CD34?+ cell dose and outcome of patients undergoing reduced-intensity-conditioning allogeneic peripheral blood stem cell transplantation

CD34+ cell yield among healthy donors: Large-scale model development and validation

BACKGROUND

Successful engraftment in hematopoietic stem cell transplantation necessitates the collection of an adequate dose of CD34+ cells. Thus, the precise estimation of CD34+ cells harvested via apheresis is critical. Current CD34+ cell yield prediction models have limited reproducibility. This study aims to develop a more reliable and universally applicable model by utilizing a large dataset, enhancing yield predictions, optimizing the collection process, and improving clinical outcomes.

MATERIALS AND METHODS

A secondary analysis was conducted using the Center for International Blood and Marrow Transplant Research database, involving data from over 17 000 healthy donors who underwent filgrastim-mobilized hematopoietic progenitor cell apheresis. Linear regression, gradient boosting regressor, and logistic regression classification models were employed to predict CD34+ cell yield.

RESULTS

Key predictors identified include pre-apheresis CD34+ cell count, weight, age, sex, and blood volume processed. The linear regression model achieved a coefficient of determination (R2) value of 0.66 and a correlation coefficient (r) of 0.81. The gradient boosting regressor model demonstrated marginally improved results with an R2 value of 0.67 and an r value of 0.82. The logistic regression classification model achieved a predictive accuracy of 96% at the 200 × 106 CD34+ cell count threshold. At thresholds of 400, 600, 800, and 1000 × 106 CD34+ cell count, the accuracies were 88%, 83%, 83%, and 88%, respectively. The model demonstrated a high area under the receiver operator curve scores ranging from 0.90 to 0.93.

CONCLUSION

This study introduces advanced predictive models for estimating CD34+ cell yield, with the logistic regression classification model demonstrating remarkable accuracy and practical utility.

Magnetically empowered bone marrow cells as a micro-living motor can improve early hematopoietic reconstitution

BACKGROUND AIMS

Bone marrow-derived hematopoietic stem cell transplantation/hematopoietic progenitor cell transplantation (HSCT/HPCT) is widely used and one of the most useful treatments in clinical practice. However, the homing rate of hematopoietic stem cells/hematopoietic progenitor cells (HSCs/HPCs) by routine cell transfusion is quite low, influencing hematopoietic reconstitution after HSCT/HPCT.

METHODS

The authors developed a micro-living motor (MLM) strategy to increase the number of magnetically empowered bone marrow cells (ME-BMCs) homing to the bone marrow of recipient mice.

RESULTS

In the in vitro study, migration and retention of ME-BMCs were greatly improved in comparison with non-magnetized bone marrow cells, and the biological characteristics of ME-BMCs were well maintained. Differentially expressed gene analysis indicated that ME-BMCs might function through gene regulation. In the in vivo study, faster hematopoietic reconstitution was observed in ME-BMC mice, which demonstrated a better survival rate and milder symptoms of acute graft-versus-host disease after transplantation of allogeneic ME-BMCs.

CONCLUSIONS

This study demonstrated that ME-BMCs serving as MLMs facilitated the homing of HSCs/HPCs and eventually contributed to earlier hematopoietic reconstitution in recipients. These data might provide useful information for other kinds of cell therapies.

Allogeneic stem cell transplantation in the treatment of acute myeloid leukemia: An overview of obstacles and opportunities

As an important treatment for acute myeloid leukemia, allogeneic hematopoietic stem cell transplantation (allo-HSCT) plays an important role in reducing relapse and improving long-term survival. With rapid advancements in basic research in molecular biology and immunology and with deepening understanding of the biological characteristics of hematopoietic stem cells, allo-HSCT has been widely applied in clinical practice. During allo-HSCT, preconditioning, the donor, and the source of stem cells can be tailored to the patient’s conditions, greatly broadening the indications for HSCT, with clear survival benefits. However, the risks associated with allo-HSCT remain high, i.e. hematopoietic reconstitution failure, delayed immune reconstitution, graft-versus-host disease, and post-transplant relapse, which are bottlenecks for further improvements in allo-HSCT efficacy and have become hot topics in the field of HSCT. Other bottlenecks recognized in the current treatment of individuals diagnosed with acute myeloid leukemia and subjected to allo-HSCT include the selection of the most appropriate conditioning regimen and post-transplantation management. In this paper, we reviewed the progress of relevant research regarding these aspects.

Emerging strategies for enhancing the homing of hematopoietic stem cells to the bone marrow after transplantation

Bone marrow failure is the primary cause of death after nuclear accidents or intentional exposure to high or low doses of ionizing radiation. Hematopoietic stem cell transplantation is the most potent treatment procedure for patients suffering from several hematopoietic malignancies arising after radiation injuries. Successful hematopoietic recovery after transplantation depends on efficient homing and subsequent engraftment of hematopoietic stem cells in specific niches within the bone marrow. It is a rapid and coordinated process in which circulating cells actively enter the bone marrow through the process known as transvascular migration, which involves the tightly regulated relay of events that finally leads to homing of cells in the bone marrow. Various adhesion molecules, chemokines, glycoproteins, integrins, present both on the surface of stem cells and sinusoidal endothelium plays a critical role in transvascular migration. But despite having an in-depth knowledge of homing and engraftment and the key events that regulate it, we are still not completely able to avoid graft failures and post-transplant mortalities. This deems it necessary to design a flawless plan for successful transplantation. Here, in this review, we will discuss the current clinical methods used to overcome graft failures and their flaws. We will also discuss, what are the new approaches developed in the past 10-12 years to selectively deliver the hematopoietic stem cells in the bone marrow by adopting proper targeting strategies that can help revolutionize the field of regenerative and translational medicine.

Impact of a Low CD34+ Cell Dose on Allogeneic Peripheral Blood Stem Cell Transplantation

Although the CD34⁺ cell dose in allogeneic peripheral blood stem cell transplantation (PBSCT) is considered to be associated with transplantation outcomes, a lower acceptable threshold has not been defined. We retrospectively analyzed 2919 adult patients with hematologic malignancies who underwent related PBSCT in Japan between 2001 and 2014. According to the number of CD34⁺ cells in the graft, we categorized 2494 patients in the standard group (2 to 5 × 10⁶ cells/kg), 377 patient in the low group (1 to 2 × 10⁶ cells/kg), and 48 patients in the very low group (<1 × 10⁶ cells/kg). Compared with the standard group, the low and very low groups showed delayed neutrophil recovery (93.8%, 89.5%, and 78.3%, respectively at day +28; P < .001) and platelet recovery (69.3%, 53.0%, and 45.5%, respectively at day +28; P < .001). The 2-year overall survival (OS) in the 3 groups was 45.5%, 45.3%, and 29.8%, respectively, with inferior survival in the very low group. However, a higher percentage of high-risk patients may account for the inferior survival in the very low group, and no significant difference in OS was found in a multivariate analysis. There were no differences in relapse, nonrelapse mortality, or the development of graft-versus-host disease among the 3 groups. In conclusion, allogeneic PBSCT with low CD34⁺ cell doses of 1 to 2 × 10⁶ cells/kg gives acceptable results, whereas further investigations are needed to evaluate the effects of lower doses of <1 × 10⁶ cells/kg owing to the smaller number and the higher percentage of patients with adverse prognostic factors in this cohort.

Transplantation Dose Alters the Differentiation Program of Hematopoietic Stem Cells

Hematopoietic stem cell (HSC) transplantation is the most prevalent stem cell therapy, but it remains a risky procedure. To improve this treatment, it is important to understand how transplanted stem cells rebuild the blood and immune systems and how this process is impacted by transplantation variables such as the HSC dose. Here, we find that, in the long term following transplantation, 70%-80% of donor-HSC-derived clones do not produce all measured blood cell types. High HSC doses lead to more clones that exhibit balanced lymphocyte production, whereas low doses produce more T-cell-specialized clones. High HSC doses also produce significantly higher proportions of early-differentiating clones compared to low doses. These complex differentiation behaviors uncover the clonal-level regeneration dynamics of hematopoietic regeneration and suggest that transplantation dose can be exploited to improve stem cell therapy.

Dendritic cell reconstitution is associated with relapse-free survival and acute GVHD severity in children after allogeneic stem cell transplantation

DCs are potent APCs and key regulators of innate and adaptive immunity. After allo-SCT, their reconstitution in the peripheral blood (PB) to levels similar to those in healthy individuals tends to be slow. We investigate the age- and sex-dependant immune reconstitution of myeloid (mDC) and plasmacytoid DC (pDC) in the PB of 45 children with leukaemia or myelodysplastic syndrome (aged 1-17 years, median 10) after allo-SCT with regard to relapse, acute GVHD (aGVHD) and relapse-free survival. Low pDC/μL PB up to day 60 post SCT are associated with higher incidence of moderate or severe aGVHD (P=0.035), whereas high pDC/μL PB up to day 60 are associated with higher risk of relapse (P<0.001). The time-trend of DCs/μL PB for days 0-200 is a significant predictor of relapse-free survival for both mDCs (P<0.001) and pDCs (P=0.020). Jointly modelling DC reconstitution and complications improves on these simple criteria. Compared with BM, PBSC transplants tend to show slower mDC/pDC reconstitution (P=0.001, 0.031, respectively), but have no direct effect on relapse-free survival. These results suggest an important role for both mDCs and pDCs in the reconstituting immune system. The inclusion of mDCs and pDCs may improve existing models for complication prediction following allo-SCT.

Strategies in haploidentical stem cell transplantation in adults

Haploidentical related donors are alternative stem cell sources for patients without human leukocyte antigen (HLA)-matched related or unrelated donors. Immediate access to the donor, availability for patients with rare haplotypes, ease of stem cell procurement, and lack of a requirement for a physical cord blood bank or an extensive HLA database render this type of hematopoietic stem cell transplantation particularly attractive despite the high histoincompatibility barrier between the recipient and the haploidentical graft. In this review, we answer the following questions: 1) What are the current transplant strategies used to overcome the histoincompatibility barrier in haploidentical stem cell transplantation and their clinical results? 2) How should we choose the donor when there is more than one available haploidentical donor? 3) How does transplantation from haploidentical donors compare to that from umbilical cord blood?

Conflict of interest:None declared.

Higher doses of CD34+ progenitors are associated with improved overall survival without increasing GVHD in reduced intensity conditioning allogeneic transplant recipients with clinically advanced disease

OBJECTIVE

The influence of CD34+ cell dose on the outcome of allogeneic peripheral blood stem cell (PBSC) transplantation after reduced intensity conditioning (RIC) remains controversial. The impact of the number of CD34+ hematoprogenitors infused on transplant outcome and on the incidence of graft versus host disease (GVHD) was analyzed.

MATERIALS AND METHODS

Data of 138 patients with advanced hematological diseases who received an allogeneic PBSC transplant after RIC were analyzed. Donors were mobilized with granulocyte colony-stimulating factor and underwent one to three apheresis procedures. Incidence of acute and chronic GVHD and overall and event-free survival (OS and EFS) was determined.

RESULTS

The median number of CD34+ cells infused was 5.57 × 10(6) kg(-1) (range: 1.1-15.6). There was no relationship between CD34+ cell dose and neutrophil or platelet engraftment. Patients receiving ≥5 × 10(6) kg(-1) CD34+ cells had a 63.1% 5-year OS when compared with 48.2% for those receiving a lower number (P = 0.024). At 5-year follow-up, there was no significant difference in EFS between the groups (44% vs. 42.8%, P = 0.426). No relationship between CD34+ cell dose and acute GVHD was found (P = 0.1). Relapse rate was the same in patients with and without acute GVHD (P = 0.117). A nonsignificant improvement on OS and EFS in patients who developed chronic GVHD was found (P = 0.57 and 0.41).

CONCLUSION

A CD34+ cell dose ≥5 × 10(6) kg(-1) was associated with a significantly higher OS, but no improved EFS in high-risk patients. The number of CD34+ progenitors infused had no influence on the incidence of acute or chronic GVHD.

Mobilized peripheral blood stem cells compared with bone marrow from HLA-identical siblings for reduced-intensity conditioning transplantation in acute myeloid leukemia in complete remission: a retrospective analysis from the Acute Leukemia Working Party of EBMT

Reduced-intensity conditioning (RIC)-alloSCT is increasingly used for acute myelogenous leukemia. Limited data are available for the comparison of peripheral blood stem cells with bone marrow for RIC-alloSCT. We used the European Group for Blood and Marrow Transplantation (EBMT) ALWP data to compare the outcome of mobilized peripheral blood stem cells (PBSC) (n = 1430) vs. bone marrow (BM) (n = 107) for acute myelogenous leukemia (AML) patients with complete remission that underwent RIC-alloSCT from compatible sibling donors. The leukemia features, the disease status, and the time from diagnosis were similar between the two groups. Engraftment was achieved in 99% and 93% in the PBSC and BM groups, respectively (P < 0.0001). The day of engraftment was significantly earlier for the PBSC vs. the BM group, 15 (1-59) and 19 (5-69), respectively (P < 0.001). Acute GVHD, severe GVHD (grade III-IV) and chronic GVHD did not differ between the groups. leukemia-free survival (LFS), relapse, and non-relapsed mortality (NRM) were 51 ± 2%, 32 ± 1%, and 17 ± 1% vs. 50 ± 6%, 38 ± 6%, and 12 ± 3% for the PBSC and BM groups, respectively. Our results indicate faster engraftment, but no difference in GVHD, LFS, relapse, and NRM when comparing PBSC to BM grafts from sibling donors following RIC conditioning. This is the first study comparing PBSC to BM grafts in the RIC setting, analyzing a homogeneous population of patients with AML in remission. Whether PBSC should be preferred for advanced phases of the disease, where the outcome is dominated by relapse incidences, needs further investigation.

Mobilized peripheral blood stem cells compared with bone marrow as the stem cell source for unrelated donor allogeneic transplantation with reduced-intensity conditioning in patients with acute myeloid leukemia in complete remission: an analysis from the Acute Leukemia Working Party of the European Group for Blood and Marrow Transplantation

Reduced-intensity conditioning allogeneic stem cell transplant (RIC-alloSCT) is being increasingly used for patients with acute myelogenous leukemia (AML) with comorbidities. Few published data are currently available regarding for the use of peripheral blood stem cells (PBSCs) compared to bone marrow (BM) in the RIC-alloSCT using unrelated donors (URDs). This retrospective report compared the outcomes of PBSC versus BM RIC-alloSCT. Between 2000 and 2007, 602 patients with AML in complete remission (CR) underwent RIC-alloSCT from URDs with PBSC (508) or BM (94) grafts. Recipient's age was higher in the PBSC versus BM groups 57 (range, 17-77 years) and 51 (range, 17-76 years), respectively (P < .0001). Leukemia features and disease status at RIC-alloSCT were also comparable between the PBSC versus BM groups. Engraftment was achieved in 97% and 96% with BM versus peripheral blood (PB), respectively. Acute graft-versus-host disease (aGVHD) grade >II was significantly higher in the PBSC group: 27% versus 12% in the BM group (P < .002). Similarly, chronic graft-versus-host disease (cGVHD; at 2 years) was somewhat higher in the PBSC group with 43% ± 3% versus 35% ± 6% in the BM group, respectively (P = .04). The 2-year probabilities of leukemia-free survival (LFS) were 46% ± 3% for the PBSC group in comparison to 43% ± 6% for the BM transplant group (P = NS), whereas relapse incidence was significantly higher in the BM versus the PB transplant group: 46% ± 6% versus 32% ± 3%, respectively (P = .014). Non-relapse mortality (NRM) was significantly higher for the PBSC versus the BM group: 28% ± 2% versus 13% ± 4%, respectively (P = .004). In multivariate analysis, after adjustment for differences between both groups, the PBSC group was associated with a higher incidence of aGVHD (grade II-IV; hazard ratio [HR] = 2.33; P = .06), higher NRM (HR = 2.3; P = .015), and a decreased relapse incidence (HR, 0.61; P = .02) with no statistical difference of LFS between the 2 groups (P = .88). In conclusion, our results indicate significantly higher incidence of aGVHD and NRM and a lower incidence of relapse but not statistically different LFS comparing unrelated PBSC to BM grafts after RIC-alloSCT.

Effect of splenectomy on pancytopenia after a peripheral blood stem cell transplantation

To analyze the effect of a splenectomy on pancytopenia after a peripheral blood stem cell transplantation (PBSCT) in chronic myeloid leukemia (CML) patients. Three CML patients diagnosed with splenomegaly in our department from 2002 to 2006 received a splenectomy after PBSCT. Patient 1, a 42-year-old male in chronic phase (CP), received an HLA-identical sibling allo-PBSCT. Patient 2, a 28-year-old female in aggressive phase (AP), received a PBSCT from her twin. Patient 3, a 26-year-old male in chronic phase (CP), received a PBSCT from an unrelated donor. The conditioning regimen included busulfan and cyclophosphamide (BU/CY2). Patients 1, 2, and 3 received splenectomies on days 168, 51, and 114, respectively. Bcr-abl transcripts were detected using the polymerase chain reaction (PCR). Chimerism was documented by PCR amplification of a variable number of tandem repeat (VNTR) polymorphrisms. Neither metrisone (2 mg/kg/day for 7 days), mycophenolic acid (MMF) (0.5 g twice daily for 1 month), high-dose γ-globulin (0.4 g/kg/day for 5 days), granulocyte colony-stimulating factor (G-CSF) therapy, nor erythropoietin (EPO) therapy had produced post-PBSCT hematopoiesis recovery. Patients 1 and 2 had 5% Ph-positive chromosomes while patient 3 exhibited graft-versus-host disease (GVHD). After receiving the splenectomy, all three had a rapid hematopoeitic recovery with no evidence of Ph-positive chromosomes, and patients 1 and 3 showed complete donor chimerism (CDC). Patient 1 developed chronic GVHD (cGVHD) on day 210 postsplenectomy that was treated successfully with prednisone. Patient 2 had acute GVHD on day 55 that was treated successfully with dexamethasone (10 mg), administered intravenously once a day for 3 days with good clinical response. To date, patients 1, 2, and 3 have survived postprocedure for 85, 49, and 25 months, respectively. Splenectomy is an effective option for the patients who have pancytopenia after PBSCT and the patients recovered a good graft function after splenectomy without procedure-related complication and with long-time survival. GVHD can develop in both allo-PBSCT and syngeneic PBSCT. A splenectomy after PBSCT may increase the risk of GVHD, enhance the effect of graft versus leukemia (GVL), promote CDC formation.

Association of IL6 and CCL2 gene polymorphisms with the outcome of allogeneic haematopoietic stem cell transplantation

Various polymorphisms of non-HLA genes have recently been investigated as candidate risk factors in allogeneic haematopoietic SCT (aHSCT). Our study aimed at exploring possible associations of IL6 and CCL2 single nucleotide polymorphisms (SNP) with aHSCT outcome. A total of 166 HLA-identical aHSCT pairs recruited in were genotyped for IL6 -174 G/C, IL6 -597 G/A, CCL2 -2518 A/G and CCL2 -2076 A/T SNPs by PCR with sequence-specific primers (PCR-SSP). The association between IL6 -174 GG genotype and increased risk of acute GVHD was found in whole study group (P=0.03) and in the subgroup of related aHSCT (P=0.01), association between IL6 -597 GG genotype and the occurrence of acute GVHD was detected only in the related aHSCT pairs (P=0.02). Furthermore, reduction in OS was revealed among recipients possessing IL6 -174(*)G allele in the group of related aHSCT pairs (P=0.04). Presence of CCL2 -2076 TT genotype was associated with decrease of OS (P=0.04) and increase of TRM (P=0.02) in patients transplanted by related donor. These results, in the context of previous findings, suggest that IL6 gene polymorphisms may be associated with aHSCT outcome, particularly in patients transplanted from a related donor.

Impact of natural killer cell dose and donor killer-cell immunoglobulin-like receptor (KIR) genotype on outcome following human leucocyte antigen-identical haematopoietic stem cell transplantation

To define the role of quantitative graft composition and donor killer-cell immunoglobulin-like receptor (KIR) genotype in clinical outcome following unmanipulated peripheral blood stem cell transplantation (PBSCT) from human leucocyte antigen (HLA)-identical siblings, 43 consecutive transplants for haematological malignancies were analysed retrospectively. Twenty-four patients underwent myeloablative conditioning and 19 received busulphan/fludarabine-based reduced intensity conditioning (RIC). In patients with acute myelogenous leukaemia or myelodysplastic syndrome (AML/MDS; n = 18), no relapse occurred following transplants meeting both a high (above median) natural killer (NK) cell count and missing HLA-ligand(s) to donor's KIR(s), compared to all other AML/MDS patients (0% versus 44%; P = 0.049). Missing HLA-B and/or HLA-C ligand combined with missing HLA-A3/11 (KIR3DL2 unblocked) predicted for reduced relapse incidence regardless of diagnosis or conditioning type (P = 0.028). Moreover, in AML/MDS patients, this constellation predicted superior overall survival (OS) (P = 0.046). Transplants with more than two different activating donor KIRs were associated with an increased risk for non-relapse mortality (NRM), both by univariate and multivariate analysis. Quantitative graft composition had a significant impact exclusively in RIC transplants. Here, a trend towards reduced relapse incidence was found in patients receiving high numbers of NK cells (16% versus 54%; P = 0.09). In patients receiving high versus low T cell numbers, OS was superior (83% versus 37%; P = 0.01), due mainly to reduced NRM (0% versus 33%; P = 0.046). By multivariate analysis, relapse risk was decreased significantly in patients receiving high NK cell numbers (P = 0.039). These data suggest that both the number of transplanted NK cells and the donor KIR genotype play a role in graft-versus-malignancy mechanisms in HLA-identical PBSCT.

Improving outcome of allogeneic stem cell transplantation by immunomodulation of the early post-transplant environment

There has been great progress in understanding the alloresponse and the process of immune recovery after stem cell transplantation. Here, we highlight ways in which transplant outcome is determined by unique immunological features of the early post-transplant period that modulate the growth and function of the grafted donor T cells and stem cells. Better understanding of these early events and more detailed knowledge of the phenotype and function of transplanted donor cells facilitate strategies to optimize immune recovery, prevent graft-versus-host disease (GVHD) and boost immunity to viruses and leukemia. Approaches that optimize CD34 cell dose, techniques to remove GVHD-reacting T cells by T cell subset selection, suicide gene insertion or selective allodepletion, and the adoptive transfer of antigen-specific T cells have reached the stage of clinical trials. Furthermore, murine transplant experiments indicate ways to prevent GVHD while preserving immune function by depletion of naïve cells, T cytotoxic 1 and T helper 1 cells, or by enrichment of regulatory T cells. Many of these approaches appear feasible in clinical transplantation and have yielded promising initial results, but proof that the goal of controlled selective immune reconstitution can be achieved is still awaited.

Evidence that donor intrinsic response to G-CSF is the best predictor of acute graft-vs-host disease following allogeneic peripheral blood stem cell transplantation

OBJECTIVE

Risk factors of acute graft-vs-host disease (GVHD) following allogeneic bone marrow transplantation have been well described before. In this study, we tested the hypothesis that acute GVHD after allogeneic peripheral blood stem cell (PBSC) transplant might be associated with donors' responsiveness to granulocyte colony-stimulating factor (G-CSF), rather than the dose of CD34(+) cells infused.

PATIENTS AND METHODS

We retrospectively analyzed mobilization and transplant data (demographic characteristics, donor blood cell subsets after G-CSF, graft composition) in 149 consecutive HLA-identical donor/recipient pairs in order to identify acute GVHD risk factors.

RESULTS

In 25% of donors, G-CSF mobilization led to an outstanding response, defined as greater than 117 x 10(6) CD34(+) cells/L. Overall, incidence of grades II-IV acute GVHD was 20.1% (95% CI: 16.6-23.6). Following univariate analysis, the incidence increased significantly in recipients receiving greater than 10 x 10(6) CD34(+) cells/kg (35% vs 15%; p = 0.007), and those transplanted from outstanding mobilizers (41% vs 12%, p < 0.0001). In multivariate analysis, only transplantation from outstanding mobilizers remained significant (p = 0.02). Donor or recipient demographic characteristics and lymphocyte subsets reinfused in the graft had no impact.

CONCLUSIONS

We demonstrate for the first time that donor responsiveness to G-CSF is associated with acute GVHD following PBSC transplantation. If confirmed, this correlation will help to identify recipients who could potentially benefit from improved prophylaxis. As further corollary, decreasing the dose of CD34(+) cells infused is unlikely to prevent acute GVHD. Future studies should focus on the molecular bases of interindividual discrepancies in response to G-CSF.