ABSTRACT

Most patients with acute myeloid leukaemia (AML) experience disease recurrence after chemotherapy largely due to the development of drug resistance. Small extracellular vesicles (sEVs) are known to play a significant role in leukaemia drug resistance by delivery of anti-apoptotic proteins and genes conferring resistance to recipient cells. sEV levels are elevated in AML patients’ plasma at the time of diagnosis and remain elevated in complete remission after chemotherapy. The mechanism of enhanced sEV secretion in AML is unknown. We speculated that cholesterol synthesis by AML blasts may be related to elevated sEV secretion. Intracellular levels of cholesterol and of HMGCR (3-hydroxy-3-methyl-glutaryl-coenzyme A reductase), the rate-limiting enzyme in cholesterol synthesizing mevalonate pathway, significantly increased in cultured AML cells or primary human non-malignant cells treated with cytarabine or decitabine. Concomitantly, levels of sEVs produced by these cells also increased. Treatment with an HMGCR inhibitor, Simvastatin, or siRNAs targeting HMGCR blocked the chemotherapy-induced enhancement of sEV secretion in AML cells. sEVs carry HMGCR and chemotherapy enhances HMGCR levels in sEVs. HMGCR⁺ sEVs upregulate intracellular cholesterol and promote AML cell proliferation. A pharmacologic blockade of HMGCR emerges as a potential future therapeutic option for disrupting sEV signalling leading to cholesterol-driven chemo-resistance in AML.

摘要

大多数急性髓细胞性白血病（AML）患者在化疗后都会经历疾病复发，这在很大程度上是由于耐药性的发展。众所周知，小细胞外囊泡（sEVs）通过递送抗凋亡蛋白和赋予受体细胞抗性的基因，在白血病的耐药性中发挥重要作用。诊断时AML患者血浆中sEV水平升高，化疗后完全缓解时sEV水平保持升高。AML中增强的sEV分泌的机制尚不清楚。我们推测AML母细胞合成胆固醇可能与sEV分泌增加有关。胆固醇和HMGCR（3-羟基-3-甲基-戊二酰辅酶A还原酶）（胆固醇合成甲羟戊酸途径中的限速酶）的细胞内水平，在用阿糖胞苷或地西他滨处理的AML细胞或原发性人类非恶性细胞中显着增加。同时，这些细胞产生的sEVs水平也增加了。使用HMGCR抑制剂，辛伐他汀或靶向HMGCR的siRNA进行治疗可阻断AML细胞中化疗诱导的sEV分泌增强。sEV携带HMGCR，化学疗法可提高sEV中的HMGCR水平。肝癌⁺ sEVs上调细胞内胆固醇并促进AML细胞增殖。HMGCR的药理学障碍已成为一种潜在的未来治疗选择，可用于破坏sEV信号，从而导致AML中胆固醇驱动的化学耐药性。