Scripps Research Institute Scientists Find Potential New Use for Cancer Drug in Gene Therapy for Blood Disorders

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Newswise LA JOLLA, CA June 26, 2014 Scientists working to make gene therapy a reality have solved a major hurdle: how to bypass a blood stem cells natural defenses and efficiently insert disease-fighting genes into the cells genome.

In a new study led by Associate Professor Bruce Torbett at The Scripps Research Institute (TSRI), a team of researchers report that the drug rapamycin, which is commonly used to slow cancer growth and prevent organ rejection, enables delivery of a therapeutic dose of genes to blood stem cells while preserving stem cell function.

These findings, published recently online ahead of print by the journal Blood, could lead to more effective and affordable long-term treatments for blood cell disorders in which mutations in the DNA cause abnormal cell functions, such as in leukemia and sickle cell anemia.

Improving Gene Delivery to Blood Stem Cells

Viruses infect the body by inserting their own genetic material into human cells. In gene therapy, however, scientists have developed gutted viruses, such as the human immunodeficiency virus (HIV), to produce what are called viral vectors. Viral vectors carry therapeutic genes into cells without causing viral disease. Torbett and other scientists have shown that HIV vectors can deliver genes to blood stem cells.

For a disease such as leukemia or leukodystrophy, where mutations in the DNA cause abnormal cell function, efficiently targeting the stem cells that produce these blood cells could be a successful approach to halting the disease and prompting the body to produce healthy blood cells.

If you produce a genetic modification in your blood stem cells when you are five years old, these changes are lifelong, said Torbett. Furthermore, the gene-modified stem cells can develop into many types of cells that travel throughout the body to provide therapeutic effects.

However, because cells have adapted defense mechanisms to overcome disease-causing viruses, engineered viral vectors can be prevented from efficiently delivering genes. Torbett said that when scientists extract blood stem cells from the body for gene therapy, HIV viral vectors are usually able to deliver genes to only 30 to 40 percent of them. For leukemia, leukodystrophy or genetic diseases where treatment requires a reasonable number of healthy cells coming from stem cells, this number may be too low for therapeutic purposes.

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Scripps Research Institute Scientists Find Potential New Use for Cancer Drug in Gene Therapy for Blood Disorders

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