目的　探讨miR-200a在儿童急性B淋巴细胞白血病中的表达及临床意义。方法　收集B细胞ALL患儿45例，以非血液病患儿18例为对照组，采集骨髓标本，qRT-PCR检测各组miR-200a的表达，并分析B细胞ALL患儿中miR-200a的表达与临床指标间的相关性。结果　miR-200a在B淋巴细胞ALL患儿组中的表达为(3.9±1.4)×10－4，低于对照组(25.7±10.3)×10－4，差异有统计学意义(P<0.05)。在≥10岁B淋巴细胞ALL患儿中miR-200a的表达低于<10岁患儿，差异有统计学意义(P<0.05)。不同治疗阶段和危险度分组miR-200a表达的差异有统计学意义(P<0.05)；以治疗第12周以及低危组的表达较高。结论　miR-200a低表达与儿童B细胞ALL的发生发展以及预后密切相关，可作为儿童B细胞ALL预后判断的潜在指标和治疗靶点。

　Objective　To explore the expression and clinical significance of microRNA-200a in childhood B-cell acute lymphoblastic leukemia (ALL). Methods　Bone marrow samples were collected from 45 children with B-cell ALL and 18 children without hematology disease as control. Total RNA was acquired from bone marrow. qRT-PCR was performed to detect the expression level of miR-200a. Results　The relative expression level of miR-200a in B-cell ALL group was significantly lower than that in control group (p<0.05); the expression of miR-200a in children over 10 years old was significantly lower than those in children under 10 years old (p<0.05); the expression of miR-200a in newly diagnosed samples was lower than those in those samples taken on Day 33 and at Week 12, respectively (p<0.05, p<0.01). In addition, the expression of miR-200a in low-risk group was higher than those in mid-risk and high-risk group, respectively (p<0.05). Conclusions　Low level of miR-200a had a close correlation with the development and prognosis of childhood B cell ALL, which could be used as a potential target of therapy and a biomarker of childhood B cell ALL in the future.