Possibility of progenitor cell mobilization during the hematological recovery following peripheral blood stem cell autograft

Twenty-four patients with hematological malignancies were studied during recovery following autografting in order to establish the proportion of patients that show CD34+ cell mobilization and the kinetics of mobilized CD34-positive cells. The patients showed a peak in peripheral blood (PB) CD34+ cells after a median of 14 days (range 12-20) following reinfusion. According to the number of circulating CD34+ cells, two groups could be clearly distinguished: 17 patients (group A) with <10 PB CD34+ cells/microl (median 1.2, range 0-5) and 7 patients (group B) with >10 CD34+ cells/microl (median 51, range 13-123). Compared to group A, patients of group B showed a faster hematological reconstitution of both polymorphonuclear leukocytes >500/microl (12 vs. 15 days) and platelets >50,000/microl (12 vs. 17 days). The expression of the beta1 integrin CD49d was similar in the two groups of patients, while a lower expression of the beta2 integrin CD11a and a greater expression of the L-selectin CD62L were observed in the PB CD34+ cells of group B patients. Both in the PB and in the BM, the number of CFU-GEMM, CFU- GM, CFU-E and BFU-E of group B was significantly greater than that of group A. However, when the clonogenic potential of a single CD34+ cell was evaluated, no major differences in the number of colonies produced per CD34+ cell were found between the two groups.

Granulocyte-colony stimulating factor increases CD123hi blood dendritic cells with altered CD62L and CCR7 expression

Changes in blood dendritic cell (BDC) counts (CD123(hi)BDC and CD11c(+)BDC) and expression of CD62L, CCR7, and CD49d were analyzed in healthy donors, multiple myeloma (MM), and non-Hodgkin lymphoma (NHL) patients, who received granulocyte-colony stimulating factor (G-CSF) containing peripheral blood stem cell (PBSC) mobilization protocols. Low-dose G-CSF in healthy donors (8-10 microg/kg/d subcutaneously) and high-dose G-CSF in patients (30 microg/kg/d) increased CD123(hi)BDC (2- to 22-fold, mean 3.7 x 10(6)/L-17.7 x 10(6)/L and 1.9 x 10(6)/L-12.0 x 10(6)/L) in healthy donors and MM but decreased CD11c(+)BDC (2- to 10-fold, mean 5.7 x 10(6)/L-1.6 x 10(6)/L) in NHL patients, on the day of apheresis, compared with steady state. After apheresis, CD123(hi)BDC counts remained high, whereas low CD11c(+)BDC counts tended to recover in the following 2-5 days. Down-regulation of CD62L and up-regulation of CCR7 on CD123(hi)BDC were found in most healthy donors and MM patients. CD49d expression was unchanged. Thus, PBSC mobilization may change BDC counts by altering molecules necessary for BDC homing from blood into tissues.

Highly active antiretroviral therapy corrects hematopoiesis in HIV-1 infected patients: interest for peripheral blood stem cell-based gene therapy

OBJECTIVES

To study, in asymptomatic HIV-1-infected (HIV+) patients, whether peripheral blood hematopoietic progenitor/stem cells (PBPC) mobilized by granulocyte colony stimulating factor (G-CSF), can be used as a source of cells for retroviral gene therapy.

DESIGN

PBPC from two groups of HIV+ patients (treated or untreated by highly active antiretroviral therapy) and from seronegative donors were mobilized with G-CSF.

METHODS

PBPC collected by leukapheresis were enriched for CD34 cells, immunophenotypically and functionally characterized, cultured and infected with retroviral vectors. HIV proviral integration was studied on fresh and cultured cells.

RESULTS

G-CSF moderately and transiently increased the viral load in untreated patients only, and induced in both groups of HIV+ patients mobilization of percentages and numbers of CD34 cells comparable to those of seronegative volunteers. The most immature CD34 cell subset, the clonogenic progenitor and long-term culture initiating cells were significantly decreased in leukapheresis products and CD34-enriched fractions from untreated HIV+ patients but not in those from treated HIV+ patients. Cell cycle activation and growth factor responses of CD34 cells from both groups of HIV+ patients were not different from those of the control group. Culture and retroviral infection of CD34 cells from HIV+ patients did not enhance HIV replication, and yielded transduction levels similar to those obtained using CD34 cells from seronegative donors.

CONCLUSIONS

G-CSF-mobilized PBPC can be safely used for HIV retroviral gene therapy in asymptomatic treated patients while highly active antiretroviral therapy would control the G-CSF-induced increase in viral load and correct the defective hematopoiesis observed in untreated patients, without inhibiting the retroviral transduction of PBPC.

Delivery of Flt3 ligand (Flt3L) using a poloxamer-based formulation increases biological activity in mice

Fms-like tyrosine kinase (Flt3L) is a potent stimulator of hematopoietic progenitor cell (HPC) expansion and mobilization; however, this requires 7-10 days of administration. We investigated whether sustained delivery of Flt3L using a poloxamer-based matrix (PG) could accelerate and/or improve the hematopoietic activity of Flt3L in mice. A single injection of PG-Flt3L stimulated significantly more rapid and greater HPC mobilization to the spleen and peripheral blood than the daily injection of Flt3L formulated in saline. Pharmacokinetic analysis demonstrated that the formulation of Flt3L in PG prolonged its elimination (Tbeta) half-life (2.3-fold) and increased its bioavailability (>two fold) and the time to maximum serum concentration (T(max)) (2.7-fold). Further, coadministration of G-CSF and PG-Flt3L allowed lower doses of Flt3L to be active, with significantly greater hematopoietic and mobilization activity, compared to the same total dose of G-CSF, Flt3L or G-CSF and Flt3L formulated in saline. These data demonstrate that formulation of Flt3L in PG significantly accelerates and increases HPC expansion and mobilization. The observation of increased bioactivity by PG-Flt3L in rodents suggests the potential for improved clinical efficacy of Flt3L by reducing the time required for HPC mobilization.

Purine nucleoside analogues in the treatment of myleoid leukemias

The purine nucleoside analogues (PNA), fludarabine (FA), cladribine (2-chlorodeoxyadenosine, 2-CdA) and 2'-deoxycoformycin (DCF), represent a novel group of cytotoxic agents with high activity in low-grade lymphoid malignancies. However, several investigations have revealed that these agents are active also in acute myeloid leukemia (AML) and chronic myelogenous leukemia (CML). Synergistic interaction between FA or 2-CdA with cytarabine (Ara-C) have been demonstrated in both preclinical and clinical studies. PNA enhance the cell concentration of Ara-CTP, which is active metabolite of Ara-C. It is likely that the addition of granulocyte colony stimulating factor (G-CSF) may further improve the effects of FA (FLAG) or 2-CdA (CLAG). The addition of anthracyclines to induction therapy does not appear to result in a substantial advantage in terms of CR achievement and duration. An alternative approach to increase FLAG activity might be the addition of investigational drugs with novel mechanism of action, such as topoiromerase I inhibitors. The addition of anthracyclines to induction therapy does not appear to result in a substantial advantage in terms of CR achievement and duration. Clinical studies have confirmed the efficacy of PNA alone or in combination protocols in the treatment of AML. These regimens seem to produce superior results with acceptable toxicities in previously treated and relapsed, poor risk AML. However, early relapses remain a significant problem in a majority of refractory or relapsed patients in CR after treatment with PNA based regimens. To prolong remission duration or even cure AML, auto--or allo stem cell transplantation should be considered. However, FAMP or 2-CdA containing regimens may impair mobilization and collection of stem cells from peripheral blood for autotransplantation. Few studies have analyzed the role of PNA in CML. 2-CdA, FAMP and DCF can induce hematologic response in chronic phase of CML but cytogenetic responses have not been observed. Preliminary results suggest, that PNA used alone or in combination may be used as palliation in blast phase of the disease. However, currently, the role of these agents in CML is insignificant because of the high activity of Glivec in this disease. Finally, PNA, especially FA play an important role in non-myeloablative conditioning regimens for allogenic stem cell transplantation in high-risk patients, possibly also with myeloid malignancies.

Low-dose or intermediate-dose cyclophosphamide plus granulocyte colony-stimulating factor for progenitor cell mobilisation in patients with multiple myeloma

Cyclophosphamide (CY) combined with granulocyte colony-stimulating factor (G-CSF) is commonly used to mobilise blood progenitor cells to support high-dose therapy in patients with multiple myeloma (MM). The optimal dose of CY in this setting is unknown. We have retrospectively analysed mobilisation efficiency and need for supportive care in 57 patients with newly diagnosed myeloma previously treated with VAD+/-local radiotherapy. The patients were mobilised either with low-dose CY (LD-CY, 1.2-2 g/m(2)) (n=25) or intermediate-dose CY (ID-CY, 4 g/m(2)) (n=32) plus G-CSF. Both regimens proved to be effective in the progenitor cell mobilisation. At least 2 x 10(6)/kg CD34+ cells were collected from 88% and 84% of the patients with a single apheresis, respectively. Only one patient in the LD-CY group (4%) failed to mobilise vs none in the ID-CY group. Patients mobilised with LD-CY plus G-CSF had less toxicity: fewer hospital days during the mobilisation and apheresis procedures (5 vs 9 days, P<0.001), lower frequency of fever (20 vs 73%, P<0.001) and less need for supportive care including platelet transfusions (0 vs 24%, P=0.004) and days on parenteral antibiotics (0 vs 4 days, P<0.001). While these regimens seem to be equally effective in terms of progenitor cell mobilisation in newly diagnosed patients with MM, LD-CY+G-CSF is preferential because of more optimal resource utilisation and more favourable toxicity profile.

Ex vivo expansion of human adult stem cells capable of primary and secondary hemopoietic reconstitution

OBJECTIVE

Ex vivo expansion of human hemopoietic stem cells (HSC) is an important issue in transplantation and gene therapy. Encouraging results have been obtained with cord blood, where extensive amplification of primitive progenitors was observed. So far, this goal has been elusive with adult cells, in which amplification of committed and mature cells, but not of long-term repopulating cells, has been described.

METHODS

Adult normal bone marrow (BM) and mobilized peripheral blood (MPB) CD34(+) cells were cultured in a stroma-free liquid culture in the presence of Flt-3 ligand (FL), thrombopoietin (TPO), stem cell factor (SCF), interleukin-6 (IL-6), or interleukin-3 (IL-3). Suitable aliquots of cells were used to monitor cell production, clonogenic activity, LTC-IC output, and in vivo repopulating capacity.

RESULTS

Here we report that BM and MPB HSC can be cultured in the presence of FL, TPO, SCF, and IL-6 for up to 10 weeks, during which time they proliferate and produce large numbers of committed progenitors (up to 3000-fold). Primitive NOD/SCID mouse repopulating stem cells (SRC) are expanded sixfold after 3 weeks (by limiting dilution studies) and retain the ability to repopulate secondary NOD/SCID mice after serial transplants. Substitution of IL-6 with IL-3 leads to a similarly high production of committed and differentiated cells but only to a transient (1 week) expansion of SRC(s), which do not possess secondary repopulation capacity.

CONCLUSION

We report evidence to show that under appropriate culture conditions, adult human SRC can also be induced to expand with limited differentiation.

High-dose immune suppression and autologous hematopoietic stem cell transplantation in refractory Crohn disease

Two patients with severe Crohn disease, defined by a Crohn Disease Activity Index (CDAI) higher than 250 despite anti-tumor necrosis factor alpha (TNF-alpha), were treated by intense immune suppression and autologous hematopoietic stem cell transplantation (HSCT). Stem cells were mobilized from the peripheral blood using cyclophosphamide (2.0 g/m2) and granulocyte colony-stimulating factor (G-CSF; 5 micro g/kg/d), enriched ex vivo by CD34+ selection, and reinfused after immune conditioning with cyclophosphamide (200 mg/kg) and equine anti-thymocyte globulin (ATG; 90 mg/kg). Patients have remained in remission (CDAI < 100) for 1 year since HSCT. We conclude that further HSCT studies for severe Crohn disease appear warranted.

Spontaneous circulation of myeloid-lymphoid-initiating cells and SCID-repopulating cells in sickle cell crisis

The only curative therapy for sickle cell disease (SCD) is allogeneic hematopoietic stem cell (HSC) transplantation. Gene therapy approaches for autologous HSC transplantation are being developed. Although earlier engraftment is seen when cells from GCSF-mobilized blood are transplanted than when bone marrow is transplanted, administration of GCSF to patients with SCD can cause significant morbidity. We tested whether primitive hematopoietic progenitors are spontaneously mobilized in the blood of patients with SCD during acute crisis (AC-SCD patients). The frequency of myeloid-lymphoid-initiating cells (ML-ICs) and SCID-repopulating cells (SRCs) was significantly higher in blood from AC-SCD patients than in blood from patients with steady-state SCD or from normal donors. The presence of SRCs in peripheral blood was not associated with detection of long-term culture-initiating cells, consistent with the notion that SRCs are more primitive than long-term culture-initiating cells. As ML-ICs and SRCs were both detected in blood of AC-SCD patients only, these assays may both measure primitive progenitors. The frequency of ML-ICs also correlated with increases in stem cell factor, GCSF, and IL-8 levels in AC-SCD compared with steady-state SCD and normal-donor sera. Because significant numbers of ML-ICs and SRCs are mobilized in the blood without exogenous cytokine treatment during acute crisis of SCD, collection of peripheral blood progenitors during crisis may yield a source of autologous HSCs suitable for ex-vivo correction by gene therapy approaches and subsequent transplantation.

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.

Transplantation of highly purified CD34+ progenitor cells from unrelated donors in pediatric leukemia

Unrelated donors are commonly used for hematopoietic stem cell transplants, but graft-versus-host disease (GVHD) is a major problem. We investigated whether transplantation of purified mobilized peripheral-blood CD34(+) stem cells from unrelated donors would prevent acute and chronic GVHD in pediatric patients with leukemia and avert the need for pharmacologic immunosuppression. Thirty-one pediatric patients with acute lymphoblastic leukemia (ALL, n = 16), acute myeloid (n = 7), chronic myeloid (n = 6), or juvenile myelomonocytic leukemia (n = 2) underwent transplantation. The median purity of CD34(+) cells after positive magnet-activated cell sorting was 98.5%. Patients received a median of 8.0 x 10(6) CD34(+) cells and 6 x 10(3) CD3(+) T lymphocytes per kilogram, with no posttransplantation pharmacologic immunosuppression. Primary acute GVHD > or = grade II was seen in only 10% of patients (n = 3) and occurred only after human herpesvirus 6 (HHV 6) infection. Two patients had limited chronic GVHD. Engraftment occurred in all patients (primary engraftment, n = 26; engraftment after reconditioning, n = 5). The 2-year survival estimate was 38% for all patients and 63% for patients with ALL in complete remission. Patients with myeloid malignancies had a poor outcome. In comparison to a historical control group who received unmanipulated bone marrow, our patients had a lower incidence of GVHD (P <.001). No difference was observed in the probability of relapse or survival. Study patients with ALL in remission showed a trend toward better survival (P =.07). Transplantation of purified peripheral-blood CD34(+) cells from unrelated donors effectively minimizes GVHD and may be a good therapeutic option for patients with relapsed ALL.

Use of filgrastim for stem cell mobilisation and transplantation in high-dose cancer chemotherapy

Myeloablative or high-dose chemotherapy regimens utilise doses that are significantly greater than those used in standard treatments. The neutropenia caused by these high-dose therapies can be associated with an increased incidence of bacterial and fungal infections and remains an important clinical issue among patients with advanced-stage cancers. Filgrastim is approved for stem cell mobilisation in both chemotherapy-treated patients and normal donors. Harvested peripheral blood progenitor cells have been used effectively in allogeneic and autologous transplantation, increasing the speed and extent of neutrophil and platelet recovery. Accelerated haematopoietic recovery is associated with a significantly shorter hospital stay and, therefore, leads to a reduction in treatment costs. The contribution of filgrastim to the acceleration of haematopoietic recovery after peripheral blood progenitor cell transplant has been assessed in a number of prospective clinical trials after high-dose chemotherapy. Controversy remains over whether growth factors should be administered shortly after stem cell infusion or after several days. The recently approved, once-weekly form of filgrastim, pegfilgrastim, has been shown to have efficacy comparable to that of the native molecule and can be expected to enhance patient quality of life through the need for fewer injections. This article will review the role of filgrastim for stem cell mobilisation and transplantation in patients receiving high-dose chemotherapy.

Rituximab: enhancing outcome of autologous stem cell transplantation in non-Hodgkin's lymphoma

High-dose chemotherapy and autologous stem cell transplantation (ASCT) is a potentially curative therapy for younger patients with relapsed aggressive non-Hodgkin's lymphoma, and is under investigation as first-line treatment and as therapy for indolent and mantle cell non-Hodgkin's lymphoma. However, between 40% and 70% of all patients relapse after ASCT because of contamination of the stem cell product or persistence of residual tumor cells. Evidence is emerging that the administration of rituximab as an in vivo purging agent before ASCT is effective in eliminating lymphoma cell contamination, as measured by clearance of bcl-2-positive cells from stem cell harvests. Furthermore, in vivo purging with rituximab does not adversely affect the stem cell yield or function. Maintenance therapy with rituximab post-transplantation has also been explored as a means of eliminating residual tumor cells. Results suggest that rituximab may eradicate minimal residual disease post-transplant and help prevent relapse. The efficacy of both in vivo purging and maintenance therapy with rituximab is currently being investigated in a large, multicenter, randomized trial by the European Group for Blood and Bone Marrow Transplantation in patients with follicular non-Hodgkin's lymphoma. Results from this and other ongoing trials will confirm the full potential of rituximab in ASCT.

Clinical usefulness of the hematopoietic progenitor cell counts in predicting the optimal timing of peripheral blood stem cell harvest

Although enumeration of CD34+ cells in the peripheral blood (PB) on the day of apheresis predicts the quantity of those cells collected, the flow cytometric techniques used are complex and expensive, and several hours are required to obtain the result in the clinical practice setting. The Sysmex SE-9000 automated haematology analyzer provides an estimate of immature cells, called hematopoietic progenitor cells (HPC). The aim of this study was to evaluate the clinical usefulness of HPC in predicting the optimal timing of peripheral blood progenitor cells (PBPC) harvest. Studies were performed on 628 aphereses from 160 patients with hematologic or solid malignancies. Spearman's rank statistics was used to assess correlation between HPC, WBC, mononuclear cells (MNC), and CD34+ cells. A receiver operating characteristic (ROC) curve was drawn for cutoff value of HPC, and predictive values of the chosen cutoff value of HPC for different target CD34+ cell collections were calculated. The PB HPC had a stronger correlation (rho=0.592, p<0.001) with collected CD34+ cells than did PB WBC and PB MNC. The ROC curve showed that the best cutoff value of HPC was 50 x 10(6)/L for the target CD34+ cells > or =1 x 10(6)/kg with sensitivity of 75%. Positive and negative predictive values of HPC > or =50 x 10(6)/L for CD34+ cells > or =1 x 10(6)/kg were 59.7% and 81.1%, respectively. In the clinical practice setting, applying variable cutoff values of HPC would be a useful tool to predict the optimal timing of PBPC collection.

Use of percutaneous radial artery catheter for peripheral blood progenitor cell collection in pediatric patients

BACKGROUND

Leukapheresis procedures require adequate flow rates, which in children may frequently involve invasive vascular access placement.

STUDY DESIGN AND METHODS

A minimally invasive peripheral radial artery catheter was used for drawing blood in 85 leukapheresis procedures performed in 33 pediatric patients. Blood return to the patients was provided by either a central Broviac-type catheter or a peripheral venous access. The patients' age range was 1 to 18 years (median, 9.5) and the weight range was 9 to 73 kg (median, 29 kg). Vasocan Braunüle Luer Lock IV cannulas (22 gauge in 78 and 20 gauge in 7) were placed percutaneously under local anesthesia, and in 8 patients, catheter placement was carried out during general anesthesia for other procedures. A continuous flow cell separator was used in all cases (Fresenius AS104 in 23 and AS204 in 62).

RESULTS

Flow rates ranged from 18 to 45 mL per minute, the mean number of total blood volumes processed was 2.07 (range, 0.51-2.51), and the mean duration of the procedures was 150 minutes (range, 90-260). The 22-gauge cannulas provided adequate flow rates independently of patient age and weight. No significant thrombotic, embolic, hemorrhagic, ischemic, or infectious complications were observed.

CONCLUSION

Peripheral radial artery catheters are safe, are minimally invasive, and provide steady, high-flow rates, and they should be considered for patients requiring leukapheresis and lacking a suitable vascular access for drawing blood.

[Middle-high dose of cyclophosphamide or conventional routine chemotherapy with increased dose of cyclophosphamide combined with G-CSF for mobilizing peripheral blood progenitor cells in patients with tumor]

OBJECTIVE

To investigate the clinical value of glycosylated G-CSF combined with middle-high dose cyclophosphamide (Cy) or conventional chemotherapy with increased dose of Cy for mobilizing peripheral blood progenitor cells in patients with tumor.

METHODS

Thirty patients from four hospitals in Beijing region were enrolled in this clinical study. Diagnoses of the patients were non-Hodgkin' lymphoma (n = 21), Hodgkin disease (n = 1), breast cancer (n = 7) and ovary cancer (n = 1). Autologous peripheral blood progenitor cells (APBPC) were mobilized by middle-high dose Cy or conventional chemotherapy with increased dose of Cy combined with G-CSF. G-CSF was given subcutaneously from the nadir of the white blood cell (WBC) count to the end of PBPC collection. The dosage of G-CSF was 250 microg/d in 29 patients and 500 microg/d in 1 patient. When WBC count was > 5 x 10(9)/L, APBPC were harvested with CS 3000 plus/COBE Spectra.

RESULTS

The average dosage of Cy was 3.95 g (2.3 g/m(2)). The doses of G-CSF were 3.1 approximately 6.4 microg x kg(-1) x d(-1). Thirteen patients (43%) were collected twice, 14 patients (47%) three times and 3 patients (10%) four times. All of the patients could tolerate the treatment regimens. Seven patients had bone pain after G-CSF injection and one was severe, one patient had headache and one had nausea and vomiting.

CONCLUSION

250 microg glycosylated G-CSF combined with middle-high Cy or conventional chemotherapy with increased dose of Cy combined G-CSF is an optimal method for APBPC mobilization in tumor patients.

Role of adhesion molecules in mobilization of hematopoietic cells

OBJECTIVE

To study the changes of adhesion molecules' expressions during the recombinant human granulocyte-colony-stimulating factor (rhG-CSF) mobilization in peripheral blood stem cell transplantation (PBSCT), and to confirm the influence of rhG-CSF on hematopoietic stem cells, which are proposed to guide mobilization in PBSCT.

METHODS

Mice were injected subcutaneously with diluted rhG-CSF or normal saline for 7 days. The blood Sca-1(+) stem cell count and bone marrow (BM) nucleated cell count were enumerated. The expressions of CD49d and CD44 and the adhesive ability of mononuclear cells to bone marrow matrix (fibronectin) were examined by flow cytometry and (51)Cr adhesive assay, respectively.

RESULTS

The mobilizing effect of rhG-CSF on mice was the same as on humans. The number of Sca-1(+) cells in peripheral blood reached the peak on the seventh day, the BM nucleated cell count was reduced, and the expressions of CD49d and the cells' adhesive ability in BM and PB declined.

CONCLUSIONS

rhG-CSF can reduce some cell adhesion molecules' expressions and the adhesive ability of hematopoietic stem cells to BM matrix, therefore mobilizing hematopoietic stem cells (HSC) from the BM to the peripheral blood.

Granulocyte colony-stimulating factor induces the release in the bone marrow of proteases that cleave c-KIT receptor (CD117) from the surface of hematopoietic progenitor cells

OBJECTIVE

Administration of granulocyte colony-stimulating factor (G-CSF) results in the mobilization of hematopoietic progenitor and stem cells from the bone marrow into the peripheral blood. Although the mechanisms leading to the mobilization of primitive hematopoietic cells is not fully understood, it has been noted that the yield of mobilization in humans is correlated to the down-regulation of c-KIT/CD117 expression on mobilized cells. We sought to determine the mechanisms responsible for the reduced expression of c-KIT on mobilized hematopoietic progenitor cells.

MATERIALS AND METHODS

Mice were mobilized with G-CSF and primitive hematopoietic cells were collected from bone marrow and blood to analyze c-KIT expression. Using cell lines expressing mouse and human c-KIT and a recombinant protein comprising the entire extracellular domain of human c-KIT, we analyzed by flow cytometry and immunoblotting the proteolytic cleavage of c-KIT by proteases released in bone marrow extracellular fluids extracted from mobilized mice.

RESULTS

Administration of G-CSF into mice results in the reduction of c-KIT expression on primitive hematopoietic cells in bone marrow and peripheral blood. Bone marrow extracellular fluids isolated from G-CSF-mobilized mice contain serine proteases that cleave c-KIT into discrete fragments. Proteases capable of cleaving c-KIT include neutrophil elastase, cathepsin G, proteinase-3 and matrix metalloproteinase-9.

CONCLUSIONS

In addition to transcriptional controls, exocytosis, and ligand-induced internalization, the direct proteolytic cleavage of c-KIT by neutrophil and macrophage proteases represents a novel pathway to regulate the levels of c-KIT expression at the surface of hematopoietic cells and may be responsible in part for the down-regulation of c-KIT expression on mobilized hematopoietic progenitors in vivo.

Leukapheresis after high-dose chemotherapy and autologous peripheral blood progenitor cell transplantation: a novel approach to harvest a second autograft

BACKGROUND

Autologous peripheral blood progenitor cells (PBPCs) are usually collected after the administration of conventional-dose chemotherapy (CDCT) and growth factors. However, there are no data available concerning the collection of PBPCs after high-dose chemotherapy (HDCT) and autologous hematopoietic transplantation in a larger series.

STUDY DESIGN AND METHODS

Patients (n = 30) underwent leukapheresis for PBPC harvest after CDCT. After HDCT and autografting, the collection of a second PBPC autograft was attempted.

RESULTS

Leukapheresis was performed after CDCT in all cases at a median of 118 CD34+ cells per microL (range, 18-589) and resulted in 6.4 x 10(6) CD34+ cells per kg (range, 1.7-29.0). After HDCT and autografting, 24 patients (80%) underwent secondary leukapheresis, although they had a significantly lower median of peripheral blood (PB) CD34+ cells (30/microL; range, 10-171; p < 0.001). In these patients a median of 3.6 x 10(6) CD34+ cells per kg (range, 1.6-10.1) was collected in the post-transplantation course. In the remaining six patients (20%) with PB CD34+ cells < 10 per microL, no PBPC harvesting was performed. These so-called poor mobilizers had received significantly less CD34+ cells for autologous transplantation than patients with successful post-HDCT mobilization (median, 2.5 x 10(6)/kg [range, 1.7-3.0] vs. 6.5 x 10(6)/kg [range, 3.2-19.6]; p < 0.001).

CONCLUSION

Collection of PBPCs is possible in most patients during the recovery phase of hematopoiesis after HDCT plus autografting, and the number of circulating PBPCs may be related to the CD34+ cell dose transfused by the preceding autograft.

Elevated transforming growth factor beta levels in the plasma of cytokine-treated cancer patients and normal allogeneic stem cell donors

BACKGROUND

Allogeneic blood stem-cell donors demonstrate more vigorous mobilization of CD34(+) cells to the circulation in response to cytokine administration than do autologous donors. Transforming growth factor (TGF-beta1) has been implicated as a mobilization inhibitor. A study was designed to determine whether plasma TGF-beta1 levels are elevated in cytokine-mobilized autologous cancer donors compared with cytokine-mobilized normal donors.

METHODS

Plasma collected from 29 autologous cancer donors and 33 normal allogeneic stem-cell donors following administration of mobilizing cytokines just prior to the first collection was assayed for TGF-beta1 using a sandwich-type ELISA. Plasma from three volunteers not treated with cytokine was also analyzed. Comparisons were made using the Student's t test on log-transformed data.

RESULTS

Average TGF-beta1 levels in the plasma of cancer patients were significantly higher than in allogeneic stem-cell donors (4.4 ng/mL versus 7.2 ng/mL; p = 0.038). The allogeneic donors required fewer collections to harvest greater numbers of CD34(+) cells and colony-forming unit granulocyte-macrophage (CFU-GM) than autologous donors. Plasma from three untreated volunteers had mean TGF-beta1 levels of 0.36 ng/mL, with all three levels below the 25th percentile for allogeneic donors and the 5th percentile for cancer patients.

DISCUSSION

Cytokine administration was associated with increased plasma TGF-beta1 levels. The levels were higher in cancer patients being mobilized for stem-cell collection than in allogeneic blood stem-cell donors. These differences could underlie the increased number of apheresis procedures required to harvest autologous graft products from cancer patients.

[Stem cell transplantation in primary systemic vasculitis]

BACKGROUND

Many patients with various autoimmune diseases fail to respond to conventional immunosuppressive therapy and develop irreversible organ damage. In some cases the complications might be fatal. Furthermore, prolonged immunosuppression with cyclophosphamide or corticosteroids often leads to long-term side effects, cumulative organ damage, and development of secondary malignancies.

THERAPY

Thus, short-term, high-dose immunosuppressive therapy with autologous stem cell transplantation might be an alternative for otherwise refractory patients. This concept has been used mainly in patients with scleroderma, systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis.

PATIENTS

Patients with primary systemic vasculitis (PSV) seem to be suitable candidates for high-dose chemotherapy (HDCT). Although complete, long-term remissions are possible with standard immunosuppressive therapy, there is a subgroup of patients who cannot be cured by standard therapy. They need long-term immunosuppression and eventually die due to progression of the disease or cumulative therapy-related toxicity. In large series, the 5-year mortality rate was > 20%. The severity of vasculitis rather than the distinction between subgroups should determine whether HDCT might be a life-saving treatment.

RESULTS AND CONCLUSION

Careful patient selection with the help of scoring systems and determination of the optimal time in the course of disease are now the major goals in the approach to HDCT. First reports as well as our own single-center experience in HDCT with a limited number of patients with severe PSV have shown that long-term remissions are possible even in patients refractory to conventional immunosuppression.

Disruption of the CXCR4/CXCL12 chemotactic interaction during hematopoietic stem cell mobilization induced by GCSF or cyclophosphamide

Hematopoietic progenitor cells (HPCs) normally reside in the bone marrow (BM) but can be mobilized into the peripheral blood (PB) after treatment with GCSF or chemotherapy. In previous studies, we showed that granulocyte precursors accumulate in the BM during mobilization induced by either GCSF or cyclophosphamide (CY), leading to the accumulation of active neutrophil proteases in this tissue. We now report that mobilization of HPCs by GCSF coincides in vivo with the cleavage of the N-terminus of the chemokine receptor CXCR4 on HPCs resident in the BM and mobilized into the PB. This cleavage of CXCR4 on mobilized HPCs results in the loss of chemotaxis in response to the CXCR4 ligand, the chemokine stromal cell-derived factor-1 (SDF-1/CXCL12). Furthermore, the concentration of SDF-1 decreased in vivo in the BM of mobilized mice, and this decrease coincided with the accumulation of serine proteases able to directly cleave and inactivate SDF-1. Since both SDF-1 and its receptor, CXCR4, are essential for the homing and retention of HPCs in the BM, the proteolytic degradation of SDF-1, together with that of CXCR4, could represent a critical step leading to the mobilization of HPCs into the PB in response to GCSF or CY.

Pilot evaluation of high-dose carboplatin and paclitaxel followed by high-dose melphalan supported by peripheral blood stem cells in previously untreated advanced ovarian cancer: a gynecologic oncology group study

OBJECTIVES

To evaluate the efficacy and safety of multiple cycles of high-dose carboplatin and paclitaxel and one consolidation cycle of high-dose melphalan with all cycles supported by hematopoietic stem cells and cytokine, in previously untreated patients with optimally debulked stage III epithelial ovarian cancer.

PATIENTS AND METHOD

Patients had histologically documented epithelial ovarian cancer and optimal initial cytoreductive surgery. No prior chemotherapy was permitted. Adequate performance status, bone marrow, hepatic, and renal function was required. After being mobilized with cyclophosphamide 3 g/m(2), paclitaxel 300 mg/m(2), and filgrastim 5 microg/kg/day, peripheral blood stem cells (PBSC) were collected by leukapheresis. Patients received three cycles of carboplatin AUC 15 mg. min/ml iv, paclitaxel 250 mg/m(2), and PBSC with filgrastim every 28 days, followed by one cycle of melphalan 140 mg/m(2) and hematopoietic support.

RESULTS

Nine patients entered the trial and received all planned cycles of chemotherapy. Of the eight patients who consented to surgical reassessment upon completing therapy, four had residual small-volume macroscopic disease, three had microscopic residual disease, and one had pathologic complete response. The estimated probability of a pathologic complete response was 12.5% (95% confidence interval: 0.3-52.7%). Hematologic toxicity was severe but manageable. Eleven of 45 cycles (24.4%) resulted in hospital admission for neutropenic fever, dehydration +/- diarrhea, syncope, or shortness of breath and pain secondary to tense ascites.

CONCLUSIONS

The low pathological complete response rate did not justify toxicity; thus, the study was closed. High-dose chemotherapy as first-line treatment for epithelial ovarian cancer remains experimental and should be restricted to clinical trials.

Phase III randomized study comparing 5 or 10 microg per kg per day of filgrastim for mobilization of peripheral blood progenitor cells with chemotherapy, followed by intensification and autologous transplantation in patients with nonmyeloid malignancies

BACKGROUND

It is not known whether increasing the dose of filgrastim after mobilizing chemotherapy improves collection of peripheral blood progenitor cells (PBPC) and leads to faster hematopoietic engraftment after autologous transplantation.

STUDY DESIGN AND METHODS

A randomized, open-label, multicenter trial was carried out in patients with breast cancer, multiple myeloma, and lymphoma, in which patients were randomized to receive 5 or 10 microg per kg per day of filgrastim after standard chemotherapy to mobilize PBPCs. After high-dose chemotherapy, the components from the first two leukapheresis procedures were returned, and all patients received 5 microg per kg day of filgrastim after transplantation.

RESULTS

A total of 131 patients were randomized, of whom 128 were mobilized (Group A, 5 microg/kg, n = 66; Group B, 10 microg/kg, n = 62) and 112 were transplanted. Only six patients were not transplanted because of insufficient CD34+ cell numbers. The median number of CD34+ cells collected in the first two leukapheresis procedures tended to be higher in Group B than in Group A (12.0 vs. 7.2 x 10(6)/kg, NS), but after transplantation there was no significant difference in median times to platelet (9 days in both groups) or neutrophil (8 days in both groups) engraftment or the number of platelet transfusions (three in both groups). A subsequent subgroup analysis separating patients transplanted after first- or second-line chemotherapy also showed no measurable impact of filgrastim dose on the median CD34+ cell yield or on platelet engraftment in either subgroup.

CONCLUSION

PBPC mobilization with chemotherapy and 5 microg per kg of filgrastim is very efficient, and 10 microg per kg of filgrastim does not provide additional clinical benefit.

An Engineered Heparin-Binding Form of VEGF-E (hbVEGF-E). Biological effects in vitro and mobilizatiion of precursor cells

Vascular endothelial growth factor (VEGF-A) is the founding member of a family of angiogenic proteins with various binding abilities to three cognate VEGF receptors. Previously, a gene encoding from the genome of parapox orf virus (OV) with about 25% amino acid identity to mammalian VEGF-A was named VEGF-E and shown to bind and specifically activate the vascular endothelial growth factor receptor VEGFR-2 (KDR/flk-1). Here, we have generated a novel heparin-binding form of VEGF-E by introducing the heparin-domain of the human VEGF-A(165) splice variant into the viral VEGF-E protein. Recombinant heparin-binding VEGF-E (hbVEGF-E) is shown to stimulate proliferation and sprout formation of macro- and microvascular endothelial cells to a similar extent as the parental OV-VEGF-E but fails to activate peripheral mononuclear cells. However, hbVEGF-E is more potent in binding competition assays with primary human endothelial cells when compared to the OV-VEGF-E. This can be explained by our finding that binding of hbVEGF-E but not of parental OV-VEGF-E to the VEGFR-2 is strongly increased by the addition of neuropilin-1 (NP-1), a cognate co-receptor for VEGF-A. The engineered hbVEGF-E was compared with the VEGFR-1 selective and also heparin-binding form of placenta growth factor (PlGF-2) in vivo. Both heparin-binding homologues induced mobilization of endothelial progenitor cells from the bone marrow and gave rise to similar colony numbers of myeloic cells in a colony-forming assay. These findings suggest that both VEGFR-1 and VEGFR-2 are involved in stem cell mobilization.