Recombinant carcinoembryonic antigen as a reporter gene for molecular imaging

  • Vania Kenanova
  • Bhaswati Barat
  • Tove Olafsen
  • Arion Chatziioannou
  • Harvey R. Herschman
  • Jonathan Braun
  • Anna M. Wu
Original Article

DOI: 10.1007/s00259-008-0921-z

Cite this article as:
Kenanova, V., Barat, B., Olafsen, T. et al. Eur J Nucl Med Mol Imaging (2009) 36: 104. doi:10.1007/s00259-008-0921-z

Abstract

Purpose

Reporter genes can provide a way of noninvasively assessing gene activity in vivo. However, current reporter gene strategies may be limited by the immunogenicity of foreign reporter proteins, endogenous expression, or unwanted biological activity. We have developed a reporter gene based on carcinoembryonic antigen (CEA), a human protein with limited normal tissue expression.

Methods

To construct a CEA reporter gene for PET, a CEA minigene (N-A3) was fused to the extracellular and transmembrane domains of the human FcγRIIb receptor. The NA3-FcγRIIb recombinant gene, driven by a CMV promoter, was transfected in Jurkat (human T cell leukemia) cells. Expression was analyzed by flow cytometry, immunohistochemistry (IHC), and microPET imaging.

Results

Flow cytometry identified Jurkat clones stably expressing NA3-FcγRIIb at low, medium, and high levels. High and medium NA3-FcγRIIb expression could also be detected by Western blot. Reporter gene positive and negative Jurkat cells were used to establish xenografts in athymic mice. IHC showed staining of the tumor with high reporter gene expression; medium and low N-A3 expression was not detected. MicroPET imaging, using an anti-CEA 124I-labeled single-chain Fv-Fc antibody fragment, demonstrated that only high N-A3 expression could be detected. Specific accumulation of activity was visualized at the N-A3 positive tumor as early as 4 h. MicroPET image quantitation showed tumor activity of 1.8 ± 0.2, 15.2 ± 1.3, and 4.6 ± 1.2 percent injected dose per gram (%ID/g) at 4, 20, and 48 h, respectively. Biodistribution at 48 h demonstrated tumor uptake of 4.8 ± 0.8%ID/g.

Conclusion

The CEA N-A3 minigene has the potential to be used as a reporter gene for imaging cells in vivo.

Keywords

T cells CEA reporter gene Jurkat xenograft 124I-labeled scFv-Fc antibody fragment MicroPET/microCT imaging 

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Vania Kenanova
    • 1
  • Bhaswati Barat
    • 1
  • Tove Olafsen
    • 1
  • Arion Chatziioannou
    • 1
  • Harvey R. Herschman
    • 1
  • Jonathan Braun
    • 2
  • Anna M. Wu
    • 1
  1. 1.Crump Institute for Molecular Imaging, Department of Molecular and Medical PharmacologyDavid Geffen School of Medicine at the University of California Los AngelesLos AngelesUSA
  2. 2.Department of Pathology and Laboratory MedicineDavid Geffen School of Medicine at the University of California Los AngelesLos AngelesUSA

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