Thrombopoietin in normal and neoplastic stem cell development.

It has been known for sometime that thrombopoietin acts on megakaryocytic progenitor cells to stimulate platelet production. It has recently been discovered that it also stimulates the self-renewal and expansion of normal murine and human haematopoietic stem cells (HSCs) by acting on its cognate receptor, the product of the myeloproliferative leukaemia (c-MPL) proto-oncogene. The c-MPL receptor may also play an important role in the development of human myeloproliferative disorders, essential thrombocythemia, myelofibrosis and polycythemia vera, cooperating with the dysregulated Janus kinase JAK2V(617)F.