Ex vivo cytokine expansion of peripheral blood Ph-negative cells in chronic myeloid leukaemia

Hematopoietic progenitors can be expanded ex vivo in the presence of variou s cytokine combinations. Since normal early progenitor or stem cells persis t in the blood and bone marrow of patients with Philadelphia chromosome [Ph ]-positive chronic myeloid leukaemia (CML), the selection of normal (Ph-neg ative) progenitor cells from CML patients would be of considerable clinical Value for ex vivo purging and autologous transplantation. To obtain these cells, CD34-positive (progrenitor) cells from the peripheral blood (PB) of CML patients were either pretreated or not with 5-fluorouracil (5FU) and th en grown in suspension culture for 7 days with a combination of cytokines. We compared different combinations of cytokines containing interleukin-1 al pha (IL1), interleukin-3 (IL3), stem cell factor (SCF), leukemia inhibitor factor (LIF), Flt3-ligand (FLT3L), and thrombopoietin (TPO). 5FU decreased cell proliferation in the liquid culture but concurrently increased the exp ansion of CFU-GM. While the addition of cytokines such as FLT3L and TPO imp roved CFU-GM expansion. FISH and RT-PCR analysis showed that this method si gnificantly favored a higher frequency of Ph-negative cells after expansion in liquid culture. Therefore ex vivo expansion of putatively normal hemato poietic progenitor cells from cytapheresis is feasible in CML.