- 學位論文
紡錘體監控因子BubR1在非小細胞肺癌轉移上扮演輔助的角色
The role of spindle assembly checkpoint BubR1 in metastasis of non-small cell lung cancer
摘要
肺癌的死亡率在世界上名列前茅，特別是肺癌中的非小細胞肺癌，它在所有肺癌的死亡率中佔有80%。除此之外，非小細胞肺癌擁有強大的轉移能力，往往轉移至腦部、肝臟、以及骨頭之中。由於上述的因素，找出非小細胞肺癌轉移的機制和合適的基因標誌來預測肺癌症病患者的預後，以及搭配適當的治療方法，都是有其迫切需要的。因此，我們以BubR1作為本研究的探討方向。BubR1 是紡锤監控機制 (spindle assembly checkpoint) 分子的主要成員，當細胞進行有絲分裂間期，負責監控染色體在中期板上排列以及並往兩極分離的穩定性與準確性。然而，BubR1 的存在與否對細胞基因的穩定性有密切關係，部份文獻指出在染色體套數不穩定的癌細胞中，常伴隨著BubR1的異常過量的表現。過去指出， BubR1 在被認為扮演一個維護以及監控有絲分裂的良好角色，然而，在許多惡性腫瘤細胞中常伴隨過量的BubR1表現。 在我們這次的研究當中發現， BubR1 的蛋白質表現在非小細胞肺癌中的大細胞肺癌組織以及 H1299 細胞株當中，有異常高的表現。因此，以 shRNA 把 H1299 細胞株中的 BubR1 降解，接著進行細胞轉移能力的實驗，包括模擬傷口癒合的能力、侵入能力、非貼附環境下的生長的能力、以及測量 Gelatinase 中的 MMP-2 和 MMP-9 的表現。上述參與細胞轉移的能力的測試都會受到 BubR1 的表現量下降而減弱。此外，在 BubR1 表現量下降的細胞中，其促進細胞移動的指標蛋白: N-cadherin 和 p-paxillin (Tyr118) 也有下降的現象。Cyclooxygenase-2 (COX-2) 和 p-p65 (serine276) 的表現量也伴隨 BubR1 基因表現減弱而下降。我們的結果推測，BubR1可能扮演著連接 PI3K 和 NF-κB 之間的橋梁，進而促進癌細胞的入侵。
並列摘要
Abstract Lung cancer is analyzed statistically to be the leading cause of cancer death worldwide. Especially, the non-small cell lung cancer (NSCLC) accounts for 80% among lung cancer and easily metastasizes to brain, liver and bone. In order to clarify the mechanisms involving in cancer progression and identify the biomarkers that could predict prognosis or response to suitable therapies, we hypothesized that the BubR1 gene which is a key component of spindle assembly checkpoint (SAC), is essential for managing the proper attachment of the duplicated chromosome to microtubules during mitosis. However, decreased strength of SAC signaling would accelerate the rate of chromosomal gains or loss and enhance the possibility of tumorigenesis. In addition, previous studies have reported that the overexpression of BubR1 is frequently found in many cancers. Therefore, we found that the protein level of BubR1 was abundant in lung large cell carcinoma cells and was significantly present in cytoplasm. Consequently, we used shRNA to knockdown the expression of BubR1 to examine the several malignant properties of cancer cells, including cellular viability, migration, invasion, and anchorage independent growth (AIG). BubR1 knockdown did not affect the cell growth of H1299, whereas significantly decreased the migration and invasion ability by wound healing assay and Boyden's chamber assay, respectively. Furthermore, knockdown of BubR1 accompanied with down-regulation of N-cadherin and p-paxillin (Tyr 118). We found that the protein expression of BubR1 is governed by PI3K signaling pathway. Interestingly, our data showed that BubR1-promoted invasion is not dependent on Snail, which is a major transcription factors to trigger the EMT, had been showed to be regulated by GSK3β activity. On the contrary, we found that the cyclooxgenase-2 (COX-2) might be a candidate for BubR1-promoted invasion. Knockdown of BubR1 also inhibited the phosphorylation of NF-κB p65 in serine 276 residue. Our finding provided BubR1 as a bridge to link the PI3K and NF-κB pathways to synergistically promote cancer invasion.