The effects of thrombopoietin on the growth of acute myeloblastic leukemia cells.

Thrombopoietin (TPO) is a novel hematopoietic growth factor that was cloned as a ligand for c-mpl proto-oncogene. The c-mpl proto-oncogene is expressed on various types of human leukemia cell lines derived from erythroid, megakaryocytic, and stem-cell leukemia cells. Also, c-mpl mRNA is detectable on blast cells in about half of acute myeloblastic leukemia (AML) cases regardless of French-American-British (FAB) classification. In the cases with myelodysplastic syndrome, c-mpl is expressed in a substantial fraction of refractory anemia with excess of blast (RAEB), RAEB in trasformation. and chronic myelomonocytic leukemia cells, but not in refractory anemia or sideroblastic anemia. Little or no expression of c-mpl mRNA is observed in human lymphoid cell lines and blast cells of acute lymphoblastic leukemia cases. The in vitro treatment of AML cells with TPO resulted in proliferation in about 70% of c-mpl-positive AML cases. The proliferative responses of AML cells to TPO were observed not only in M7-type, ...