Subsets of CD34+ and early engraftment kinetics in allogeneic peripheral SCT for AML

Uncovering the expression of circPVT1 in the extracellular vesicles of acute myeloid leukemia patients

Extracellular vesicles (EVs) act as molecular mediators in the tumor microenvironment, by shuttling information contained within malignant cells and functioning as regulators of the immune system. Circular (circ)RNAs are characterized by a closed loop-like structure that makes them more stable in the extracellular milieu and suitable to be packaged inside EVs. circPVT1 (hsa_circ_0001821) showed an oncogenic role in several cancer types and immunosuppressive properties in myeloid and lymphoid cell subsets. In this study, we characterized EVs from acute myeloid leukemia (AML) patients in terms of size, concentrations, surface markers and circPVT1 cargo. We showed that circPVT1 is overexpressed by primary blast cells from newly-diagnosed AML patients compared with hematopoietic stem-progenitor cells and is released as cell-free RNA in the plasma. We isolated EVs from the plasma of AML patients and healthy subjects by size exclusion chromatography and characterized them by nanoparticle tracking analysis. EVs from patients' plasma are larger compared with those from healthy subjects and their surface profile is characterized by higher levels of the leukemic cell markers CD133, CD105, CD49e and other immune-related epitopes, with differences according to AML molecular profile. Moreover, digital PCR analysis revealed that circPVT1 is more abundant inside EVs from the plasma of AML patients compared with healthy subjects. Our findings provide new insights on the features and content of AML EVs and suggest a role of circPVT1 in the crosstalk between AML cells and the tumor microenvironment.

Predictive factors for rapid neutrophil and platelet engraftment after allogenic peripheral blood stem cell transplantation in patients with acute leukemia

The aim of this study was to investigate predictive factors for rapid engraftment after allogeneic peripheral blood stem cell transplantation (alloPBSCT) in patients with acute leukemia. Two hundred sixty-two patients receiving alloPBSCT were analyzed. Subset analyses of donor stem cells were conducted using a flow cytometric method. The correlation between rapid engraftment of neutrophils, platelets, and donor stem cells doses, as well as other recipient and donor clinical factors, was analyzed. In univariate analysis, factors correlated with neutrophil engraftment (≥0.5 × 10(9)/L) by day 12 were achievement of complete remission (CR) after induction chemotherapy (CR1) before hematopoietic cell transplantation (HCT) and high numbers of CD34+ cells, CD3+ T cells, and CD3+/CD4+ T cells. Factors correlated with platelet engraftment (≥20 × 10(9)/L) by day 12 were achievement of CR1 before HCT, donor and recipient sex mismatch, and high numbers of mononuclear cells, CD34+ cells, CD3+ T cells, CD3+/CD4+ T cells, CD3+/CD8+ T cells, and CD56+ NK cells. In multivariate analysis, independent predictive factors for rapid neutrophil and platelet engraftment were CR1 before HCT (p < 0.001 and p = 0.002, respectively), high number of donor CD34+ cells (p = 0.005 and p < 0.001, respectively), and high number of CD3+ T cells (p = 0.005 and p = 0.001, respectively). In conclusion, achieving CR1 before HCT, as well as larger quantities of donor CD34+ and CD3+ T cells, may predict rapid neutrophil and platelet engraftment after PBSCT.

Prospective cohort study of the circadian rhythm pattern in allogeneic sibling donors undergoing standard granulocyte colony-stimulating factor mobilization

Introduction

Prior in vivo murine studies suggest circadian oscillations for hematopoietic stem cell release, which are maintained following administration of granulocyte colony-stimulating factor (G-CSF) or plerixafor. Furthermore, retrospective data analysis of healthy donors who underwent G-CSF-induced mobilization demonstrated significantly increased CD34⁺ cell yields when collected in the afternoon compared with the morning.

Methods

A prospective study was conducted to directly examine the number of peripheral blood CD34⁺ and CD34⁺CD38^– progenitor/stem cells at baseline and then every 6 hours for 24 hours on days 4 to 5 of G-CSF (10 μg/kg/day in the morning) mobilization in 11 allogeneic donors. Data were analyzed using mixed-model analysis of repeated measures.

Results

Whereas we observed a significant increase in CD34⁺ cell counts toward the evening, counts were then sustained on the morning of day 5. The correlation between CD34⁺CD38^– cell counts and the less defined CD34⁺ populations was weak.

Conclusions

Our results suggest that the pharmacodynamic activity and timing of G-CSF may alter endogenous progenitor rhythms. Donor age, medical history, and medications may also impact circadian rhythm. Further studies should examine the circadian rhythm at the peak of G-CSF mobilization and should consider potential confounders such as the time of G-CSF administration and the age of the subjects.