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  • Effect of acute myeloid leukemia-derived exosomes on the bone marrow mesenchymal stromal cells: Downregulation of autophagy-related genes
  • Maryam Nabigol,1 Mehdi Allahbakhshian Farsani,2,*
    1. Department of Hematology and blood bank, School of Allied Medical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
    2. Department of Hematology and blood bank, School of Allied Medical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran


  • Introduction: Introduction: Acute myeloid leukemia (AML) is a heterogeneous clonal disorder arising from the bone marrow (BM), with symptoms such as anemia, infection, and bleeding. Until recently, AML research was focused on the identification of hematopoietic stem cells (HSCs)-related events leading to leukemogenesis. New studies have demonstrated that primary alterations in the bone marrow stromal cells, especially mesenchymal stromal cells (MSCs), can induce AML in mice and also in patients. Moreover, AML cells recruit various factors, including exosomes, to modify MSCs in order to create a niche favorable to leukemia growth and escape therapy. Therefore, it seems that MSCs' presence and survival is crucial for AML initiation and persistence. Our study aims to investigate the effect of AML exosomes on the survival-related properties of BM-MSCs, especially alteration in the expression of autophagy-related genes, as a cell death pathway.
  • Methods: Methods: Human BM-MSCs were obtained from healthy donors. AML cells (HL-60 cell line) were purchased from the Pastor Institute of Iran. Exosomes were isolated from the supernatants of HL-60 cells using an exosome isolation kit. TEM (Transmission Electron Microscopy) was used to determine the isolated particles' morphology. To evaluate the exosome nanostructure, the DLS (Dynamic Light Scattering) technique was utilized. Exosome-specific markers (CD9, CD63, and CD81) were identified via flow cytometry. Exosome protein content was assessed using a BCA protein assay in order to determine the concentration of exosomes. Then, MSCs were co-cultured with different concentrations of AML exosomes. The effect of exosomes on the metabolic activity of MSCs was assessed by the MTT assay, while ROS levels, proliferation, apoptosis, and cell cycle progression were evaluated by flow cytometry. Gene expression analysis was also performed by qRT-PCR.
  • Results: Results: Isolated particles were mainly positive for exosome-specific markers, including CD9, CD63, and CD81. According to the DLS results, the separated exosomes' size range was between 70-110 nm. The globular shape of the extracted exosomes was confirmed using TEM. Our results showed higher metabolic activity, decreased apoptosis, increased proliferation, lower ROS levels, and induced cell cycle progression in MSCs treated with a 50 μg/ml dose of AML exosomes compared with the control group. qRT-PCR data demonstrated that the pro-autophagic genes Beclin-1, Atg7, and Atg10 were downregulated in MSCs treated with 50 μg/ml of AML exosomes in comparison to their untreated counterparts (P<0.05).
  • Conclusion: Conclusion: Since MSCs' presence is important for AML onset and progression, our results suggest that, through exosome secretion, AML decreases autophagic cell death while increasing the viability and proliferation of MSCs so that leukemic cells can exploit them to generate a protective microenvironment for leukemia growth and therapy resistance.
  • Keywords: Keywords: Acute myeloid leukemia, Exosome, Mesenchymal stromal cell, Autophagy