Department of Pathology, First Affiliated Hospital and College of Basic Medical Sciences, China Medical University, Heping, Shenyang, Liaoning 110001, PR China.
Int J Oncol. 2013 May;42(5):1734-42. doi: 10.3892/ijo.2013.1861. Epub 2013 Mar 21.
MicroRNAs (miRNAs) function as genetic modulators that regulate gene expression, and are, thus, involved in a wide range of biological roles, including tumor cell migration and invasion. MiR-125a-3p is a mature form of miR-125a, derived from the 3'-end of pre-miR-125a. Our group has previously reported that miR-125a-3p functions as a tumor suppressor gene that inhibits the migration and invasion of lung cancer cells. Here, we report the discovery of a new regulatory layer of the RhoA-actomyosin pathway through which miR-125a-3p controls tumor cell migration. Overexpression of miR-125a-3p by transfection of sense‑miR‑125a-3p resulted in decreased RhoA protein levels, while the levels of RhoA mRNA remained constant. The concentrations of both RhoA-GTP protein and actin filaments decreased after miR-125a-3p overexpression in the A549 lung cancer cell line. Conversely, knockdown of miR-125a-3p by transfection of antisense-miR-125a-3p resulted in increased RhoA protein levels while the levels of RhoA mRNA remained unchanged. However, the concentration of both RhoA-GTP protein and actin filaments increased. To further demonstrate that RhoA is a potential target of miR‑125a-3p, luciferase reporter constructs containing the RhoA 3'UTR demonstrated reduced reporter activity after ectopic expression of miR-125a-3p. Moreover, luciferase reporter constructs containing the RhoA 3'UTR mutant did not show significantly changed reporter activity. Furthermore, A549 cells demonstrated reduced migratory capacity after treatment with the Rho inhibitor CT04. Our results indicate that the loss of miR-125a‑3p-controlled regulation of the RhoA-actomyosin pathway can lead to increased migration of tumor cells because of the upregulation of RhoA expression. In particular, an increased intracellular concentration of RhoA-GTP protein in A549 cells leads to the accumulation of actin filaments. These results provide new insights into the role of the miR-125a family in lung cancer.
微小 RNA（miRNA）作为遗传调节剂发挥作用，调节基因表达，因此参与广泛的生物学作用，包括肿瘤细胞迁移和侵袭。miR-125a-3p 是 miR-125a 的成熟形式，来源于 pre-miR-125a 的 3'端。我们的研究小组之前报道过，miR-125a-3p 作为一种肿瘤抑制基因发挥作用，抑制肺癌细胞的迁移和侵袭。在这里，我们报告发现了 RhoA-肌动蛋白通路的一个新的调控层，miR-125a-3p 通过该通路控制肿瘤细胞迁移。转染 sense-miR-125a-3p 使 miR-125a-3p 过表达导致 RhoA 蛋白水平降低，而 RhoA mRNA 水平保持不变。在 A549 肺癌细胞系中转染 miR-125a-3p 后，RhoA-GTP 蛋白和肌动蛋白丝的浓度均降低。相反，转染 antisense-miR-125a-3p 使 miR-125a-3p 下调导致 RhoA 蛋白水平升高，而 RhoA mRNA 水平不变。然而，RhoA-GTP 蛋白和肌动蛋白丝的浓度均增加。为了进一步证明 RhoA 是 miR-125a-3p 的潜在靶点，含有 RhoA 3'UTR 的荧光素酶报告基因构建体显示在外源性表达 miR-125a-3p 后报告基因活性降低。此外，含有 RhoA 3'UTR 突变的荧光素酶报告基因构建体没有显示出明显改变的报告基因活性。此外，A549 细胞在用 Rho 抑制剂 CT04 处理后迁移能力降低。我们的结果表明，miR-125a-3p 对 RhoA-肌动蛋白通路的调控丢失可能导致肿瘤细胞迁移增加，因为 RhoA 表达上调。特别是，A549 细胞中 RhoA-GTP 蛋白的细胞内浓度增加导致肌动蛋白丝的积累。这些结果为 miR-125a 家族在肺癌中的作用提供了新的见解。
