Summary. Some patients unexpectedly fail to mobilize sufficient numbers of haematopoietic progenitor cells (HPCs) into the peripheral blood for autologous transplantation. Considering the important role of the chemokine stromal cell-derived factor 1 (SDF-1) in HPC homing, we investigated a possible relationship between SDF1 gene polymorphism and HPC mobilization capacity in 63 patients with malignancy. Some 67% of the good mobilizers ($ 50 CD34 1 cells/ml) and only 36% of the intermediate/poor mobilizers were SDF1-3 0 A allele carriers (P 0´032). In multivariate analysis, the presence of the SDF1-3 0 A allele was the only factor predictive of good CD341 cell mobilization (P 0´025). This is the first report showing the involvement of genetic factors for HPC mobilization in humans and suggests a significant role for SDF-1 in this process.

Summary. 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.

This study opens new perspectives for the clinical utilisation of L-asparaginase. This mode of administration of the drug is able to improve pharmacodynamic parameters and enzymic efficacy and to increase the general tolerance of the treatment.

Forty-six patients with non-Hodgkin's lymphoma (NHL) were treated with autologous bone marrow transplantation (ABMT) in two different institutions. All patients were pretreated with conventional chemotherapy. Three different conditioning regimens were used, and 20 patients underwent bone marrow purging. Twelve patients were treated in first complete remission (CR); eight are in unmaintained CR 8 to 104 months after ABMT. Five patients were grafted in first partial remission (PR) after conventional therapy; all achieved CR, and all remain in prolonged CR (first CR for four patients, second CR for one patient). Of 21 patients with chemosensitive relapses, 13 patients are in prolonged unmaintained CR 8 to 94 months after ABMT. Eight patients with resistant disease remained uncured by ABMT; all eight died, six from progressive illness and two from toxicity. The current 3-year disease-free probability is 60% for all patients, 0% for refractory disease; 82% for first PR or CR, and 60% for sensitive relapses (SRs). These results confirm the efficacy of ABMT in the treatment of chemosensitive NHL with bad prognosis.

We assessed the effect of antitumoural therapy at intensive doses on the haemopoietic system using long-term marrow cultures (LTMC) established from 33 patients (25 with haematological diseases and eight with solid tumours) after autologous bone marrow transplantation (ABMT). When compared to 42 pre-graft patients, a decreased CFU-GM production and a defect in stromal layer (SL) confluence were found after ABMT on day 90 but also on day 365. However, these abnormalities were observed only in patients with haematological diseases and no differences between pre-graft and post-graft results were found in patients with solid tumours. Among the patients with haematological diseases, on day 90 those with acute lymphoid leukaemias showed lower CFU-GM production whereas patients with non-Hodgkin's lymphomas developed more frequently subconfluent or confluent SL. Other factors studied such as sex, patient age, disease status, marrow purging and post-graft administration of growth factors did not appear to influence post-graft LTMC results. Multivariate analysis including all the patients has shown (a) that solid tumours were associated with higher CFU-GM production, and (b) that conditioning regimens with total body irradiation (TBI) or busulfan led more frequently to non-confluent SL. In conclusion, high-dose therapy followed by ABMT can induce a persistent impairment of the stem cell and stromal cell compartments, particularly in patients with haematological diseases conditioned with TBI, despite the absence of any alloimmune reaction and post-graft immunosuppressive therapy.

To evaluate the modification of pharmacodynamic parameters induced by the administration of L-asparaginase loaded into red blood cells, 13 patients received a single dose of L-asparaginase internalised into the carrier. The enzyme was loaded using a reversible lysis-resealing process. The dose per patient ranged from 30 to 200 i.u. kg-1. Considerable heterogeneity occurred between patients. the level of L-asparaginase circulating after 24 h represented 47% of the total injected dose as compared to 74.8% for red blood cells (RBCs). However, the half-life of the enzyme remaining in the circulation was very similar to that of the RBC carrier, i.e. 29 days and 27 days, respectively, compared with 8-24 h for the free enzyme. Sustained elimination of plasma L-asparagine occurred, the duration of which was dependent on the injected dose. A single injection of 30.i.u.kg-1 was sufficient to eliminate plasma L-asparagine over 10 days. With 150-200 IU.kg-1 the elimination period was extended to 50 days. These data show that the use of RBCs as carriers of L-asparaginase greatly improves the pharmacodynamic parameters of the drug.

Marrow stromal cells were evaluated several months after autologous BMT for their capacity to support both normal hemopoiesis and secrete the main growth factors involved in its control, G-CSF, GM-CSF, IL-3 and SCF. Stromal layers (SL) were obtained by long-term marrow cultures (LTMC) established from 15 patients (9 with hematologic malignancies and 6 with solid tumors) 3 months after autologous BMT and were compared to pre-graft patients. After irradiation, both post-graft and pre-graft SL were recharged with the same inoculum of normal marrow cells. As compared to pre-graft values, CFU-GM production on post-graft SL was significantly increased during the first 2 weeks of culture whereas it was decreased from week 3 to week 8. These findings were only observed in patients with hematologic malignancies and not in patients with solid tumors. Growth factor secretion was evaluated by ELISA in the supernatants of unstimulated and IL-1-stimulated SL from 10 post-graft patients, 13 pre-graft patients and 5 normal controls. In any group of patients, IL-3 was undetectable either spontaneously or after IL-1-stimulation. As compared to controls, secretion by IL-1-stimulated SL was not different for GM-CSF in pre- and post-graft patients but tended to be decreased for G-CSF in post-graft patients. SCF secretion, which was not induced by IL-1, appeared dramatically decreased in both pre- and post-graft patients. The capacity of post-graft SL to support CFU-GM growth in LTMC was correlated at week 1 with G-CSF secretion and from week 3 to week 8 with SCF secretion. These results suggest that microenvironment remains qualitatively damaged several months after BMT involving a decreased capacity both to support early hemopoiesis and to secrete SCF, particularly in patients grafted for hemopoietic malignancies.

We report a patient with relapsing hereditary hemolytic uremic syndrome (HUS) that began in the neonatal period with life-threatening jaundice and hemolytic anemia. He progressed to end-stage renal failure at 14 years of age and had a cerebrovascular accident while on dialysis. The cause of HUS was a constitutional deficiency in the von Willebrand factor cleaving protease. Hematological features of HUS significantly improved following bilateral nephrectomy. After renal transplantation, he had an early recurrence of HUS associated with two episodes of retinal and cerebral ischemia. Long-term treatment with fresh-frozen plasma exchanges prevented recurrence of HUS, cerebrovascular attacks, and early loss of the graft.