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In situ use of suicide genes for cancer therapy
S M Freeman1, K A Whartenby, J L Freeman
1Department of Pathology, Tulane University Medical School, New Orleans, Louisiana, USA.
Abstract:
Gene therapy has now become a standard experimental approach for treating cancers that have failed conventional therapies. As the understanding of the molecular nature of carcinogenesis develops, new approaches are being taken to directly target tumor cells, thus bypassing the difficulties of killing cells that are resistant to chemotherapy and radiation. One emerging gene therapy approach has been through the genetic modification of tumor cells with a suicide gene such as the herpes simplex virus thymidine kinase gene (HSV-TK) and ganciclovir (GCV) therapy. Death of tumor cells modified with the HSV-TK gene leads to killing of unmodified in situ tumor cells in a phenomenon termed the "bystander effect." The basis both for this effect and other gene therapy trials underway for the treatment of cancer will be discussed.
Insights
Gene therapy offers a novel cancer treatment by genetically modifying tumor cells with a suicide gene. This approach, using the herpes simplex virus thymidine kinase gene (HSV-TK) and ganciclovir (GCV), triggers a "bystander effect" to eliminate nearby cancer cells.
Area of Science:
- Oncology
- Molecular Biology
- Biotechnology
Background:
- Gene therapy is an emerging standard for refractory cancers.
- Advances in understanding carcinogenesis enable targeted tumor cell treatments.
- Conventional therapies face challenges with resistant cancer cells.
Purpose of the Study:
- To discuss emerging gene therapy approaches for cancer treatment.
- To explain the mechanism of the 'bystander effect' in gene therapy.
- To review ongoing gene therapy trials for cancer.
Main Methods:
- Genetic modification of tumor cells with suicide genes, specifically the herpes simplex virus thymidine kinase (HSV-TK) gene.
- Administration of ganciclovir (GCV) to activate the suicide gene therapy.
- Observation and analysis of the 'bystander effect' where modified cells induce death in adjacent unmodified tumor cells.
Main Results:
- The HSV-TK gene combined with ganciclovir (GCV) therapy effectively targets and eliminates modified tumor cells.
- The 'bystander effect' demonstrates that modified tumor cells can induce the death of neighboring unmodified tumor cells.
- This gene therapy approach bypasses resistance issues associated with chemotherapy and radiation.
Conclusions:
- Gene therapy, particularly using suicide genes like HSV-TK, presents a promising strategy for cancer treatment.
- The 'bystander effect' is a key mechanism enhancing the efficacy of tumor-targeted gene therapy.
- Further gene therapy trials are underway, building on these foundational principles for cancer intervention.