Leukaemia is a cancer of the white blood cells
Immune cells grown from umbilical cord blood may one day be used to improve leukaemia treatment, researchers say.
A team took natural killer (NK) cells from cord blood and multiplied them 30-fold in the laboratory, a conference for blood and cancer specialists heard.
When given to mice with aggressive human leukaemias, the NK cells cut the circulating cancer cells by 60 to 85%, the University of Texas team reported.
Cancer specialists said the results now need to be replicated in humans.
Patients with leukaemia can be treated with stem cell transplants.
But one potentially fatal side effect of this therapy is when immune cells called T cells in the transplanted blood react against the patient's own cells - a condition called graft-versus-host disease.
The researchers said NK cells operate differently from T cells, leaving normal cells alone while targeting and killing the cancerous cells.
For this reason there has been a lot of research into NK cells as leukaemia treatments but previous efforts to grow enough cells out of cord blood have not been successful.
Presenting the research at the American Society of Pediatric Hematology/Oncology annual conference in Cincinnati, Dr Patrick Zweidler-McKay, from The University of Texas MD Anderson Cancer Center, said they had managed to generate more than 150 million NK cells from one cord blood unit.
As the NK cells multiplied in the laboratory over a three-week period they were treated with substances which helped to keep them active.
The resulting cells had retained their anti-cancer properties, they said.
"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," he said.
The NK cells can be transplanted to patients without prior chemotherapy, he added and he also predicts this type of transplant could be used for adults who have already had a transplant or for those adult and children who cannot have other stem cell transplants.
Dr Kat Arney, senior science information offer at Cancer Research UK, said: "At the moment, these experiments have only been done in animals, so we will have to wait and see if they can be repeated in cancer patients during clinical trials.
"The discovery that NK cells from umbilical cord blood can be grown up in the lab is an important step in the development of an effective, widely available treatment.
"The immune system is a powerful tool in beating cancer and many researchers are interested in the potential of NK cells for treating leukaemia."
Dr David Grant, scientific director of the Leukaemia Research Fund, said knowledge over how exactly cord blood transplants worked in treating leukaemia was growing and this research added to that.
"The downside is making it into a clinically realistic treatment.
"It's expensive and time-consuming so it might appear an attractive option but the practicalities might be difficult."