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Children's News
Children's Fund
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Beyond Bone Marrow Transplants
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Kenneth Weinberg, MD |
Resolving these kinds of challenges is the goal of Kenneth Weinberg, MD, the Anne T. and Robert M. Bass Professor in Pediatric Cancer and Blood Diseases. The answers, he says, lie in acquiring deeper understanding of the molecular and cellular mechanisms of stem cells and using that knowledge to fine-tune existing therapies and to develop new, individualized treatments.
''We have a 40-year track record of using hematopoietic stem cell transplants to cure children with very serious diseases,'' Weinberg says. ''What is so exciting now is that advances from this type of transplantation have put us on the verge of successfully transplanting other types of stem cells to cure different diseases.''
Packard already is implementing new techniques that expand the options beyond bone marrow transplant, notes Weinberg, who was appointed to the Bass professorship in 2006. Today, instead of extracting stem cells only from the bone marrow, physicians can use circulating (peripheral) blood, which is easier on the donor and often can provide better results for the patient. Physicians also can use stem cells from umbilical cord blood, which are more versatile because an infant’s immune system cells are less likely to cause an adverse reaction.
As these sources of stem cells expand, the transplant donor pool expands as well, says Weinberg, making stem cell transplants available to a greater number of patients. This can be especially important for ethnic minorities and children of mixed ethnicity, who may have a more difficult time finding a suitably matched donor.
As director of Packard’s Division of Stem Cell Transplantation, Weinberg coordinates efforts on dual fronts: basic and clinical research, and a growing network of patient care.
About 65 children receive hematopoietic stem cell transplants at Packard each year. A new 12-bed transplant unit is scheduled to open this summer, where patients and their families will receive individualized care from teams of physicians, specially trained nurses, nutritionists, therapists, and social workers. ''The children are dependent on a whole network here--they would not be able to thrive without outstanding supportive services,'' Weinberg says. ''We work together as a team, and we consider the whole family as our patient.''
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Stem cells in Jacob White's bone marrow provided a crucial enzyme to treat a rare genetic disease in his sister, Makynna. |
For Tasha and Craig White of McKinleyville, Calif., that teamwork made all the difference in the world. Their daughter, Makynna, age 2, was diagnosed with Hurler’s syndrome, a rare genetic disease that causes progressive deterioration of the central nervous system, when she was 9 months old. Her older brother, Jacob, donated his bone marrow for a transplant about a year and a half ago. His stem cells provided an enzyme that was missing in his sister’s cells, which stopped the disease’s progression and started to repair her damaged organs and tissues. The improvement was almost immediate.
''We saw changes almost right away,'' says Tasha White. ''Makynna was responsive and seemed happier. She was walking about four months later, and we still see improvement. She was so far behind, and now she does something new every day. The transplant was a hard thing to go through, but we were confident we were getting the best possible care for her.''
As a practicing pediatrician, Weinberg has first-hand experience of this kind of promise from stem cells, tempered by the realization that science still has a long way to go. Many nonmalignant genetic diseases, such as sickle cell disease, appear to be curable by hematopoietic stem cell transplants if done early enough, he says, while others appear to be significantly improved. But cancer can be more problematic, he adds, because it appears that the chemotherapy used to destroy malignant cells when preparing a patient for a transplant can leave behind the most insidious cancer stem cells; these can be reintroduced in certain kinds of transplants and are more likely to elude assault from the stem cells’ new immune system.
''We need to identify early on which children may most benefit before their cancers are resistant to therapy,'' he says. Researchers are currently looking at genetic markers that may indicate which kinds of cancer will respond best to a stem cell transplant.
Packard’s stem cell program is an integral part of Stanford’s Institute for Stem Cell Biology and Regenerative Medicine, a university-wide consortium of researchers developing new tactics to harness the power of stem cells to improve human health. Weinberg oversees Packard’s participation in this initiative, helping to identify original research that might develop into safer and more effective methods for children’s stem cell transplants.
Weinberg himself is an expert in isolating the blood stem cells that can regenerate the immune system rapidly and effectively. He leads a team that is exploring the relationship between immune deficiency and the growth of lymphocytes, a kind of white blood cell involved in the body’s defense system.
''Most immune deficiencies occur because of mutations in genes necessary for lymphocyte development, survival, or function,'' he says. ''That makes immune deficiency diseases ideal models for understanding the molecular and cellular biology of the lymphocyte.''
Weinberg’s earlier work in understanding how the thymus processes white blood cells led to the discovery of a defect in the production of a protein called interleukin-2 that caused a form of severe combined immune deficiency disease (SCID or Bubble Boy syndrome). He also identified a protein called interleukin-7 that plays an important role in stimulating the immune system after a bone marrow transplant. His findings may further streamline the benefits of stem cell transplants for children with SCID, leukemia, and other immune deficiencies.
Weinberg also leads clinical research to track patient response to therapy to determine whether young adults benefit more from pediatric or adult protocols. And, working closely with Packard’s Division of Child and Adolescent Psychiatry, he is studying long-term neurocognitive outcomes of transplant patients, who often demonstrate more learning disorders than their peers. Their work may reveal whether this condition is from the disease itself or from the intense chemotherapy and radiation therapy that is needed to prepare the child for a transplant.
''We may find that we can change therapies to minimize these kinds of after-effects and maximize the recovery,'' says Weinberg.
This is just one aspect of the exciting developments he sees ahead for pediatric stem cell transplantation.
''I am committed to translating new knowledge to the care of children as quickly as possible,'' he says. ''But, in the meantime, any time a patient shows improvement or remission of symptoms, I consider that a day well spent.''
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