In vitro evaluation of the haemopoietic defect of CD34(+) cells from patients with acute myeloid leukaemia in first remission

Haemopoietic cells from patients with acute myeloid leukaemia (AML) in firs t complete remission (CR1) show ill vitro, a haemopoietic defect and a decr eased expansion potential. To better characterize this haemopoietic defect, CR1 AML and normal CD34(+) cells were analysed for immunophenotype, viabil ity, cell cycle and progenitor content before and during expansion culture in stroma-conditioned medium supplemented with cytokines. The production of haemopoiesis inhibitor by patient cells and the influence of high concentr ations of stem cell factor (SCF) and Flt3-ligand (FL) on cell survival and es vivo expansion potential were also studied. Before expansion, patient CD 34(+) cells showed viability and cell-cycle phase distribution similar to n ormal but lower percentages of CD34(+)DR(-) or CD34(+)CD38(-) cells and low er progenitor content. After 48 h of culture +/-30% of patient cells had di ed regardless of the cytokine combination used, whereas only 15% of normal cells died, After 7 d of culture, viability and cell cycle analyses showed comparable data for normal and patient samples. Co-culture of patient and n ormal cells did not show any evidence for haemopoiesis inhibitor production by patient cells. Even at high cytokine concentrations, a low progenitor e xpansion and a decrease in CD34(+) cell numbers was observed for patient sa mples in contrast to normal samples, In conclusion, CR1 AML CD34+ cells sho wed excessive early cell mortality. No evidence for cell-cycle arrest or ha emopoiesis inhibitor production was shown, SCF and FL used at high concentr ations did not correct the patient cell expansion defect.