MBP-1在腫瘤形成時的蛋白功能之探討

Study on the biological functions of MBP-1 in tumorigenesis

許凱文(Kai-Wen Hsu)

指導教授 ： 蔡郁惠

共同指導教授 ： 葉添順

臺北醫學大學/醫學院/醫學科學研究所/博士(2009年)

https://doi.org/10.6831/TMU.2009.00083

摘要

Notch受體蛋白之訊息傳遞路徑於腫瘤形成 （tumorigenesis）過程中扮演了促進或抑制之重要角色。Notch1受體蛋白細胞膜內區域 (Notch1 receptor intracellular domain, N1IC)，為活化態Notch1受體蛋白，會活化c-myc致癌基因之表現；且N1IC會與轉錄因子YY1相互結合，並結合於c-myc啟動子 (promoter)上之YY1結合位，並活化c-myc基因表現，此機制是透過非CBF1所媒介。本論文研究結果證明N1IC會與c-myc調控蛋白??-enolase及c-myc promoter binding protein 1 (MBP-1)相互結合，並透過YY1結合於c-myc啟動上，抑制由N1IC所活化的c-myc啟動子之活性，而此機制是非CBF1所媒介。此外，K562細胞中N1IC的大量表現會抑制由hemin所誘發紅血球分化之能力，而此抑制作用會因為??-enolase及MBP-1同時表現後隨即被回復；??-enolase及MBP-1會藉由調控c-myc基因之表現抑制由N1IC所誘發的細胞聚落 (colony formation)之能力。這些結果指出活化態Notch1受體蛋白與??-enolase或MBP-1之相互結合，會透過YY1結合於c-myc啟動子上並共同調控c-myc基因之表現，影響腫瘤形成。
MBP-1不僅會抑制c-myc啟動子之活性也會調控著腫瘤形成，目前被認為是腫瘤抑制基因 (tumor suppress gene)。在台灣，胃癌高居癌症致死率前五名，此癌症病患多數死亡於腫瘤轉移，目前對於胃癌形成之詳細分子機制仍尚未完全瞭解，故本論文進一步探討MBP-1在胃癌形成過程中所扮演之角色。本研究結果證明人類胃腺癌SC-M1細胞株中大量表現MBP-1蛋白後，會抑制其細胞增生之能力。另外大量表現MBP-1蛋白後，也同時抑制了SC-M1細胞之細胞聚落、細胞移動 (migration)及細胞侵襲 (invasion)之能力。在動物實驗中，大量表現MBP-1蛋白之SC-M1細胞株，會抑制裸鼠腫瘤生長的能力；由尾靜脈注射大量表現MBP-1蛋白之SC-M1細胞後，更會降低胃癌細胞轉移 (metastasis)之能力並延長老鼠的存活率；同時也發現大量表現MBP-1蛋白後，會抑制SC-M1細胞株epithelial-mesenchymal transition (EMT)之作用。此外，本論文研究結果更進一步證明MBP-1蛋白會直接結合於COX-2啟動子上，抑制COX-2基因及蛋白之表現，降低SC-M1胃癌細胞腫瘤之生成。而大量表現MBP-1蛋白於AGS及NUGC-3兩株不同胃癌細胞中，也會抑制其腫瘤形成之能力。綜合以上結果本論文研究證明MBP-1蛋白會抑制COX-2蛋白表現，降低胃癌細胞細胞生長及腫瘤形成之能力。

關鍵字

腫瘤形成 ； Notch1受體蛋白細胞膜內區域 ； 啟動子 ； 細胞聚落 ； 細胞移動 ； 細胞侵襲 ； 細胞轉移

並列摘要

The Notch signal pathway plays multifaceted roles to promote or suppress tumorigenesis. The Notch1 receptor intracellular domain (N1IC), the activated form of the Notch1 receptor, activates the c-myc protooncogene. The complex of N1IC and transcription factor YY1 binds to the human c-myc promoter to enhance c-myc expression in a CBF1-independent manner. Here, it was demonstrated that N1IC interacted with the c-Myc-regulating proteins ??-enolase and c-myc promoter binding protein 1 (MBP-1). Both ??-enolase and MBP-1 suppressed the N1IC-enhanced activity of the c-myc promoter in a CBF1-independent manner. The YY1 response element in front of the P2 c-myc promoter was essential and sufficient for the modulation of c-myc by N1IC and ??-enolase or MBP-1. Furthermore, N1IC, YY1, and ??-enolase or MBP-1 but not CBF1 bound to the c-myc promoter through associating with the YY1 response element. Hemin-induced erythroid differentiation was suppressed by N1IC in K562 cells. This suppression was relieved by the expression of ??-enolase and MBP-1. In addition, both ??-enolase and MBP-1 suppressed the N1IC-enhanced colony-forming ability through c-myc. These results indicate that the activated Notch1 receptor and ??-enolase or MBP-1 cooperate in controlling c-myc expression through binding the YY1 response element of the c-myc promoter to regulate tumorigenesis.
The MBP-1 is a transcriptional suppressor of c-myc expression and involved in control of tumorigenesis. Gastric cancer is one of the most frequent neoplasms and lethal malignancies worldwide. So far, the regulatory mechanism of its aggressiveness has not yet been clearly characterized. Here, roles of MBP-1 in gastric cancer progression were studied. It was found that cell proliferation was inhibited by MBP-1 overexpression in human stomach adenocarcinoma SC-M1 cells. Colony formation, migration, and invasion abilities of SC-M1 cells were suppressed by MBP-1 overexpression, whereas promoted by MBP-1 knockdown. Furthermore, the xenografted tumor growth of SC-M1 cells was suppressed by MBP-1 overexpression. Metastasis in lungs of mice was inhibited by MBP-1 after tail vein injection with SC-M1 cells. MBP-1 also suppressed epithelial-mesenchymal transition (EMT) in SC-M1 cells. Additionally, MBP-1 bound on cyclooxygenase 2 (COX-2) promoter and down-regulated COX-2 expression. The MBP-1-suppressed tumor progression in SC-M1 cells were through inhibition of COX-2 expression. MBP-1 also exerted a suppressive effect on tumor progression of other gastric cancer cells such as AGS and NUGC-3 cells. Taken together, these results suggest that MBP-1-suppressed COX-2 expression plays an important role in the inhibition of growth and progression of gastric cancer.

並列關鍵字

tumorigenesis ； Notch1 receptor intracellular domain ； N1IC ； promoter ； colony formation ； migration ； invasion ； metastasis

參考文獻

〔70〕 Department of Health, Executive Yuan, R.O.C. Leading causes of death from cancer, Taiwan area 1994-2003.

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