Can cord blood stem cells be used for gene therapy?

Answer: Yes. Traditionally, patients with severe hereditary disorders of the immune system were given a Stem Cell transplant to replace the defective gene. This is kind of like fixing a broken transmission by replacing the whole car. Plus, while the patient’s hereditary disorder may be fixed, there are new medical problems associated with a transplant that is not a perfect match.

The more sophisticated approach is to transplant the patient’s own Stem Cells after they have been genetically engineered to fix the defective gene. The genetic engineering is done with a virus. The patient’s own Cord Blood is an ideal source of matching Stem Cells.

Example: Transplants of genetically engineered Cord Blood have been successfully used to cure some forms of “bubble boy syndrome”, or SCID. Initially, the SCID results were touted as the first success story of gene therapy. Unfortunately, this clinical trial was halted in 2003 when two of the children subsequently developed leukemia. It is not clear at present if the leukemia was triggered by the gene insertion process, or if the SCID patients simply had a greater predilection towards leukemia than the population at large.

References:

• Parkman R, et al. 2000, Annual Rev Med 51:33-47 (ADA-SCID)
• Salima Hacein-Bey-Abina, et al. 2002, NEJM 346:1185-1193 (X-linked SCID)
• Antoine C, et al. 2003, Lancet 361(9357):541-2. “Long-term survival and transplantation of haemopoietic Stem Cells for immunodeficiencies: report of the European experience 1968-99.”
• Sara M. Mariani 2003, Highlights of the 2003 meeting of the American Association of Immunologists, reported by Medscape 6/3/03