A test developed by St. Jude improves the selection process for bone marrow transplants.
When 7-year-old Texas resident Regan Peel underwent treatment for acute myeloid leukemia (AML) several years ago, the chemotherapy made her violently ill. But that’s all it did. Because of a genetic mutation, the AML, a cancer of the white blood cells, did not respond to treatment.
The Texas hospital had good news: They had identified an unrelated donor. But they also had bad news: The transplant would cost the family $200,000, because the procedure was not covered by insurance.
Fortunately, the family obtained a referral to St. Jude Children’s Research Hospital, which has the world’s highest survival rates for high-risk leukemia patients undergoing haploidentical, or partially matched, transplants.
Not only would the family never receive a bill for Regan’s treatment, but the little girl would benefit from new research that would help save her life.
Defeating cancer with NK cells
A few years before Regan arrived at St. Jude, the hospital’s researchers had made an exciting discovery about certain cancer-fighting immune cells, called natural killer (NK) cells. Scientists had learned that NK cells with a certain protein on their surface are adept at killing cancer cells.
The protein on those NK cells is a specialized product of the KIR gene. Everyone is born with KIRgenes, but some people possess a more potent form of this particular gene and some have a weaker form.
St. Jude scientists found that patients who received bone marrow from donors with the more potent form of KIR had dramatically better outcomes than children who received NK cells containing the weaker form.
An innovative blood test
Based on that research, the St. Jude transplant team developed a simple blood test to reveal whether a potential donor’s NK cells contained the preferred KIR protein. The new test now occurs as part of the routine donor screening process at St. Jude.
“If we have 10 potential donors, for example, we are able to use this test to discern which donor has the strongest gene,” explains Wing Leung, MD, PhD, St. Jude Bone Marrow Transplantation and Cellular Therapy chair. “The stronger NK cells control the leukemia; therefore, the risk of relapse after transplant is smaller and the outcome is better.”
The new blood test, coupled with existing screening criteria, indicated that Regan’s dad, Kelly, was the best match for a successful transplant.
A perfect match
St. Jude investigators were the first to show that donor KIR typing is crucial in improving transplant outcomes. A recent study published in the Journal of Clinical Oncology confirmed the success of the new screening test.
“We have been able to double the survival rate for patients who have bone marrow transplants for childhood leukemia,” Leung observes.
In transplants using the best donor identified by the new test, the risk of death was reduced by 60 percent and the risk of disease progression by 62 percent.
St. Jude has licensed the test, which will soon be available to transplant centers worldwide. Leung says the KIR gene family may also have applications for disorders such as diabetes, scleroderma, psoriatic arthritis, chronic hepatitis C or HIV infections.
Today, Regan maintains a high academic standing and a busy schedule. She also focuses on her career goals.
“The whole experience at St. Jude inspired me to go into nursing—maybe oncology; definitely pediatrics,” she says.
Regan is convinced that it will be another perfect match.
Abridged from Promise, Winter 2014