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

ABSTRACT

Hematopoietic progenitors can be expanded ex vivo in the presence of various cytokine combinations. Since normal early progenitor or stem cells persist in the blood and bone marrow of patients with Philadelphia chromosome [Ph]-positive chronic myeloid leukaemia (CML), the selection of normal (Ph-negative) progenitor cells from CML patients would be of considerable clinical value for ex vivo purging and autologous transplantation. To obtain these cells, CD34-positive (progenitor) cells from the peripheral blood (PB) of CML patients were either pretreated or not with 5-fluorouracil (5FU) and then grown in suspension culture for 7 days with a combination of cytokines. We compared different combinations of cytokines containing interleukin-1 alpha (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 expansion of CFU-GM. While the addition of cytokines such as FLT3L and TPO improved CFU-GM expansion. FISH and RT-PCR analysis showed that this method significantly favored a higher frequency of Ph-negative cells after expansion in liquid culture. Therefore ex vivo expansion of putatively normal hematopoietic progenitor cells from cytapheresis is feasible in CML.