Natural killer (NK) immune system cells found in umbilical cord blood have shown promise by destroying human leukemia cells in mice, researchers at the University of Texas M. D. Anderson Cancer Center have revealed.
This method found by Patrick Zweidler-McKay, M.D., Ph.D., assistant professor of paediatrics from the Children's Cancer Hospital at M. D. Anderson, works by expanding the number of NK cells from a single cord blood unit while retaining the cells' anti-leukaemia effects.
While earlier efforts to expand cord blood have resulted in ineffective NK cells, the researchers have found a novel process may increase NK cells in cord blood more than 30-fold, generating more than 150 million NK cells from one cord blood unit while maintaining their activation to find and kill acute leukaemia cells.
When mice with aggressive human leukaemias were administered with this method, NK cells reduced the circulating human acute lymphocytic leukaemia (ALL) and acute myelogenous leukaemia (AML) cells by 60 to 85 percent.
"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," said Zweidler-McKay.
The method of operation of NK cells is different from T cells, leaving normal cells alone while targeting and killing the cancerous cells.
The study deals with selecting out NK cells from cord blood. As the cord blood is expanded to multiply in number, the NK cells are given a cytokine, interleukin-2, and a target cell, K562, which keep the NK cells active throughout the three-week expansion.
After the completion of the process, the NK cells can be transplanted to patients without prior chemotherapy.
Zweidler-McKay also predicted that this type of transplant could be used for adults who have already had a transplant or for those adult and paediatric patients who aren't candidates for other stem cell transplants due to blood counts or illness.
"These NK cells demonstrate significant cytotoxic activity against human AML and ALL cell lines and patient leukaemia blasts. Most importantly, mouse models of human AML and ALL were sensitive to NK cell infusions. These results support the evaluation of cord blood-derived NK cells as a potential immuno-therapeutic approach in acute leukaemia," said Zweidler-McKay.
The study was presented at the American Society of Pediatric Hematology/Oncology annual conference.