Influence of introducing SLC22A18 gene on the radiosensitivity of human glioma U251 cells

Objective:To study the effect of SLC22A18 gene on the radiosensitivity of human glioma U251 cells.Methods:The eukaryotic expression plasmid pIRES2-EGFP-SLC22A18 was constructed and introduced by Lipofectamine 2000 into cultured U251 cells.SLC22A18 mRNA and protein expression was detected by RT-PCR and Western blot assay.U251 cells were divided into 4 groups:control group,transfected group,radiation group and combined treatmemt group.The number of colonies was assessed using a clonogenic assay.The cell growth inhibitition and apoptosis was assessed by MTT and flow cytometry.The tumor growth inhibition effect was further studied in vivo.The pIRES2-SLC22A18 was injected iniratumorally into established subcutaneous U251 glioma in nude mice mediated by Lipofectamine 2000.Results:The transfection of SLC22A18 gene into U251 cells was confirmed by RT-PCR and Western blot assay.The number of colonies was assessed using a clonogenic assay in the transfected group(60.6 ± 5.2).That induced by radiation was decreased [(30.0 ± 3.6),(13.0 ± 3.0),(4.0 ± 1.0) ]with the increase of radiation doses(3,6,9 Gy).MTT showed that SLC22A18 gene by itself induced strong inhibition effect on the growth of U251 cells [inhibition rate,IR(80.12 ± 5.75) ].The killing effect of radiation by itself on U251 cells was not strong [IR(17.05 ± 4.24) %,(17.34 ± 1.62) %,(18.71 ± 4.59) %]and increased with the increase of radiation doses(3,6,9 Gy).When combined treatment of SLC22A18 gene transfection and radiation was used,that was significantly increased [IR(81.45 ± 5.32) %,(90.45 ± 1.65) %,(92.62 ± 2.12) %].The apoptotic rate of U251 cells induced by SLC22A18 gene transfection was 17.68%.That induced by radiation was increased(4.64%,4.87%,5.42%) with the increase of radiation doses(3,6,9 Gy).The apoptotic rate was also significantly increased(18.42%,21.48%,23.92%) after combined treatment of SLC22A18 and radiation with different doses(3,6,9 Gy).The antitumor enhancement ratio of SLC22A18 at 6 Gy was 1.81 for U251 cells in vivo.Conclusion:Introduction of SLC22A18 gene into human glioma U251 cells can increase their radiosensitivity.