Molecular Signaling Section, Medical Oncology Branch, Center for Cancer Research, National Cancer Institute, 10 Center Drive MSC 1906, Bethesda, MD 20892, USA.
Angiogenesis. 2012 Mar;15(1):33-45. doi: 10.1007/s10456-011-9241-1. Epub 2011 Dec 22.
Exosomes, microvesicles of endocytic origin released by normal and tumor cells, play an important role in cell-to-cell communication. Angiogenesis has been shown to regulate progression of chronic myeloid leukemia (CML). The mechanism through which this happens has not been elucidated. We isolated and characterized exosomes from K562 CML cells and evaluated their effects on human umbilical endothelial cells (HUVECs). Fluorescent-labeled exosomes were internalized by HUVECs during tubular differentiation on Matrigel. Exosome localization was perinuclear early in differentiation, moving peripherally in cells undergoing elongation and connection. Exosomes move within and between nanotubular structures connecting the remodeling endothelial cells. They stimulated angiotube formation over a serum/growth factor-limited medium control, doubling total cumulative tube length (P = 0.003). Treatment of K562 cells with two clinically active tyrosine kinase inhibitors, imatinib and dasatinib, reduced their total exosome release (P < 0.009); equivalent concentrations of drug-treated exosomes induced a similar extent of tubular differentiation. However, dasatinib treatment of HUVECs markedly inhibited HUVEC response to drug control CML exosomes (P < 0.002). In an in vivo mouse Matrigel plug model angiogenesis was induced by K562 exosomes and abrogated by oral dasatinib treatment (P < 0.01). K562 exosomes induced dasatinib-sensitive Src phosphorylation and activation of downstream Src pathway proteins in HUVECs. Imatinib was minimally active against exosome stimulation of HUVEC cell differentiation and signaling. Thus, CML cell-derived exosomes induce angiogenic activity in HUVEC cells. The inhibitory effect of dasatinib on exosome production and vascular differentiation and signaling reveals a key role for Src in both the leukemia and its microenvironment.
外泌体是正常和肿瘤细胞释放的内吞起源的微小囊泡，在细胞间通讯中发挥重要作用。血管生成已被证明可调节慢性髓细胞白血病 (CML) 的进展。但发生这种情况的机制尚未阐明。我们从 K562 CML 细胞中分离并鉴定了外泌体，并评估了它们对人脐静脉内皮细胞 (HUVEC) 的影响。荧光标记的外泌体在 Matrigel 上进行管状分化时被 HUVEC 内化。外泌体在分化早期定位于核周，在细胞伸长和连接过程中向细胞外周移动。外泌体在重塑内皮细胞之间的纳米管状结构内和之间移动。它们在血清/生长因子有限的培养基对照中刺激血管形成，使总累积管长度增加一倍 (P = 0.003)。用两种临床活性酪氨酸激酶抑制剂伊马替尼和达沙替尼处理 K562 细胞可减少其总外泌体释放 (P < 0.009)；等效浓度的药物处理的外泌体诱导类似程度的管状分化。然而，达沙替尼处理 HUVEC 可显著抑制 HUVEC 对药物对照 CML 外泌体的反应 (P < 0.002)。在体内小鼠 Matrigel 塞模型中，K562 外泌体诱导血管生成，并被口服达沙替尼治疗阻断 (P < 0.01)。K562 外泌体诱导 HUVEC 中达沙替尼敏感的Src 磷酸化和下游 Src 途径蛋白的激活。伊马替尼对 HUVEC 细胞分化和信号的外泌体刺激作用作用最小。因此，CML 细胞来源的外泌体诱导 HUVEC 细胞的血管生成活性。达沙替尼对产生外泌体和血管分化及信号的抑制作用表明 Src 在白血病及其微环境中均发挥关键作用。
