Thesis
Evaluation of thermostable yeast cytosine deaminase and herpes simplex virus thymidine kinase fusions in double suicide gene therapy for cancer
Washington State University
Master of Science (MS), Washington State University
2009
Handle:
https://hdl.handle.net/2376/100361
Abstract
Suicide gene therapy is a promising alternative treatment for cancer that specifically targets tumor cells for destruction by delivering a gene encoding a suicide enzyme that is able to convert an anticancer prodrug to a cytotoxic product. Two widely studied and clinically used enzyme/prodrug systems are cytosine deaminase (CD) with 5-fluorocytosine (5FC) and Herpes Simplex Virus thymidine kinase (HSV-TK) with ganciclovir (GCV). Both enzyme/prodrug systems have shown positive results in clinical studies but still exhibit limitations such as low transduction efficiency due to current delivery systems and low enzyme activity towards the prodrug. An approach to overcome the latter limitation is to create a fusion of both CD and HSV-TK in what is known as double suicide gene therapy (DSGT). DSGT takes advantage of two enzyme/prodrug systems to create a synergistic cytotoxic effect with the lowest prodrug doses possible. DSGT studies with bacterial CD (bCD) and TK fusion started in the late 1990s and showed enhanced tumor growth inhibition and radiosensitization following 5FC and GCV treatment. 5FC effect on deoxynucleotide pools by allosteric regulation of the enzyme ribonucleotide reductase was suggested as the cause of the synergistic effect observed in bCD/TK. In contrast to bCD/TK studies, synergistic experiments are yet to be done for yCD/TK fusions. Previous studies in our laboratory have created CD and TK mutants (yCDdouble, yCDtriple and SR39, respectively), with either improved thermostabilization or improved prodrug activity. These mutants were created using computational design (yCD) or regio-specific random mutagenesis (TK). As CD mutants and SR39 mutant showed improved activity and/or a greater tumor killing efficiency in comparison to wild type enzymes, we sought to evaluate the synergistic effect of mutant fusion enzymes. Even though yCD/SR39 fusions have been used with positive results in clinical trials, we hypothesize that by using thermostabilized yCD in fusion with SR39 a greater killing effect could be obtained.
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Details
- Title
- Evaluation of thermostable yeast cytosine deaminase and herpes simplex virus thymidine kinase fusions in double suicide gene therapy for cancer
- Creators
- Marilyn Sanchez-Bonilla
- Contributors
- Margaret E. Black (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Pharmacy and Pharmaceutical Sciences, College of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525002301842
- Language
- English
- Resource Type
- Thesis