Circulating hematopoietic progenitor cells in polycythemia vera: the in vivo effect of hydroxyurea.

The in vivo effects of hydroxyurea (HU) on circulating erythroid (BFU-E) and granulocyte-macrophage progenitors (CFU-GM) in patients with polycythemia vera (PV) have been evaluated. HU induced a strong decrease of both BFU-E and CFU-GM in the first month of treatment. During the following 4 months of treatment the level of circulating progenitors remained at very low values, until the end of the period of observation. HU activity involved both erythroid and myeloid committed progenitors and both erythropoietin-stimulated (normal) and endogenous (derived from the abnormal PV clone) BFU-E.