In vivo long-term imaging and radioiodine therapy by sodium-iodide symporter gene expression using a lentiviral system containing ubiquitin C promoter

To establish stable and long-term gene expression in vitro and in vivo, we developed a lentiviral vector system carrying sodium iodide symporter (hNIS) gene under UbC promoter, and transfected this into a colon cancer cell line. The in vitro and in vivo kinetics of radioiodine and [^99mTc]- pertechnetate were then investigated, and the therapeutic effect of I-131 was evaluated in this system. The hNIS gene was transferred into CT26 cells using lentivirus containing UbC promoter. In vitro iodide uptake and efflux were measured in CT26-hNIS cells at various time points. In addition, scintigraphic images were acquired at 30 min after injecting [^99mTc]-pertechnetate i.p. into Balb/C mice for 27 days after CT26-hNIS induction. Biodistribution studies were performed at 10 and 30 min and at 1.5, 6 and 24 h after [ ^99mTc]-pertechnetate injections, and the therapeutic effects of radioiodine were investigated by measuring tumor size using a caliper or by quantifying tumor radioactivity levels in scintigraphic images. The iodide uptakes of CT26-hNIS tumors were 10-fold greater than those of CT26 tumors. In addition, iodide uptake was completely blocked by 100 μM potassium perchlorate. The accumulation of [^99mTc]-pertechnetate in hNIS expressing tumor cells was found to be positively related to tumor growth. In biodistribution studies, the %ID/g values of CT26-hNIS were 84.0 ± 4.5 at 1.5 h and 40.8 ± 3.9 at 24 h and these were approximately 60 times greater than those of CT26 at these time points. Tumor growth in mice treated with 131I was retarded until 46 days post-tumor challenge. The devised lentiviral vector system carrying hNIS controlled by UbC promoter was found to be suitable for the long-term monitoring and radionuclide therapy of cancer in living organism.