Lnc RNA GAS5来源的pi-sno75通过乙酰化上调FOXO4表达抑制乳腺癌细胞转移的分子机制研究

Piwi-interacting RNA (piRNA) is a novel class of small noncoding RNA. It silences the transposons or induces epigenetic modifications in the invertebrates. It is thought to be germline-specific RNAs because of the enrichment in them. However, recent studies have shown that there are many piRNAs distributed in somatic cells，which expand the function of them. However, its function in the mammalian somatic cells remains largely unknown. Our data has demonstrated that there piRNAs exist in normal breast tissue and breast cancer tissue，and showed a lower expression in breast cancer tissue. We got information from a mRNA chip programme that FOXO4, a member of Forkhead box family, was upregulated by these GAS5 derived piRNAs, in which pi-sno75 showed the most significant phenomenon. Also In vivo experiments shows inhibition of tumor growth and metastasis. So here we Put forward the scientific problems: may pi-sno75 inhibit the growth and metastasis of breast cancer by upregulates the transcription of FOXO4? So, this research will aim to identify the mechanism of how pi-sno75 activates the tumor suppressor FOXO4: Demonstrate pi-sno75 activates FOXO4 by induces epigenetic modifications in the promotor of this gene. This research will reveal a novel mechanism of how a piRNA specifically mediates a cascade of events leading to epigenetic activation. Importantly, we have also indicated that GAS5, a well-known long non-coding RNA, functions as a tumor-suppressor by further generating a piRNA to induce FOXO4 expression in the breast cancer cells, and consequently inhibit the tumor metastasis. Also, this research is promising in find new target spot in precise treatment of breast cancer.

piRNA是一组新的小分子非编码RNA，它们在生殖细胞内沉默转座子元件和重复序列或诱导表观遗传学修饰以维持基因组的稳定性和完整性，而其在体细胞内的功能尚不明确。我们的研究表明piRNA参与调控乳腺癌的生长。预实验结果证实LncRNA GAS5来源的pi-sno75在乳腺癌中低表达，且pi-sno75可以上调乳腺癌细胞中FOXO4基因的表达，动物实验证实pi-sno75能够抑制乳腺癌生长且抑制了肿瘤转移关键因子的表达，所以我们认为pi-sno75是通过调控FOXO4抑制乳腺癌细胞增殖和转移。因此，本项目将对pi-sno75对FOXO4作用的靶点在其启动子进行分析并加以验证；研究pi-sno75通过诱导该靶点的表观遗传学修饰；拟进行细胞功能实验阐明pi-sno75在体内体外调控FOXO4影响乳腺癌转移的分子机制，以期揭示pi-sno75诱导基因表观遗传学激活的过程从而抑制乳腺癌转移.

导致乳腺癌死亡的主要原因是肿瘤转移，探索乳腺癌转移的相关机制意义重大。我们证实了piRNA参与调控乳腺癌的生长，并且体内体外实验证实了pi-sno75是通过调控抑癌基因FOXO4抑制乳腺癌细胞增殖和转移。本项目主要研究目的是验证FOXO4受到调控从而影响乳腺癌转移的机制：1. 对pi-sno75对FOXO4 启动子DNA 乙酰化修饰进行分析并加以验证，并对pi-sno75可能招募的调控乳腺癌转移的基因进行筛选，发现Sam68调控了FOXO4并且参与了肿瘤转移；2. 本研究验证了SAM68在乳腺癌高表达且在伴有淋巴结转移的乳腺癌中高表达，乳腺癌组织中Sam68的表达与淋巴结转移呈正相关；Sam68增强乳腺癌细胞的侵袭及转移并且可以诱导乳腺癌细胞上皮间质转化；抑制乳腺癌细胞中的Sam68能够抑制小鼠体内异种瘤的生长及转移；通过高通量测序证实了Sam68在乳腺癌细胞中发挥作用的靶基因是EPHA3和FOXO4。3. 从小分子RNA深度测序中筛选出另一个可能参与肿瘤转移的miR103A，小分子RNA大多作用于基因5’-UTR从而抑制基因的表达，而在我们的研究中miR103A通过作用于RGS2基因启动子从而抑制其表达，从而促进了肿瘤的进展。并且miR103A在淋巴结转移以及HER2+的乳腺癌中高表达；对miR103A的抑制有可能实现对RGS2的去抑制，进而抑制肿瘤的进展。该项目的研究成果有助于完善极为复杂的肿瘤转移调节网络，有助于临床对肿瘤转移的了解，为肿瘤治疗的研发提供理论基础。

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