European Journal of Nuclear Medicine and Molecular Imaging

, Volume 37, Issue 10, pp 1926–1934

Rapid optical imaging of EGF receptor expression with a single-chain antibody SNAP-tag fusion protein

  • Florian Kampmeier
  • Judith Niesen
  • Alexander Koers
  • Markus Ribbert
  • Andreas Brecht
  • Rainer Fischer
  • Fabian Kießling
  • Stefan Barth
  • Theo Thepen
Original Article

DOI: 10.1007/s00259-010-1482-5

Cite this article as:
Kampmeier, F., Niesen, J., Koers, A. et al. Eur J Nucl Med Mol Imaging (2010) 37: 1926. doi:10.1007/s00259-010-1482-5

Abstract

Purpose

The epidermal growth factor receptor (EGFR) is overexpressed in several types of cancer and its inhibition can effectively inhibit tumour progression. The purpose of this study was to design an EGFR-specific imaging probe that combines efficient tumour targeting with rapid systemic clearance to facilitate non-invasive assessment of EGFR expression.

Methods

Genetic fusion of a single-chain antibody fragment with the SNAP-tag produced a 48-kDa antibody derivative that can be covalently and site-specifically labelled with substrates containing 06-benzylguanine. The EGFR-specific single-chain variable fragment (scFv) fusion protein 425(scFv)SNAP was labelled with the near infrared (NIR) dye BG-747, and its accumulation, specificity and kinetics were monitored using NIR fluorescence imaging in a subcutaneous pancreatic carcinoma xenograft model.

Results

The 425(scFv)SNAP fusion protein accumulates rapidly and specifically at the tumour site. Its small size allows efficient renal clearance and a high tumour to background ratio (TBR) of 33.2 ± 6.3 (n = 4) 10 h after injection. Binding of the labelled antibody was efficiently competed with a 20-fold excess of unlabelled probe, resulting in an average TBR of 6 ± 1.35 (n = 4), which is similar to that obtained with a non-tumour-specific probe (5.44 ± 1.92, n = 4). When compared with a full-length antibody against EGFR (cetuximab), 425(scFv)SNAP-747 showed significantly higher TBRs and complete clearance 72 h post-injection.

Conclusion

The 425(scFv)SNAP fusion protein combines rapid and specific targeting of EGFR-positive tumours with a versatile and robust labelling technique that facilitates the attachment of fluorophores for use in optical imaging. The same approach could be used to couple a chelating agent for use in nuclear imaging.

Keywords

Single-chain antibodyhAGT (SNAP)-tagNIR optical imagingSite-specific labellingMolecular imagingTumour targeting

Abbreviations

hAGT

Human O6-alkyl-DNA alkyltransferase

NIR

Near infrared

scFv

Single-chain variable fragment

EGFR

Epidermal growth factor receptor 1

BG

Benzylguanine

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Florian Kampmeier
    • 1
  • Judith Niesen
    • 1
  • Alexander Koers
    • 1
  • Markus Ribbert
    • 1
  • Andreas Brecht
    • 2
  • Rainer Fischer
    • 1
    • 3
  • Fabian Kießling
    • 4
  • Stefan Barth
    • 1
    • 5
  • Theo Thepen
    • 1
  1. 1.Fraunhofer Institute for Molecular Biology and Applied EcologyAachenGermany
  2. 2.Covalys Biosciences AGWitterswilSwitzerland
  3. 3.Institute for Molecular BiotechnologyRWTH Aachen UniversityAachenGermany
  4. 4.Department of Experimental Molecular Imaging, Medical FacultyRWTH Aachen UniversityAachenGermany
  5. 5.Department of Experimental Medicine and Immunotherapy, Helmholtz Institute for Biomedical EngineeringRWTH Aachen UniversityAachenGermany