Effect of LiCl on Iodine Kinetics in Thyroid Cancer Cell Lines Transduced by Recombinant Adenovirus Containing Sodium Iodide Symporter(NIS) Gene / 대한내분비학회지

ABSTRACT

BACKGROUND: Lithium is known to increase the retention of iodide in the thyroid gland, or in well differentiated thyroid cancer tissue. The effects of lithium on the function of the sodium iodide symporter (NIS) protein, especially when the lithium is increased in the retention of iodide in NIS-producing cells, the effect of lithium, on the kinetics of undifferentiated thyroid cancer cells transduced by a recombinant adenovirus containing the NIS gene, were checked. METHOD: Human NIS cDNA was inserted into pAxCAwt, a recombinant adenoviral cosmid vector, where the E1 & E2 genes have been deleted, making Rad-hNIS, which was propagated in 293 cells. The iodide uptake was evaluated by the 125I uptake assay in the undifferentiated thyroid cancer cells, ARO, FRO and NPA, following the infection with Rad-hNIS (1 or 10 MOI) in the presence, or absence, of LiCl at optimized concentrations. The iodide efflux was evaluated by the 125I efflux assay, for 1 hour, in the same cells expressing the NIS in the presence, or absence, of LiCl. Similar experiments were performed in the normal thyroid cell line, FRTL-5, cultured in 6H5 media. RESULTS: LiCl, at concentrations over 1.0mM, caused a significant decrease in the cell viability, as evaluated by trypan blue dye exclusion, in a dose dependent manner. When infected with Rad-hNIS, the iodide uptake was not affected by the LiCl in the ARO or NPA cells. However, LiCl(0.1and 1.0mM) increased the iodide uptake by 50 to 100%(vs. control) in the Rad-hNIS transduced FRO cells. In the Rad-hNIS transduced FRO cells, the iodide was released rapidly from the cells, with only 20.7+/-4.8% of the iodide uptake remaining at 1 hour, which was no different in the presence of LiCl (24.5+/-7.9%). The iodide efflux was not affected by the LiCl in the FRTL-5 cells cultured in the presence of TSH. CONCLUSION: These results suggest that the lithium-induced iodide retention in the thyroid gland, or in well differentiated thyroid cancer tissue, is not caused by the effect of the lithium on the NIS function, or the function of proteins or channels, involved in iodide transport via cell membranes. Although the iodide uptake can be markedly increased by the expression of NIS, with the transduction of Rad-hNIS, in undifferentiated thyroid cancer cells, the iodide taken up is rapidly released from the cells. A method for inducing the iodide retention in the cell should be elucidated in order to render the NIS gene therapy effective.