CD34(-COLONY-STIMULATING FACTOR (G-CSF) ARE FUNCTIONALLY DIFFERENT FROM CD34(+) CELLS MOBILIZED BY G-CSF() CELLS MOBILIZED BY CYCLOPHOSPHAMIDE AND GRANULOCYTE)

Mobilized peripheral blood progenitor cells (PBPC) are increasingly us ed as an alternative to bone marrow for autografting procedures. Curre ntly, cyclophosphamide (CY) followed by granulocyte colony-stimulating factor (G-CSF) or G-CSF alone are the most commonly used PBPC mobiliz ation schedules, In an attempt to investigate whether the use of these two mobilization regimens could result in the collection of functiona lly different CD34(+) cells, we analyzed nucleated cells (NC), CD34(+) cells, committed progenitor cells and long-term culture initiating-ce lls (LTC-IC) in 52 leukaphereses from 26 patients with lymphoid malign ancies, mobilized either by CY+G-CSF (n = 16) or G-CSF alone (n = 10). Thirty-four aphereses from the CY+G-CSF group and 18 aphereses from t he G-CSF group were investigated, According to the study design, leuka phereses were carried out until an average number of 7 x 10(6) CD34(+) cells/kg body weight were collected. The mean (+/- s.e.m.) numbers of CD34(+) cells mobilized per apheresis by CY+G-CSF and G-CSF were not significantly different (2.76 +/- 0.6 x 10(8) vs 2.53 +/- 0.4 x 10(8), P less than or equal to 0.7). This resulted from a mean number of NC that was significantly lower in the CY+G-CSF products than in the G-CS F products (12.4 +/- 1.7 x 10(9) vs 32 +/- 5.4 x 10(9), P less than or equal to 0.0001) and a mean incidence of CD34(+) cells that was signi ficantly higher in the CY+G-CSF products than in the G-CSF products (2 .9 +/- 0.6% vs 0.9 +/- 0.2%, P less than or equal to 0.0018). The mean (+/- s.e.m.) number of CFU-GM collected per apheresis was significant ly higher in the CY+G-CSF group than in the G-CSF group (37 +/- 7 x 10 (6) vs 14 +/- 2 x 10(6), P less than or equal to 0.03). Interestingly, CY+G-CSF-mobilized CD34(+) cells had a significantly higher plating e fficiency than G-CSF-mobilized CD34(+) cells (25.5 +/- 2.9% vs 10.8 +/ - 1.9%, P less than or equal to 0.0006). In addition, the mean number of LTC-IC was significantly higher in the CY+G-CSF products than in th e G-CSF products (6.3 +/- 1 x 10(6) vs 3.3 +/- 0.3 x 10(6), P less tha n or equal to 0.05). In conclusion, our data provide evidence that CYG-CSF and G-CSF induce the mobilization of CD34(+) cells with differen t clonogenic potential, As mobilized PBPC containing large numbers of progenitors lead to safer transplantation, this issue may have implica tions for planning mobilization strategies.