臺灣博碩士論文加值系統

近二十年以來，癌症一直是人類重要的死亡原因，而肺癌更為全球癌症死亡的首位。癌細胞遠處器官的轉移與旁邊組織的侵犯是導致治療失敗的主要原因，一般而言，癌細胞越後期轉移性越強，除了少部份惡性度比較強的種類，例如，肺腺上皮細胞癌，常常在未診斷出原位癌之前，已經轉移到肝、骨、腎上腺、腎、中樞神經系統。因此了解調控轉移的分子機制及其與上皮細胞的轉形的關聯性，也許可以找出另一條癌症治療的方向。正常上皮細胞一般大量表現上皮細胞黏著因子(E-cadherin)，但臨床證據顯示，部份癌症如肝癌，前列腺癌，隨著病情的進程，E-cadherin的表現跟著消失，此項消失使得上皮細胞移動性增加並具侵犯性，同時轉形生長因子(transforming growth factor β1, TGFβ1)過量表現。在本研究，肺癌細胞(A549)接受TGFβ1的刺激，E-cadherin的表現消失並伴隨著細胞的轉形(epithelial-to-mesenchymal transition, EMT)，且證據顯示slug可能在此扮演抑制E-cadherin的角色。而E-cadherin的聯結蛋白β-catenin脫離細胞膜而進入細胞核，表示部份促癌基因可能有被活化。轉形後的A549細胞具有纖維母細胞(myofibroblast)的特性，表現smooth muscle acin (SMA) ，分泌膠原蛋白(collagen)，結締組織生長因子(connective tissue growth factor, CTGF)來啟動纖維化反應。藉由動物以及病人檢體，我們觀察到腫瘤的組織當中含有大量的膠原蛋白，顯示纖維化的過程可能與癌細胞惡性度有關。運用A549細胞，我們發現當細胞接受到轉形生長因子的刺激，金屬蛋白酶(matrix metalloprotease)的表現增加，伴隨著此酵素活性的上升。運用細胞移行試驗，我們發現轉形生長因子增加細胞的移動性。以上結果顯示轉形生長因子誘發的肺癌上皮細胞轉形，導致纖維化的反應，而此進程可能促進了癌細胞的轉移能力。

Malignant solid tumors typically lead to metastases, making cancer hard to eradicate. Clinical studies show that loss of E-cadherin is common to many tumors. Recent studies have implicated a significant role of transforming growth factor β1 (TGFβ1) in cell transformation in which a tumor comprising mostly sedentary epithelial type of cells is changed into a tumor with invasive and metastatic fibroblastic type of cells. Several previous works have revealed that epithelial-to-mesenchymal transition (EMT) play a crucial role in the progression and aggressiveness of many cancer types. Slug, a transcription repressor, plays a crucial role in the regulation of EMT by suppressing several epithelial markers and adhesion molecules including E-cadherin in breast and colorectal carcinoma; the slug expression is accompanied with shorter survival. The present study aims at investigating the significance of TGFβ1 in EMT-related tumorigenesis. Using human alveolar epithelial cell line A549, we found that TGFβ1 treatment significantly down-regulated the expression of E-cadherin and up-regulated the expression of slug. In addition, down-regulated E-cadherin was followed by the redistribution of its binding protein, β-catenin, which moved from cell membrane to the nucleus, implicating that some genes related to cell adhesion and proliferation might have been activated. We found that TGFβ1 induced A549 cells to express smooth muscle actin (SMA) which is usually expressed in active myofibroblast. Consistently, we also observed in A549 cells the synthesis of collagen mRNA and the expression of connective tissue growth factor (CTGF). The SMA expression and cross-linking collagen composition were also detectable in study animals and in lung cancer patients. At the same time, using A549 cells, we also found that TGFβ1 up-regulated the expression of matrix metalloprotease-2 (MMP-2). The observation suggests that cells had adopted a more invasive potential with morphogenic alteration. In an in vitro metastasis assay, TGFβ1 was also found to promote cell migration. Our investigation taken together supports the notion that TGFβ1 induces epithelial transition that leads to fibrogenesis and eventually contributes to metastatic process.

考試合格證明.....................................I
Abstract...............................................II
Abstract in Chinese............................III
Acknowledgement..............................V
Index.................................................IX
Abbreviation......................................XI
Introduction..........................................1
Materials and Methods........................10
Results and Discussion........................21
Tables and Figures..............................29
References..........................................58
Appendix............................................64
Curriculum Vitae................................66

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