Profile of cell-derived microvesicles in B-cell Acute Lymphoblastic Leukemia pediatric patients undergoing induction therapy: A pilot study

Introduction: Microvesicles (MVs) are particles derived from plasma membranes released by normal and cancer cells. Their presence in biological fluids can be associated with the severity of pathological processes, and their role as potential biomarkers of diseases and therapeutic targets has been highlighted. Methods: A longitudinal study was carried out at the Fundação Hospitalar de Hematologia e Hemoterapia do Amazonas (HEMOAM), a reference center for the diagnosis and treatment of oncohematological diseases in Manaus, to characterize the profile of cell-derived MVs in B-cell acute lymphoblastic leukemia (B-ALL). Peripheral blood (PB) plasma and bone marrow (BM) samples were collected from 20 pediatric patients with B-ALL at 3 time points of induction therapy, referred to as: diagnosis baseline (D0), day 15 of induction therapy (D15), and the end of the induction therapy (D35). In addition, PB samples were collected from 10 healthy children (single time point). MVs were measured by flow cytometry, with size range analysis carried out using calibration microspheres, and sample acquisition was performed in CytoFLEX S flow cytometer.  For labeling the MVs subsets we used fluorescent-labeled specific cellular markers against: Annexin-V (phosphatidylserine), CD235a (erythrocyte), CD41a (platelet), CD51/CD61 (endothelial cell), CD45 (leukocyte), CD66b (neutrophil), CD14 (monocyte), CD3 (T lymphocyte), CD19 (B lymphocyte/B lymphoblast), CD34 (Leukemic blast), and CD10 (B lymphoblast). This study was submitted to and approved by the Ethics Committee at Fundação HEMOAM, under protocol registration number #739.563/2014. Results: Our data demonstrated that B-ALL patients had a marked production of MV-CD51/61⁺, MV-CD10⁺, and MV-CD19⁺, and a decrease production of MV-CD41a⁺ on D0. However, by evaluating the kinetics and signature of production during induction therapy, it was possible to observe an evident decline in the number of MV-CD10⁺ and MV-CD19⁺, and an increased number of MV-CD41a⁺ on D35. Furthermore, through constructing of integrative networks, we observed that B-ALL patients exhibited a network rich in interactions among MV populations on D35, and a opposite profile on D0. Finally, the fold change signatures, and receiver operator characteristic (ROC) curve demonstrate that MV-CD10⁺ levels on D0 are associated with B-ALL, and showed moderate/high performance and good general accuracy in discriminating B-ALL patients from healthy controls. Conclusion: B-ALL patients exhibited dynamic MV kinetics and signatures, and complex biological networks during induction therapy, exhibiting opposite profiles on D0 and D35. Noteworthy, MV-CD10⁺ stood out as potential diagnostic and prognostic biomarkers. As far as we know, this is the first study to describe the count, size range, immunophenotype, and kinetics of cell-derived microvesicles in B-ALL patients during remission induction therapy.