Background: Radiogenetic therapy is a novel approach in the treatment of cancer, which employs genetic modification\nto alter the sensitivity of tumor cells to the effect of applied radiation.\nAim: To select a potent radiation inducible promoter in the context of brain tumors and to investigate if CArG radio\nresponsive motifs or other elements in the promoter nucleotide sequences can correlate to its response to radiation.\nMethods: To select initial candidates for promoter inducible elements, the levels of mRNA expression of six different\npromoters were assessed using Quantitative RTPCR in D54 MG cells before and after radiation exposure. Recombinant\nAd/reporter genes driven by five different promoters; CMV, VEGF, FLT-1, DR5 and survivin were constructed.\nGlioma cell lines were infected with different multiplicity of infection of the (promoter) Ad or CMV Ad. Cells were then\nexposed to a range of radiation (0ââ?¬â??12 Gy) at single fraction. Fluorescent microscopy, Luc assay and X-gal staining was\nused to detect the level of expression of related genes. Different glioma cell lines and normal astrocytes were infected\nwith Ad survivin and exposed to radiation. The promoters were analyzed for presence of CArG radio-responsive motifs\nand CCAAT box consensus using NCBI blast bioinformatics software.\nResults: Radiotherapy increases the expression of gene expression by 1.25ââ?¬â??2.5 fold in different promoters other\nthan survivin after 2 h of radiation. RNA analysis was done and has shown an increase in copy number of tenfold for\nsurvivin. Most importantly cells treated with RT and Ad Luc driven by survivin promoter showed a fivefold increase in\nexpression after 2 Gy of radiation in comparison to non-irradiated cells. Presence or absence of CArG motifs did not\ncorrelate with promoter response to radiation. Survivin with the best response to radiation had the lowest number of\nCCAAT box.\nConclusion: Survivin is a selective potent radiation inducible promoter for glioblastoma viral gene therapy and this\nresponse to radiation could be independent of CArG motifs.
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