PERIPHERAL-BLOOD EXPANSION OF EARLY PROGENITOR CELLS AFTER HIGH-DOSE CYCLOPHOSPHAMIDE AND RHGM-CSF

In 20 patients with non-Hodgkin lymphoma or breast cancer, high-dose cyclophosphamide induced, during the post-nadir period of rapid leucocyte recovery, on median day 19 about a 30-fold increase in the peak concentration of granulocyte-macrophage (CFU-GM) and erythroid (BFU-E) colony-forming cells, and an even higher increase in the more immature pluripotent progenitors (CFU-Mix, 72-fold). After infusion of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF), peak concentration was reached earlier (median day 15) and with further enhancements (159, 116 and 283-fold, respectively, in the number of CFU-GM, BFU-E and CFU-Mix). Most CFU-GM were immature, lacking the differentiation antigen CD15, and gave rise to large myeloid colonies, reflecting a high proliferative capacity of the founder cells. Very immature maphosphamide-resistant progenitors were detectable. The marked expansion in the circulating pool was predictable and reliable, allowing harvesting, after two or three leukaphereses, of sufficient haematopoietic progenitors for autologous bone-marrow reconstitution.