已知miR-21调控大量重要肿瘤相关基因与多种癌症发生相关。由于胞内miRNA与靶基因的动态变化很难用软件预测，因此其他miRNA、靶mRNA以及内源竞争性非编码RNA（ceRNA）等都会直接或间接与miR-21对细胞癌变调控相关。为深入研究miR-21在癌细胞中作用机制，我们计划以正常和抑制miR-21表达的乳腺癌MCF-7细胞系为模型，运用Ribo-minus深度测序方法对mRNA、miRNA及长非编码RNA（lncRNA）的表达进行系统分析，组建相互作用网络，解析miR-21调控下转录组整体变化。筛选一批影响miR-21作用的关键基因和其它因子，并在已构建的乳腺癌从永生到癌变细胞模型中检测它们与miR-21的相关性，继而取乳腺癌样本及相应癌旁组织进行临床意义分析。此研究将使我们深入了解癌细胞中非编码RNA功能及不同类非编码RNA间的相互作用机制。

miR-21 regulates a great number of cancer-related genes and plays an important role in the development of many different cancers. Although there are ample software tools to be used in predicting target genes, it is difficult to predict how these target mRNAs vary in the cells. We analyze other miRNAs, target mRNAs, ceRNAs and other factors, which influence the miR-21 regulatory network directly or indirectly, to study the molecular mechanisms of miR-21 in cancer cells in depth and throughly based on deep transcriptomic sampling. We will first analyze the expression of mRNAs and long non-coding RNAs in normal and miR-21-repressed breast cancer cell line MCF-7 by using a Ribo-minus RNA-seq method, and then build interaction networks to illustrate the mechanisms. In addition, we will integrate the information of miRNAs to investigate the variation of the whole transcriptome of cancer cells under the miR-21 regulatory netwrok. We will select the key factors that can influence miR-21's function to investigate their correlation with the expression of miR-21 in the breast cancer cell models (nornal, immortal and tumorigenic cells) we have constructed, and then we analyze their clinical significance using clinical breast cancer tissues and the corresponding normal tissues. This study will expand our understanding on the regulatory mechanisms of non-coding RNAs and interactions among different non-coding RNAs. In a long term, we want to deveolp therapeutic tools for cancers based on our finding on RNA-centric regulatory mechanisms.