Signal control of hematopoietic stem cell fate: Wnt, Notch, and Hedgehog as the usual suspects

Abstract

Although Wnt, Notch, and Hedgehog signaling pathways have been implicated in self-renewal and proliferation in vivo, modulation of these pathways alone does not result in substantive expansion of hematopoietic stem cells ex vivo. In addition to these signaling pathways, Bcl-2 family members may have an important role in inducing survival in hematopoietic stem cells both in vivo and ex vivo. Understanding the complex relationship between these unique signaling pathways is essential to achieve successful ex-vivo expansion toward enhanced hematopoietic stem cell transplantation-based therapies.