A Comparative Study of Affibody, Panitumumab, and EGF for Near-Infrared Fluorescence Imaging of EGFR- And EGFRvIII-expressing Tumors

Cancer Biol Ther. 2014 Feb;15(2):185-93. doi: 10.4161/cbt.26719. Epub 2013 Nov 1.

Abstract

Aberrant overexpression and/or activation of epidermal growth factor receptor (EGFR) is associated with many types of cancers. EGFR variant III (EGFRvIII) is a common in-frame deletion mutant, which lacks a large part of the extracellular portion (exons 2-7), including components of the ligand-binding domain. Although EGFR has been extensively studied as a molecular imaging target, information about EGFRvIII-targeted molecular imaging is lacking. In this study, the EGFR-specific affibody, therapeutic antibody panitumumab, and ligand EGF were labeled with IRDye 800CW (Ex/Em: 774/789 nm), yielding Aff800, Pan800, and EGF800, respectively. The binding affinities of the labeled agents were compared in cell-based assays using a rat glioma cell line F98 parental (F98-p) lacking EGFR expression, and 2 F98-derived transgenic cell lines expressing EGFR or EGFRvIII (designated as F98-EGFR and F98-vIII, respectively). Results showed that all agents could bind to F98-EGFR, with Pan800 having the highest binding affinity, followed by Aff800 and EGF800. Pan800 and Aff800, but not EGF800, also bound to F98-vIII. In vivo animal imaging demonstrated that compared with F98-p tumors, F98-EGFR tumors generated higher signals with all three agents. However, in the case of F98-vIII, only Pan800 and Aff800 signals were higher. Analysis of tissue lysates showed that a large portion of Pan800 was degraded into small fragments in F98-EGFR and F98-vIII tumors, possibly due to proteolytic digestion after its specific binding and internalization. In conclusion, Pan800 and Aff800 could be used as imaging agents for both wild-type EGFR and EGFRvIII, whereas EGF800 only targets wild-type EGFR.

Keywords: epidermal growth factor receptor; fluorescence; in vivo imaging; near-infrared; tumor.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Antibodies, Monoclonal / chemistry*
  • Benzenesulfonates / chemistry
  • Binding, Competitive
  • Cell Line, Tumor
  • Epidermal Growth Factor / chemistry*
  • ErbB Receptors / immunology
  • ErbB Receptors / metabolism*
  • Fluorescent Dyes
  • Heterografts
  • Humans
  • Indoles / chemistry
  • Mice
  • Molecular Imaging
  • Optical Imaging
  • Panitumumab
  • Rats
  • Rats, Inbred F344

Substances

  • Antibodies, Monoclonal
  • Benzenesulfonates
  • Fluorescent Dyes
  • IRDye 800CW
  • Indoles
  • epidermal growth factor receptor VIII
  • Epidermal Growth Factor
  • Panitumumab
  • ErbB Receptors