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27 November 2013 12:59 pm ,
Vol. 342 ,
The new head of the National Center for Science Education promises to "fight the good fight" against attacks on...
Analyses of the H7N9 strains isolated from four new cases show that the virus is evolving rapidly, heightening anxiety...
In 2009, Jack Szostak shared a Nobel Prize for his part in discovering the role of telomeres, the end bits of...
Science has exposed a thriving academic black market in China involving shady agencies, corrupt scientists, and...
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Data collected by satellites and floating probes have chronicled a 2-decade rise in the temperature and thickness of a...
Cholesterol, the artery-clogging molecule that contributes to cardiovascular disease, has another nasty trick up its...
- 27 November 2013 12:59 pm , Vol. 342 , #6162
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Gene Therapy Approach Raises Questions
23 January 2002 (All day)
Treating patients with gene therapies requires a safe vehicle to ferry in helpful genes, and adeno-associated virus (AAV) is widely regarded as one of the safest. But new research shows that at least some human cancer cells treated with the virus develop abnormal chromosomes, raising concerns about the long-term safety of AAV-based gene therapies.
Some researchers thought AAV was safer for gene therapy than other so-called viral vectors, because infection with AAV is common and causes no known ill effects. AAV-based therapies have also passed muster in several safety trials. Still, it's been unclear exactly how the virus delivers and activates genes inside human cells. Scientists wondered how AAV's DNA jumped into the cell chromosomes and whether it damaged them by doing so.
To find out, geneticist David Russell of the University of Washington, Seattle, and his colleagues studied AAV's impact on genes in a cultured cancer cell line. The researchers used an AAV strain designed to pop out of chromosomes when the cells are treated with a certain drug, carrying nearby pieces of chromosome with it. By then analyzing the DNA sequences of those chromosome pieces, the team could reconstruct how AAV had altered the cell's chromosomes when inserting itself.
As reported in the February issue of Nature Genetics, the cell chromosomes had small pieces missing or added where the virus had inserted itself. In one cell line two different chromosomes had abnormally fused. Despite this link, it's not clear whether the type of cells studied--a line of cancer cells commonly used by researchers--somehow enabled AAV to wreak extra damage. More testing on other kinds of cells is needed, Russell says, to determine whether patients treated with AAV are at higher risk of chromosomal disruption, which can lead to cancer.
The study raises a warning flag. "We're going to have to follow these patients" enrolled in safety trials, says gene therapist Malcolm Brenner of Baylor College of Medicine in Houston, who adds the results suggest that AAV vectors are probably no safer than other viral vectors currently used. Still, Brenner adds, it's far too soon to consider jettisoning AAV, given that other evidence suggests it's safe.