Glial fibrillary acidic protein promoters directed sodium iodide symporter expression in malignant gioma radioiodine therapy

Abstract

Objective To fred the possibility that the glial fibrillary acidic protein （GFAP） promoters modulate the human sodium iodide symporter （hNIS） expression in glioma and lead transecting hNIS gene into glioma cells for radioactive iodide treatment. Methods PGL3-Basic, PGL3-Control and PGL3-GFAP plasmids were transfected into U251, U87 and MRC-5 cells, respectively, with the help of liposome Lipofectamine 2000; 24 h after that, the reactivity of these cells was detected and the efficiency of GFAP promoter was tested under chemiluminescence apparatus. Recombinant adenovirus vector Ad-GFAP-hNIS in which GFAPpromoter could modulate the hNIS gene expression was constructed, and then, the vector was transfected into the U251, U87 and MRC-5 cells; Western blotting was employed to detect the protein expressions of GFAP and hN1S. Ad-CMV-EGFP group （blank control） and Ad-CMV-hNIS group （negative control） and Ad-GFAP-hNIS group were employed; the 131I uptake and effiux abilities and the cell amount after gentian violet staining in the three groups were measured by counter; the clonogenecity rate of them was calculated. BALB/c female nude mice （n=20） was divided into four groups： group of injecting Ad-GFAP-hNIS without ~31I, group of injecting Ad-GFAP-hNIS with 131I, group of injecting Ad-CMV-EGFP without 13q and group of injecting Ad-CMV-EGFP with 131I （n=5）; U87 cells were transfected into the nude mice, and then, the tumor growth was observed and the life cycle of the mice was noted. Nude mice bearing the U87 tumors were injected Ad-GFAP-hNIS and Ad-CMV-EGFP, followed by 1mCi ^99TcO4 via intraperitoneal injection; single photon emission computed tomography （SPECT） was performed. Results As compared with that of cells being transfected with PGL3-blank plasmid, the relative reactivity of U251 and U87 cells being transfected with PGL3-GFAP plasmid was decreased with significant difference （P〈0.05）. Western blotting revealed GFAP and hNIS proteins in U87 and U251 cells. 125I uptake of U87 and U251 cells after Ad-GFAP-hNIS transfection increased 69.5 and 70.8 times; the 125I effective half-life was shortened. The cloning efficiency of U87 cells being transfected with Ad-GFAP-hNIS was （9.31±0.50）% and （9.33±1.15）%, respectively, which was significantly higher than that of U87 cells being transfected with Ad-CMV-EGFP and Ad-CMV-hNIS （P〈0.05）. After treatment with 131I and injection of Ad-GFAP-hNIS, the survival of U87 tumor loading nude mice were prolonged most （44.00±0.58 d）. Cells in the Ad-GFAP-hNIS group could uptake the radionuclide, while those in the Ad-CMV-EGFP could not. Conclusion The gliomas after Ad-GFAP-hNIS transfection can uptake iodine and also effectively direct radioactive iodine therapy. Key words: Glioma; Sodium iodide symporter; Glial fibrillary acidic protein promoter; Radioiodine therapy