致癌蛋白MCT-1調控三陰性乳癌細胞之微小核糖核酸表現

Oncoprotein MCT-1 regulates microRNAs expression in triple negative breast cancer cells.

劉奕宏(Yi-Hong Liu)

指導教授 ： 徐欣伶 ； 楊嘉鈴

國立清華大學/生命科學院/生物科技研究所/碩士(2014年)

摘要

MCT-1 (Multiple copies in T-cell malignancy 1) 最先被發現於淋巴癌細胞株，MCT-1是一種核醣核酸結合蛋白能夠和DENR互相交互作用在訊息核醣核酸的5 '端，經過我們研究也發現MCT-1在人類肺腺癌以及乳腺癌細胞中有過度表現的情況。MCT-1主要的的功能包括參與細胞增生、細胞存活和造成基因體的不穩定。近期研究指出，MCT-1蛋白能夠調控目標蛋白質的轉譯效率，我們推測MCT-1可能會經由影響微小核醣核酸的表現量達到調控特定訊息核醣核酸的穩定性。本論文主要探討的研究主題在MCT-1蛋白在調控微小核醣核酸過程中所扮演的角色。我們發現在三陰性乳癌細胞中抑制MCT-1蛋白的表現，能夠顯著抑制異植腫瘤生長及致癌性微小核醣核酸的表現量，另一方面過度表現MCT-1蛋白會顯著抑制抗癌性微小核醣核酸的含量。此外，在這些乳癌細胞中降低MCT-1的含量會導致誘導性核醣核酸靜默複合體中主要負責攜帶微小核醣核酸以及具有內切性核醣核酸水解酶活性的蛋白-Argonaute 2 (Ago2) 表現量下降，有可能是MCT-1會影響微小核醣核酸含量的主要原因之一。近年來的文獻指出，在缺氧的環境中EGFR的表現量會增加並進入細胞質中和Ago2 共同影響部分微小核醣核酸的成熟過程，而我研究發現MCT-1的表現量會同時影響EGFR和Ago2之間直接交互作用的強度，由此推測MCT-1能夠抑制抗癌性微小核醣核酸的表現可能是經由影響EGFR-Ago2 (誘導性核醣核酸靜默複合體) 複合體的穩定程度所致，達到抑制致癌性微小核醣核酸表現的癌細胞，明顯的抑制細胞遷移能力及侵入能力。基於上述致癌蛋白MCT-1能夠影響目標基因的轉譯效率可能經由調控微小核醣核酸的表現或是影響其分子穩定性。目前我正在深入探討其作用機轉及重要相關訊息途徑。

關鍵字

三陰性乳癌細胞 ； 微小核糖核酸表現

並列摘要

The oncoprotein MCT-1 (Multiple copies in T-cell malignancies) was firstly identified in a human lymphoma cell line. MCT-1 is a RNA binding protein that is able to interact with DENR at 5 ' cap mRNA. Our researchs have discovered that MCT-1 is also overexpressed in both human lung and breast carcinomas. Overexpression MCT-1 plays multiple cellular functions such as cell survival, mitotic regulation, cell proliferation, genomic instability, tumor growth and translation regulation. Recent studies indicate that MCT-1 can regulate gene transcription and protein translation of the tumor suppressors and the oncogenic kinases, suggesting that MCT-1 may influence the stability of certain messenger RNA through modulating the biosynthesis of key microRNAs. Therefore, my main project is study: 1) Whether MCT-1 deregulates microRNAs expression in the tumor and the cancer cells? 2) Whether knockdown of MCT-1 decreases the oncomicroRNA expression level but increased the tumor suppressor microRNA presention? 3) Whether overexpression of MCT-1 can upregulate the oncomicroRNA but downregulate the tumor suppressor microRNA? 4) Is it possible that reduced MCT-1 activity can decrease one of RISC (RNA induced silencing complex) components Argonaute 2 (Ago2) that lead to downregulate the microRNAs and Ago2 endo-nuclease activity? The conclusion is that MCT-1 influences the expression levels of certain microRNAs in both TNBC cells and TNBC xenograft tumor. Because of increased activation of EGFR can interact with Ago2 and induce its phosphorylation that influences the maturation procedure of microRNAs in hypoxia condition. Similarly, I discovered that MCT-1 status can influence the activity of EGFR and the association between EGFR and Ago2, thus depleting MCT-1 inhibits the oncomicroRNA expression but elevates the tumor-suppressor microRNA presentation, probablely acting through its disruption on the formation of EGFR-Ago2 (RISC) complex. In summary, MCT-1 oncoprotein deregulates the transcription of specific genes persumbably through modulating the microRNA biosysthesis or by alterating their stabilities. The molecular mechanism and the potential of anti-metastaticity via controlling the maturation of miRNAs upon targeting the MCT-1 oncogenicity will be further investigated.

並列關鍵字

MCT-1

參考文獻

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