A comparative study of affibody, panitumumab, and EGF for near-infrared fluorescence imaging of EGFR- and EGFRvIII-expressing tumors

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
• tumor
• in vivo imaging
• near-infrared
• fluorescence

10.4161/cbt.26719

Disclosure of Potential Conflicts of Interest

During these studies H.G., J.L.K., L.C., and D.M.O. were employees at LI-COR Biosciences.

Acknowledgments

We thank Affibody AB for providing affibody molecules and Dr Paul van Bergen en Henegouwen (Utrecht University) for providing nanobody 7D12. We also thank Drs Amy Schutz-Geschwender, Nisha Padhye, and Teresa Urlacher for critical reading of the manuscript.

Supplemental Materials

Supplemental materials may be found here:

http://www.landesbioscience.com/journals/cbt/article/26719/