May 16 (HealthDay News) A treatment that uses natural killer (NK) immune system cells from umbilical cord blood effectively destroys human leukemia cells in mice, researchers say.

The NK cells reduced by 60 percent to 85 percent human acute lymphocytic leukemia (ALL) and acute myelogenous leukemia (AML) cells in test mice with aggressive human leukemias, according to the study.

The findings are to be presented at the May 16 American Society of Pediatric Hematology/Oncology annual conference, in Cincinnati.

Previous efforts like this one, which require the number of NK cells from a single cord blood to be expanded, resulted in ineffective NK cells. The new technique manages to increase NK cells in cord blood more than 30-fold while allowing the cells to retain their ability to target and kill acute leukemia cells.

"Cord blood is a promising source of natural killer cells, because the NK cells have enhanced sensitivity to stimulation, decreased potential to cause graft-versus-host disease and are available from cord banks throughout the country and world," investigator Dr. Patrick Zweidler-McKay, assistant professor of pediatrics from the Children's Cancer Hospital at The University of Texas M. D. Anderson Cancer Center, said in a prepared statement.

Graft-versus-host disease is a common side effect of patients receiving stem cell transplants. It is fatal if not controlled.

The new process allows the NK cells to be transplanted to leukemia patients without the need for prior chemotherapy. Zweidler-McKay said that adults who have already had a transplant, or any age leukemia patient who is not eligible for other stem cell transplants due to blood counts or illness, may be available to use his new transplant method.

"These NK cells demonstrate significant cytotoxic activity against human AML and ALL cell lines and patient leukemia blasts. Most importantly, mouse models of human AML and ALL were sensitive to NK cell infusions," Zweidler-McKay said.

SOURCE: University of Texas M. D. Anderson Cancer Center, news release, May 16, 2008