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Evaluation of two internalizing carcinoembryonic antigen reporter genes for molecular imaging.

  • Author(s): Barat, Bhaswati
  • Kenanova, Vania E
  • Olafsen, Tove
  • Wu, Anna M
  • et al.
Abstract

PURPOSE:The objective of this article is to develop internalizing positron emission tomography (PET) reporter genes for tracking genetically modified T cells in vivo. PROCEDURES:The transmembrane and cytoplasmic domains of the human transferrin receptor (TfR) and CD5 were each fused to the carcinoembryonic (CEA) minigene N-A3 and expressed in Jurkat T cells. Internalization was evaluated by confocal microscopy or by intracellular uptake of ¹²⁵I-labeled anti-CEA scFv-Fc. Reporter gene-transfected Jurkat xenografts in mice were analyzed by immunohistochemistry (IHC) and imaged by PET using ¹²⁴I- or ⁶⁴Cu-scFv-Fc as tracers. RESULTS:Surface expression of TR(1-99)-NA3 was lower than that of NA3-CD5. Both reporter genes were internalized following binding of the anti-CEA antibody fragment. IHC of tumors showed strong staining of NA3-CD5, whereas TR(1-99)-NA3 stained weakly. Specific targeting of TR(1-99)-NA3 or NA3-CD5 was shown by PET in xenografted mice. CONCLUSIONS:The in vivo imaging studies suggest a potential application of the internalizing form of CEA (N-A3) as a PET reporter gene.

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