Normal primitive haemopoietic progenitors are more frequent than their leukaemic counterpart in newly diagnosed patients with chronic myeloid leukaemia but rapidly decline with time

We carried out studies to quantify Ph-negative progenitors both in steady s tate and during regeneration after chemotherapy and G-CSF in 23 newly diagn osed chronic myeloid leukaemia (CML) patients (group A) and in 14 individua ls more than a year from diagnosis (nine in chronic and five in accelerated phase, group B), In steady state bone marrow Ph-negative long-term culture initialing cells (LTC-IC) and Ph-negative colony-forming-cells (CFC) were detected in 18/23 and 14/23 patients of group A versus 3/14 and 3/14 patien ts of group B (P< 0.001 and P< 0.02, respectively), The absolute number of mobilized Ph-negative progenitors was markedly higher in group A versus gro up B (P <0.02 for LTC-TC, P< 0.003 for CFC), 12/16 newly diagnosed patients mobilized Ph-negative LTC-IC only and the yield was in the range of normal allogeneic donors, Overall the frequency of Ph-negative LTC-IC in the bone marrow predicted the yield of Ph-negative LTC-IC mobilized into peripheral blood (P<0.001). The bone marrow frequency of Ph-positive LTC-IC was consi derably lower than the normal counterpart, Taken together these findings su ggest that normal progenitors are relatively well preserved in newly diagno sed CML patients, but tend to rapidly decline with time. This observation h elps in the understanding of the pathogenesis of CML and has potential impl ications for autografting, The optimal time for a successful collection of Ph-negative circulating progenitors would appear to be soon after diagnosis .