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To investigate human sodium/iodide symporter (hNIS) induced iodine uptake in human lung adeno- carcinoma via baculovirus, a recombinant baculovirus encoding hNIS gene was constructed under the control of CMV promoter (Bac-CMV-hNIS). In vitro, baculovirus infected A549 cells accumulated about 27 times more 125I than that of noninfected cells. The 125I uptake was maximal after 30-min incubation of the cells, and efflux of the radioactivity was rapid, with 50% lost during the first 2 min after 125I-containing medium had been replaced by nonradioactive medium. Competition experiments in the presence of sodium perchlorate revealed a dose-dependent decrease of 125I uptake. Bac-CMV-hNIS infected tumor cells were selectively killed by exposure to 131I, as revealed by clonogenic assays. In nude mice, Bac-CMV-hNIS infected A549 cells accumulated more 131I than that of the control monitored by 1-h scintigraphy after 131I administration. The transduction of hNIS gene through baculovirus is sufficient to induce iodine transporting in A549 cells in vitro and in vivo, outlining the potential of this novel tumor gene imaging approach. But a rapid efflux of radioactivity from the tumor was shown in vivo and the in vivo therapy test showed no sign of effect.