What is gene therapy

Some diseases are caused by missing or damaged genes – the biological units of heredity. Instead of giving a patient a drug to treat or control the symptoms of a genetic disorder, in gene therapy doctors attempt to correct the underlying problem by introducing healthy copies of the damaged or missing genes into some of the patient's cells. 

Other diseases, such as cancer, can also be targeted by gene therapy. Genes can be introduced into tumours to directly kill cancerous cells or make them more susceptible to chemotherapy drugs. Alternatively gene therapy can be used to manipulate the immune system to help the body’s natural defences recognise and target cancer cells or infectious agents such as viruses.

Genes may either be introduced directly into cells in the patient's body, usually by giving the patient an injection, or may be introduced into cells in a test tube prior to their transplantation into the patient. A “vector” is needed to get the genes into cells. Some gene therapy approaches use highly modified and disabled viruses to achieve this whilst others complex DNA with chemicals or proteins that help it to cross cell membranes.
Viruses can be used as vectors because they have evolved over millions of years to deliver their own genetic material into cells. Gene therapists highjack this natural process by stripping out harmful genes from viruses and packing the therapeutic payload into space this creates in the viral genome.

GTAC's definition of gene therapy is:

"The deliberate introduction of genetic material into human somatic cells for therapeutic, prophylactic ordiagnostic purposes."

This includes techniques for delivering:

• synthetic or recombinant nucleic acids into humans:
• genetically modified biological vectors (such as viruses or plasmids)
• genetically modified stem cells
• oncolytic viruses
• nucleic acids associated with delivery vehicles
• naked nucleic acids
• antisense techniques (for example, gene silencing, gene correction or gene modification)
• Genetic vaccines
• DNA or RNA technologies such as RNA interference
• xenotransplantation of animal cells (but not solid organs).

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copyright: © | last updated: 26 September 2008

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