| Research Abstract |
We attempted to establish a novel adenovirus-based gene therapy system, in which astrocytoma is targeted. Forthis purpose the Cre recombinase (Cre)/IoxP system together with astrocytoma (06 glioma cell) specific promoter, GEAP promoter, was used. We constructed adenovirus vector (Ad), which expresses Cre under the control of the GFAP promoter (AxGFAPNCre). Another Ad having two switching unit in the vector was constructed. This Ad contains a stuffer sequence encoding GFP (AxCALGLTK) with a functional polyadenylation signal between two IoxP sites under the CAG promoter, and the herpes simplex virus thymidine kinase (HSV-TK) gene is attached downstream. In this system, gene expression of either stuffer sequence (GFP) or downstream gene (TK) is switched on by the co-expression of Cre recombinase. The co-infection of AxGFAPNCre and AxCALGLTK resulted in expression of TK in 06 glioma cells and reactive astrocytes, where as GFP was expressed in other types of cells around the injected site. Likewise the co-infection of AxGFAPNCre resulted in expression of TK in the glioma cells, whereas GFP was expressed in the remaining cell species. Two weeks after the transplantation of 06 glioma into the rat striatum the combination of Ads was injected into the tumor region. The ganciclovir (GCV) administration after the co-infections significantly suppressed the tumor growth and killed the tumor cells, while such significant loss of tumor was not seen in control. The present results suggest that cell-type specific gene therapy using the Cre/IoxP adenovirus system appears working and effective at least against astrocytoma.
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