Clonogenic potential and phenotypic analysis of CD34+ cells mobilized by different chemotherapy regimens.

BACKGROUND AND OBJECTIVE Since limited data concerning quantitative and qualitative differences of CD34+ cells collected after different mobilization schedules are available, we investigated phenotype, proliferative capacity and primitive progenitor cell content of CD34+ cells mobilized with four different regimens. DESIGN AND METHODS The number, phenotype, and progenitor cell content of CD34+ cells were investigated in 46 patients mobilized with cyclophosphamide (CY) 7 g/m(2) plus granulocyte colony-stimulating factor (G-CSF, 5 microg/kg) (CY7+G-CSF) (n=16), CY 4 g/m(2) plus G-CSF (CY4+G-CSF) (n=8), IVE [ifosphamide (2.5 g/m(2) for 3 d), etoposide (150 mg/m(2) for 3 d), epirubicin (100 mg/m(2) on day 1)] plus G-CSF (IVE+G-CSF) (n=9), or G-CSF (10 microg/kg) alone (n=13). RESULTS The number of CD34+ cells collected per liter of processed blood was significantly higher in the CY7+G-CSF group than in the CY4+G-CSF and G-CSF groups (p </= .005), but not the IVE+G-CSF group. As compared to patients in the CY4+G-CSF group, those mobilized with CY7+G-CSF and IVE+G-CSF produced significantly lower percentages of CD34+ cells lacking CD38, CD33, CD45RA, and HLA-DR (p </= .016, at least). In addition, CY4+G-CSF mobilized CD34+ cells had a significantly higher plating efficiency than the cells mobilized in other ways (p </= r .036). In the G-CSF group, colony-forming cells and long-term culture-initiating cells were significantly lower than in the CY groups (p </= .0014 and </= 013, respectively). INTERPRETATION AND CONCLUSIONS Our data demonstrate that: (i) different mobilization regimens allow the collection of CD34+ cells with distinct phenotypic and proliferative features; (ii) evaluation of the absolute number of CD34+ cells by itself is not a reliable indicator of the clonogenic content of blood mobilized with different chemotherapy regimens; (iii) because of the substantial impact that chemotherapy regimens have on the quantity and quality of collected CD34+ cells, anticancer effects and optimal blood progenitor cell yields should be evaluated for each chemotherapy schedule.