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

Efficacy of hematopoietic stem cell mobilization regimens in patients with hematological malignancies: a systematic review and network meta-analysis of randomized controlled trials

Background

Efficient mobilization of hematopoietic stem cells (HSCs) from bone marrow niche into circulation is the key to successful collection and transplantation in patients with hematological malignancies. The efficacy of various HSCs mobilization regimens has been widely investigated, but the results are inconsistent.

Methods

We performed comprehensive databases searching for eligible randomized controlled trials (RCTs) that comparing the efficacy of HSCs mobilization regimens in patients with hematological malignancies. Bayesian network meta-analyses were performed with WinBUGS. Standard dose of granulocyte colony-stimulating factor (G-CSF SD) was chosen as the common comparator. Estimates of relative treatment effects for other regimens were reported as mean differences (MD) or odds ratio (OR) with associated 95% credibility interval (95% CrI). The surface under the cumulative ranking curve (SUCRA) were obtained to present rank probabilities of all included regimens.

Results

Databases searching and study selection identified 44 eligible RCTs, of which the mobilization results are summarized. Then we compared the efficacy of mobilization regimens separately for patients with multiple myeloma (MM) and non-Hodgkin lymphoma (NHL) by including 13 eligible trials for network meta-analysis, involving 638 patients with MM and 592 patients with NHL. For patients with MM, data are pooled from 8 trials for 6 regimens, including G-CSF in standard dose (SD) or reduced dose (RD) combined with cyclophosphamide (CY), intermediate-dose cytarabine (ID-AraC) or plerixafor. The results show that compared with G-CSF SD alone, 3 regimens including ID-AraC + G-CSF SD (MD 14.29, 95% CrI 9.99–18.53; SUCRA 1.00), G-CSF SD + Plerixafor SD (MD 4.15, 95% CrI 2.92–5.39; SUCRA 0.80), and CY + G-CSF RD (MD 1.18, 95% CrI 0.29–2.07; SUCRA 0.60) are associated with significantly increased total number of collected CD34⁺ cells (× 10⁶/kg), among which ID-AraC + G-CSF SD ranked first with a probability of being best regimen of 100%. Moreover, ID-AraC + G-CSF SD and G-CSF SD + Plerixafor SD are associated with significantly higher successful rate of achieving optimal target (collecting ≥ 4–6 × 10⁶ CD34⁺ cells/kg). For patients with NHL, data are pooled from 5 trials for 4 regimens, the results show that compared with G-CSF SD alone, G-CSF SD + Plerixafor SD (MD 3.62, 95% CrI 2.86–4.38; SUCRA 0.81) and G-CSF SD plus the new CXC chemokine receptor-4 (CXCR-4) antagonist YF-H-2015005 (MD 3.43, 95% CrI 2.51–4.35; SUCRA 0.69) are associated with significantly higher number of total CD34⁺ cells collected. These 2 regimens are also associated with significantly higher successful rate of achieving optimal target. There are no significant differences in rate of achieving optimal target between G-CSF SD + Plerixafor SD and G-CSF + YF-H-2015005.

Conclusions

In conclusion, ID-AraC plus G-CSF is associated with the highest probability of being best mobilization regimen in patients with MM. For patients with NHL, G-CSF in combination with plerixafor or YF-H-2015005 showed similar improvements in HSCs mobilization efficacy. The relative effects of other chemotherapy-based mobilization regimens still require to be determined with further investigations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02802-6.

GENESIS: Phase III trial evaluating BL-8040 + G-CSF to mobilize hematopoietic cells for autologous transplant in myeloma

Effective hematopoietic cell transplantation relies upon collecting adequate numbers of CD34⁺ hematopoietic stem cells, typically from peripheral blood. A minimum of ≥2 × 10⁶ CD34⁺ cells/kg are necessary, while transplants of ≥5-6 × 10⁶ CD34⁺ cells/kg are associated with improved hematopoietic recovery. Granulocyte colony stimulating factor (G-CSF) remains the gold standard for hematopoietic stem cell mobilization. However, in randomized trials for autologous-hematopoietic cell transplantation in multiple myeloma, approximately 45% of patients remain unable to optimally mobilize with G-CSF alone despite multiple injections and apheresis days. Therefore, reducing mobilization failures remains an unmet need. The study objective is to evaluate the superiority of one dose of BL-8040 plus G-CSF over placebo plus G-CSF to mobilize ≥6.0 × 10⁶ CD34⁺ cells/kg in up to two apheresis days. ClinicalTrials.gov: NCT03246529.

Efficacy and safety of plerixafor for the mobilization/collection of peripheral hematopoietic stem cells for autologous transplantation in Japanese patients with multiple myeloma

To evaluate the efficacy and safety of plerixafor for the mobilization/collection of peripheral hematopoietic stem cells (HSCs) for autologous transplantation in Japanese patients with multiple myeloma (MM). In a randomized study, patients received G-CSF (filgrastim, 400 µg/m²/day) for 4 days prior to the first dose of plerixafor. Starting on Day 4 evening and for up to 4 days, patients received either plerixafor (240 µg/kg/day) + G-CSF group (PG group) or G-CSF alone (G group). Daily apheresis started on Day 5 for up to 4 days, or until ≥6 × 10⁶ CD34+ cells/kg were collected. A total of 7 patients were randomized in each treatment group. Five patients in PG group and no patients in G group achieved a collection of ≥6 × 10⁶ CD34+ cells/kg in ≤2 days of apheresis [difference of 71.4% (90%CI 29-100%)]. These results were supported by the shorter median time to collect ≥6 × 10⁶ CD34+ cells/kg (2 days in PG group; no patient in G group). The incidence of treatment emergent adverse events (TEAEs) was higher in PG group than in G group. Plerixafor was well tolerated, and effective for the mobilization/collection of peripheral HSCs for autologous transplantation in Japanese patients with MM.

How to manage poor mobilizers for high dose chemotherapy and autologous stem cell transplantation?

Today, peripheral blood stem cells are the preferred source of stem cells over bone marrow. Therefore, mobilization plays a crutial role in successful autologous stem cell transplantation. Poor mobilization is generally defined as failure to achieve the target level of at least 2×10⁶ CD34⁺ cells/kg body weight. There are several strategies to overcome poor mobilization: 1) Larger volume Leukapheresis (LVL) 2) Re-mobilization 3) Plerixafor 4) CM+Plerixafor (P)+G-CSF and 5) Bone Marrow Harvest. In this review, the definitions of successful and poor mobilization are discussed. Management strategies for poor mobilization are defined. The recent research on new agents are included.

New agents in HSC mobilization

Mobilized peripheral blood (PB) is the most common source of hematopoietic stem cells (HSC) for autologous transplantation. Granulocyte colony stimulating factor (G-CSF) is the most commonly used mobilization agent, yet despite its widespread use, a considerable number of patients still fail to mobilize. Recently, a greater understanding of the interactions that regulate HSC homeostasis in the bone marrow (BM) microenvironment has enabled the development of new molecules that mobilize HSC through specific inhibition, modulation or perturbation of these interactions. AMD3100 (plerixafor), a small molecule that selectively inhibits the chemokine receptor CXCR4 is approved for mobilization in combination with G-CSF in patients with Non-Hodgkin's lymphoma and multiple myeloma. Nevertheless, identifying mobilization strategies that not only enhance HSC number, but are rapid and generate an optimal "mobilized product" for improved transplant outcomes remains an area of clinical importance. In recent times, new agents based on recombinant proteins, peptides and small molecules have been identified as potential candidates for therapeutic HSC mobilization. In this review, we describe the most recent developments in HSC mobilization agents and their potential impact in HSC transplantation.

Prospective noninterventional study on peripheral blood stem cell mobilization in patients with relapsed lymphomas

High-dose chemotherapy followed by autologous stem cell transplantation (ASCT) to rescue hematopoiesis is considered standard care for patients with a relapsed chemosensitive lymphoma, but diagnosis of lymphoma has been a risk factor for poor mobilization in several studies. The aim of this prospective noninterventional clinical audit was to review the mobilization strategies used by EBMT centers in relapsed lymphoma and to evaluate their efficacy. Between 2010 and 2014, 275 patients with relapsed lymphoma from 30 EBMT centers were prospectively registered. Almost all patients were mobilized with chemotherapy plus G-CSF (96%), but there was a large variation in chemotherapy schedules. Thirty (11%) of them were poor mobilizers (<2 × 10⁶ CD 34+ cells/kg body weight) at the first mobilization. Poor mobilization was not associated with gender, age, bone marrow involvement at diagnosis, primary diagnosis, number of previous chemotherapy lines, previous radiotherapy or mobilization with G-CSF alone. The use of high dose cyclophosphamide alone was associated with mobilization failure (P = 0.0006), whereas the use of a platinum-containing regimen was associated with a good mobilization outcome (P = 0.013). Because failure rate is low, we can conclude from this study that PBSC mobilization failure in relapsed lymphomas is not an important problem in the EBMT centers.

Optimizing mobilization strategies in difficult-to-mobilize patients: The role of plerixafor

Peripheral blood stem cell collection is currently the most widely used source for hematopoietic autologous transplantation. Several factors such as advanced age, previous chemotherapy, disease and marrow infiltration at the time of mobilization influence the efficacy of CD34(+) progenitor cell mobilization. Despite the safety and efficiency of the standard mobilization protocols (G-CSF ± chemotherapy), there is still a significant amount of mobilization failure rate (10-40%), which necessitate novel agents for effective mobilization. Plerixafor, is a novel agent, has been recently approved for mobilization of hematopoietic stem cells (HSCs). The combination of Plerixafor with G-CSF provides the collection of large numbers of stem cells in fewer apheresis sessions and can salvage those who fail with standard mobilization regimens. The development and optimization of practical algorithms for the use Plerixafor is crucial to make hematopoietic stem cell mobilization more efficient in a cost-effective way. This review is aimed at summarizing how to identify poor mobilizers, and define rational use of Plerixafor for planning mobilization in hard-to-mobilize patients.

Plerixafor prescription modalities in autologous haematopoietic stem cell mobilization in Belgium

OBJECTIVES

The efficacy and safety of plerixafor, an antagonist of the CXCR4 receptor, in combination with G-CSF has been demonstrated in patients suffering from Iymphoma and multiple myeloma (MM) eligible for autologous haematopoietic stem cell collection. However, different reimbursement criteria have been applied in different countries to select patients eligible for treatment with plerixafor. The objective of this observational study was to describe the plerixafor prescription modalities in daily practice in Belgium.

METHODS

This open-label, prospective, observational study was conducted in 11 Belgian centres in 114 patients with lymphoma (Hodgkin's and non-Hodgkin's lymphoma) or MM who were treated with plerixafor according to the SmPC between April 2011 and October 2012. Patients included in another clinical trial with plerixafor were excluded from the study.

RESULTS

The use of plerixafor in patients with MM or lymphoma was effective, with a success rate (defined as a total yield >2×10(6) CD34+ cells/kg) of 77%, and well tolerated (one SAE reported). Optimal collection (defined as a total yield >4×10(6) CD34+ cells/kg) was obtained for 43% of the study population (31% in lymphoma patients, compared to 61% in patients with MM). The use of plerixafor was in line with the SmPC and the Belgian reimbursement criteria for all patients.

CONCLUSION

This study is showing that the use of plerixafor according to Belgian reimbursement criteria results in similar efficacy and safety as in other centres and countries worldwide.

The role of stem cell factor and granulocyte-colony stimulating factor in treatment of stroke

Stroke is a serious cerebrovascular disease that causes high mortality and persistent disability in adults worldwide. Stroke is also an enormous public health problem and a heavy public financial burden in the United States. Treatment for stroke is very limited. Thrombolytic therapy by tissue plasminogen activator (tPA) is the only approved treatment for acute stroke, and no effective treatment is available for chronic stroke. Developing new therapeutic strategies, therefore, is a critical need for stroke treatment. This article summarizes the discovery of new routes of treatment for acute and chronic stroke using two hematopoietic growth factors, stem cell factor (SCF) and granulocyte-colony stimulating factor (G-CSF). In a study of acute stroke, SCF and G-CSF alone or in combination displays neuroprotective effects in an animal model of stroke. SCF appears to be the optimal treatment for acute stroke as the functional outcome is superior to G-CSF alone or in combination (SCF+G-CSF); however, SCF+G-CSF does show better functional recovery than G-CSF. In a chronic stroke study, the therapeutic effects of SCF and G-CSF alone or in combination appear differently as compared with their effects on the acute stroke. SCF+G-CSF induces stable and long-lasting functional improvement; SCF alone also improves functional outcome but its effectiveness is less than SCF+G-CSF, whereas G-CSF shows no therapeutic effects. Although the mechanism by which SCF+G-CSF repairs the brain in chronic stroke remains poorly understood, our recent findings suggest that the SCF+G-CSF-induced functional improvement in chronic stroke is associated with a contribution to increasing angiogenesis and neurogenesis through bone marrow-derived cells and the direct effects on stimulating neurons to form new neuronal networks. These findings would assist in developing new treatment for stroke. The article presents some promising patents on role of stem cell factor and granulocyte-colony stimulating factor in treatment of stroke.

Pharmacoeconomic impact of up-front use of plerixafor for autologous stem cell mobilization in patients with multiple myeloma

BACKGROUND AIMS

Stem cell collection can be a major component of overall cost of autologous stem cell transplantation (ASCT). Plerixafor is an effective agent for mobilization; however, it is often reserved for salvage therapy because of its high cost. We present data on the pharmacoeconomic impact of the use of plerixafor as an up-front mobilization in patients with multiple myeloma (MM).

METHODS

Patients with MM who underwent ASCT between January 2008 and April 2011 at the Mount Sinai Medical Center were reviewed retrospectively. In April 2010, practice changes were instituted for patients with MM to delay initiation of granulocyte-colony-stimulating factor (G-CSF) support from day 0 to day +5 and to add plerixafor to G-CSF as an up-front autologous mobilization. Targets of collection were 5-10 × 10(6) CD34(+) cells/kg.

RESULTS

Of 50 adults with MM who underwent ASCT, 25 received plerixafor/filgrastim and 25 received G-CSF alone as an up-front mobilization. Compared with the control, plerixafor mobilization yielded higher CD34(+) cell content (16.1 versus 8.4 × 10(6) CD34(+) cells/kg; P = 0.0007) and required fewer sessions of apheresis (1.9 versus 3.1; P = 0.0001). In the plerixafor group, the mean number of plerixafor doses required per patient was 1.8. Although the overall cost of medications was higher in the plerixafor group, the cost for blood products and overall cost of hospitalization were similar between the two groups.

CONCLUSIONS

Up-front use of plerixafor is an effective mobilization strategy in patients with MM and does not have a substantial pharmacoeconomic impact in overall cost of hospitalization combined with the apheresis procedure.

PBSC mobilization in lymphoma patients: analysis of risk factors for collection failure and development of a predictive score based on the kinetics of circulating CD34+ cells and WBC after chemotherapy and G-CSF mobilization

Autologous stem cell transplantation (ASCT) is a potentially curative treatment of lymphoma, but peripheral blood stem cell (PBSC) mobilization fails in some patients. PBSC mobilizing agents have recently been proved to improve the PBSC yield after a prior mobilization failure. Predictive parameters of mobilization failure allowing for a preemptive, more cost-effective use of such agents during the first mobilization attempt are still poorly defined, particularly during mobilization with chemotherapy + granulocyte colony-stimulating factor (G-CSF). We performed a retrospective analysis of a series of lymphoma patients who were candidates for ASCT, to identify factors influencing PBSC mobilization outcome. Premobilization parameters-age, histology, disease status, mobilizing protocol, and previous treatments-as well as white blood cell (WBC) and PBSC kinetics, markers potentially able to predict failure during the ongoing mobilization attempt, were analyzed in 415 consecutive mobilization procedures in 388 patients. We used chemotherapy + G-CSF in 411 (99%) of mobilization attempts and PBSC collection failed (<2 × 10(6) CD34+ PBSC/kg) in 13%. Multivariable analysis showed that only a low CD34+ PBSC count and CD34+ PBSC/WBC ratio, together with the use of nonplatinum-containing chemotherapy, independently predicted mobilization failure. Using these three parameters, we established a scoring system to predict risk of failure during mobilization ranging from 2 to 90%, thus allowing a selective use of a preemptive mobilization policy.

Hematopoietic stem cell mobilization for gene therapy: superior mobilization by the combination of granulocyte-colony stimulating factor plus plerixafor in patients with β-thalassemia major

Successful stem cell gene therapy requires high numbers of genetically engineered hematopoietic stem cells collected using optimal mobilization strategies. Here we focus on stem cell mobilization strategies for thalassemia and present the results of a plerixafor-based mobilization trial with emphasis on the remobilization with granulocyte-colony stimulating factor (G-CSF)+plerixafor in those patients who had previously failed mobilization. Plerixafor rapidly mobilized CD34(+) cells without inducing hyperleukocytosis; however, 35% of patients failed to reach the target cell dose of ≥6×10(6) CD34(+) cells/kg. Four subjects who failed on either plerixafor or G-CSF were remobilized with G-CSF+plerixafor. The combination proved highly synergistic; the target cell dose was readily reached and the per-apheresis yield was significantly increased over initial mobilization, ultimately resulting in single-apheresis collections, despite a more than 50% reduction of the dose of G-CSF in splenectomized patients to avoid hyperleukocytosis. The total stem and progenitor cells mobilized in G-CSF+plerixafor patients were higher than in patients treated by plerixafor alone. Importantly, the G-CSF+plerixafor-mobilized cells displayed a primitive stem cell phenotype and higher clonogenic capacity over plerixafor-mobilized cells. G-CSF+plerixafor represents the optimal strategy when very high yields of stem cells or a single apheresis is required. The high yields and the favorable transplantation features render the G-CSF+plerixafor-mobilized cells the optimal CD34(+) cell source for stem cell gene therapy applications.

Advances in stem cell mobilization

Use of granulocyte colony stimulating factor (G-CSF)-mobilized peripheral blood hematopoietic progenitor cells (HPCs) has largely replaced bone marrow (BM) as a source of stem cells for both autologous and allogeneic cell transplantation. With G-CSF alone, up to 35% of patients are unable to mobilize sufficient numbers of CD34 cells/kg to ensure successful and consistent multi-lineage engraftment and sustained hematopoietic recovery. To this end, research is ongoing to identify new agents or combinations which will lead to the most effective and efficient stem cell mobilization strategies, especially in those patients who are at risk for mobilization failure. We describe both established agents and novel strategies at various stages of development. The latter include but are not limited to drugs that target the SDF-1/CXCR4 axis, S1P agonists, VCAM/VLA-4 inhibitors, parathyroid hormone, proteosome inhibitors, Groβ, and agents that stabilize HIF. While none of the novel agents have yet gained an established role in HPC mobilization in clinical practice, many early studies exploring these new pathways show promising results and warrant further investigation.

Optimizing autologous stem cell mobilization strategies to improve patient outcomes: consensus guidelines and recommendations

Autologous hematopoietic stem cell transplantation (aHSCT) is a well-established treatment for malignancies such as multiple myeloma (MM) and lymphomas. Various changes in the field over the past decade, including the frequent use of tandem aHSCT in MM, the advent of novel therapies for the treatment of MM and lymphoma, and the addition of new stem cell mobilization techniques, have led to the need to reassess current stem cell mobilization strategies. Mobilization failures with traditional strategies are common and result in delays in treatment and increased cost and resource utilization. Recently, plerixafor-containing strategies have been shown to significantly reduce mobilization failure rates, but the ideal method to maximize stem cell yields and minimize costs associated with collection has not yet been determined. A panel of experts convened to discuss the currently available data on autologous hematopoietic stem cell mobilization and transplantation and to devise guidelines to optimize mobilization strategies. Herein is a summary of their discussion and consensus.

The evolving role of plerixafor in hematopoietic progenitor cell mobilization

The introduction of plerixafor as a peripheral blood stem cell mobilization agent has allowed more patients with multiple myeloma, non-Hodgkin's lymphoma, and Hodgkin's disease to mobilize sufficient hematopoietic progenitor cells (HPCs) to proceed to autologous transplantation. Because of the high cost of plerixafor, it is not routinely used in all patients undergoing HPC mobilization. If cost were not an issue, an argument could be made that plerixafor could be added to every mobilization regimen, but cost is an issue so in an attempt to be more cost-effective, many centers have limited plerixafor use to patients who have failed or who are predicted to fail collection of adequate numbers of cells by other methods. Additionally, plerixafor is now under investigation both for HPC collection of healthy donors for allogeneic stem cell transplantation and as an adjunct therapy (i.e., chemosensitizing agent) for acute leukemias. This article briefly reviews the role of plerixafor in autologous and allogeneic transplantation as well as its emerging role in the treatment of acute leukemias. Emphasis is placed on the choice of appropriate patients for plerixafor use to assure an adequate stem cell yield while maximizing the cost effectiveness of using plerixafor. The role of prophylactic collections and future areas of research are also presented.

The combination of stem cell factor and granulocyte-colony stimulating factor for chronic stroke treatment in aged animals

Background

Stroke occurs more frequently in the elderly population and presents the number one leading cause of persistent disability worldwide. Lack of effective treatment to enhance brain repair and improve functional restoration in chronic stroke, the recovery phase of stroke, is a challenging medical problem to be solved in stroke research. Our early study has revealed the therapeutic effects of stem cell factor (SCF) in combination with granulocyte-colony stimulating factor (G-CSF) (SCF+G-CSF) on chronic stroke in young animals. However, whether this treatment is effective and safe to the aged population remains to be determined.

Methods

Cortical brain ischemia was produced in aged C57BL mice or aged spontaneously hypertensive rats. SCF+G-CSF or equal volume of vehicle solution was subcutaneously injected for 7 days beginning at 3–4 months after induction of cortical brain ischemia. Using the approaches of biochemistry assays, flow cytometry, pathology, and evaluation of functional outcome, several doses of SCF+G-CSF have been examined for their safety and efficiency on chronic stroke in aged animals.

Results

All tested doses did not show acute or chronic toxicity in the aged animals. Additionally, SCF+G-CSF treatment in chronic stroke of aged animals mobilized bone marrow stem cells and improved functional outcome in a dose-dependent manner.

Conclusions

SCF+G-CSF treatment is a safe and effective approach to chronic stroke in the aged condition. This study provides important information needed for developing a new therapeutic strategy to improve the health of older adults with chronic stroke.

The plasminogen system in regulating stem cell mobilization. J Biomed Biotechnol. 2012;2012:437920. [PMID: 23118508 PMCID: PMC3478786 DOI: 10.1155/2012/437920]

The treatment of patients with hematopoietic progenitor and stem cells (HPSCs) to reconstitute hematopoiesis after myeloablative therapy or to repair ischemia after myocardial infarction has significantly improved clinical outcomes. Successful blood or bone marrow transplants require a sufficient number of HPSCs capable of homing to the injured site to regenerate tissue. Granulocyte-colony stimulating factor (G-CSF) is widely used clinically for stem cell mobilization. However, in some patients the response is poor, thus a better understanding of the mechanisms underlying G-CSF-regulated stem cell mobilization is needed. The pasminogen (Plg) system is the primary fibrinolytic pathway responsible for clot dissolution after thrombosis. Recent evidence suggests that Plg plays a pivotal role in stem cell mobilization from the bone marrow to the peripheral circulation, particularly in HPSC mobilization in response to G-CSF. This paper will discuss the potential mechanisms by which the Plg system regulates stem cell mobilization, focusing on stepwise proteolysis and signal transduction during HPSC egress from their bone marrow niche. Clear elucidation of the underlying mechanisms may lead to the development of new Plg-based therapeutic strategies to improve stem cell mobilization in treating hematological and cardiovascular diseases.

Challenges for heart disease stem cell therapy

Cardiovascular diseases (CVDs) are the leading cause of death worldwide. The use of stem cells to improve recovery of the injured heart after myocardial infarction (MI) is an important emerging therapeutic strategy. However, recent reviews of clinical trials of stem cell therapy for MI and ischemic heart disease recovery report that less than half of the trials found only small improvements in cardiac function. In clinical trials, bone marrow, peripheral blood, or umbilical cord blood cells were used as the source of stem cells delivered by intracoronary infusion. Some trials administered only a stem cell mobilizing agent that recruits endogenous sources of stem cells. Important challenges to improve the effectiveness of stem cell therapy for CVD include: (1) improved identification, recruitment, and expansion of autologous stem cells; (2) identification of mobilizing and homing agents that increase recruitment; and (3) development of strategies to improve stem cell survival and engraftment of both endogenous and exogenous sources of stem cells. This review is an overview of stem cell therapy for CVD and discusses the challenges these three areas present for maximum optimization of the efficacy of stem cell therapy for heart disease, and new strategies in progress.

Hematopoietic stem cell mobilization with agents other than G-CSF

Hematopoietic stem and progenitor mobilization has revolutionized the field of hematopoietic transplantation. Currently, hematopoietic grafts acquired from the peripheral blood of patients or donors treated with granulocyte-colony stimulating factor (G-CSF) are the preferred source for transplantation. G-CSF mobilization regimens, however, are associated with known morbidities and a significant number of normal donors and patient populations fail to mobilize sufficient numbers of hematopoietic stem and progenitor cells for transplantation, necessitating the need for non-G-CSF mobilization strategies. Mechanistic studies evaluating hematopoietic bone marrow niche interactions have uncovered novel agents with the capacity for hematopoietic mobilization. This chapter provides a comprehensive overview of mobilizing agents, other than G-CSF, and experimental procedures and technical aspects important to evaluate and define their hematopoietic mobilizing activities alone and in combination.

Tandem autologous-allogeneic nonmyeloablative sibling transplantation in relapsed follicular lymphoma leads to impressive progression-free survival with minimal toxicity

Autologous stem cell transplantation (ASCT) prolongs survival in patients with relapsed follicular lymphoma. ASCT is usually not curative, however. Myeloablative allogeneic transplantation has produced long-term survival at a cost of significant transplantation-related mortality (TRM), whereas reduced-intensity transplantation entails less TRM but has a higher relapse rate. We thus initiated a protocol consisting of ASCT followed by nonmyeloablative allogeneic transplantation (NMT) for relapsed follicular lymphoma to mimic myeloablative allogeneic transplantation without the associated toxicity. The NMT was non-T cell-depleted, and all donors were HLA-identical siblings. We report results in 27 patients with a median age of 49 years (range, 34-65 years). Five patients demonstrated histological progression toward an aggressive lymphoma. The patients had received a median of 3 lines of previous therapy. Disease status before ASCT included 8 patients in complete remission, 14 in partial remission, and 5 refractory. Five patients developed grade II-IV acute graft-versus-host disease, and 20 patients developed chronic graft-versus-host disease requiring systemic therapy. With a median follow-up of 39 months after NMT, overall survival and progression-free survival were 96% at 3 years. We conclude that the combined ASCT-NMT strategy appears to be safe, with excellent progression-free survival even in refractory and transformed cases. This novel approach warrants further investigation in larger prospective studies.

How I treat patients who mobilize hematopoietic stem cells poorly

Transplantation with 2-5 × 106 mobilized CD34+cells/kg body weight lowers transplantation costs and mortality. Mobilization is most commonly performed with recombinant human G-CSF with or without chemotherapy, but a proportion of patients/donors fail to mobilize sufficient cells. BM disease, prior treatment, and age are factors influencing mobilization, but genetics also contributes. Mobilization may fail because of the changes affecting the HSC/progenitor cell/BM niche integrity and chemotaxis. Poor mobilization affects patient outcome and increases resource use. Until recently increasing G-CSF dose and adding SCF have been used in poor mobilizers with limited success. However, plerixafor through its rapid direct blockage of the CXCR4/CXCL12 chemotaxis pathway and synergy with G-CSF and chemotherapy has become a new and important agent for mobilization. Its efficacy in upfront and failed mobilizers is well established. To maximize HSC harvest in poor mobilizers the clinician needs to optimize current mobilization protocols and to integrate novel agents such as plerixafor. These include when to mobilize in relation to chemotherapy, how to schedule and perform apheresis, how to identify poor mobilizers, and what are the criteria for preemptive and immediate salvage use of plerixafor.

Plasminogen regulates stromal cell-derived factor-1/CXCR4-mediated hematopoietic stem cell mobilization by activation of matrix metalloproteinase-9

OBJECTIVE

Granulocyte colony-stimulating factor (G-CSF) is a widespread therapeutic agent for stimulation of hematopoietic progenitor and stem cell (HPSC) mobilization from bone marrow (BM). Plasminogen (Plg) has been shown to be critical for HPSC mobilization. Here, we investigated the role of Plg in G-CSF-induced HPSC mobilization and the underlying mechanism.

METHODS AND RESULTS

By using gene-targeted mice, our data show that Plg is required for G-CSF-induced HPSC egress to sinusoidal capillaries in BM and subsequent mobilization to peripheral circulation. G-CSF induced Plg-dependent activation of matrix metalloproteinase-9 (MMP-9) in BM, and MMP-9 neutralization or deficiency suppressed HPSC migration and mobilization. Reconstitution of MMP-9 activity by BM transplantation after lentiviral overexpression rescued HPSC mobilization in Plg-deficient mice, indicating that MMP-9 activation is required for Plg-mediated HPSC mobilization. Interestingly, after G-CSF simulation, Plg downregulated stromal cell-derived factor-1 in BM and spatiotemporally regulated the expression of C-X-C chemokine receptor type 4 (CXCR4) on mobilized HPSCs, and reconstitution of MMP-9 activity in Plg-deficient mice reversed CXCR4 expression on HPSCs in plasma and BM, suggesting that CXCR4 serves as a new downstream signal of Plg/MMP-9 in HPSC mobilization.

CONCLUSIONS

Our data elucidated a novel mechanism that Plg regulates MMP-9-dependent CXCR4 expression to facilitate HPSC mobilization in response to G-CSF.

Assessing the charges associated with hematopoietic stem cell mobilization and remobilization in patients with lymphoma and multiple myeloma undergoing autologous hematopoietic peripheral blood stem cell transplantation

BACKGROUND

The purpose of this study was to perform a detailed analysis of the charges associated with chemomobilization and remobilization of autologous hematopoietic stem cells (HSCs) and to quantify medical costs and resource utilization associated with these procedures.

STUDY DESIGN AND METHODS

Patients with lymphoma underwent chemomobilization with ifosfamide and etoposide with or without rituximab (IE ± R). Patients with multiple myeloma (MM) received a modified hyperfractionated cyclophosphamide, vincristine, doxorubicin, dexamethasone (hyper-CVAD) regimen after failing to mobilize with growth factors only.

RESULTS

Between January 2004 and October 2006, 98 patients with lymphoma underwent HSC mobilization with IE ± R. Mobilization with IE ± R was effective, with 90.8% of patients collecting at least 2 × 10(6) CD34+ cells/kg. The total charges for treatment were $27,996 and $37,667 for patients mobilized with IE and IE + R, respectively. Hospital readmission for complications occurred in 26.5% of patients, resulting in additional charges of $10,356. The preapheresis procedure charge was estimated to be $2522, the charge for a 2-day apheresis session was $5160, and the postapheresis phase resulted in charges of $8040. Our analysis determined that reducing apheresis by 1 day has the potential to save $6600. We also performed a retrospective analysis of 16 patients with MM remobilized with a modified hyper-CVAD regimen. Remobilization was successful, with 87.5% of patients. Our analysis determined that mobilization, preapheresis, apheresis, and postapheresis phase charges were $24,968, $2522, $6158, and $12,060, respectively.

CONCLUSIONS

Optimization of HSC mobilization regimens to reduce failure rates would not only benefit patients but also reduce the overall medical costs.

Current status of stem cell mobilization

New advances in effective mobilization of peripheral blood stem cells have permitted a greater proportion of patients to benefit from autologous stem cell transplantation. In this review, the relative merits of peripheral blood and mobilized bone marrow are discussed. All available agents are reviewed. A critical assessment of the appropriate dosing and frequency of available growth factors is undertaken, and the most commonly used chemotherapy plus growth factor combinations are covered. Specific recommendations for patients who are poor mobilizers are dealt with including the role of plerixafor.

Targeting stem cell niches and trafficking for cardiovascular therapy

Regenerative cardiovascular medicine is the frontline of 21st-century health care. Cell therapy trials using bone marrow progenitor cells documented that the approach is feasible, safe and potentially beneficial in patients with ischemic disease. However, cardiovascular prevention and rehabilitation strategies should aim to conserve the pristine healing capacity of a healthy organism as well as reactivate it under disease conditions. This requires an increased understanding of stem cell microenvironment and trafficking mechanisms. Engagement and disengagement of stem cells of the osteoblastic niche is a dynamic process, finely tuned to allow low amounts of cells move out of the bone marrow and into the circulation on a regular basis. The balance is altered under stress situations, like tissue injury or ischemia, leading to remarkably increased cell egression. Individual populations of circulating progenitor cells could give rise to mature tissue cells (e.g. endothelial cells or cardiomyocytes), while the majority may differentiate to leukocytes, affecting the environment of homing sites in a paracrine way, e.g. promoting endothelial survival, proliferation and function, as well as attenuating or enhancing inflammation. This review focuses on the dynamics of the stem cell niche in healthy and disease conditions and on therapeutic means to direct stem cell/progenitor cell mobilization and recruitment into improved tissue repair.

Ancestim (r-metHuSCF) plus filgrastim and/or chemotherapy for mobilization of blood progenitors in 513 poorly mobilizing cancer patients: the French compassionate experience

Ancestim (r-MetHuSCF) is available in France for compassionate use in patients who are candidates for high-dose chemotherapy and autologous transplantation, and who failed in previous attempts at mobilization and collection. We report here data from 513 adult patients who benefited from this program, between January 1998 and July 2007. Given with systematic premedication, ancestim was generally well tolerated, although severe but not life-threatening adverse events were reported in 12 individuals. Overall, a graft was obtained or completed for 235 patients (46%). The median number of collected CD34+ cells was 3.00 × 10(6)/kg (range: 0.03-39.50). The target threshold of 2 × 10(6) CD34+ cells/kg was reached in 161 patients (31%). Factors associated with collection were diagnosis of myeloma, no previous autologous transplant, no more than one previous failed attempt and a mobilization regimen including cytotoxic agents. A total of 207 patients (40%) proceeded to high-dose chemotherapy and autologous transplantation. The median time to reach 0.5 × 10(9)/L neutrophils and 20 × 10(9)/L platelets was 12 (6-40) and 13 (0-31) days, respectively. We conclude that a combination of ancestim with filgrastim successfully mobilized CD34+ cells in peripheral blood, and allowed adequate collection in preparation for autologous transplantation in approximately one-third of poorly mobilizing patients.

Innate immunity as orchestrator of stem cell mobilization

Hematopoietic stem and progenitor cells (HSPCs), as well as other types of stem cells, circulate under steady-state conditions at detectable levels in peripheral blood (PB), with their numbers increasing in response to stress, inflammation and tissue/organ injury. This mobilization process may be envisioned as a danger-sensing response mechanism triggered by hypoxia or mechanical or infection-induced tissue damage that recruits into PB different types of stem cells that have a role in immune surveillance and organ/tissue regeneration. Mobilization is also significantly enhanced by the administration of pharmacological agents, which has been exploited in hematological transplantology as a means to obtain HSPCs for hematopoietic reconstitution. In this review we will present mounting evidence that innate immunity orchestrates this evolutionarily conserved mechanism of HSPC mobilization.

Priming with r-metHuSCF and filgrastim or chemotherapy and filgrastim in patients with malignant lymphomas: a randomized phase II pilot study of mobilization and engraftment

SCF has been shown to synergize with G-CSF to mobilize CD34(+) PBPCs. In this study we report results from this combination after a phase II trial of 32 patients with malignant lymphoma randomized to receive recombinant methionyl human SCF (ancestim, r-metHuSCF) in combination with recombinant methionyl human G-CSF (filgrastim, r-metHuG-CSF) (experimental arm A) or routine chemotherapy plus filgrastim (conventional arm B). The primary objective was to evaluate the side effects and toxicity during priming and mobilization. The secondary objectives were efficacy by the level of blood-circulating PBPCs, the number of harvest days and the time to three-lineage engraftment after autografting. First, during priming 5 patients had 8 serious events, 4 in each arm. A summary of all adverse events revealed 30 (94%) patients suffering from 132 events of all grading. Second, neutropenia and thrombocytopenia was documented in arm B. Third, 9/14 (64%) patients in arm A reached the target of 5 million CD34(+) cells/kg body weight (bw) compared with 13/15 (87%) in arm B. The results represent the first randomized trial of growth factor plus chemotherapy priming and indicate that a formal phase III trial very unlikely may challenge chemotherapy plus r-metHuG-CSF priming in candidates for high-dose therapy.

Novel insight into stem cell mobilization-plasma sphingosine-1-phosphate is a major chemoattractant that directs the egress of hematopoietic stem progenitor cells from the bone marrow and its level in peripheral blood increases during mobilization due to activation of complement cascade/membrane attack complex. Leukemia. 2010;24:976-985. [PMID: 20033053 PMCID: PMC2838235 DOI: 10.1038/leu.2009.271]

We reported that complement cascade (CC) becomes activated in bone marrow (BM) during mobilization of hematopoietic stem/progenitor cells (HSPCs) induced by granulocyte-colony stimulating factor (G-CSF) and C5 cleavage plays an important role in optimal egress of HSPCs. In the current work, we explored whether CC is involved in mobilization of HSPCs induced by the CXCR4 antagonist, AMD3100. To address this question, we performed mobilization studies in mice that display a defect in the activation of the proximal steps of CC (Rag^−/−, SCID, C2.Cfb^−/−) as well as in mice that do not activate the distal steps of CC (C5^−/−). We noticed that proximal CC activation-deficient mice (above C5 level), in contrast to distal step CC activation-deficient C5^−/− ones mobilize normally in response to AMD3100 administration. We hypothesized that this discrepancy in mobilization could be explained by AMD3100 activating C5 in Rag^−/−, SCID, C2.Cfb^−/− animals in a non-canonical mechanism involving activated granulocytes. To support this granulocytes i) as first egress from BM and ii) secrete several proteases that cleave/activate C5 in response to AMD3100. We conclude that AMD3100-directed mobilization of HSPCs, similarly to G-CSF-induced mobilization, depends on activation of CC; however, in contrast to G-CSF, AMD3100 activates the distal steps of CC directly at the C5 level. Overall, these data support that C5 cleavage fragments and distal steps of CC activation are required for optimal mobilization of HSPCs.

Successful stem cell remobilization using plerixafor (mozobil) plus granulocyte colony-stimulating factor in patients with non-hodgkin lymphoma: results from the plerixafor NHL phase 3 study rescue protocol

In a phase 3 multicenter, randomized, double-blinded, placebo-controlled study of 298 patients with non-Hodgkin lymphoma (NHL), granulocyte colony-stimulating factor (G-CSF) plus plerixafor increased the proportion of patients who mobilized >or=5 x 10(6) CD34(+) hematopoietic stem cells (HSCs)/kg compared with placebo plus G-CSF (P < .001). Patients in either study arm who failed mobilization (< 0.8 x 10(6) CD34(+) cells/kg in 2 collections or <2 x 10(6) CD34(+) cells/kg in 4 collections) were eligible to enter the opened-label rescue protocol. Following a 7-day minimum rest period, these patients received G-CSF (10 microg/kg/day) for 4 days, followed by daily plerixafor (0.24 mg/kg) plus G-CSF and apheresis for up to 4 days. Of the 68 patients failing initial mobilization (plerixafor, n = 11; placebo, n = 57), 62 patients (91%) entered the rescue procedure (plerixafor, n = 10; placebo, n = 52). Four of 10 patients (40%) from the plerixafor group and 33 of 52 (63%) from the placebo group mobilized sufficient CD34(+) cells (>or= 2 x 10(6) cells/kg) for transplantation from the rescue mobilization alone (P = .11). Engraftment of neutrophils (11 days) and platelets (20 days) was similar to that in patients who did not fail initial mobilization, and all patients had durable grafts at the 12-month follow-up. Common plerixafor-related adverse events (AEs) included mild gastrointestinal (GI) effects and injection site reactions. There were no drug-related serious AEs. These data support that plerixafor plus G-CSF can safely and effectively remobilize patients with NHL who have failed previous mobilization.

Binding of proteins to PEGylated liposomes and improvement of G-CSF efficacy in mobilization of hematopoietic stem cells

We have previously shown that formulation of coagulation factor VIII and activated factor VII with PEGylated liposomes (PEGLip) results in an extension of circulation time and an increase in hemostatic efficacy. Here we identified additional proteins that associate with PEGLip, including granulocyte colony-stimulating factor (G-CSF). Surface plasmon resonance analyses indicated that G-CSF bound noncovalently but with high affinity and specificity to PEGLip. A pharmacokinetic study in mice demonstrated that PEGLip formulation of G-CSF extended its circulation time and resulted in higher G-CSF levels several hours after both subcutaneous and intravenous injection. PEGLip-formulated G-CSF had a significantly improved efficacy in the mobilization of hematopoietic stem cells (HSC) from the bone marrow to the peripheral blood. The results suggest that PEGLip-formulated G-CSF may function as an effective and safe tool for the mobilization of HSC prior to bone marrow transplantation. We also identified an amino acid sequence present in proteins that associate with PEGLip but absent from those that do not. A peptide based on this consensus sequence bound PEGLip. The results suggest that PEGLip formulation may serve as a platform for the delivery of additional short-half-life proteins/peptides having the relevant consensus sequence.

Adult stem cells and their trans-differentiation potential--perspectives and therapeutic applications

Stem cells are self-renewing multipotent progenitors with the broadest developmental potential in a given tissue at a given time. Normal stem cells in the adult organism are responsible for renewal and repair of aged or damaged tissue. Adult stem cells are present in virtually all tissues and during most stages of development. In this review, we introduce the reader to the basic information about the field. We describe selected stem cell isolation techniques and stem cell markers for various stem cell populations. These include makers for endothelial progenitor cells (CD146/MCAM/MUC18/S-endo-1, CD34, CD133/prominin, Tie-2, Flk1/KD/VEGFR2), hematopoietic stem cells (CD34, CD117/c-Kit, Sca1), mesenchymal stem cells (CD146/MCAM/MUC18/S-endo-1, STRO-1, Thy-1), neural stem cells (CD133/prominin, nestin, NCAM), mammary stem cells (CD24, CD29, Sca1), and intestinal stem cells (NCAM, CD34, Thy-1, CD117/c-Kit, Flt-3). Separate section provides a concise summary of recent clinical trials involving stem cells directed towards improvement of a damaged myocardium. In the last part of the review, we reflect on the field and on future developments.

Peripheral blood stem cell mobilization: new regimens, new cells, where do we stand. Curr Opin Hematol. 2008;15:285-292. [PMID: 18536564 DOI: 10.1097/moh.0b013e328302f43a]

PURPOSE OF REVIEW

Granulocyte colony-stimulating factor-mobilized peripheral blood stem cells are widely used to reconstitute hematopoiesis; however, preclinical and clinical studies show that improvements to this mobilization can be achieved. We discuss the development of new mobilizing regimens and evaluation of new findings on mobilized stem cell populations that may improve the utility and convenience of peripheral blood stem cell transplant.

RECENT FINDINGS

Chemokines and their receptors regulate leukocyte trafficking, and altering chemokine signaling pathways mobilizes stem cells. In recent trials, combination use of the chemokine (C-X-C motif) receptor 4 antagonist AMD3100 and granulocyte colony-stimulating factor mobilized more CD34 cells in fewer days than granulocyte colony-stimulating factor alone and allowed more patients to proceed to autotransplant. In preclinical studies the chemokine GRObeta synergizes with granulocyte colony-stimulating factor and when used alone or with granulocyte colony-stimulating factor mobilizes more primitive hematopoietic stem cells with less apoptosis, higher integrin activation, lower CD26 expression and enhanced marrow homing compared with granulocyte colony-stimulating factor. Hematopoietic stem cells mobilized by GRObeta or AMD3100 demonstrate superior engraftment and contribution to chimerism in primary and secondary transplant studies in mice, and peripheral blood stem cells mobilized by AMD3100 and granulocyte colony-stimulating factor in patients demonstrate enhanced engraftment capabilities in immunodeficient mice.

SUMMARY

Alternate regimens differentially mobilize stem cell populations with unique intrinsic properties with the potential to expand the utility of hematopoietic transplantation. Continued mechanistic evaluation will be critical to our understanding of mechanisms of mobilization and their use in regenerative medicine.

Mobilizing stem cells from normal donors: is it possible to improve upon G-CSF?

Currently, granulocyte colony stimulating factor (G-CSF) remains the standard mobilizing agent for peripheral blood stem cell (PBSC) donors, allowing the safe collection of adequate PBSCs from the vast majority of donors. However, G-CSF mobilization can be associated with some significant side effects and requires a multi-day dosing regimen. The other cytokine approved for stem cell mobilization, granulocyte-macrophage colony stimulating factor (GM-CSF), alters graft composition and may reduce the development of graft-versus-host disease, but a significant minority of donors fails to provide sufficient CD34+ cells with GM-CSF and some experience unacceptable toxicity. AMD3100 is a promising new mobilizing agent, which may have several advantages over G-CSF for donor mobilization. As it is a direct antagonist of the interaction between the chemokine stromal-derived factor-1 and its receptor CXCR4, AMD3100 mobilizes PBSCs within hours rather than days. It is also well tolerated, with no significant side effects reported in any of the clinical trials to date. Studies of autologous and allogeneic transplantation of AMD3100 mobilized grafts have demonstrated prompt and stable engraftment. Here, we review the current state of stem cell mobilization in normal donors and discuss novel strategies for donor stem cell mobilization.

Hematopoietic growth factors pass through the blood-brain barrier in intact rats

We have previously demonstrated that receptors for hematopoietic growth factors, stem cell factor (SCF) and granulocyte-colony stimulating factor (G-CSF) are expressed in the neurons and the neural progenitor cells (NPCs) of the adult rat brain, and that systemic administration of SCF and G-CSF in the first week after induction of cortical brain ischemia (3 h-7 days post-ischemia) significantly improves functional outcome, augments NPC proliferation, and reduces infarct volume in rats. The purpose of the present study is to determine whether SCF and G-CSF pass through the blood-brain barrier (BBB) in intact rats. The growth factors were labeled with iodine (I(125)), a radioactive compound. I(125)-SCF and I(125)-G-CSF were intravenously administered and the concentrations of I(125)-SCF and I(125)-G-CSF in the blood plasma and the brain were determined at 10, 30, 60, and 120 min after injection. We observed that both SCF and G-CSF were slowly and continuously transported from the blood stream to the brain in the same rate. In addition, both immunofluorescent staining and Western blots showed that receptors for SCF and G-CSF were expressed in the capillaries of the adult rat brain, suggesting that SCF and G-CSF entry to the brain may be mediated via receptor-mediated transport, one of the endogenous transports in the BBB. These data indicate that both SCF and G-CSF were able to pass through the BBB in intact animals. This observation will help in further exploring the physiological role of peripheral SCF and G-CSF in the brain and therapeutic possibility to chronic stroke.

Mobilization of bone marrow-derived progenitors

Bone marrow (BM) is a source of various stem and progenitor cells in the adult, and it is able to regenerate a variety of tissues following transplantation. In the 1970s the first BM stem cells identified were hematopoietic stem cells (HSCs). HSCs have the potential to differentiate into all myeloid (including erythroid) and lymphoid cell lineages in vitro and reconstitute the entire hematopoietic and immune systems following transplantation in vivo. More recently, nonhematopoietic stem and progenitor cells have been identified that can differentiate into other cell types such as endothelial progenitor cells (EPCs), contributing to the neovascularization of tumors as well as ischemic tissues, and mesenchymal stem cells (MSCs), which are able to differentiate into many cells of ectodermal, endodermal, and mesodermal origins in vitro as well as in vivo. Following adequate stimulation, stem and progenitor cells can be forced out of the BM to circulate into the peripheral blood, a phenomenon called "mobilization." This chapter reviews the molecular mechanisms behind mobilization and how these have led to the various strategies employed to mobilize BM-derived stem and progenitor cells in experimental and clinical settings. Mobilization of HSCs will be reviewed first, as it has been best-explored--being used extensively in clinics to transplant large numbers of HSCs to rescue cancer patients requiring hematopoietic reconstitution--and provides a paradigm that can be generalized to the mobilization of other types of BM-derived stem and progenitor cells in order to repair other tissues.

Initial chemotherapy with mitoxantrone, chlorambucil, prednisone impairs the collection of stem cells in patients with indolent lymphomas—results of a randomized comparison by the German Low-Grade Lymphoma Study Group

Myeloablative radio-chemotherapy with subsequent autologous stem cell transplantation (ASCT) significantly prolongs progression free and probably overall survival in follicular lymphoma (FL) in first remission. The current trial explored prospectively the rate of successful stem cell mobilization in patients with advanced stage FL after initial therapy with either Mitoxantrone, Chlorambucil, Prednisone (MCP) or Cyclophosphamide, Doxorubicin, Vincristine, Prednisone (CHOP) as part of a prospective randomized comparison of both regimens. ASCT patients received Dexa-BEAM (Dexamethasone, BCNU, Melphalan, Etoposide, Cytarabine) for mobilization of stem cells. Stem cells were collected and a minimum of 2x2.0x106/kg bw CD34+ was required for ASCT. Of 79 evaluable patients, 58 (73%) had follicular lymphoma, 13 (16%) mantle cell lymphoma and 8 (10%) lymphoplasmacytic lymphoma. In the 45 patients assigned to CHOP, stem cell collection was successful in 42 cases (93%, 95% CI 82% to 99%). This high mobilization rate after CHOP could be confirmed in 61 subsequent patients (87%). In contrast, after MCP therapy stem cell collection was successful in only 15 of 34 patients (44%, 95% CI 27% to 62%; P=0.0003). In conclusion, initial therapy with MCP significantly impairs the ability to collect stem cells and should be avoided for first line therapy of younger patients potentially qualifying for high dose consolidation and ASCT in first remission.

An ex vivo model of hematopoietic stem cell mobilization

BACKGROUND

Mobilization of hematopoietic stem cells to the circulation facilitates their collection, thereby providing a non-marrow source of these cells for transplantation. Hematopoietic cytokine administration induces mobilization for most, but not all, donors. Because the underlying biology of mobilization is not well understood, improving the process on a rational basis is difficult. The design of an in vitro mobilization model was pursued to facilitate investigations of the process.

METHODS

MS5 murine stromal cell line cells were grown to confluence on microporous transwell membranes. Murine femoral marrow plugs were placed on top of the prepared transwell membranes. The transwells were then seated in wells containing media and hematopoietic growth factors. Cells that were released from the marrow plugs over time and migrated through the stromal layer into the wells were assayed for stem cell/progenitor cell characteristics.

RESULTS

Few or no GM-CSF (progenitors) were found in wells containing media alone or media plus mobilizing cytokines after 24 h. After 120 h, the numbers of cells in the cytokine-containing wells increased, as did the numbers of CD34(+) cells. Cells in the wells at the time progenitor cells were most frequent were shown to include side population (SP) hematopoietic stem cells. After 120 h in the presence of cytokines, cells pooled from the wells were transplanted to lethally irradiated mice. Eighty per cent of the transplanted mice survived 30 days or more, demonstrating that radioprotective stem cells were present in the wells.

DISCUSSION

An ex vivo model has been designed that may aid investigations of the various steps of stem cell mobilization.

Actions and therapeutic potential of G-CSF and GM-CSF in cardiovascular disease

Despite their names, the cytokines granulocyte- and granulocyte-macrophage-colony stimulating factor (G-CSF and GM-CSF respectively) have actions far beyond simply stimulating the proliferation of neutrophil and monocyte lineage cells. A comprehensive body of evidence now exists demonstrating that G-CSF and GM-CSF effectively mobilize bone-marrow-derived progenitor cells into the peripheral circulation. These mobilized progenitor cells can be conveniently harvested for use in reconstituting bone marrow by transplantation after myelo-ablative treatment of hematological malignancies. In addition, much evidence has recently emerged to suggest that these cytokines may have multiple direct and indirect beneficial cardiovascular effects--including neovascularization of ischemic myocardium and reducing the extent of myocardial damage after infarction. Based on this knowledge and a strong safety record in hematological applications, a number of early clinical trials have evaluated the use of G-CSF or GM-CSF in patients with both acute and chronic myocardial ischemia. Although the interpretation of these trials is complicated by heterogeneity in study design, small patient numbers and methodological concerns related to appropriate selection and blinding of patients, the results of ongoing larger phase II/III trials should soon be available to determine if these agents will be useful additions to the cardiovascular armamentarium.

Low doses of GM-CSF (molgramostim) and G-CSF (filgrastim) after cyclophosphamide (4 g/m2) enhance the peripheral blood progenitor cell harvest: results of two randomized studies including 120 patients

The use of a combination of G-CSF and GM-CSF versus G-CSF alone, after cyclophosphamide (4 g/m2) was compared in two randomized phase III studies, including 120 patients. In study A, 60 patients received 5 x 2 microg/kg/day of G-CSF and GM-CSF compared to 5 mug/kg/day of G-CSF. In study B, 60 patients received 2.5 x 2 microg/kg/day G-CSF and GM-CSF compared to G-CSF alone (5 microg/kg/day). With the aim to collect at least 5 x 10(6)/kg CD34 cells in a maximum of three large volume leukapherises (LK), 123 LK were performed in study A, showing a significantly higher number of patients reaching 10 x 10(6)/kg CD34 cells (21/29 in G+GM-CSF arm vs 11/27 in G-CSF arm, P=0.00006). In study B, 109 LK were performed, with similar results (10/27 vs 15/26, P=0.003). In both the study, the total harvest of CD34 cells/kg was twofold higher in G-CSF plus GM-CSF group (18.3 x 10(6) in study A and 15.85 x 10(6) in study B) than in G-CSF group (9 x 10(6) in study A and 8.1 x 10(6) in study B), a significant difference only seen in multiple myeloma, with no significant difference in terms of mobilized myeloma cells between G-CSF and GM-CSF groups.

Placental Growth Factor-1 Potentiates Hematopoietic Progenitor Cell Mobilization Induced by Granulocyte Colony-Stimulating Factor in Mice and Nonhuman Primates

The complex hematopoietic effects of placental growth factor (PlGF) prompted us to test in mice and nonhuman primates the mobilization of peripheral blood progenitor cells (PBPCs) elicited by recombinant mouse PlGF-2 (rmPlGF-2) and recombinant human PlGF-1 (rhPlGF-1). PBPC mobilization was evaluated by assaying colony-forming cells (CFCs), high-proliferative potential-CFCs (HPP-CFCs), and long-term culture-initiating cells (LTC-ICs). In mice, both rmPlGF-2 and rhPlGF-1 used as single agents failed to mobilize PBPCs, whereas the combination of rhPlGF-1 and granulocyte colony-stimulating factor (rhG-CSF) increased CFCs and LTC-ICs per milliliter of blood by four- and eightfold, respectively, as compared with rhG-CSF alone. rhPlGF-1 plus rhG-CSF significantly increased matrix metalloproteinase-9 plasma levels over rhG-CSF alone, suggesting a mechanistic explanation for rhPlGF-1/rhG-CSF synergism. In rhesus monkeys, rhPlGF-1 alone had no mobilization effect, whereas rhPlGF-1 (260 microg/kg per day) plus rhG-CSF (100 microg/kg per day) increased rhG-CSF-elicited mobilization of CFCs, HPP-CFCs, and LTC-ICs per milliliter of blood by 5-, 7-, and 15-fold, respectively. No specific toxicity was associated with the administration of rhPlGF-1 alone or in combination. In conclusion, our data demonstrate that rhPlGF-1 significantly increases rhG-CSF-elicited hematopoietic mobilization and provide a preclinical rationale for evaluating rhPlGF-1 in the clinical setting.