SMYD3在TGF-β1诱导乳腺癌细胞EMT过程中的作用机制研究

Epithelial-mesenchymal transition (EMT) is an important process of tumor development. Upon undergoing EMT, cells acquire the ability to migrate, drug resistance and some other characteristics of malignant transformation. SMYD3 is a novel anticancer target which acts as epigenetic modifying enzyme, transcription factor, and oncogene meanwhile, and it is closely related to the development of breast cancer and many other cancers. Our previous studies indicated that SMYD3 might be an important downstream mediator of TGF-β1 signal pathway, and play essential roles in TGF-β1-induced EMT. To confirm these speculations, in the present project, the transcriptional modulation effects of TGF-β1 signal pathway on SMYD3 and the regulation effects of SMYD3 on the EMT markers, would be detected with the methods of Real time RT-PCR, Western blot and luciferase reporter assay. The core binding sites and histone methylation in the promoter region of the target genes would be analyzed using chromatin immunoprecipitation assay. The key domains for the potential interaction between SMYD3 and transcription factors of TGF-β1 pathway would be investigated by co-immunoprecipitation. Taken together, these studies would lend further understanding to the effects of SMYD3 in the EMT process of breast cancer cells and its roles in the TGF-β1 signal pathway, and these findings might throw light on the development of novel prevention or therapeutic approaches to breast cancer, and provide a new theoretical guidance for the rational clinical use and R&D of anti-tumor drugs.

上皮间质转化（EMT）是肿瘤细胞获得迁移能力、耐药性等恶变特征的重要过程。SMYD3是兼具表观遗传修饰酶、转录因子、癌基因三大特性的新型抗癌药物靶点，与乳腺癌等肿瘤的发生发展有密切的关系。我们的前期研究提示SMYD3很可能是TGF-β1的重要下游分子，并在TGF-β1诱导的EMT中发挥了不可或缺的作用。为证实这些作用，本课题将通过Real time RT-PCR、Western Blot、荧光素酶报告分析等方法明确TGF-β1对SMYD3以及SMYD3对EMT标志物的转录调控作用；应用ChIP技术分析上述转录调控作用的关键位点及组蛋白甲基化状况；采用CoIP方法确定SMYD3与TGF-β1下游转录因子间的相互作用及其关键结构域。最终在分子-细胞-组织-整体水平阐明SMYD3对乳腺癌细胞EMT的诱导作用及其在TGF-β1信号通路中的角色，为乳腺癌的防治、合理用药及新药研发提供新的理论基础。

上皮间质转化（EMT）是肿瘤细胞获得迁移能力、耐药性等恶变特征的重要过程。SMYD3是兼具表观遗传修饰酶、转录因子、癌基因三大特性的新型抗癌药物靶点，与乳腺癌等肿瘤的发生发展有密切的关系。本课题通过Real time RT-PCR、Western Blot、荧光素酶报告分析、ChIP等方法，研究发现：在TGF-β1诱导乳腺癌细胞EMT过程中会伴随着SMYD3的表达升高，而通过RNAi等技术将SMYD3敲低后则可明显阻断TGF-β1对EMT的诱导作用。在TGF-β1对SMYD3的调控中，可能涉及到一定的直接启动子转录激活作用，但并却不是主要作用机制，更重要的机制是TGF-β1可以经由NF-κB信号通路，通过DNA甲基化等调节机制，抑制miR-124、miR-506并从而上调SMYD3。SMYD3过表达可以直接促进肿瘤细胞发生EMT，使细胞的增殖、迁移及对缺氧与化疗药物的耐受能力明显提高。对荷瘤裸鼠及临床乳腺癌样本也证实TGF-β1可促进裸鼠肿瘤EMT，在肿瘤及临床样本中SMYD3和间质细胞标志基因表达量明显高于癌旁组织，而上皮细胞标志基因E-cadherin则与SMYD3的表达量呈现一定的负相关，且彼此在空间定位方面也呈现出显著的一致性。进一步探索发现：SMYD3促进EMT作用主要与其对EMT密切相关的vimentin等编码基因、miR-200c等miRNA、MALAT1等lncRNA产生系统性的转录激活作用有关。综上所述，本课题在分子-细胞-组织-整体水平阐明了SMYD3对乳腺癌细胞EMT的诱导作用及其在TGF-β1信号通路中的角色，为乳腺癌的防治、合理用药及新药研发提供了新的理论基础。