新疆地区Sirt1基因SNP通过染色质重塑调控Notch1表达对不同民族乳腺癌发生发展的作用机制研究

The morbidity and mortality rates of breast cancer in Xinjiang Han, Uighur and Kazak population are obviously different. Preliminary study and literatures show that Sirt1 protein inhibits the development of breast cancer and SNP (Single Nucleotide Polymorphism) genetics regulate Sirt1 expression. In addition, the expression of Sirt1 and Notch1 which is a downstream target gene of Srit1 are obviously associated with the breast carcinoma. However, the mechanism of Sirt1 SNP regulating Notch1 expression is elusive. Sirt1, as a histone deacetylase, plays an epigenetic modification role on modifying histone deacetylation, and non-histone such as DNA transmethylase (DNMT) deacetylate resulting in target genes methylation. Thus, we propose a hypothesis that the Sirt1 SNP regulates the Nocth1 expression by the means of affecting the acylation of histone on Notch1 gene, DNMT, and Notch1 protein. This project intends to detect the acylation of histone on Notch1 gene, the acylation of DNMT, the acylation of Notch1 protein, the methylation of Notch1 gene, and Notch1 expression in breast cancer tissues, to analyze the effect of Notch1 acylation on the gene expression. Next, in breast cancer cells with Sirt1 SNP, we will examine the interaction sites between Sirt1 protein or DNMT protein and Notch1 gene for discussing the mechanism of Sirt1 SNP acylation on Notch1. This study will provide a reference for the precise treatment of breast cancer with different genetic backgrounds.

新疆汉、维吾尔、哈萨克族乳腺癌发病率和致死率明显不同。前期实验和文献发现Sirt1蛋白抑制乳腺癌，Sirt1表达受SNP遗传学调控，并且Sirt1和靶基因Notch1表达与乳腺癌密切相关。然而，Sirt1SNP调控Notch1作用机制尚不清楚。Sirt1作为去乙酰化酶具有修饰组蛋白酰基化、非组蛋白例如DNMT酰基化进而影响靶基因甲基化的表观遗传学功能。提出假说，Sirt1SNP可能通过修饰Notch1基因上组蛋白、DNMT分子或Notch1蛋白酰基化调控Notch1表达。本项目在组织中检测上述蛋白乙酰化、Notch1甲基化及表达等，研究Sirt1SNP修饰Notch1对其表达的影响及与乳腺癌的关系；在细胞中构建民族相关Sirt1SNP基因型，检测Sirt1或DNMT与Notch1基因作用位点等，探讨Sirt1SNP对Notch1酰基化修饰的作用机制，为不同民族乳腺癌治疗提供参考。

新疆汉、维吾尔、哈萨克族乳腺癌发病率和致死率明显不同。本研究发现，去乙酰化酶Sirt1基因rs3758391（T/C）、rs35706870（A/C）、rs2394443（G/C）位点分别是新疆汉族、维吾尔族、哈萨克族女性乳腺癌发生的高风险SNP，具有遗传易感性。前期报道Notch1通路分子促进乳腺癌发生发展，Notch1蛋白功能受多种翻译后修饰调控，那么，Sirt1 SNP基因型是否乙酰化修饰Notch1蛋白及相关分子以及对不同民族乳腺癌发生发展有影响呢？结果显示，Sirt1 SNPs分别通过乙酰化修饰Notch1蛋白（p＜0.05）、乙酰化修饰Notch1基因启动子区组蛋白H3K9和H4K16（p＜0.05）后，调控了Notch1蛋白表达和活性（p＜0.05），进而促进不同民族乳腺癌发生发展（p＜0.05）。有一篇文献提示，SIRT1分子与甲基转移酶DNMT有相关性并调控Notch1基因甲基化水平，本实验发现，乳腺癌组织中Sirt1基因三个不同SNP位点DNMT3b乙酰化水平没有变化，但体外乳腺癌细胞中显示Sirt1基因三个不同SNP位点DNMT1（DNMT3b的同家族成员）乙酰化水平有显著变化（p＜0.05），并明显影响Notch1基因甲基化水平、蛋白表达和活性（p＜0.05），进而促进了不同民族乳腺癌发生发展（p＜0.05）。我们从人组织水平观察到体外细胞探讨Sirt1基因SNPs通过乙酰化修饰Notch1蛋白和Notch1基因启动子区组蛋白、以及乙酰化修饰DNMT进而甲基化修饰Notch1基因这三种方式影响染色质重塑进而调控Notch1表达对新疆三个民族乳腺癌发生发展的作用机制研究，为后续治疗提供一些参考。