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A New Source of Stem Cellsby Don Norwood A bone marrow transplant can mean new hope for life for someone with leukemia or another serious blood disease. But each year, many people who need a transplant aren’t able to have one because a matching donor can’t be found. However, a new source of stem cells has become an emerging source of hope for such patients: umbilical cord blood. Once discarded, the umbilical cord is now prized for its wealth of stem cells that can be used in bone marrow transplants. The University of Texas M. D. Anderson Cancer Center is now on the front line in the collection and use of cord blood with the establishment of the M. D. Anderson Cord Blood Bank. M. D. Anderson has the largest stem cell transplantation program in the world, so establishing a Cord Blood Bank was a logical step, according to Elizabeth Shpall, M.D., a professor in the Department of Blood and Marrow Transplantation and director of the Cord Blood Bank. Officially in operation since April, the still-new Cord Blood Bank collects umbilical cords from consenting maternity patients at selected hospitals in the Houston area. The cords are collected just after birth, and the blood is extracted, processed, frozen, and inventoried. It is then made available to transplant centers worldwide. “We take the cords from the hospital, and we bring them here and test them for everything that we would test in a normal donor,” said Dr. Shpall. “When they’re found to be good, we freeze them and put them in our bank, and they are ready to go as a source of stem cells.” Upon accreditation, which is pending, the M. D. Anderson Cord Blood Bank will join a number of transplant registries, starting with the National Marrow Donor Program. The bank is currently a member of NETCORD, which maintains a worldwide cord blood database. Through these registries, the human leukocyte antigen (HLA) types of the cord blood specimens will be made available around the world. The M. D. Anderson Cord Blood Bank currently has a partnership with the Women’s Hospital of Texas and is negotiating another with Ben Taub General Hospital, both of which are near M. D. Anderson. These partnerships guarantee not only a large source of cord blood but also cord blood from a very diverse population, increasing the chances that an appropriate match can be found for a given patient.
The first transplantation choice for someone with leukemia is always bone marrow from a sibling. However, only one patient in three or four has a sibling who is a match. The next option is the National Marrow Donor Program, which finds HLA matches for about 65% of applicants. This avenue offers less hope for minorities because most of the donors in the registries are white and of Western European descent. In comparison, cord blood specimens are collected from a more diverse group of donors, creating options for people who might otherwise have had little hope of finding a matched donor. Furthermore, patients who receive stem cells from cord blood are less likely to develop graft-versus-host disease than those who receive stem cells from bone marrow because of the naivete of cord blood. Stem cells from cord blood also seem to work particularly well in conjunction with fludarabine when compared with other chemotherapeutic agents. Yet another advantage of cord blood stem cell transplants is that they can be used for immune deficiency and genetic diseases. In particular, these transplants have been shown to correct neurologic deficits in patients with Krabbe’s disease, Dr. Shpall said. Cord blood does have a disadvantage. Namely, it has fewer stem cells than bone marrow and peripheral blood, making for a longer engraftment period. However, two recent studies published in The New England Journal of Medicine report similar survival rates in a comparison of cord blood transplants with transplants using marrow from unrelated donors. Also, researchers at M. D. Anderson are working to counteract the long engraftment period. “The patient is especially at risk during engraftment,” said Dr. Shpall. “So, our laboratory has been focused for a decade on trying to expand the stem cells from cords ex vivo before implanting them. We have trials looking at two different expansion strategies, and we’re about to embark on a third, which we think is the most promising. “Basically, we take an umbilical cord and we pull out the stem cells and combine them in the lab with vitamins and growth factors, expanding 100-fold the stem cells we think are necessary to engraft. We then infuse the expanded cells instead of unmanipulated cells. It’s still too early to know for sure whether it’s working, but we’re encouraged by our preliminary findings.” Because the number one risk before engraftment is life-threatening infection, researchers in the Department of Blood and Marrow Transplantation have expanded their study of cord blood to the T cells also contained in it. Dr. Shpall said this will be a major focus of future research in the department. “We’re doing a lot of work to try to reduce infections in transplant patients, so another whole area of research in our laboratory is expanding the T cells from cord blood. We take a fraction of the umbilical cord and expand the T cells. Once we confirm in the laboratory that those T cells have the potential to be effective, we plan to infuse them into the patient separately to bolster the immune system, in hopes it will recover more quickly after transplant. That’s a critical area, which if successful, will lead to major improvements in outcomes for cord blood transplant patients.”For more information on this topic or for questions about M. D. Anderson’s treatments, programs, or services, call the M. D. Anderson Information Line at (800) 392-1611 (in the United States) or (713) 792-3245 (in Houston and outside the United States). Other articles in OncoLog, September 2005 issue:
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