腺病毒E1A基因抑制癌細胞轉移機制的探討; E1A Suppresses Cancer Metastasis Through Regulation of human microRNA, miR-520h

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题名:	腺病毒E1A基因抑制癌細胞轉移機制的探討;E1A Suppresses Cancer Metastasis Through Regulation of human microRNA, miR-520h
作者:	陳柏森;Poshen Chen
贡献者:	中國醫藥大學：癌症生物學研究所
关键词:	癌細胞轉移;腺病毒基因治療;E1A;cancer metastasis;miR-520h
日期:	2009-06-29
上传时间:	2009-08-12 13:50:04 (UTC+8)
摘要:	腺病毒蛋白 type 5 E1A (E1A) 是有效的抗腫瘤基因, 目前已被運用於多種癌症如乳癌、卵巢癌及頭頸癌的臨床基因治療試驗, 最近研究指出E1A基因治療可以有效的增強腫瘤細胞對化學治療的藥物敏感度, 因此E1A基因治療被視為相當有濳力的治療方式, 不過E1A可以抑制癌細胞轉移方面的機制目前還未盡全然了解。microRNA屬於小片段不轉譯的RNA, 透過microRNA可以調控許多細胞內的訊息傳遞路徑。首先我們利用microRNA矩陣分析去調查在E1A過度表現時, 癌細胞中是否確實有miRNA會受到調控, 根據microRNA矩陣分析的資料中, 我們發現E1A確實會調控許多不同microRNA的表現, 同時我們利用及時定量的PCR技術去再次確認矩陣分析的資料。在這些受E1A所調控的microRNA中, 我們的研究發現其中一個microRNA (miR-520h)會幫助癌細胞增強轉移能力, 而E1A則可以抑制此microRNA表現, 使用與miR-520h序列互補的核酸引子, 可以抑制多種腫瘤細胞轉移的能力, 在動物實驗中也發現, 當去過度表現miR-520h時, 可以增強癌細胞轉移的能力。根據目前不同的生物統計資料庫, 我們發現絲氨酸/蘇氨酸磷酸酶2A催化次單元(PP2A/C; Protein Phosphatase 2A catalytic subunit)是miR-520h所調控的目標蛋白之一, 更進一步,我們發現miR-520h透過抑制PP2A/C蛋白質的產生, 去增強癌細胞中Akt與NF-κB路徑的活性, 進而誘導使得與轉移相關的基因, Twist, 表現量增加, 因此我們提供關於E1A抗腫瘤轉移方面一個新的分子機轉。同時因為目前較無常效的抑制劑可以去抑制這些致癌的microRNA表現, 根據我們的結果E1A或許也有濳力可以運用成為常效的microRNA抑制劑在目前的臨床治療上。 The adenoviral type 5 E1A gene as an effective tumor suppression gene has been applied to multiple clinical trials for breast, ovarian and head/neck cancer. Recent studies have shown that the E1A gene therapy might be a promising strategy to enhance the sensitivity of tumor cells to chemotherapy. However, the role of E1A in mediating tumor metastasis still remains largely unexplored. MicroRNAs (miRNAs) are small non-coding RNAs that have been implicated in regulating diverse cellular pathways. First, we apply vector control transfected and E1A transfected cells for microRNA microarray analysis. From the array data, we find that E1A regulate several miRNA expression. Here we provide evidence that miR-520h, positively promotes cell motility, is down-regulated by E1A. The expression of miR-520h is downregulated in E1A-transfected cancer cells including breast and ovarian cancer. Using miRNA inhibitors, we demonstrate that certain cancer cell lines require the activity of miR-520h to promote migration and invasion in vitro. In the experimental metastasis animal model, we find that overexpression of miR-520h enhances cancer cell metastatic ability. From different miRNA target prediction database, we identify that protein phosphatase 2A catalytic subunit (PP2A/C) is one target gene of miR-520h. The miR-520h proceeds to inhibit translation of the messenger RNA encoding protein phosphatase 2A catalytic subunit (PP2A/C), resulting in activation of Akt and NF-κB signaling pathway. Furthermore, the inhibition of PP2A/C by miR-520h increases expression of well-characterized pro-metastatic gene, Twist, through NF-κB signaling pathway. Taken together, these results suggest that miR-520h is regulated by E1A and may play a key role in E1A-mediated metastasis suppression. Meanwhile, our results indicate that miR-520h is functionally linked to promote metastasis in cancer cells and therefore provide new insights into the role of E1A-mediated miRNA regulation in metastasis. Since it is hampered at present to stably silence miRNA over extended periods of time, these results also indicates that E1A gene therapy may serve as a miRNA inhibitor to stably silence oncogenic miRNA in malignant cancer.
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