Improvement of radioiodine accumulation in non-thyroidal tumors by transfecting the sodium iodide symporter (NIS) gene has been successfully investigated in many studies. However, regarding the uncertain iodine influx and efflux efficiencies in different cells, the optimal imaging time by radioiodine following NIS gene transport remains unclear. This study aimed to investigate the serial expression of NIS under control of survivin promoter in prostate cancer PC-3 cells and xenografts by adenoviral vector (Ad-Sur-NIS), and determine the optimal imaging time for radioiodine application. In vitro, the 125I accumulation in Ad-Sur-NIS-infected PC-3 cells was 44 times higher than that in control cells (P<0.05). Moreover, the expression efficiency of NIS reached a peak at 48 h post transfection, at which a 1.9-fold or 1.4-fold increase of 125I accumulation was found compared with 24 h or 72 h. In the clonogenic assay, the cell inhibition rates induced by 131I were 93.4 ± 11.2% in Ad-Sur-NIS and 71.8 ± 10.1% in Ad-NIS infected cells, both of which were significantly higher than that in Ad-Sur-GFP infected cells (10.9 ± 1.9%, P<0.05). In in vivo studies, the 131I uptake of tumor-to-muscle ratios were more prominent on day 2 (15.23 ± 4.55) and day-9 (9.78 ± 2.34) compared to the day 16 (1.29 ± 0.49), which showed a gradual reduction (P<0.05). Therefore, the Ad-Sur-NIS transfection allowed PC-3 tumor imaging by iodine-131 with an optimal time no later than 9 days post-transfection.
Keywords: Prostate carcinoma; radioiodine imaging; sodium iodide symporter; survivin.
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