New hope for cancer patients

Duke Medicine researchers have found that epidermal growth factor speed the recovery of blood-making stem cells after exposure to radiation.

The finding could open new options for treating cancer patients and victims of dirty bombs or nuclear disasters.

 The researchers explored what had first appeared to be an anomaly among certain genetically modified mice with an abundance of epidermal growth factor in their bone marrow. The mice were protected from radiation damage, and the researchers questioned how this occurred.

"Epidermal growth factor was not known to stimulate hematopoiesis, which is the formation of blood components derived from hematopoietic stem cells. However, our studies demonstrate that the epidermal growth promotes hematopoietic stem cell growth and regeneration after injury," said senior author John Chute, MD, a professor of medicine and professor of pharmacology and cancer biology at Duke University.

 Hematopoietic stem cells, which constantly churn out new blood and immune cells, are highly sensitive to radiation damage. Protecting these cells or improving their regeneration after injury could benefit patients who are undergoing bone marrow transplantation, plus others who suffer radiation injury from accidental environmental exposures such as the Japanese nuclear disaster in 2011.

 The Duke researchers launched their investigation using mice specially bred with deletions of two genes that regulate the death of endothelial cells, which line the inner surface of blood vessels and are thought to regulate the fate of hematopoietic stem cells. Blood vessels and the hematopoietic system in these mice were less damaged when exposed to high doses of radiation, improving their survival.

 An analysis of secretions from bone marrow endothelial cells of the protected mice showed that epidermal growth factor (EGF) was significantly elevated - up to 18-fold higher than what was found in the serum of control mice. The researchers then tested whether EGF could directly spur the growth of stem cells in irradiated bone marrow cultured in the lab.

It did, with significant recovery of stem cells capable of repopulating transplanted mice. Additional studies showed that EGF improved survival from a lethal radiation exposure, with 93 per cent of mice surviving the radiation dose if they subsequently received treatment with EGF, compared to 53 per cent surviving after treatment with a saline solution.