Prolonged release and c-kit expression of haemopoietic precursor cells mobilized by stem cell factor and granulocyte colony stimulating factor

Mobilization of haemopoietic precursor cells into the circulation by the co mbination of cytokines, stem cell factor (SCF) and G-CSF in previously untr eated patients with carcinoma of the breast resulted in increased yield of collected peripheral blood precursor cells (PBPC). This mobilization of PBP C by SCF with G-CSF lasted several days after ceasing the cytokines in comp arison to the rapid fall of PBPC after ceasing G-CSF Possible mechanisms fo r this increased and prolonged mobilization were investigated. Immunologica l phenotyping with CD38, Thy-1 and MDR-1 of the CD34-positive mobilized PBP C detected no difference in maturity compared to PBPC mobilized by G-CSF al one. However, the down-regulation of c-kit, which is associated with the me chanism of mobilization, was much greater in the PBPC mobilized by SCT and G-CSE The potential clinical implication of increased and prolonged mobiliz ation is increased yield. allowing transplantation of heavily pretreated pa tients, transplantation with PBPC from a single apheresis, or PBSC support for multiple courses of high-dose therapy from one mobilization procedure.