A randomized phase 2 study of PBPC mobilization by stem cell factor and filgrastim in heavily pretreated patients with Hodgkin's disease or non-Hodgkin's lymphoma

Peripheral blood stem cell mobilization: the CXCR2 ligand GRObeta rapidly mobilizes hematopoietic stem cells with enhanced engraftment properties

Chemokines direct the movement of leukocytes, including hematopoietic stem and progenitor cells, and can mobilize hematopoietic cells from marrow to peripheral blood where they can be used for transplantation. In this review, we will discuss the stem cell mobilizing activities and mechanisms of action of GRObeta, a CXC chemokine ligand for the CXCR2 receptor. GRObeta rapidly mobilizes short- and long-term repopulating cells in mice and/or monkeys and synergistically enhances mobilization responses when combined with the widely used clinical mobilizer, granulocyte colony-stimulating factor (G-CSF). The hematopoietic graft mobilized by GRObeta contains significantly more CD34(neg), Sca-1+, c-kit+, lineage(neg) (SKL) cells than the graft mobilized by G-CSF. In mice, stem cells mobilized by GRObeta demonstrate a competitive advantage upon long-term repopulation analysis and restore neutrophil and platelet counts significantly faster than cells mobilized by G-CSF. Even greater advantage in repopulation and restoration of hematopoiesis are observed with stem cells mobilized by the combination of GRObeta and G-CSF. GRObeta-mobilized SKL cells demonstrate enhanced adherence to vascular cell adhesion molecule-1 and VCAM(pos) endothelial cells and home more efficiently to bone marrow in vivo. The marrow homing ability of GRObeta-mobilized cells is less dependent on the CXCR4/SDF-1 axis than cells mobilized by G-CSF. The mechanism of mobilization by GRObeta requires active matrix metalloproteinase-9 (MMP-9), which results from release of pro-MMP-9 from peripheral blood, and marrow neutrophils, which alters the stoichiometry between pro-MMP-9 and its inhibitor tissue inhibitor of metalloproteinase-1, resulting in MMP-9 activation. The efficacy and rapid action of GRObeta and lack of proinflammatory activity make it an attractive agent to supplement mobilization by G-CSF. In addition, GRObeta may also have clinical mobilizing efficacy on its own, reducing the overall time and costs associated with peripheral blood stem cell transplantation.

Mechanisms of hematopoietic stem cell mobilization: When innate immunity assails the cells that make blood and bone

Mobilization is now used worldwide to collect large numbers of hematopoietic stem and progenitor cells (HSPCs) for transplantation. Although the first mobilizing agents were discovered largely by accident, discovery of more efficient mobilizing agents will require a better understanding of the molecular mechanisms responsible. During the past 5 years, a number of mechanisms have been identified, shedding new light on the dynamics of the hematopoietic system in vivo and on the intricate relationship between hematopoiesis, innate immunity, and bone. After briefly reviewing the mechanisms by which circulating HSPCs home into the bone marrow and what keeps them there, the current knowledge of mechanisms responsible for HSPC mobilization in response to hematopoietic growth factors such as granulocyte colony-stimulating factor, chemotherapy, chemokines, and polyanions will be discussed together with current strategies developed to further increase HSPC mobilization.

Mobilization of Human Lymphoid Progenitors after Treatment with Granulocyte Colony-Stimulating Factor

Hemopoietic stem and progenitor cells ordinarily residing within bone marrow are released into the circulation following G-CSF administration. Such mobilization has a great clinical impact on hemopoietic stem cell transplantation. Underlying mechanisms are incompletely understood, but may involve G-CSF-induced modulation of chemokines, adhesion molecules, and proteolytic enzymes. We studied G-CSF-induced mobilization of CD34+ CD10+ CD19- Lin- and CD34+ CD10+ CD19+ Lin- cells (early B and pro-B cells, respectively). These mobilized lymphoid populations could differentiate only into B/NK cells or B cells equivalent to their marrow counterparts. Mobilized lymphoid progenitors expressed lymphoid- but not myeloid-related genes including the G-CSF receptor gene, and displayed the same pattern of Ig rearrangement status as their bone marrow counterparts. Decreased expression of VLA-4 and CXCR-4 on mobilized lymphoid progenitors as well as multipotent and myeloid progenitors indicated lineage-independent involvement of these molecules in G-CSF-induced mobilization. The results suggest that by acting through multiple trans-acting signals, G-CSF can mobilize not only myeloid-committed populations but a variety of resident marrow cell populations including lymphoid progenitors.

Successful mobilization of peripheral blood stem cells using recombinant human stem cell factor in heavily pretreated patients who have failed a previous attempt with a granulocyte colony-stimulating factor-based regimen

To assess the efficacy of recombinant human stem cell factor (rHuSCF), 48 patients who had failed to mobilize >2.0 x 10(6) CD34+ cells/kg with granulocyte colony-stimulating factor (G-CSF) (10 microg/kg twice daily) with, or without, concomitant chemotherapy (G-CSF-based regimen), were remobilized with the addition of rHuSCF (20 microg/kg/day). In all, 18/48 (38%) achieved a total of >2.0 x 10(6) CD34+ cells/kg with the second rHuSCF-based mobilisation alone and 29/48 (60%) achieved a cumulative total of >2.0 x 10(6) CD34+ cells/kg following remobilization. Inclusion of chemotherapy in the mobilization regimen resulted in a higher yield of CD34+ cells/kg for both the initial G-CSF-based and subsequent rHuSCF-based regimens (0.90 vs 0.54, P < 0.01 and 2.36 vs 1.34, P < 0.01, respectively). The total peripheral blood stem cells PBSC collected from the G-CSF-based regimen, performance status, baseline platelet count and albumin were significantly associated with successful remobilization. Patients with multiple myeloma were also more likely to successfully remobilize. There was no threshold of total collected from the failed G-CSF-based regimen below which successful remobilization with the rHuSCF-based regimen was not possible. We therefore propose a predictive model [PBSC expected = 0.6+(G-CSF-based total collection)+2 (rHuSCF-based day 1 collection)] to calculate the cumulative total of PBSC expected following a maximum of five leukaphereses. This algorithm may permit the early identification of patients who are unlikely to achieve sufficient PBSC for transplantation and allow physicians to direct the resources involved in PBSC collection in a more appropriate and economical manner.

New strategies for mobilization of hematopoietic stem cells

A significant number of tumor patients fail peripheral blood progenitor cell (PBPC) mobilization and thus cannot receive potentially curative high-dose chemotherapy with subsequently required PBPC transplantation. New insights into the physiology of mobilization have revealed the pivotal role of the CXCR4/stromal derived factor-1α receptor–ligand interaction for stem cell retention in the bone marrow. New CXCR4 antagonists such as AMD3100 are currently in clinical studies. They act synergistically with the established mobilizing agent granulocyte colony-stimulating factor (G-CSF); thus, patients can collect more PBPCs in fewer apheresis sessions, and others that previously failed can now successfully collect sufficient PBPCs for transplantation. Experimental and clinical data suggest that the quality of AMD3100-mobilized PBPC may even be superior to PBPCs mobilized following standard therapy. CXCR4 antagonists are the most exciting development in the field of PBPC mobilization for over a decade. Additionally, new analogs of G-CSF are being introduced with favorable pharmacologic features.

Ancestim (recombinant human stem cell factor, SCF) in association with filgrastim does not enhance chemotherapy and/or growth factor-induced peripheral blood progenitor cell (PBPC) mobilization in patients with a prior insufficient PBPC collection

Up to a third of autologous transplantation candidates fail to mobilize hematopoietic progenitors into the peripheral blood with chemotherapy and/or growth factor treatment, thus requiring innovative mobilization strategies. In total, 20 cancer patients unable to provide adequate PBPC products after a previous mobilization attempt were treated with ancestim (20 microg/kg/day s.c.) and filgrastim (10 microg/kg/day s.c.). In 16 patients, the pre-study mobilization was with filgrastim alone. Eight patients underwent single large volume leukapheresis (LVL) and 12 multiple standard volume leukaphereses (SVL) in both mobilizations. Pairwise comparison of peripheral blood CD34(+) cell concentrations on the day of first leukapheresis failed to document synergism - median CD34(+)/microl of 3.2 (<0.1 to 15.4) and 4.5 (1-28.56) for the pre-study and on-study mobilizations (P = 0.79, sign test), and 4.2 (<0.1-15.4) and 5 (1-28.56), respectively, for the 16 patients previously mobilized with filgrastim alone (P = 1, sign test). The number of CD34(+) cells/kg collected per unit of blood volume (BV) processed was similar in both mobilizations - median 0.1 x 10(6)/kg/BV and 0.09 x 10(6)/kg/BV, respectively (P = 1, sign test). In this phase II study, the combination of ancestim and filgrastim did not allow adequate PBPC mobilization and collection in patients with a previous suboptimal PBPC collection.

Use of recombinant human growth hormone (rhGH) plus recombinant human granulocyte colony-stimulating factor (rhG-CSF) for the mobilization and collection of CD34+ cells in poor mobilizers

The activity of recombinant human growth hormone (rhGH) in enhancing CD34+ cell mobilization elicited by chemotherapy plus recombinant human granulocyte colony-stimulating factor (rhG-CSF) was evaluated in 16 hard-to-mobilize patients, that is, those achieving a peak of circulating CD34+ cells 10/μL or less, or a collection of CD34+ cells equal to or less than 2 × 106/kg. Patients who had failed a first mobilization attempt with chemotherapy plus rhG-CSF (5 μg/kg/d) were remobilized with chemotherapy plus rhG-CSF and rhGH (100 μg/kg/d). As compared with rhG-CSF, the combined rhGH/rhG-CSF treatment induced significantly higher (P ≤ .05) median peak values for CD34+ cells/μL (7 versus 29), colony-forming cells (CFCs)/mL (2154 versus 28 510), and long-term culture-initiating cells (LTC-ICs)/mL (25 versus 511). Following rhG-CSF and rhGH/rhG-CSF, the median yields of CD34+ cells per leukapheresis were 1.1 × 106/kg and 2.3 × 106/kg (P ≤ .008), respectively; the median total collections of CD34+ cells were 1.1 × 106/kg and 6 × 106/kg (P ≤ .008), respectively. No specific side effect could be ascribed to rhGH, except a transient hyperglycemia occurring in 2 patients. Reinfusion of rhGH/rhG-CSF-mobilized cells following myeloablative therapy resulted in prompt hematopoietic recovery. In conclusion, our data demonstrate that in poor mobilizers addition of rhGH to rhG-CSF allows the patients to efficiently mobilize and collect CD34+ cells with maintained functional properties. (Blood. 2004;103: 3287-3295)

Analysis of remobilization success in patients undergoing autologous stem cell transplants who fail an initial mobilization: risk factors, cytokine use and cost

Inadequate stem cell mobilization is seen in approximately 25% of patients undergoing autotransplantation for hematologic malignancies. Remobilization strategies include chemotherapy/cytokine combinations or high-dose cytokines alone or in combination. From 1/1997 to 7/2002, we remobilized 86 patients who failed an initial mobilization (median total CD34=0.72 x 10(6)/kg) in sequential cohorts using high-dose G-CSF (32 microg/kg/day) or G-CSF(10 microg/kg/day)+GM-CSF (5 microg/kg/day). No difference in CD34/kg yields were seen (G-CSF alone: 2.2 x 10(6) and G-CSF+GM-CSF 1.6 x 10(6)) in the median 3 aphereses performed (P=0.333). Of the 86, 23 (27%) failed the second mobilization; 14 were remobilized again (yield=1.5 x 10(6) CD34/kg; three aphereses). Of the 86, 93% went to transplant: three progressed, and three had inadequate stem cells. Significant risk factors for a failed remobilization were: number of stem-cell-damaging regimens (P=0.015), time between last chemotherapy and first mobilization (P=0.028), and higher WBC at initiation of first mobilization (P=0.04). High-dose G-CSF (32 microg/kg/day) was more costly @ USD $9,016, vs $5,907 for the G-CSF+GM-CSF combination (P<0.001). Most patients failing an initial mobilization benefit from a cytokine only remobilization. Lower cost G-CSF+GM-CSF is as effective as high-dose G-CSF.

Neutrophil-derived MMP-9 mediates synergistic mobilization of hematopoietic stem and progenitor cells by the combination of G-CSF and the chemokines GRObeta/CXCL2 and GRObetaT/CXCL2delta4

Mobilized peripheral blood stem cells (PBSCs) are widely used for transplantation, but mechanisms mediating their release from marrow are poorly understood. We previously demonstrated that the chemokines GRObeta/CXCL2 and GRObetaT/CXCL2Delta4 rapidly mobilize PBSC equivalent to granulocyte colony-stimulating factor (G-CSF) and are synergistic with G-CSF. We now show that mobilization by GRObeta/GRObetaT and G-CSF, alone or in combination, requires polymorphonuclear neutrophil (PMN)-derived proteases. Mobilization induced by GRObeta/GRObetaT is associated with elevated levels of plasma and marrow matrix metalloproteinase 9 (MMP-9) and mobilization and MMP-9 are absent in neutrophil-depleted mice. G-CSF mobilization correlates with elevated neutrophil elastase (NE), cathepsin G (CG), and MMP-9 levels within marrow and is partially blocked by either anti-MMP-9 or the NE inhibitor MeOSuc-Ala-Ala-Pro-Val-CMK. Mobilization and protease accumulation are absent in neutrophil-depleted mice. Synergistic PBSC mobilization observed when G-CSF and GRObeta/GRObetaT are combined correlates with a synergistic rise in the level of plasma MMP-9, reduction in marrow NE, CG, and MMP-9 levels, and a coincident increase in peripheral blood PMNs but decrease in marrow PMNs compared to G-CSF. Synergistic mobilization is completely blocked by anti-MMP-9 but not MeOSuc-Ala-Ala-Pro-Val-CMK and absent in MMP-9-deficient or PMN-depleted mice. Our results indicate that PMNs are a common target for G-CSF and GRObeta/GRObetaT-mediated PBSC mobilization and, importantly, that synergistic mobilization by G-CSF plus GRObeta/GRObetaT is mediated by PMN-derived plasma MMP-9.

Enhanced antileukemic activity of allogeneic peripheral blood progenitor cell transplants following donor treatment with the combination of granulocyte colony-stimulating factor (G-CSF) and stem cell factor (SCF) in a murine transplantation model

Allogeneic peripheral blood progenitor cells (PBPCs) have mostly been mobilized by granulocyte colony-stimulating factor (G-CSF). There is neither clinical nor experimental data available addressing the question if other hematopoietic growth factors or combinations thereof might influence engraftment, graft-versus-host disease (GvHD), and graft-versus-leukemia (GvL) effects after allogeneic peripheral blood progenitor cell transplantation (PBPCT). We used a murine model to investigate these parameters after transplantation of PBPCs mobilized with G-CSF and SCF either alone or in combination. Treatment of splenectomized DBA and Balb/c mice with 250 microg/kg/day G-CSF for 5 days resulted in an increase of CFU-gm from 0 to 53/microl. The highest progenitor cell numbers (147/microl) were observed after treatment with 100 microg/kg/day SCF administered in conjunction with G-SCF. No differences were detected with regard to the number of T cells (CD3+), T cell subsets (CD4+, CD8+), B cells (CD19+) and NK cells (NK1.1+) in PBPC grafts mobilized by G-CSF plus SCF compared to those mobilized with G-CSF alone. The antileukemic activity of syngeneic and MHC-identical allogeneic PBPC grafts was investigated in lethally irradiated Balb/c mice bearing the B-lymphatic leukemia cell line A20. In this model, PBPCs mobilized by G-CSF plus SCF exerted a significantly higher antileukemic activity compared to grafts mobilized by G-CSF alone (94 vs 71% freedom from leukemia at day 100, P<0.05). The antileukemic effect was lowest after BMT (38% freedom from leukemia). Since significant differences in the incidence of lethal GvHD were not observed, improved GVL-activity resulted in superior overall survival. Our data demonstrate that the utilization of specific hematopoietic growth factors not only improve the yield of hematopoietic progenitor cells but can also significantly enhance the immunotherapeutic potential of allografts.

Plasma from poorly mobilizing human subjects inhibits cytokine-induced murine blood stem-cell mobilization

BACKGROUND

Cytokine-induced mobilization of hematopoietic stem/progenitor cells to the circulation facilitates efficient harvest of blood stem cells by leukapheresis. Up to 30% of autologous, and 10-20% of allogeneic blood stem-cell donors respond poorly to mobilizing cytokines and preliminary studies implicated a circulating inhibitor of mobilization.

METHODS

In this study, plasma from 11 allogeneic and 23 autologous stem cell donors was assayed for inhibition of mobilization in mice.

RESULTS

There were significant correlations between CD34(+) cells collected/kg human donor weight and spleen weight, CD34(+) CD45(+) cells, GMCFC and HPP-CFC per spleen in murine recipients of these plasma samples. Overall, there was a positive association between transforming growth factor beta (TGF-beta) levels and CD34(+) cells per liter of blood processed (LBP). However, when arbitrarily segregated into good versus poor mobilizers, based on less or greater than 15 million CD34(+) cells collected per LBP, the majority (64%) of normal donors were good mobilizers. The majority of the poor mobilizers (83%) were patients. For a subset of 12 individuals whose plasma strongly inhibited mobilization in the mouse, a significant positive correlation of the extent of inhibition with TGF-beta levels was found. For 11 individuals whose plasma, based on colony assays, enhanced mobilization when injected into mice, no correlation with TGF-beta levels was evident.

DISCUSSION

Elevated plasma TGF-beta levels in some stem-cell donors may be associated with poor stem-cell mobilization. It remains to be determined whether elevation of TGF-beta levels is a cause of, or a compensatory response to, poor mobilization.

Successful mobilization of peripheral blood stem cells after addition of ancestim (stem cell factor) in patients who had failed a prior mobilization with filgrastim (granulocyte colony-stimulating factor) alone or with chemotherapy plus filgrastim

This study assessed the ability of recombinant human stem cell factor (rHuSCF) to mobilize stem cells in 44 patients who had failed a prior mobilization (CD34(+) yield 0.5-1.9 x 10(6)/kg BW) with filgrastim-alone or chemotherapy-plus-filgrastim. The same mobilization regimen was used with the addition of rHuSCF. In the filgrastim-alone group (n=13), rHuSCF 20 microg/kg was started 3 days before filgrastim and continued for the duration of filgrastim. In the chemotherapy-plus-filgrastim group (n=31), rHuSCF 20 microg/kg/day plus filgrastim 5-10 microg/kg/day were administered concurrently. Leukaphereses were continued to a maximum of four procedures or a target of >or=3 x 10(6) CD34(+) cells/kg. In both groups, CD34(+) yield (x 10(6)/kg BW) of the study mobilization was higher than that of the prior mobilization (median: 2.42 vs 0.84 P=0.002 and 1.64 vs 0.99 P=<0.001, respectively). In all 54 and 45% of patients in the filgrastim-alone group and chemotherapy-plus-filgrastim group, respectively, reached the threshold yield of 2 x 10(6)/kg. The probability of a successful mobilization was the same in those with a CD34+ yield of 0.5-0.75 x 10(6)/kg BW in the prior mobilization as in those with 0.76-1.99 x 10(6)/kg BW. Downmodulation of c-kit expression and a lower percentage of Thy-1 positivity in the mobilized CD34(+) cells were noted in the successful mobilizers compared with those in the poor mobilizers. This study shows that rhuSCF is effective in approximately half the patients who had failed a prior mobilization and allows them to proceed to transplant. It also points to the likely role of the SCF/c-kit ligand pair in mobilization.

Treatment of aggressive non-Hodgkin's lymphoma with chemotherapy in combination with filgrastim

Non-Hodgkin's lymphoma (NHL) is one of the ten most common cancers in the developed world. The incidence has increased significantly over the past two decades and it is a particular burden in patients over the age of 60 years. The gold standard for primary treatment of aggressive NHL is combination chemotherapy with cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP). Haematological growth factors, such as granulocyte colony-stimulating factor (G-CSF), can be used to ameliorate chemotherapy-induced neutropenia, thus facilitating delivery of chemotherapy at the planned dose intensity. The International Prognostic Index is able to identify high-risk patients who are unlikely to be cured with standard primary chemotherapy. In these patients, the use of dose-intensive therapy, including high-dose chemotherapy with stem cell support, is being evaluated as potential primary therapy. Stem cell transplantation is currently the treatment of choice for patients with relapsed NHL or those with chemosensitive refractory disease. Autologous peripheral blood stem cells mobilised into the circulation by G-CSF help achieve rapid haematological reconstitution and are now the preferred source of stem cells over bone marrow for this form of therapy. G-CSF is also used to support allogeneic transplantation, which exerts a therapeutic graft-versus-lymphoma effect. Administration of G-CSF following autologous or allogeneic peripheral blood stem cell transplantation accelerates neutrophil recovery.

High-dose ara-C with autologous peripheral blood progenitor cell support induces a marked progenitor cell mobilization: an indication for patients at risk for low mobilization

A high-dose (HD) chemotherapy scheme was designed for the collection of large numbers of peripheral blood progenitor cells (PBPC) in lymphoma patients who were candidates for myeloablative therapy with autograft. The scheme included the sequential administration of HD cyclophosphamide (CY) (7 g/m(2)) and HD ara-C (2 g/m(2) twice a day for 6 consecutive days), followed by final consolidation with PBPC autograft. PBPC harvests were scheduled following both HD CY and HD ara-C. To minimize hematologic toxicity, small aliquots of PBPC (<or=3 x 10(6) CD34(+) cells/kg) collected following HD CY were reinfused following HD ara-C. The treatment was delivered to 112 patients (median age: 43 years) with lymphoid malignancies (107 non-Hodgkin's lymphoma, four Hodgkin's lymphoma, one amyloidosis); 75 patients were at disease onset, whereas 37 had relapsed or were refractory after first-line conventional therapy. PBPC mobilization was assessed in terms of peak values of circulating CD34(+) cells/microl, as well as total CD34(+) cells/kg collected. In a few patients CFU-GM/kg were also evaluated. At the time of maximal mobilization following HD CY, 93 'high-mobilizer' patients had >20 circulating CD34(+) cells/microl, whereas the remaining 19 'low-mobilizer' patients did not reach this cut-off value. In spite of poor mobilization after HD CY, 16 out of 19 low mobilizers provided good harvests following HD ara-C; overall, median collected CD34(+) cells x 10(6)/kg were 1.4 (0-3.1) and 10.2 (0-37) after HD CY and HD ara-C, respectively (P = 0.00007). Similar patterns were observed when PBPC were evaluated by CFU-GM/kg. Complete and durable hemopoietic reconstitution followed autograft with post HD ara-C PBPC. Within the high-mobilizer group, 88 patients received HD ara-C and 79 (90%) still showed high mobilization; overall, median collected CD34(+)cells x 10(6)/kg were 17.8 (range 3-94) and 19 (range 0-107) after HD CY and HD ara-C respectively (P = NS). Thus, the scheme allowed sufficient PBPC collections for autografting in low mobilizer patients; in addition, the scheme could be considered whenever extensive chemotherapy debulking is needed prior to PBPC collection.

Optimising parameters for peripheral blood leukapheresis after r-metHuG-CSF (filgrastim) and r-metHuSCF (ancestim) in patients with multiple myeloma: a temporal analysis of CD34(+) absolute counts and subsets

Patients (n = 69) with multiple myeloma undergoing peripheral blood stem cell collection (PBSC) were treated with cyclophosphamide and a combination of recombinant methionyl human granulocyte colony-stimulating factor (r-metHuG-CSF, filgrastim) and recombinant methionyl human stem cell factor (r-metHuSCF, ancestim). The objectives of this study were to determine: (1) The proportion of patients reaching a target yield of >or=5 x 10(6) CD34(+) cells/kg in one or two successive large-volume (20 liter) leukapheresis procedures; (2) the optimal collection time for leukapheresis; (3) mobilization kinetics of CD34(+) subsets in response to G-CSF/SCF. All patients were mobilized with cyclophosphamide (2.5 g/m(2)) on day 0 followed by filgrastim (10 microg/kg ) plus ancestim (20 microg/kg) commencing day 1 and continuing to day 11 or 12. Of the 65 evaluable patients, 57 were considered not heavily pretreated and 96.5% obtained a target of >or=5 x 10(6)/kg in one collection. The median CD34(+) cells/kg was 39.5 x 10(6) (range: 5.2-221.2 x 10(6)). Subset analysis demonstrated the number of CD38(-), CD33(-), and CD133(+) peaked at day 11; and CD34(+), CD90(+) cells peaked at day 10. The optimum day for leukapheresis was determined to be day 11. The median absolute peripheral blood CD34(+) cell numbers on day 11 was 665 x 10(6)/l (range: 76-1481 x 10(6)/l). Eight of the 10 heavily pretreated patients were evaluable: three achieved the target dose in one leukapheresis (37.5%) and three (37.5%) achieved the target dose with two leukaphereses. Use of this mobilization strategy allowed the collection of high numbers of CD34(+) cells and early progenitors and the ability to predictably schedule leukapheresis.

The composition of leukapheresis products impacts on the hematopoietic recovery after autologous transplantation independently of the mobilization regimen

BACKGROUND

Effects of mobilization regimen on the composition of leukapheresis products (LPs) and on hematopoietic reconstitution after autologous peripheral blood progenitor cell transplantation (PBPCT) are not well known.

STUDY DESIGN AND METHODS

The effects of three different mobilization regimens--stem cell factor (SCF) plus granulocyte colony stimulating factor (G-CSF) plus cyclophosphamide (CCP), G-CSF alone, and G-CSF plus CCP--on the composition of LPs from patients with nonhematologic PBPC malignancies compared to LPs from G-CSF-mobilized healthy donors and normal marrow (BM) samples were analyzed. The impact of LP composition on both short- and long-term engraftment after autologous PBPCT was also evaluated.

RESULTS

The most effective regimen for mobilization of CD34+ hematopoietic progenitor cells (HPCs) into peripheral blood was SCF, G-CSF, and CCP, providing the highest numbers of all CD34+ HPCs subsets analyzed. Patients mobilized with SCF plus G-CSF plus CCP showed the highest numbers of neutrophils and monocytes, whereas the highest numbers of lymphocytes and NK cells were observed in LPs from G-CSF-mobilized patients. The overall number of CD34+ HPCs was the strongest factor for predicting recovery of platelets, whereas the number of myelomonocytic-committed CD34+ precursors was the most powerful independent prognostic factor for WBC and neutrophil recovery. The overall number of CD4+ T cells returned showed an independent prognostic value for predicting the occurrence of infections, during the first year after transplant.

CONCLUSIONS

The use of different mobilization regimens modifies the overall number of CD34+ HPCs obtained during leukapheresis procedures, and also affects both the absolute and the relative composition of the LPs in different CD34+ and CD34- cell subsets.

Cyclophosphamide, etoposide and G-CSF to mobilize peripheral blood stem cells for autologous stem cell transplantation in patients with lymphoma

We aimed to assess the effectiveness of cyclophosphamide, etoposide and G-CSF (C+E) to mobilize peripheral blood stem cells for autologous stem cell transplantation in patients with lymphoma. A matched cohort study was performed comparing patients mobilized with C+E to patients mobilized with cyclophosphamide and G-CSF (C alone). Patients were matched for disease, prior radiotherapy and a chemotherapy score reflecting the amount and type of prior chemotherapy. Thirty-eight consecutive patients mobilized with C+E were compared with 38 matched controls. C+E was equivalent to C alone in terms of numbers of patients achieving a minimum threshold of > or =2 x 10(6)/kg CD34(+)cells (82% vs 79%, P = 0.74). C+E was superior, however, in terms of total CD34(+) yield (6.35 vs 3.3 x 10(6)/kg, P < 0.01), achieving a target graft of > or =5 x 10(6)/kg (55% vs 34%, P = 0.04) and obtaining both a minimum (61% vs 32%, P < 0.01) and target (45% vs 13%, P < 0.01) graft in one apheresis. This superiority was largely confined to patients with lower chemotherapy scores. There was no difference in neutrophil and platelet recovery or transfusion requirements for those who subsequently received high-dose therapy and stem cell transplantation. Thus, C+E improves the efficiency of peripheral blood stem cell collection, but does not increase the number of patients who can proceed to transplantation. Most of the benefit of the regimen was confined to patients who had not received extensive prior therapy. Novel strategies are required to increase the collection efficiency of 'hard to mobilize' patients.

The synergy between stem cell factor (SCF) and granulocyte colony-stimulating factor (G-CSF): molecular basis and clinical relevance

Stem cell factor (SCF), an essential growth factor in normal hematopoiesis, exerts potent effects when combined with cytokines. In particular, its synergy with granulocyte colony-stimulating factor (G-CSF) results in important biologic responses. These include enhancement of ex vivo long-term expansion of human primitive hematopoietic cells and increased mobilization of peripheral blood progenitor cells (PBPC) for transplantation. Despite the clinical importance of the interaction between SCF and G-CSF, the absence of a model system in which it could be studied at the cellular level had impaired the ability to understand the basis of their co-operation. To overcome this impediment, a system was recently generated which recapitulates the biologic synergy between SCF and G-CSF. MO7e-G cells have allowed the identification of key events in the synergistic actions of these cytokines on proliferation and gene expression. Among the biochemical and molecular events mediated by these cytokines are the down-regulation of p27kip1 and the independent phosphorylation of STAT3 on tyrosine and serine residues. Recent work has provided increasing evidence for the clinical importance of the combination of SCF and G-CSF. The elucidation of the intracellular events triggered by their receptors is now shedding light on key mediators of their synergistic effects. The identification of these pathways is of considerable importance for understanding fundamental aspects of hematopoiesis, and as potential targets for therapeutic intervention.

Hematopoietic stem cell transplantation in Hodgkin disease

Intensive therapy and autologous stem cell transplantation represent the standard of care in most patients whose Hodgkin disease has not been cured with conventional chemotherapy. With more prolonged follow-up of autografted patients, the problems with autologous stem cell transplantation are clear. In particular, recurrent disease and late transplant-related complications limit the effectiveness of this approach. A number of autologous stem cell transplantation studies have reported prognostic factors that will help identify patients at high risk for relapse. Several new approaches for decreasing recurrence rates are discussed, including novel immune strategies and re-evaluation of allogeneic stem cell transplantation. Although the risk of secondary malignancy and other causes of late morbidity and mortality after autologous stem cell transplantation is relatively low, current studies contribute to understanding of the pathogenesis of these complications and may diminish their impact in the future.

A randomized phase II study of amifostine used as stem cell protectant in non-hodgkin lymphoma patients receiving cisplatin-based salvage chemotherapy prior to stem cell transplant

Stem cell mobilization may be inadequate in many lymphoma patients in need for autologous stem cell transplant (SCT). In this study, we sought to evaluate a potential role of amifostine as a stem cell chemoprotective agent in lymphoma patients receiving DHAP chemotherapy in preparation for high-dose chemotherapy (HDC) and stem cell transplant (SCT). In the beginning of the DHAP course, patients were randomized 1:1 to receive amifostine at 740 mg/m(2). Stem cells were mobilized with GCSF after the last cycle of DHAP. Stem cell collection started upon ANC recovery over 1000/mm(3). Standard 10 lt. apheresis daily with a goal of a minimum of 2 x 10(6) stem cells/kg were performed. Twenty-one patients have been enrolled; 10 received amifostine pretreatment (age, 20-64) and 11 were randomized to the control arm (age, 18-63). Prior chemotherapy was balanced in the two groups. The median number of DHAP treatments for each group was 2. Amifostine was well tolerated and was associated with higher stem cell collection. Toxicity and time to engraftment were comparable between the two groups. Our preliminary results may suggest a role of amifostine in protecting stem cells during salvage chemotherapy, thus facilitating stem cell collection.