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.