De Soumasree, Das Sayantani, Mukherjee Srimoyee, Das Sainy, Sengupta Bandyopadhyay Sumita
Department of Biophysics, Molecular Biology and Bioinformatics, University of Calcutta, 92A.P.C. Road, Kolkata, WB 700009, India.
Department of Biophysics, Molecular Biology and Bioinformatics, University of Calcutta, 92A.P.C. Road, Kolkata, WB 700009, India.
Exp Cell Res. 2017 Dec 1;361(1):85-92. doi: 10.1016/j.yexcr.2017.10.005. Epub 2017 Oct 5.
Messenchymal to epithelial transition (MET) is a significant physiological phenomenon involved in embryogenesis and cancer. This study aims at investigating the mechanism of microRNA-20a (miR-20a) mediated regulation of mesenchymal to epithelial transition and identification of its direct target genes in breast cancer cell-line, MDA-MB-231. Reduced migratory and invasive property, altered cellular morphology along with reduced capability for attachment to basement membrane was acquired by over-expression of miR-20a in invasive MDA-MB-231 cell-line initially expressing low level of this micro-RNA, indicating direct correlation between abundance of miR-20a and metastatic property. The switch from mesenchymal to epithelial cells mediated by miR-20a involved post-transcriptional down-regulation of twist1, which in turn controls downstream epithelial markers like E-cadherin, claudin and mesenchymal markers like N-cadherin, fibronectin, the crucial players of mesenchymal to epithelial transition (MET). Furthermore, another key component, TGF-β and one of its receptors (TGFBR2) were found to be down-regulated by miR-20a. Additionally, reporter assay established that post-transcriptional down-regulation of TGFBR2 occurred through direct binding of miR-20a to its 3'UTR, thus abrogating the TGF-β signaling pathway resulting in inhibition of MET. Delineating the underlying molecular mechanism of miR-20a-mediated MET and defining the target genes will help us to introduce a miRNA-mediated effective therapeutic strategy against breast cancer.
间充质向上皮转化(MET)是一种参与胚胎发育和癌症的重要生理现象。本研究旨在探讨微小RNA-20a(miR-20a)介导的间充质向上皮转化调控机制,并鉴定其在乳腺癌细胞系MDA-MB-231中的直接靶基因。在最初低表达这种微小RNA的侵袭性MDA-MB-231细胞系中过表达miR-20a,可使其迁移和侵袭特性降低,细胞形态改变,同时与基底膜附着的能力下降,这表明miR-20a的丰度与转移特性直接相关。miR-20a介导的从间充质细胞向上皮细胞的转变涉及twist1的转录后下调,而twist1又控制下游的上皮标志物如E-钙黏蛋白、紧密连接蛋白,以及间充质标志物如N-钙黏蛋白、纤连蛋白,这些都是间充质向上皮转化(MET)的关键参与者。此外,还发现另一个关键成分转化生长因子-β(TGF-β)及其受体之一(TGFBR2)被miR-20a下调。另外,报告基因检测证实TGFBR2的转录后下调是通过miR-20a直接结合其3'非翻译区实现的,从而废除了TGF-β信号通路,导致MET受到抑制。阐明miR-20a介导的MET的潜在分子机制并确定靶基因,将有助于我们引入一种针对乳腺癌的miRNA介导的有效治疗策略。