Survivin a radiogenetic promoter for glioblastoma viral gene therapy independently from CArG motifs

George E Naoum,Donald J Buchsbaum,David T Curiel,Zeng B Zhu,Waleed O Arafat

doi:10.1186/s40169-017-0140-y

Abstract

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

Highlights

Radiogenetic therapy is a novel approach in the treatment of cancer, which employs genetic modification to alter the sensitivity of tumor cells to the effect of applied radiation
Survivin is a selective potent radiation inducible promoter for glioblastoma viral gene therapy and this response to radiation could be independent of CArG motifs
The aim of this study is to investigate and select the best radiation inducible promoter in the context of viral brain tumors therapy

Summary

Introduction

Radiogenetic therapy is a novel approach in the treatment of cancer, which employs genetic modification to alter the sensitivity of tumor cells to the effect of applied radiation. Brain tumor gliomas are among the most aggressive of human malignancies. In this regard, the molecular and genetic basis underlying pathogenesis and treatment resistance of these tumors. An important mediator of both tumorigenesis and resistance to treatment involves inhibition of apoptosis [7]. Survivin has been characterized as an important member of the inhibitor of apoptosis family, with a very complex biology that has not been fully understood yet [8]. It has been found to be abundantly expressed in a wide variety of human malignancies, including brain tumors [9]

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