Quantitative and qualitative alterations of long-term culture-initiating cells in patients with acute leukaemia in complete remission

Summary. Bone marrow (BM) samples from 24 patients with acute leukaemia (AML 17, ALL seven) in first complete remission were compared to samples from 10 normal donors with regard to their content in long-term culture-initiating cells (LTC-IC) as assessed by a limiting dilution assay and the clonogeneic capacity of these cells, in order to determine whether remission marrow cells displayed any specific defect at the primitive stem cell level. The frequency of LTC-IC in the whole patient group was 1 in 3487 6 3125 mononuclear cells (MNC) as compared to 1 in 794 6 492 MNC in normal controls (P o 0·0009), with no difference between AML and ALL. Moreover, the clonogeneic capacities were 2·66 6 0·7 (range 1·8‐1·6) and 4·0 6 1·6 (range 2·2‐7·9) CFC per LTC-IC in patients and controls respectively (P o 0·0015). These quantitative and qualitative defects were aggravated by treatment with mafosfamide at a dose of 50 mg/10 7 MNC/ ml, where the mean recovery of LTC-IC after in vitro purging was 42%. In nine patients autografted with purged marrow following high-dose radiochemotherapy, no correlation could be detected between the dose of LTC-IC (mean 6742 6 7877/kg) and the kinetics of recovery of haemopoiesis. We concluded that, in acute leukaemia patients in complete remission, the presumably normal residual stem cell pool was not only quantitatively diminished but also qualitatively altered in its capacity to give rise to clonogeneic progenitor cells.