High CD8+ lymphocyte dose in the autograft predicts early absolute lymphocyte count recovery after peripheral hematopoietic stem cell transplantation

Stem cell mobilization in multiple myeloma: challenges, strategies, and current developments

Among hematological malignancies, multiple myeloma (MM) represents the leading indication of autologous hematopoietic stem cell transplantation (auto-HCT). Auto-HCT is predominantly performed with peripheral blood stem cells (PBSCs), and the mobilization and collection of PBSCs are essential steps for auto-HCT. Despite the improved success of conventional methods with the incorporation of novel agents for PBSC mobilization in MM, mobilization failure is still a concern. The current review comprehensively summarizes various mobilization strategies for mobilizing PBSCs in MM patients and the evolution of these strategies over time. Moreover, existing evidence substantiates that the mobilization regimen used may be an important determinant of graft content. However, limited data are available on the effects of graft characteristics in patient outcomes other than hematopoietic engraftment. In this review, we discussed the effect of graft characteristics on clinical outcomes, mobilization failure, factors predictive of poor mobilization, and potential mobilization regimens for such patients.

Prediction of delayed platelet engraftment after autologous stem cell transplantation for B-cell non-Hodgkin lymphoma

Delayed platelet engraftment (DPE) is occasionally observed despite prompt neutrophil engraftment after autologous peripheral blood stem cell transplantation (auto-PBSCT). To identify risk factors for DPE and to develop a simple and clinically applicable system for predicting the time required for platelet recovery, we conducted a multi-institutional retrospective study in 144 patients with B-cell non-Hodgkin lymphoma who underwent auto-PBSCT. In a median observation period of 930 days (range: 25-5272 days), 139 patients successfully achieved platelet engraftment (≥50.0 × 10⁹/L). The median duration for platelet engraftment was 19 days, and 130 patients had platelet engraftment within 40 days after auto-PBSCT; however, the other 14 patients failed to achieve platelet engraftment within 60 days. These 14 patients with DPE required a significantly greater number of apheresis procedures and had a lower pre-apheresis absolute lymphocyte count (PA-ALC) compared to those without DPE. Importantly, multivariate analysis revealed that the number of transplanted CD34⁺ cells (≤2.0 × 10⁶/kg), number of required apheresis procedures (≥3 days), and PA-ALC (≤1.0 × 10⁹/L) were independently associated with a longer time for platelet engraftment after auto-PBSCT. By incorporating these three independent factors as variables, we generated a new scoring system for prediction of the time and probability for platelet engraftment after auto-PBSCT.

Importance of early immune recovery after autologous hematopoietic cell transplantation in lymphoma patients

Lymphomas constitute the second most common indication for autologous hematopoietic cell transplantation (AHCT). Graft infusion is followed by a rapid hematological recovery and slower immune recovery. The number of natural killer cells and CD3⁺ T lymphocytes achieve normal counts usually within a month, whereas the recovery of CD3⁺CD4⁺ T lymphocytes is much slower. Early immune recovery is usually defined as the absolute lymphocyte count (ALC) ≥0.5 × 10⁹/L, which has been associated with improved progression-free and even overall survival. Several factors have been associated with early immune recovery, including higher infused lymphocyte and CD34⁺ cell doses, both of which are affected by the choice of mobilization. This review summarizes the clinical importance of early immune recovery for long-term success of AHCT in lymphomas. Factors known to affect early immune recovery are discussed and suggestions made how to improve mobilization and collection processes to optimize immune recovery and post-transplant outcomes.

Blood graft cellular composition and posttransplant outcomes in myeloma patients mobilized with or without low-dose cyclophosphamide: a randomized comparison

BACKGROUND

Autologous stem cell transplantation is a standard treatment in multiple myeloma (MM). Blood grafts are usually collected after mobilization with granulocyte-colony-stimulating factor (G-CSF) alone or in a combination with cyclophosphamide (CY). There is limited knowledge of the possible effects of different mobilization regimens on blood graft characteristics and posttransplant outcomes.

STUDY DESIGN AND METHODS

Thirty-eight patients with MM were included in this study. The patients were randomly assigned at registration to mobilization with either low-dose CY plus G-CSF (Arm A) or G-CSF alone (Arm B) and received three cycles of lenalidomide, bortetzomib, and dexamethasone induction. Flow cytometry analysis of lymphocyte subsets in the blood grafts after cryopreservation was performed. Hematologic and immune recovery were evaluated up to 12 months posttransplant.

RESULTS

The blood grafts in Arm A contained significantly more CD34+ cells but in Arm B there was a greater proportion of CD34+CD38- cells and higher numbers of T and B lymphocytes as well as natural killer (NK) cells. The engraftment was comparable but lymphocyte count at 15 days posttransplant was higher in Arm B (0.8 × 10(9) /L vs. 0.5 × 10(9) /L, p = 0.033). At 3 and 6 months posttransplant the total number of NK cells was also higher in G-CSF-mobilized patients. There was no difference in progression-free survival between the study arms.

CONCLUSION

CY plus G-GSF yields more CD34+ cells but seems to diminish lymphocyte and NK cell counts in the grafts and hampers immune recovery after transplantation. Thus G-CSF alone might be a preferred mobilization method due to more rapid immune recovery posttransplant.

Mesenchymal stromal cells improve early lymphocyte recovery and T cell reconstitution after autologous hematopoietic stem cell transplantation in patients with malignant lymphomas

Mesenchymal stromal cells (MSCs) possess a multi-lineage potential and immunoregulatory activities and provide a great potential in cell-based technologies. However, MSC suppressive activity raises concerns regarding the possible adverse effect of MSCs on the immune recovery. The influence of autologous MSC co-transplantation on recovery of T cell subsets in patients receiving autologous hematopoietic stem cell transplantation (AHSCT) for malignant lymphomas and multiple myeloma were characterized. Co-transplantation of MSCs improved lymphocyte recovery most effectively in patients with low input of hematopoietic stem cells or low absolute lymphocyte count in apheresis product. MSC co-transplantation improved early recovery of both memory and naive T cells with more prominent effect on naive CD4(+) T cells. Patients with MSC co-transplantation showed more effective reconstitution of recent thymic emigrants. These data indicate the positive impact of MSCs on immune reconstitution and note MSC co-transplantation is feasible to optimize the outcomes of AHSCT in malignant lymphoma patients.

Mobilized peripheral blood grafts include more than hematopoietic stem cells: the immunological perspective

Although stem cell mobilization has been performed for more than 20 years, little is known about the effects of mobilizing agents on apheresis composition and the impact of graft cell subsets on patients' outcome. With the increasing use of plerixafor and the inclusion of poor mobilizers in autologous transplant procedures, new parameters other than CD34(+) stem cell dose are emerging; plerixafor seems to mobilize more primitive CD34(+)/CD38(-) stem cells compared with G-CSF, but their correlation with stable hematopoietic engraftment is still obscure. Immune recovery is as crucial as hematopoietic reconstitution, and higher T and natural killer cells infused within the graft have been correlated with better outcome in autologous transplant; recent studies showed increased mobilization of immune effectors with plerixafor compared with G-CSF, but further data are needed to clarify the clinical impact of these findings. In the allogeneic setting, much evidence suggests that mobilized T-cell alloreactivity is tempered by G-CSF, probably with the mediation of dendritic cells, even though no clear correlation with GVL and GVHD has been found. Plerixafor is not approved in healthy donors yet; early data suggest it might mobilize a GVHD protective balance of immune effectors, but further studies are needed to define its role in allogeneic transplant.

Changes in the number of CD8⁺ T lymphocytes in the peripheral blood of patients with various autoimmune diseases after autologous hematopoietic stem cell transplantations and their relations to the survival times

The changes in the number of CD8⁺ T lymphocytes were studied before (0 day) and then 30 days after the autologous hematopoietic stem cell transplantations (AHSCT) in 14 therapy refractory patients with autoimmune diseases. The years of survival and the clinical states were also evaluated. The number of CD8⁺ T cells was determined by an hematologic automat and by flow cytometry. Longer than 5-year survival times were found in 6 cases, whereas there was no progression (improvement) in 2 cases, and 4 patients were lost. The increase in the number of CD8⁺ cytotoxic T cells was gradual in the first 2 months and reached the significantly highest values among all subtypes of lymphocytes. It was of a special interest that in all the 4 patients who died, the numbers of CD8⁺ T cells were less than 150/μl on the 30th day after AHSCT, whereas all the 10 patients with a higher cell number survived. These results suggest that the early monitoring of the number (not only the ratio) of regenerating CD8⁺ T cells in the peripheral blood can be a useful and quantitative laboratory measurement after AHSCT, and it has a significant relation also to the survival times of transplanted patients.

CD34+ cell subclasses and lymphocyte subsets in blood grafts collected after various mobilization methods in myeloma patients

BACKGROUND

Cyclophosphamide (CY) combined with granulocyte-colony-stimulating factor (G-CSF) is commonly used to mobilize stem cells in multiple myeloma (MM). Plerixafor may also be used with G-CSF in patients who mobilize poorly or it may be added to chemomobilization to boost mobilization. Limited data are available on graft content collected after various mobilization methods.

STUDY DESIGN AND METHODS

Blood grafts collected from 21 MM patients were retrospectively analyzed. We analyzed CD34+ subclasses and lymphocyte subsets from cryopreserved grafts collected on the next morning after plerixafor injection in nine MM patients mobilized with G-CSF with (n = 5) or without preceding CY (n = 4). As controls we had the first collections from 12 MM patients mobilized with low-dose CY with G-CSF.

RESULTS

The proportion of the most primitive stem cells (CD34+CD133+CD38-) from all CD34+ cells in the graft was higher in the plerixafor-treated patients but there was no significant difference in the total number of these cells. The numbers of CD19+ B lymphocytes and natural killer cells were higher in patients collected after G-CSF plus plerixafor when compared to the patients mobilized with CY plus G-CSF. Early engraftment after high-dose melphalan was comparable between the groups.

CONCLUSION

Plerixafor appears to have effects on blood stem cell graft composition in myeloma patients. A higher number of grafts should be evaluated in regard to cellular content and longer follow-up of the patients is needed to evaluate the potential clinical impact of graft content.

Blood graft composition after plerixafor injection in patients with NHL

BACKGROUND

Plerixafor is used to mobilize CD34(+) hematopoietic stem cells from bone marrow to circulation. Limited data are available in regard to graft cellular content collected after plerixafor.

OBJECTIVES

The aim of this study was to assess effects of plerixafor added to chemomobilization on graft CD34(+) cell subclasses, lymphocyte subsets, engraftment, and post-transplant course in non-Hodgkin lymphoma (NHL) patients.

METHODS

Thirty-four patients with NHL were included. All patients received chemotherapy plus G-CSF to mobilize stem cells. Nineteen patients received plerixafor pre-emptively owing to poor mobilization or poor collection yields. The rest of the patients constituted the control group. Flow cytometric analyzes were performed from cryopreserved graft samples. Also, data on post-transplant engraftment and outcome were collected.

RESULTS

The proportion of primitive stem cells (CD34(+)  CD133(+)  CD38(-) ) was significantly higher after the plerixafor injection when compared to the first collection in the control group. The amount of T cells (CD3(+) ), helper (CD3(+)  CD4(+) ) T subsets, and suppressor (CD3(+)  CD8(+) ) T subsets in the graft was all significantly higher in the plerixafor group. Also, the amount of NK cells (CD3(-)  CD16/56(+) ) was higher. Engraftment after high-dose therapy was comparable between the groups, but leukocyte and platelet count at 6 months were higher in patients receiving plerixafor-mobilized grafts.

CONCLUSION

Plerixafor, when used pre-emptively in addition to chemomobilization, seems to mobilize more primitive CD34(+) stem cells, T lymphocytes, and NK cells. Whether these differences are associated with immune reconstitution, long-term engraftment, or patient outcomes needs to be evaluated in larger patient groups with longer follow-up.

Mobilisation strategies for normal and malignant cells

This review evaluates the latest information on the mobilisation of haemopoietic stem cells for transplantation, with the focus on what is the current best practice and how new understanding of the bone marrow stem cell niche provides new insights into optimising mobilisation regimens. The review then looks at the mobilisation of mesenchymal stromal cells, immune cells as well as malignant cells and what clinical implications there are.

Increased mobilization and yield of stem cells using plerixafor in combination with granulocyte-colony stimulating factor for the treatment of non-Hodgkin's lymphoma and multiple myeloma

Multiple myeloma and non-Hodgkin’s lymphoma remain the most common indications for high-dose chemotherapy and autologous peripheral blood stem cell rescue. While a CD34+ cell dose of 1 × 10⁶/kg is considered the minimum required for engraftment, higher CD34+ doses correlate with improved outcome. Numerous studies, however, support targeting a minimum CD34+ cell dose of 2.0 × 10⁶/kg, and an “optimal” dose of 4 to 6 × 10⁶/kg for a single transplant. Unfortunately, up to 40% of patients fail to mobilize an optimal CD34+ cell dose using myeloid growth factors alone. Plerixafor is a novel reversible inhibitor of CXCR4 that significantly increases the mobilization and collection of higher numbers of hematopoietic progenitor cells. Two randomized multi-center clinical trials in patients with non-Hodgkin’s lymphoma and multiple myeloma have demonstrated that the addition of plerixafor to granulocyte-colony stimulating factor increases the mobilization and yield of CD34+ cells in fewer apheresis days, which results in durable engraftment. This review summarizes the pharmacology and evidence for the clinical efficacy of plerixafor in mobilizing hematopoietic stem and progenitor cells, and discusses potential ways to utilize plerixafor in a cost-effective manner in patients with these diseases.

Mobilization strategies in hard-to-mobilize patients with lymphoid malignancies

Depending on definitions and patient characteristics, 5-40% of patients with lymphoid malignancies are hard-to-mobilize. Several premobilization factors such as previous chemotherapy (CT), disease, marrow infiltration and platelet count at the time of mobilization influence the efficacy of CD34(+) cell mobilization. In general, however, prediction of hard-to-mobilize patient is difficult. Postmobilization factors especially low blood CD34(+) counts are important in clinical practice as we have now ways to enhance mobilization at this point. Plerixafor combined with granulocyte-colony stimulating factor (G-CSF) has significantly increased efficacy of remobilization in patients who have failed a previous mobilization attempt with a success rate of about 70%. Addition of plerixafor to G-CSF or more recently to a mobilization regimen consisting of CT + G-CSF is promising as blood CD34(+) counts can be increased three to fivefold to facilitate effective collection with less aphaeresis sessions. As plerixafor is expensive, development of practical algorithms for its use is important to make blood stem cell mobilization and collection more efficient in a cost-effective way. This review attempts to summarize current treatment strategies in hard-to-mobilize patients with lymphoid malignancies.

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.

Autograft mediated adoptive immunotherapy of cancer in the context of autologous stem cell transplantation

The infused stem cell autograft in autologous stem cell transplantation (ASCT) has been viewed mainly as hematologic rescue from the myelosuppressive side effect of conditioning regimens. However, recent reports have shown that the immune effector cells collected at the same time as the stem cells can produce an autologous graft-versus-tumor effect, similar to the graft-versus-tumor effect seen in allogeneic stem cell transplantation without the detrimental effects of graft-versus-host disease. In this article, we review the different immune effector cells collected and infused from the stem cell autograft and their association with clinical outcome post-ASCT, suggesting that ASCT can be viewed not only as a therapeutic maneuver to recover bone marrow function after deliver high-dose chemotherapy, but also as an adoptive immunotherapeutic intervention capable of eradicating residual tumor cells in patients with cancer.