Table_3_Acute Myeloid Leukemia Cells Functionally Compromise Hematopoietic Stem/Progenitor Cells Inhibiting Normal Hematopoiesis Through the Release of Extracellular Vesicles.xlsx

Acute myeloid leukemia (AML) is an aggressive and heterogeneous clonal disorder of hematopoietic stem/progenitor cells (HSPCs). It is not well known how leukemia cells alter hematopoiesis promoting tumor growth and leukemic niche formation. In this study, we investigated how AML deregulates the hematopoietic process of HSPCs through the release of extracellular vesicles (EVs). First, we found that AML cells released a heterogeneous population of EVs containing microRNAs involved in AML pathogenesis. Notably, AML-EVs were able to influence the fate of HSPCs modifying their transcriptome. In fact, gene expression profile of AML-EV-treated HSPCs identified 923 down- and 630 up-regulated genes involved in hematopoiesis/differentiation, inflammatory cytokine production and cell movement. Indeed, most of the down-regulated genes are targeted by AML-EV-derived miRNAs. Furthermore, we demonstrated that AML-EVs were able to affect HSPC phenotype, modifying several biological functions, such as inhibiting cell differentiation and clonogenicity, activating inflammatory cytokine production and compromising cell movement. Indeed, a redistribution of HSPC populations was observed in AML-EV treated cells with a significant increase in the frequency of common myeloid progenitors and a reduction in granulocyte-macrophage progenitors and megakaryocyte-erythroid progenitors. This effect was accompanied by a reduction in HSPC colony formation. AML-EV treatment of HSPCs increased the levels of CCL3, IL-1B and CSF2 cytokines, involved in the inflammatory process and in cell movement, and decreased CXCR4 expression associated with a reduction of SDF-1 mediated-migration. In conclusion, this study demonstrates the existence of a powerful communication between AML cells and HSPCs, mediated by EVs, which suppresses normal hematopoiesis and potentially contributes to create a leukemic niche favorable to neoplastic development.

急性髓系白血病（Acute myeloid leukemia, AML）是一类侵袭性且具有异质性的造血干/祖细胞（hematopoietic stem/progenitor cells, HSPCs）克隆性疾病。目前学界尚未明确白血病细胞如何通过调控造血进程以促进肿瘤生长及白血病微龛（leukemic niche）的形成。本研究旨在探究急性髓系白血病细胞通过释放细胞外囊泡（extracellular vesicles, EVs）扰乱造血干/祖细胞造血过程的具体机制。首先，本研究团队发现AML细胞可释放一组异质性的细胞外囊泡，其内含与AML发病机制相关的微小RNA（microRNAs, miRNAs）。值得注意的是，AML来源的细胞外囊泡可通过改变造血干/祖细胞的转录组来调控其细胞命运。对经AML-EVs处理的造血干/祖细胞进行基因表达谱分析，共鉴定出923个下调基因与630个上调基因，这些基因涉及造血/分化、炎性细胞因子产生及细胞迁移等生物学过程。进一步分析显示，大部分下调基因可被AML-EVs携带的miRNAs靶向调控。此外，本研究证实AML-EVs可改变造血干/祖细胞的表型，调控多项生物学功能：包括抑制细胞分化与克隆形成能力、激活炎性细胞因子产生以及损害细胞迁移能力。经AML-EVs处理的造血干/祖细胞中可见群体重分布现象：普通髓系祖细胞的占比显著升高，而粒细胞-巨噬细胞祖细胞及巨核细胞-红细胞祖细胞的占比则显著降低。该效应同时伴随造血干/祖细胞集落形成能力的下降。经AML-EVs处理的造血干/祖细胞中，CCL3、IL-1B及CSF2等参与炎性反应及细胞迁移的细胞因子水平显著升高，而CXCR4的表达水平则下降，该变化与SDF-1介导的细胞迁移能力降低相关。综上，本研究证实AML细胞与造血干/祖细胞之间存在一类由细胞外囊泡介导的强效通讯机制，该机制可抑制正常造血过程，并可能有助于构建利于肿瘤发生的白血病微龛。