目的 探讨microRNA-940(miR-940)在乳腺癌组织和细胞中的表达以及对乳腺癌细胞增殖、侵袭、迁移能力的影响及其相关分子机制。 方法 实时定量聚合酶链反应（Real-time PCR）检测2016年1月~2017年1月我院手术切除的78例患者的乳腺癌组织、癌旁组织和人乳腺癌细胞系MCF-7、SK-BR-3、MDA-MB-231、BT-549及人正常乳腺细胞系MCF-10 A中miR-940的表达情况。在乳腺癌细胞系MDA-MB-231中利用脂质体LipofectaminsTM 2000转染miR-940模拟物上调miR-940的表达，CCK-8实验检测细胞增殖活性的改变，小室侵袭及迁移实验（transwell）检测细胞侵袭、迁移能力的改变。生物学信息法预测miR-940的可能作用靶基因，双荧光素酶报告实验检测miR-940与CXC趋化因子受体2 (CXCR2)的3’UTR区结合情况，Western blotting检测miR-940对CXCR2 蛋白表达的影响。 结果 miR-940在乳腺癌组织和细胞中表达明显降低（P<0.01），并且miR-940的表达与TNM分期和淋巴结转移密切相关（P<0.01）。上调MDA-MB-231细胞miR-940表达后，细胞的增殖活性明显下降（P<0.01），侵袭及迁移能力明显下降（P<0.01）。双荧光素酶报告显示，miR-940可与CXCR2 的3’UTR区特定序列结合显著抑制荧光素酶活性(P<0.01)，上调miR-940后细胞中CXCR2 蛋白的表达均明显下降(P<0.01)。 结论 miR-940在乳腺癌中的表达降低，miR-940可以通过靶向CXCR2抑制乳腺癌细胞的增殖、侵袭及迁移能力。

Objective To explore microRNA-940(miR-940) expression in breast cancer tissues and cells, as well as its effect on breast cancer cell proliferation, invasion and migration capacities and the related molecular mechanism. Methods miR-940 expression in breast cancer tissues, para-carcinoma tissues from 78 patients undergoing surgical resection in our hospital from January 2016 to January 2017, and human breast cancer cell lines MCF-7, SK-BR-3, MDA-MB-231 and BT-549, as well as that in normal human breast cell line MCF-10 A, were detected using Real-time PCR. miR-940 expression in breast cancer cell line MDA-MB-231 was up-regulated through transfection with miR-940 mimics using liposome LipofectaminsTM 2000. Changes in cell proliferation capacity were detected using CCK-8 assay, while those in cell invasion and migration capacities were detected using transwell assay. The potential target gene of miR-940 was predicted by biologic information method , binding of miR-940 with the 3’UTR of CXC chemokine receptor 2 (CXCR2) was detected using dual luciferase reporter assay, and the effect of miR-940 on CXCR2 protein expression was detected using Western blotting. Results miR-940 expression in breast cancer tissues and cells was remarkably down-regulated (P<0.01), and miR-940 expression was closely correlated with TNM stage and lymph node metastasis (P<0.01). Up-regulating miR-940 expression in MDA-MB-231 cells would lead to markedly decreased cell proliferation capacity (P<0.01), as well as notably lowered cell invasion and migration capacities (P<0.01). Dual luciferase reporter assay indicated that miR-940 might bind with specific sequences in the 3’UTR of CXCR2, thus evidently suppressing luciferase activity (P<0.01); meanwhile, up-regulating miR-940 would result in apparently reduced CXCR2 protein expression in cells (P<0.01). Conclusion miR-940 expression is down-regulated in breast cancer, which can target CXCR2 to suppress breast cancer cell proliferation, invasion and migration.