title: Generation and evaluation of bispecific affibody molecules for simultaneous targeting of EGFR and HER2.
abstract: Coexpression of several ErbB receptors has been found in many cancers and has been linked with increased aggressiveness of tumors and a worse patient prognosis. This makes the simultaneous targeting of two surface receptors by using bispecific constructs an increasingly appreciated strategy. Here, we have generated six such bispecific targeting proteins, each comprising two monomeric affibody molecules with specific binding to either of the two human epidermal growth factor receptors, EGFR and HER2, respectively. The bispecific constructs were designed with (i) alternative positioning (N- or C-terminal) of the different affibody molecules, (ii) two alternative peptide linkers (Gly(4)Ser)(3) or (Ser(4)Gly)(3), and (iii) affibody molecules with different affinity (nanomolar or picomolar) for HER2. Using both Biacore technology and cell binding assays, it was demonstrated that all six constructs could bind simultaneously to both their target proteins. N-terminal positioning of the inherent monomeric affibody molecules was favorable to promote the binding to the respective target. Interestingly, bispecific constructs containing the novel (Ser(4)Gly)(3) linker displayed a higher affinity in cell binding, as compared to constructs containing the more conventional linker, (Gly(4)Ser)(3). It could further be concluded that bispecific constructs (but not the monomeric affibody molecules) induced dimer formation and phosphorylation of EGFR in SKBR3 cells, which express fairly high levels of both receptors. It was also investigated whether the bispecific binding would influence cell growth or sensitize cells for ionizing radiation, but no such effects were observed.
authors.affiliation: Department of Radiology, Oncology and Radiation Sciences, Uppsala University, Sweden.
authors.forename: Lina
authors.initials: L
authors.lastname: Ekerljung
authors.forename: Helena
authors.initials: H
authors.lastname: Wållberg
authors.forename: Azita
authors.initials: A
authors.lastname: Sohrabian
authors.forename: Karl
authors.initials: K
authors.lastname: Andersson
authors.forename: Mikaela
authors.initials: M
authors.lastname: Friedman
authors.forename: Fredrik Y
authors.initials: FY
authors.lastname: Frejd
authors.forename: Stefan
authors.initials: S
authors.lastname: Ståhl
authors.forename: Lars
authors.initials: L
authors.lastname: Gedda
mesh_terms: D018033:Antibodies, Bispecific / Q000737:chemistry / Q000276:immunology*; D015153:Blotting, Western; D002460:Cell Line; D004797:Enzyme-Linked Immunosorbent Assay; D066246:ErbB Receptors / Q000276:immunology*; D006801:Humans; D010766:Phosphorylation; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology*; D020349:Surface Plasmon Resonance
chemical_list: D018033:Antibodies, Bispecific; D066246:ErbB Receptors; D018719:Erb-b2 Receptor Tyrosine Kinases