miR-126 Governs Human Leukemia Stem Cell Quiescence and Therapeutic Resistance [miRNA]. Homo sapiens

In acute myeloid leukemia (AML), leukemia stem cells (LSC) play a central role in disease progression and recurrence due to their intrinsic capacity for self-renewal and chemotherapy resistance. Whereas epigenetic mechanisms balance normal blood stem cell self-renewal and fate decisions, mutation and dysregulation of epigenetic regulators are considered fundamental to leukemia initiation and progression. Alterations in miRNA function represent a non-canonical epigenetic mechanism influencing malignant hematopoiesis, however the function of miRNA in human LSC remains undetermined. Here we show that miRNA profiling of fractionated AML populations defines an LSC-specific signature that is highly prognostic for patient survival. Gain- and loss-of-function analyses demonstrated that miR-126 restrained cell cycle progression, prevented differentiation, and increased self-renewal of human LSC. By targeting the G0 to G1 gatekeeper CDK3, miR-126 preserved LSC quiescence and promoted chemotherapy resistance. Thus, in AML, miRNAs influence patient outcome through post-transcriptional regulation of stemness programs in LSC. Overall design: Peripheral blood from 24 AML patients and 3 human lin-CB pools were thawed, stained for CD34/CD38 cell surface markers and sorted into 4 populations. A total of 13 AML patient samples were functionally validated for leukemia-initiating capacity by xenotransplanation into immunodeficient mice. Global miRNA profiling was performed on all sorted AML samples and 3 lin-CB samples. An LSC miRNA signature was derived by infomatically testing engrafting fractions against non-engrafting fractions.

急性髓系白血病（acute myeloid leukemia, AML）中，白血病干细胞（leukemia stem cells, LSC）凭借其固有的自我更新能力与化疗耐药性，在疾病进展与复发过程中发挥核心调控作用。表观遗传机制可平衡正常造血干细胞的自我更新与细胞命运抉择，而表观遗传调控因子的突变与失调则被认为是白血病发生与进展的根本驱动因素。微RNA（microRNA, miRNA）功能异常代表了一类影响恶性造血的非经典表观遗传调控机制，但miRNA在人类LSC中的具体功能仍未明确。本研究通过对分级分离的AML细胞群体进行miRNA谱分析，鉴定得到一套LSC特异性的miRNA特征标签，该标签对患者的生存预后具有极高的预测价值。功能获得与功能缺失实验证实，miR-126可抑制细胞周期进程、阻断细胞分化，并增强人类LSC的自我更新能力。进一步机制研究显示，miR-126通过靶向G0至G1期关卡蛋白CDK3，维持LSC的静息状态并促进其化疗耐药性。综上，在AML中，miRNA通过对LSC内干性相关程序的转录后调控，影响患者的临床结局。

整体实验设计：对24名AML患者的外周血与3份人类谱系阴性脐带血（lin-CB）混合样本进行复苏处理，随后针对CD34/CD38细胞表面标志物进行染色，并将细胞分选为4个群体。选取共计13份AML患者样本，通过向免疫缺陷小鼠进行异种移植，对其白血病起始能力开展功能验证。对所有分选得到的AML样本与3份lin-CB样本进行全基因组miRNA谱分析。通过生物信息学方法对比移植阳性组分与移植阴性组分的表达谱，推导得到LSC特异性miRNA特征标签。