Correlation of colony-forming cells, long-term culture initiating cells and CD34⁺ cells in apheresis products from patients mobilized for peripheral blood progenitors with different regimens

Peripheral blood progenitor cell (PBPC) populations used for transplantation were analyzed for the presence of CD34⁺ cells, colony-forming cells (inital CFC), and long-term culture initiating cells (LTC-IC) cultured on irradiated stroma for 5 weeks. Thirty-eight leukapheresis products were studied from 11 patients with breast cancer, 2 with non-Hodgkin's lymphoma and 1 with ovarian cancer harvested during recovery from either cyclophosphamide (CY) chemotherapy or cyclophosphamide-VP16 with G-CSF (CY-VP-G). CY-VP-G products had a threefold higher median number of mononuclear cells collected, a fivefold higher median concentration of CD34 and LTC-IC and a threefold higher concentration of inital-CFC when compared with CY products. CY-VP-G products had a significantly higher ratio of CFU-GM to BFU-E than the CY-mobilized products. Significant correlations of r = 0.89 and r = 0.68 were observed when comparing CD34 and CFC in products from CY or CY-VP-G patients, respectively. Analysis of the regression lines indicated that slopes of these regression lines were significantly different with a ratio of CD34 to initial CFC of 15:1 in the CY-VP-G products versus 5.2:1 with the CY products. These data indicate a higher cloning efficiency of the CD34⁺ population in the products from CY-mobilized patients. Significant correlations of r = 0.9 (CY) and r = 0.53 (CY-VP-G) were observed when the initial CD34 concentration and the LTC-IC were compared. Comparison of inital CFC with LTC-IC also showed significant correlations (r = 0.94, CY; r = 0.58, CY-VP-G) in samples from both patient groups. These data quantitate the levels of CFC and precursors of CFC in harvests of PBPC, demonstrate the augmentation of this population with G-CSF and show a correlation of these cells with the presence of CD34⁺ cells and each other.