Impact of microRNA processing on EMT of ovarian cancer cells

项目摘要 越来越多的证据表明，microRNA（miRNA）系统在细胞凋亡中起着积极的作用。 肿瘤相关的上皮-间质转化（EMT）和肿瘤进展。我们基于PubMed的搜索 揭示了作为EMT抑制因子的miRNAs要比促进EMT的miRNAs多得多 在卵巢癌中（23对3），表明整个miRNA系统在卵巢癌中发挥EMT抑制作用， 癌这与我们的观察一致，通过沉默Drosha和Dicer来削弱miRNA的生物合成， 诱导上皮样卵巢癌细胞中EMT性状的发生。比较EMT的丰度- 在卵巢癌细胞中，我们注意到EMT抑制性miRNA的水平非常高， 间充质样细胞系比上皮样细胞系少。有趣的是，各小学的水平 这些miRNAs中的大多数miRNAs（pri-miRNAs）在间充质样和上皮样间充质样之间是相似的。 卵巢癌细胞这些结果表明，miRNA的生物发生（pri-miRNA到miRNA的加工） 在间充质样卵巢癌细胞中无效。我们发现阻断miRNA的生物合成 需要白细胞介素增强子结合因子3（ILF 3）的存在，因为ILF 3的敲低增加了 miRNA生物发生为了了解ILF 3是如何抑制miRNA生物合成的，我们发现， 激酶Cδ（PKCδ）是一种新型PKC亚型，可使ILF 3磷酸化，且PKCδ是阻遏ILF 3所必需 间充质样卵巢癌细胞中的miRNA生物合成。基于这些发现，我们成立了 中心假设：PKCδ通过赋予ILF 3 阻止EMT抑制性miRNA生物发生的能力。这些发现也为以下方面提供了依据： 开发一种新的卵巢癌靶向治疗模式，即建立有效的miRNA加工， 卵巢癌细胞通过干扰PKCδ的功能。本申请提出了三个目的：1） 阐明PKCδ调控miRNA加工的机制; 2）明确相关机制 与PKCδ/ILF 3调节卵巢癌细胞EMT的关系; 3）研究干扰PKCδ/ILF 3调节卵巢癌细胞EMT的可能性。 PKCδ抑制卵巢肿瘤的发生。这一应用的成功将有助于我们了解 PKCδ/ILF 3功能轴如何阻断miRNA的生物合成， 卵巢肿瘤的发生。

Project Summary Accumulating evidences have clearly demonstrated that microRNA (miRNA) system plays an active role in tumor-associated epithelial-mesenchymal transition (EMT) and tumor progression. Our PubMed-based search revealed that there are overwhelmingly more miRNAs serving as EMT suppressors than those promoting EMT in ovarian cancer (23 vs 3), indicating that overall miRNA system play an EMT-suppressive role in ovarian cancer. This is consistent with our observation that impairing miRNA biogenesis by silencing Drosha and Dicer induces the occurrence of EMT traits in epithelial-like ovarian cancer cells. Comparing the abundance of EMT- suppressive miRNAs in ovarian cancer cells, we noticed that levels of EMT-suppressive miRNAs are much less in mesenchymal-like cell lines than epithelial-like ones. Intriguingly, levels of the respective primary miRNAs (pri-miRNAs) in majority of these miRNAs are similar between mesenchymal- and epithelial-like ovarian cancer cells. These results indicate that the biogenesis of miRNA (processing of pri-miRNA to miRNA) is not efficient in mesenchymal-like ovarian cancer cells. We showed that blockage of miRNA biogenesis requires the presence of interleukin enhancer-binding factor 3 (ILF3) because knockdown of ILF3 increases miRNA biogenesis. In an effort to understand how ILF3 inhibits miRNA biogenesis, we found that protein kinase Cδ (PKCδ), a novel PKC isoform, can phosphorylate ILF3 and that PKCδ is required for the deterrence of miRNA biogenesis in mesenchymal-like ovarian cancer cells. Based on these findings, we formed our central hypothesis: PKCδ promotes ovarian cancer EMT and tumor development by conferring ILF3 with the ability to deter the biogenesis of EMT-suppressive miRNAs. These findings also provide the basis to develop a novel ovarian cancer-targeted therapeutic modality that is to establish efficient miRNA processing in ovarian cancer cells through the interference of PKCδ function. Three aims are proposed in this application: 1) Elucidate the mechanism underlying PKCδ regulation of miRNA processing; 2) Define mechanisms associated with PKCδ/ILF3 regulation of EMT in ovarian cancer cells; and 3) Investigate the potential of interfering with PKCδ function to suppress ovary tumorigenesis. The success of this application will help our understanding on how PKCδ/ILF3 functional axis blocks miRNA biogenesis and also demonstrate the potential of suppressing ovary tumorigenesis by targeting PKCδ.