The role of human sodium iodide symporter as a reporter gene in molecular imaging.

摘要

The human sodium iodide symporter (hNIS) is a recently cloned gene that encodes the protein responsible for thyroidal iodide uptake. Upon transfection with hNIS cDNA, non-thyroid cells gain the ability to accumulate halide and pseudohalide ions. In this study, we investigated the role of hNIS as a reporter gene to quantitatively measure gene transfer and expression in a non-invasive manner.; NIS-expressing adenoviruses (Ad-hNIS) were delivered in vitro to MDA-MB-435 breast carcinoma cells. NIS-mediated accumulation of 125I-, 99mTcO 4-, 124I- and 76 Br- by the cells was imaged using autoradiography, gamma camera scintigraphy, and PET imaging respectively. The results showed that hNIS-mediated cellular accumulation of radionuclide was clearly visualized and quantifiable by all three imaging modalities tested. Signal intensity generated by the cells correlated linearly with both the amount of Ad-hNIS and with the activity of radionuclide.; To non-invasively evaluate in vivo pulmonary gene transfer and expression in real time, Ad-hNIS was instilled into the lungs of Cotton rats via nostril. 99mTcO4-Gamma camera scintigraphy and 124I-PET imaging were performed to measure the distribution and duration of gene transfer. To extend the results to human cells, hNIS transfer to a polarized human airway epithelial cell layer was also evaluated by phosphorimaging. The results showed that lungs in animals infected with Ad-hNIS were clearly visible on both scintigraph and PET scans. In addition, polarized human airway epithelial cells showed increasing signal intensity with increasing Ad-hNIS titer, indicating the translational potential of this strategy to clinical applications.; To image p53 and MnSOD gene transfer non-invasively, we constructed radiologically detectable dual expressing adenoviral vectors with hNIS as the reporter gene. Cells tranduced with the dual expressing vectors expressed both hNIS and the therapeutic genes at high levels determined by real time RT-PCR, western blot and iodide uptake assay. There was a close relationship between hNIS activity and therapeutic gene expression. After intratumoral injection of adenoviruses, successful gene transfer and hNIS expression was detected by 99mTcO4 - gamma camera scintigraphy. Radiological detection of hNIS derived from dual expressing adenoviral vectors is a highly effective method to monitor therapeutic gene transfer and expression in vivo in a non-invasive manner.