Evaluation of two internalizing carcinoembryonic antigen reporter genes for molecular imaging.
OBJECTIVE
The objective of this article is to develop internalizing positron emission tomography (PET) reporter genes for tracking genetically modified T cells in vivo.


METHODS
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.
Barat
Bhaswati
B
Crump Institute for Molecular Imaging, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Box 951770, 570 Westwood Plaza, Los Angeles, CA, 90095-1770, USA.
Kenanova
Vania E
VE
Crump Institute for Molecular Imaging, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Box 951770, 570 Westwood Plaza, Los Angeles, CA, 90095-1770, USA.
Olafsen
Tove
T
Crump Institute for Molecular Imaging, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Box 951770, 570 Westwood Plaza, Los Angeles, CA, 90095-1770, USA.
Wu
Anna M
AM
Crump Institute for Molecular Imaging, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Box 951770, 570 Westwood Plaza, Los Angeles, CA, 90095-1770, USA. awu@mednet.ucla.edu.
D000818:Animals; D002272:Carcinoembryonic Antigen / Q000235:genetics* / Q000378:metabolism; D004705:Endocytosis; D005260:Female; D005434:Flow Cytometry; D017930:Genes, Reporter / Q000235:genetics*; D006801:Humans; D007128:Immunoglobulin Fragments; D007150:Immunohistochemistry; D019169:Jurkat Cells; D051379:Mice; D008819:Mice, Nude; D057054:Molecular Imaging / Q000379:methods*; D049268:Positron-Emission Tomography; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D023041:Xenograft Model Antitumor Assays
D002272:Carcinoembryonic Antigen; D007128:Immunoglobulin Fragments; D011994:Recombinant Proteins