PT - JOURNAL ARTICLE AU - Buursma, Anne Rixt AU - Beerens, Antoine M.J. AU - de Vries, Erik F.J. AU - van Waarde, Aren AU - Rots, Marianne G. AU - Hospers, Geke A.P. AU - Vaalburg, Willem AU - Haisma, Hidde J. TI - The Human Norepinephrine Transporter in Combination with <sup>11</sup>C-<em>m</em>-Hydroxyephedrine as a Reporter Gene/Reporter Probe for PET of Gene Therapy DP - 2005 Dec 01 TA - Journal of Nuclear Medicine PG - 2068--2075 VI - 46 IP - 12 4099 - http://jnm.snmjournals.org/content/46/12/2068.short 4100 - http://jnm.snmjournals.org/content/46/12/2068.full SO - J Nucl Med2005 Dec 01; 46 AB - Although the herpes simplex virus thymidine kinase gene has been frequently applied as a reporter gene for monitoring gene transfection in animals, it has some intrinsic limitations for use in humans. In our search for a reporter gene that lacks these limitations, we have evaluated the feasibility of the human norepinephrine transporter (hNET) as a reporter gene in combination with the reporter probe 11C-m-hydroxyephedrine (mHED) for PET. Methods: An adenoviral vector (AdTrack-hNET) containing the hNET gene as reporter gene and the enhanced green fluorescent protein (EGFP) as a substitute for a therapeutic gene was constructed. After COS-7, A2780, and U373 cells were transiently transduced with AdTrack-hNET, hNET protein expression, EGFP fluorescence, and cellular uptake of 11C-mHED were determined. In rats, U373 tumor xenografts were grown and transiently transduced with either AdTrack-hNET or an AdTrack-Luc control adenovirus. Intratumoral accumulation of 11C-mHED was determined by PET and ex vivo biodistribution. The tumors were subsequently examined for EGFP fluorescence. Results: 11C-mHED uptake was positively correlated with AdTrack-hNET viral titer and hNET protein expression. However, large differences in transfection efficiency between cell lines were observed. The highest 11C-mHED uptake was found in hNET transfected U373 cells, in which tracer uptake was &gt;70-fold higher than that in control cells. 11C-mHED accumulation could be inhibited by desipramine, a potent inhibitor of hNET. In all cell lines, 11C-mHED uptake was positively correlated with EGFP fluorescence, implying that imaging of hNET with 11C-mHED would enable monitoring of a coexpressed therapeutic gene. In the animal model, gene transfection efficiencies were very low, as determined by EGFP fluorescence. Still, a significantly higher 11C-mHED uptake in hNET transduced tumors than that in control tumors was demonstrated by ex vivo biodistribution studies. PET with a clinical camera could visualize 1 of 3 hNET transduced tumors, indicating that the transfection efficiency was near the detection limit. Conclusion: These results indicate that monitoring of gene therapy using the hNET/11C-mHED reporter gene/probe is feasible, but further investigation with regard to the sensitivity of the technique is required.