023041:Xenograft Model Antitumor Assays
chemical_list: D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm; D000936:Antigen-Antibody Complex; D000970:Antineoplastic Agents; D000939:Epitopes; D009363:Neoplasm Proteins; D066246:ErbB Receptors