No single engineered protein has been shown previously to robustly downregulate epidermal growth factor receptor (EGFR), a validated cancer target. A panel of fibronectin-based domains was engineered to bind with picomolar to nanomolar affinity to multiple epitopes of EGFR. Monovalent and homo-and hetero-bivalent dimers of these domains were tested for EGFR downregulation. Selected orientations of non-competitive heterodimers decrease EGFR levels by up to 80 in multiple cell types, without activating receptor signaling. These heterodimers inhibit autophosphorylation, proliferation and migration, and are synergistic with the monoclonal antibody cetuximab in these activities. These small (25 kDa) heterodimers represent a novel modality for modulating surface receptor levels.
Bibliographical noteFunding Information:
The work was supported by the National Institutes of Health grant CA96504 (K.D.W), grant CA118705 (F.M.W.), and National Science Foundation Graduate Fellowship (B.J.H.). Steve Sazinsky produced the EGFR ectodo-main. Jamie Spangler performed quantification of surface EGFR levels.
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