Wang Lei, Li Ming, Zhou Yongxin, Zhao Yu
Department of Orthopaedics, The First Affiliated Hospital of Xi'an Medical University, Xi'an710077, China.
The Second Department of Geriatrics, Ninth Hospital of Xi'an, Xi'an710054, China.
Open Med (Wars). 2017 Sep 6;12:157-162. doi: 10.1515/med-2017-0023. eCollection 2017.
Aberrantly expressed microRNAs have been implicated in lots of cancers. Reduced amounts of let-7g have been found in breast cancer tissues. The function of let-7g in bone metastasis of breast cancer remains poorly understood. This study is to explore the significance of let-7g and its novel target gene in bone metastasis of breast cancer. The expression of let-7g or forkhead box C2 (FOXC2) was measured in human clinical breast cancer tissues with bone metastasis by using quantitative real-time Polymerase Chain Reaction (qRT-PCR). After transfection with let-7g or anti-let-7g in breast cancer cell linesMDA-MB-231or SK-BR3, qRT-PCR and Western blot were done to test the levels of let-7g and FOXC2. The effect of anti-let-7g and/ or FOXC2 RNA interference (RNAi) on cell migration in breast cancer cells was evaluated by using wound healing assay. Clinically, qRT-PCR showed that FOXC2 levels were higher in breast cancer tissues with bone metastasis than those in their noncancerous counterparts. Let-7g was showed to be negatively correlated with FOXC2 in human breast cancer samples with bone metastasis. We found that enforced expression of let-7g reduced levels of FOXC2 protein by using Western blot in MDA-MB-231 cells. Conversely, anti-let-7g enhanced levels of FOXC2 in SK-BR3 cells. In terms of function, anti-let-7g accelerated migration of SK-BR3 cells. Interestingly, FOXC2 RNAi abrogated anti-let-7g-mediated migration in breast cancer cells. Thus, we conclude that let-7g suppresses cell migration through targeting FOXC2 in breast cancer. Our finding provides a new perspective for understanding the mechanism of bone metastasis in breast cancer.
异常表达的微小RNA与多种癌症有关。在乳腺癌组织中发现let-7g的含量降低。let-7g在乳腺癌骨转移中的功能仍知之甚少。本研究旨在探讨let-7g及其新靶基因在乳腺癌骨转移中的意义。通过定量实时聚合酶链反应（qRT-PCR）检测人临床乳腺癌骨转移组织中let-7g或叉头框C2（FOXC2）的表达。在乳腺癌细胞系MDA-MB-231或SK-BR3中分别转染let-7g或抗let-7g后，进行qRT-PCR和蛋白质印迹法检测let-7g和FOXC2的水平。采用划痕愈合试验评估抗let-7g和/或FOXC2 RNA干扰（RNAi）对乳腺癌细胞迁移的影响。临床上，qRT-PCR显示，骨转移乳腺癌组织中FOXC2水平高于其癌旁组织。在人骨转移乳腺癌样本中，let-7g与FOXC2呈负相关。我们发现，在MDA-MB-231细胞中通过蛋白质印迹法强制表达let-7g可降低FOXC2蛋白水平。相反，抗let-7g可提高SK-BR3细胞中FOXC2的水平。在功能方面，抗let-7g可加速SK-BR3细胞的迁移。有趣的是，FOXC2 RNAi可消除抗let-7g介导的乳腺癌细胞迁移。因此，我们得出结论，let-7g通过靶向FOXC2抑制乳腺癌细胞迁移。我们的发现为理解乳腺癌骨转移机制提供了新的视角。
