Could Gene Therapy Cause Cancer?

Inserting functional genes into our genome to correct hereditary diseases caused by a single genetic defect holds great promise. This is especially true for children with X-SCID also known as severe combined immunodeficiency or “bubble boy” syndrome. These children’s immune systems cannot protect them because of a mutation in the X-linked gene IL2RG.

Gene therapy has been successful in treating a limited number of children with SCID, but there have been side effects as well. In an earlier gene therapy trial, three out of 10 children were diagnosed with T-cell leukaemia. Now, researchers have published a new study of mice where one-third developed lymphoma after a retrovirus was used as a vehicle to insert the correct DNA into their genome.

Experts from Great Ormond Street, a higihly regarded children’s hospital in the UK, do not believe gene therapy for XSCID is necessarily dangerous. They have treated nine children successfully and say the mouse study used a much higher gene dose than is typically use in humans.

Genomic technology is at a stage where we’re able to do some things, like insert genes, but we still don’t understand enough to fully monitor every step of the process. In the case of SCID, the virus used to deliver the functional gene inadvertently turned on a cancer gene (oncogene) as well. Fortunately, scientists have developed other methods, such as homologous recombination that may be more focused with fewer side effects.

In many cases, gene therapy is still worth the risk. Would you rather live in a “bubble” all your life or seize the chance to be free?

For more information on gene therapy, see Saturday Genetics Quizzes 25, 26, 27, 28

BBC News, April 27, 2006

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