Department of Molecular Biotechnology and Health Sciences, Molecular Biotechnology Center, University of Turin, Turin, Italy.
Dipartimento di Scienze della Vita e Biologia dei Sistemi, Università di Torino, Torino, Italy.
Cell Death Differ. 2017 Oct;24(10):1750-1760. doi: 10.1038/cdd.2017.103. Epub 2017 Jun 23.
Transforming growth factor (TGF)-β is one of the major inducers of epithelial to mesenchymal transition (EMT), a crucial program that has a critical role in promoting carcinoma's metastasis formation. MicroRNAs-143 and -145, which are both TGF-β direct transcriptional targets, are essential for the differentiation of vascular smooth muscle cells (VSMC) during embryogenesis, a TGF-β-dependent process reminiscent of EMT. Their role in adult tissues is however less well defined and even ambiguous, as their expression was correlated both positively and negatively with tumor progression. Here we show that high expression of both miRs-143 and -145 in mouse mammary tumor cells expressing constitutively active STAT3 (S3C) is involved in mediating their disrupted cell-cell junctions. Additionally, miR-143 appears to have a unique role in tumorigenesis by enhancing cell migration in vitro and extravasation in vivo while impairing anchorage-independent growth, which may explain the contradictory reports about its role in tumors. Accordingly, we demonstrate that overexpression of either miRNA in the non-transformed mammary epithelial NMuMG cells leads to upregulation of EMT markers and of several endogenous TGF-β targets, downmodulation of a number of junction proteins and increased motility, correlating with enhanced basal and TGF-β-induced SMAD-mediated transcription. Moreover, pervasive transcriptome perturbation consistent with the described phenotype was observed. In particular, the expression of several transcription factors involved in the mitogenic responses, of MAPK family members and, importantly, of several tight junction proteins and the SMAD co-repressor TGIF was significantly reduced. Our results provide important mechanistic insight into the non-redundant role of miRs-143 and -145 in EMT-related processes in both transformed and non-transformed cells, and suggest that their expression must be finely coordinated to warrant optimal migration/invasion while not interfering with cell growth.
转化生长因子-β（TGF-β）是上皮间质转化（EMT）的主要诱导因子之一，EMT 是促进癌转移形成的关键程序。miR-143 和 miR-145 是 TGF-β 的直接转录靶标，在胚胎发生过程中对血管平滑肌细胞（VSMC）的分化至关重要，这是一个依赖 TGF-β的过程，类似于 EMT。然而，它们在成人组织中的作用定义得较少，甚至模棱两可，因为它们的表达与肿瘤进展呈正相关和负相关。在这里，我们表明，在表达组成型激活 STAT3（S3C）的小鼠乳腺肿瘤细胞中，miR-143 和 miR-145 的高表达参与介导它们的细胞-细胞连接中断。此外，miR-143 似乎通过增强体外细胞迁移和体内渗出而在肿瘤发生中具有独特的作用，同时损害锚定非依赖性生长，这可能解释了其在肿瘤中的作用的矛盾报告。相应地，我们证明，在非转化的乳腺上皮 NMuMG 细胞中过表达任何一种 miRNA，都会导致 EMT 标志物和几种内源性 TGF-β靶标的上调，几种连接蛋白的下调和迁移率的增加，这与增强的基础和 TGF-β诱导的 SMAD 介导的转录相关。此外，观察到与所述表型一致的广泛转录组扰动。特别是，参与有丝分裂反应的几个转录因子、MAPK 家族成员的表达，以及重要的是，几个紧密连接蛋白和 SMAD 共抑制因子 TGIF 的表达显著降低。我们的研究结果为 miR-143 和 miR-145 在转化和非转化细胞中的 EMT 相关过程中的非冗余作用提供了重要的机制见解，并表明它们的表达必须精细协调，以保证最佳的迁移/侵袭，而不干扰细胞生长。
