探討SPZ1與ISX表現在肝腫瘤癌化與轉移上的調控機轉

To explore the tumorigenic and metastatic regulation mechanism of SPZ1 and ISX in hepatocellular carcinoma (HCC)

王麗婷(Li-Ting Wang)

指導教授 ： 許世賢

高雄醫學大學/醫學院/醫學研究所博士班/博士(2015年)

摘要

在癌症轉移的進程中，表皮細胞間質化(EMT) 過程扮演重要的角色，但目前對於其作用機轉仍不明確。在研究中發現SPZ1扮演調控EMT作用的上游角色，並且與被TIP60乙醯化的TWIST1產生功能性的交互結合作用。在肝癌細胞中，同時過度表現SPZ1和TWIST1，而非單獨表現TWIST1時，可以增加血管內皮生長因子(VEGF)的表現，這是藉由與BRD4結合去增強RNA pol II依存性的轉錄，並導致腫瘤微環境(tumor microenvironment)的改變。利用癌思停(Avastin)去中和VEGF的表現，可以有效的抑制因SPZ1-TWIST1複合體引起的轉移。而在肝癌病患的病理分析，發現肝癌組織中SPZ1的表現與近端轉移和較差的預後有極度顯著的相關性。因此證實SPZ1-TWIST1複合體在表皮間質化的訊號傳遞與腫瘤的形成和轉移中扮演重要調控角色。
此外，慢性發炎會促使肝腫瘤的產生，但慢性發炎因子是與肝癌誘發的主要相關原因尚未明確。因此，經由比對119位肝癌病人及11位非肝癌病人，發現箱型基因ISX的表現與肝癌組織中IL-6及cyclin D1的表現有高度的相關性。由病理上的分析發現，箱型基因ISX呈現癌組織特異性的表現，並且與病人之術後存活時間、腫瘤大小、腫瘤顆數及腫瘤的惡性度呈現高度正相關。過度表現箱型基因ISX會誘發cyclin D1表現而增加肝癌細胞的增生繁殖及癌化特性。相反，如果以小分子干擾核醣核酸的技術去抑制肝癌細胞中的箱型基因ISX表現，則可有效的抑制肝癌細胞的生長繁殖及癌化的特性。因此，由這些研究結果及癌組織特異性表現的特性說明箱型基因ISX的表現是一個重要的肝癌發生的調控者，可做為未來肝癌預後及治療的標的。

關鍵字

表皮細胞間質化 ； 肝癌

並列摘要

The epithelial–mesenchymal transition (EMT) is an important process in the progression of cancer, but its occurrence and the regulatory mechanism are not fully understood. In this study, Spermatogenic Zip 1 (SPZ1) acted both as an upstream regulator of EMT and as an essential interaction factor for cellular functions of TWIST1 in tumor initiation and progression. Mechanistically, SPZ1 upregulated and interacted directly with TWIST1 acetylated by TIP60. Ectopic expressions of SPZ1 and TWIST1, but not TWIST1 alone, was shown to enhance vascular endothelial growth factor (VEGF) expression by recruiting BRD4 to enhance Pol II-dependent transcription, leading to remodeling of the tumor microenvironment. Neutralizing VEGF by avastin effectively abrogated metastasis induced by the SPZ-TWIST1 complex. In hepatocellular carcinoma samples, significantly increased SPZ1 expression was noted, correlating with distinct clinical metastatic features and poor prognosis. These results suggest that the SPZ1–TWIST1 axis mediates EMT signaling and exerts significant regulatory effects on tumor initiation and metastasis.
Moreover, chronic inflammation drives initiation of hepatocellular carcinoma (HCC), but the underlying mechanisms linking inflammation and tumor formation remain obscure. In this study, we compared the expression of interleukin (IL)-6 and cyclin D1 (CCND1) with the IL-6–induced homeobox gene ISX (intestine-specific homeobox) in 119 paired specimens of HCCs and adjacent normal tissues and also in paired specimens from 11 patients with non-HCCs. In pathologic analysis, ISX exhibited a tumor-specific expression pattern and a high correlation to patient survival time, tumor size, tumor number, and progression stage. Enforced expression of ISX accelerated cell proliferation and tumorigenic activity in hepatoma cells through CCND1 induction. In contrast, short hairpin RNA–mediated attenuation of ISX in hepatoma cells decreased cell proliferation and malignant transformation in vitro and in vivo. A high positive correlation existed in human hepatoma tumors between ISX and CCND1 expression. Together, our results highlight ISX as an important regulator in hepatoma progression with significant potential as a prognostic and therapeutic target in HCCs.

並列關鍵字

EMT ； HCC

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