| Summary: | 碩士 === 國立中正大學 === 分子生物研究所 === 95 === Murine leukemia virus (MLV)-based replicating retroviral vectors used for cancer gene therapy are previously proven to be effective, highly stable, tumor-selective, and persistent. Recently, the gene-directed enzyme prodrug therapy (GDEPT) is a widely used approach to increase drug selectivity towards cancer cells. In this investigation, we employed replicating retroviral vectors carrying suicide genes, yeast cytosine deaminase (yCD) and yeast uracil phosphoribosyl transferase (yUPRT), as therapeutic agents for the treatment of liver and brain tumors. First, we compared the gene transfer efficiency of the three replicating retroviral vectors, such as ACE (modified from amphotropic murine leukemia virus, MLV), GS (modified from Gibbon ape leukemia virus, GaLV), and MSA (a hybrid vector containing MLV genome but GaLV’s envelope) vectors, carrying GFP gene as marker, and tried to find out which vector could mediate efficient gene delivery in tumor cells. Our flow-cytometric analysis showed that all of these viral vectors mediated efficient gene delivery in tumor cells, but ACE and GS vectors could mediate better replicative spread. Next, we used ACE and GS vectors carrying GFP and dsRed genes as markers to infect liver and brain tumors, and we found that these marker genes could be simultaneously expressed in transduced cells. In addition to marker genes, we also replaced GFP and dsRed genes in the vectors with suicide genes yCD and yUPRT, respectively, to test cell killing efficiency and to observe bystander effect of resulted vectors upon administration of prodrug 5-fluorocytosine (5-FC). Transduction of dual suicide genes could enhance more tumor cell death after exposure of 5-FC in U87 cells, but there was no significant difference from one suicide gene transferred Huh-7 cells. Therefore, this strategy of combining dual replicating retroviral vectors with dual enzyme/prodrug therapy may serve as attractive tools and provide a new option for cancer gene therapy.
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