Stromal-derived factor 1 and matrix metalloproteinase 9 levels in bone marrow and peripheral blood of patients mobilized by granulocyte colony-stimulating factor and chemotherapy.: Relationship with mobilizing capacity of haematopoietic progenitor cells

The roles of the chemokine stromal-derived factor 1 (SDF-1) and the matrix metalloproteinase 9 (MMP-9) in haematopoietic progenitor cell (HPC) mobilization are still unclear, particularly when patients are mobilized by granulocyte colony-stimulating factor (G-CSF) plus chemotherapy. We determined bone marrow ( BM) and peripheral blood (PB) plasma levels of SDF-1, together with CXC-chemokine receptor 4 (CXCR-4) expression on CD34(+) cells, and interleukin 8 (IL-8) and MMP-9 in 55 patients mobilized for autologous PB transplantation compared with 10 normal BM and PB samples. Plasma samples were tested at steady state (SS-) and after mobilization by cyclophosphamide and G-CSF administration (M-). SDF-1, CXCR-4, IL-8 and MMP-9 levels were significantly lower in SS- and M- PB than in SS- BM. Differences in SDF-1 levels between SS- PB and SS- BM were also observed after mobilization. We showed for the first time a clear relationship between the levels of circulating HPC, both at steady state and after mobilization, and those of secreted MMP-9 but not of SDF-1 or IL-8. However, a negative correlation was observed between mobilizing capacity and CXCR-4 expression on CD34(+) cells. These findings suggest that G-CSF-induced mobilization of HPC from BM involves MMP-9, without reversing the positive gradient of SDF-1 between BM and PB.