Non-invasive gamma camera imaging of gene transfer using an adenoviral vector encoding an epitope-tagged receptor as a reporter.
A model epitope-tagged receptor was constructed by fusing the hemagglutinin (HA) sequence on the extracellular N-terminus of the human somatostatin receptor subtype 2 (hSSTr2) gene. This construct was placed in an adenoviral (Ad-HAhSSTr2) vector. This study evaluated Ad-HAhSSTr2 in vitro and in vivo using FACS, fluorescent microscopy, radioactive binding assays, and gamma camera imaging techniques. Infection of A-427 non-small cell lung cancer cells with Ad-HAhSSTr2 or Ad-hSSTr2 resulted in similar expression of hSSTr2 by FACS analysis and binding assays using a (99m)Tc-labeled somatostatin analogue ((99m)Tc-P2045). HAhSSTr2 expression in A-427 cells was specific for infection with Ad-HAhSSTr2. FITC-labeled anti-HA antibody (FITC-HA) confirmed surface expression in live A-427 cells and the absence of internalization. Gamma camera imaging and gamma counter analysis of normal mice showed significantly greater (P<0.05) liver uptake of (99m)Tc-labeled anti-HA antibody ((99m)Tc-anti-HA) in mice injected i.v. 48 h earlier with Ad-HAhSSTr2 (53.6+/-6.9% ID/g) as compared to mice similarly injected with Ad-hSSTr2 (9.0+/-1.3% ID/g). In a mouse tumor model, imaging detected increased tumor localization of (99m)Tc-anti-HA due to direct intratumor injection Ad-HAhSSTr2. Gamma counter analysis confirmed significantly greater (P<0.05) uptake of (99m)Tc-anti-HA in tumors injected with Ad-HAhSSTr2 (12.5+/-4.1% ID/g) as compared to Ad-hSSTr2-infected tumors (5.1+/-1.5% ID/g). These studies demonstrate the feasibility of using an epitope-tagged reporter receptor for non-invasively imaging gene transfer.
Rogers
B E
BE
Department of Radiation Oncology, University of Alabama at Birmingham, 1825 6th Avenue South, WT1 674, Birmingham, AL 35294, USA.
Chaudhuri
T R
TR
Reynolds
P N
PN
Della Manna
D
D
Zinn
K R
KR
D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D002460:Cell Line; D000939:Epitopes / Q000235:genetics; D005260:Female; D005434:Flow Cytometry; D017930:Genes, Reporter; D005818:Genetic Engineering; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000008:administration & dosage* / Q000235:genetics; D006388:Hemagglutinins / Q000235:genetics*; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D018613:Microscopy, Confocal; D009374:Neoplasms, Experimental / Q000000981:diagnostic imaging / Q000378:metabolism; D011877:Radionuclide Imaging; D017481:Receptors, Somatostatin / Q000235:genetics*; D014161:Transduction, Genetic / Q000379:methods*
D000939:Epitopes; D006388:Hemagglutinins; D017481:Receptors, Somatostatin