Challenges In Gene Therapy – University of Utah

Posted: September 16, 2022 at 2:08 am

A good gene therapy is one that will last. Ideally, an introduced gene will continue working for the rest of the patient's life. For this to happen, the introduced gene must become a permanent part of the target cell's genome, usually by integrating, or "stitching" itself, into the cell's own DNA. But what happens if the gene stitches itself into an inappropriate location, disrupting another gene?

This happened in two gene therapy trials aimed at treating children with X-linked Severe Combined Immune Deficiency (SCID). People with this disorder have virtually no immune protection against bacteria and viruses. To escape infections and illness, they must live in a completely germ-free environment.

Between 1999 and 2006, researchers tested a gene therapy treatment that would restore the function of a crucial gene, gamma c, in cells of the immune system. The treatment appeared very successful, restoring immune function to most of the children who received it.

But later, 5 of the children developed leukemia, a blood cancer. Researchers found that the newly transferred gamma c gene had stitched itself into a gene that normally helps regulate the rate at which cells divide. As a result, the cells began to divide out of control, causing leukemia. Doctors treated 4 of the patients successfully with chemotherapy, but the fifth died.

This unfortunate incident raised important safety concerns, and researchers have since developed safer ways to introduce genes. Some newer vectors have features that target DNA integration to specific "safe" places in the genome where it won't cause problems. And genes introduced to cells outside of the patient can be tested to see where they integrated, before they are returned to the patient.

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Challenges In Gene Therapy - University of Utah

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