Current bone marrow transplant treatment of cancer patients does not include agents to amplify the number of repopulating stem cells. A step closer to developing an appropriate drug has been made by Mickie Bhatia and colleagues from the John P. Robarts Research Institute, London, Canada who report in the February issue of Nature Immunology how the sonic hedgehog protein is involved in the regulation of the human stem cell pool.

Their research indicates that the cytokine-induced proliferation of primitive human haematopoietic cells can be inhibited with antibodies to a protein called hedgehog. Conversely, treatment with sonic hedgehog protein induces the expansion of pluripotent human haematopoietic repopulating cells in immunodeficient mice. This activity is mediated by bone morphogenic protein (BMP) signals (Nat Immun 2001, 2:172-180).

Stem cells, under the influence of various immune modulators, can develop into all blood cell types, making them particularly useful in the treatment of...