Noninvasive, repetitive, quantitative measurement of gene expression from a bicistronic message by positron emission tomography, following gene transfer with adenovirus.
Gene therapy protocols are hampered by the inability to monitor the location, magnitude, and duration of ectopic gene expression following DNA delivery. Consequently, it is difficult to establish quantitative correlations and/or causal relationships between therapeutic gene expression and phenotypic responses in treated individuals. One approach to monitor "therapeutic gene" expression indirectly is to incorporate reporter genes that can be imaged in vivo into bicistronic transcription units, along with the therapeutic genes. Expression of the dopamine D2 receptor (D2R) and herpes simplex virus thymidine kinase (HSV1-TK) can both be monitored, in vivo, by positron-emission tomography (PET). We created ad.DTm, an adenovirus containing a cytomegalovirus (CMV) early promoter-driven transcription unit, in which the D2R gene is placed proximal to an encephalomyocarditis virus internal ribosomal entry site (IRES) and a modified HSV1-tk gene is placed distal to the IRES. Following intravenous ad.DTm injection into mice, correlated hepatic D2R and HSV1-sr39tk PET reporter gene expression was demonstrated. Repeated microPET scanning quantitated both D2R-dependent sequestration of a positron-emitting ligand and HSV1-TK-dependent sequestration of a positron-emitting product. It is possible, in living mice, to investigate noninvasively and to measure quantitatively and repeatedly correlated expression of two coding regions from a bicistronic transcription unit over a 3-month period following adenovirus delivery.
Liang
Qianwa
Q
The Crump Institute for Molecular Imaging, UCLA School of Medicine, Los Angeles, California 90095, USA.
Gotts
Jeff
J
Satyamurthy
Nagichettiar
N
Barrio
Jorge
J
Phelps
Michael E
ME
Gambhir
Sanjiv S
SS
Herschman
Harvey R
HR
D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D015870:Gene Expression; D005822:Genetic Vectors; D051379:Mice; D017448:Receptors, Dopamine D2 / Q000235:genetics* / Q000378:metabolism; D018139:Simplexvirus / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics* / Q000378:metabolism; D014055:Tomography, Emission-Computed
D017448:Receptors, Dopamine D2; D013937:Thymidine Kinase