Researchers in Germany recently reported in Science that while conducting research on mice designed to look at possible ill effects of gene therapy errors, they observed mice who developed leukemia after a gene therapy treatment.
The researchers were using a retrovirus designed to introduce altered genes into the bone marrow. The virus ended up inserting the altered gene into a known cancer causing gene, however. This particular gene serves an important role in initial development of organs, but is not supposed to be active in cells that develop bone marrow. The altered virus ended up switching the gene on, causing the mice to develop leukemia.
A known risk of gene therapy is the possibility that the altered genetic information might end up in the incorrect place, but this is the first time ever that animals have contracted cancer and died as a result of a faulty application of gene therapy.
This is actually very good news. On the one hand, while the risk of this sort of effect is real, it is extremely low. Ten mice dead of cancer out of hundreds of thousands of animals who have been treated with this sort of retrovirus amounts to a pretty good track record.
On the other hand, this is precisely why researchers use animal models. It is much better to find out in animals the circumstances which cause retroviruses to target the wrong chromosome, so that they can minimize this possibility before widely deploying such treatments in human beings.
Animal rights activists keep saying that all of this sort of research can be accomplished without animals, but I’d like to see their plan for duplicating this line of research without animals.
So far, very few human beings have been treated with retroviruses. The only current therapeutic use of retroviruses in humans involves treating infants born with severe combined immunodeficiency.
Source:
Gene therapy causes cancer in mice. Andy Coghlan, New Scientist, April 18, 2002.