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標題: | 探討內質網蛋白TXNDC5於大腸直腸癌之角色 The Role of ER Protein TXNDC5 in Colorectal Cancer |
作者: | 程凱琳 Kai-Lin Cheng |
指導教授: | 楊鎧鍵 Kai-Chien Yang |
關鍵字: | 大腸直腸癌,腫瘤間質,癌症相關纖維細胞,Thioredoxin domain containing 5 (TXNDC5),Transforming growth factor β (TGFβ), Colorectal cancer (CRC),Tumor stroma,Cancer-associated fibroblasts (CAFs),Thioredoxin domain containing 5 (TXNDC5),Transforming growth factor β (TGFβ), |
出版年 : | 2018 |
學位: | 碩士 |
摘要: | 研究緣起
目前已知大腸直腸癌(colorectal cancer, CRC)並不單純由惡性腫瘤細胞構成,乃是癌細胞與周邊非惡性間質細胞(non-malignant stromal cells)共同組成的複雜微環境,其中的間質纖維細胞(stromal fibroblasts)及其所活化而成的癌症相關纖維細胞(cancer-associated fibroblasts, CAFs)已被報導在促進腫瘤生成和癌症進程中扮演重要角色,主要是透過增加癌細胞分化能力、促進細胞外間質蛋白(extracellular protein, ECM)的生成以及影響癌細胞擴散等機制。我們實驗室先前的研究發現內質網蛋白TXNDC5 (thioredoxin Domain Containing 5) 在心臟纖維化中扮演重要角色。TXNDC5蛋白是一種雙硫異構酶 (protein disulfide isomerase,PDI),主要位於細胞內質網,其功能和催化ECM蛋白之摺疊以及參與氧化還原有關。而TXNDC5基因剔除 (knockout) 的小鼠可減緩因isoproterenol (ISO) 刺激所造成的心臟病變,其纖維化相關蛋白基因COL1A1、ELN、CTGF及ACTA2的表現也比野生型給ISO的組別低。而我們也發現TXNDC5在stromal fibroblasts中高度表現,並參與其活化、分化以及ECM蛋白的生成。因此我們假設TXNDC5可參與CAF之活化,進而促進癌化過程。 研究方法 透過GEO(GSE21510, 39396及35602)以及Human Protein Atlas等資料庫的再分析,我們比較了大腸直腸癌病人以及正常大腸檢體之TXNDC5基因及蛋白表現量差異。而為了探討TXNDC5於動物體內對CRC癌化過程之影響,我們利用CRISPR基因編輯技術於小鼠進行Txndc5基因剔除,並使用azoxymethane (AOM)/ dextran sulfate sodium (DSS)模型在野生型和Txndc5基因剔除小鼠中引致CRC。最後,我們再將小鼠CRC腫瘤切片以免疫及螢光染色進行分子機制的探討。 研究成果 透過生物資訊工具的分析,我們確實發現TXNDC5 mRNA在大腸直腸癌病人檢體中較正常表現量明顯為高,尤其是在其腫瘤間質。另外,病人中具有高度TXNDC5表現者經分析後也被發現有較差的存活率。而我們使用AOM/DSS模型在野生型小鼠中引致CRC,並發現TXNDC5於腫瘤中高度表現,其中尤以tumor stromal fibroblasts為最高,而非於腫瘤細胞本身。另外,我們在Txndc5 knockout小鼠引致CRC的實驗上則發現在大腸腫瘤的數目、程度及大小上與wild-type小鼠相較之下均有顯著降低,並其腫瘤間質形成及活化程度均較野生型低,且此過程與TGFβ訊息傳遞路徑相關。 結論 綜上所述,TXNDC5於大腸直腸癌之病程中確實扮演著尚未被報導的重要角色,與tumor stromal fibroblast活化為CAF相關,並進而促進CRC腫瘤生成。而透過將TXNDC5做為標的,有望可開發預防或治療大腸直腸癌的新型治療模式。 Introduction Colorectal cancer (CRC) consists of a complex mixture of malignant tumor cells and nonmalignant stromal cells that form the tumor microenvironment. Activated stromal fibroblasts, or cancer-associated fibroblasts (CAFs), characterized by increased proliferative activity, extracellular matrix protein (ECM) production, and α-smooth muscle actin (α-SMA) expression, are known to promote CRC tumorigenesis and progression. We have recently identified a stromal fibroblast-enriched protein thioredoxin domain-containing protein 5 (TXNDC5), a protein disulfide isomerase, as a critical regulator involved in endoplasmic reticulum (ER) redox activity and promoting ECM production. In our previous study, Txndc5 deletion significantly attenuated the isoproterenol-induced heart fibrosis compared with wild-type mice, so as the gene expression of fibrosis-associated genes COL1A1, ELN, CTGF, and ACTA2. Thus, we hypothesized that TXNDC5 could be a critical mediator of colon stromal fibroblast activation, thereby promoting CRC formation. Material and method To study the role of TXNDC5 in CRC carcinogenesis, we first re-analyzed GEO datasets (GSE21510, 39396 and 35602) and the Human Protein Atlas to determine TXNDC5 mRNA and protein expression levels in human colorectal cancer and normal colon tissue samples. To examine the in vivo function of TXNDC5 in CRC carcinogenesis, Txndc5-/- mice were generated using CRISPR-based genome editing technology. CRC was then induced in wild-type (WT) and Txndc5-/- mice by intraperitoneal injection of azoxymethane (AOM) in conjunction with dextran sulfate sodium (DSS) stimuli. Immunohistochemistry and immunofluorescence staining were performed on mouse CRC tumor sections. Results and discussion Bioinformatic analyses revealed strong upregulation of TXNDC5 in human CRC, especially in the tumor stroma. Increased TXNDC5 expression was correlated with higher ECM production in human CRC samples. Besides, elevated TXNDC5 expression levels are associated with worse outcomes in CRC patients. Using a mouse model of colitis-associated CRC induced by AOM/DSS treatment, we revealed that TXNDC5 expression level was specifically increased in the collagen-secreting stromal, but not in the epithelial, cells of colon tumors. Targeted deletion of Txndc5, on the other hand, resulted in significantly decreased colon tumor number and burden, compared with WT control, in response to AOM/DSS treatment. Conclusion Taken together, our data suggest an important yet previously unrecognized role of TXNDC5 in the development of CRC, possibly through activating stromal fibroblasts into CAFs that promotes tumorigenesis. Targeting TXNDC5, therefore, could be a novel therapeutic approach to treat or prevent CRC. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/77530 |
DOI: | 10.6342/NTU201802787 |
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顯示於系所單位: | 藥理學科所 |
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