E-cadherin訊息路徑相關蛋白表現與膀胱癌的相關性研究

Study of the Association of E-Cadherin Signaling Pathway Related Protein Expression and Bladder Cancer

戴慧龍(Hui-Lung Tai)

指導教授 ： 周明智

中山醫學大學/醫學院/醫學研究所/博士(2008年)

https://doi.org/10.6834/CSMU.2008.00041

摘要

研究目的：根據國際癌症研究署2002年的統計，膀胱癌其發生率在所有癌症中排名第九，而根據國內衛生署所發表台灣地區癌症登記報告，膀胱癌佔了泌尿系統癌症之大部分，而死亡率則有逐年增加的趨勢。膀胱癌的治療預後與腫瘤發生時的侵犯程度有密切關係，然而根據目前病理學而訂定的stage及grade指標，在臨床上雖然很實用，但仍嫌不足，因此發展出一種新的生物指標來預測此類疾病的癒後，進而擬定臨床治療方式實有其必要。目前已知E-cadherin與catenin之複合物如α-catenin、β-catenin、γ-catenin及p120ctn位於細胞膜上，對於細胞與細胞間黏合結構的完整性扮演重要的角色，而E-cadherin基因啟動子的甲基化被認為是造成E-cadherin表現喪失的重要原因之ㄧ，許多學者認為E-cadherin及其複合物可作為預測癌症癒後的獨立因子。
材料與方法：本研究以免疫組織化學染色法分析與細胞黏合結構相關的蛋白質如E-cadherin, α-catenin、β-catenin、γ-catenin及p120ctn蛋白，並以甲基化特殊聚合酶連鎖反應（Methylation Specific-PCR; MS-PCR）分析E-cadherin基因啟動子甲基化後對mRNA及E-cadherin蛋白表現的影響及其與臨床因子之間的相關性。
結果：本研究發現E-cadherin蛋白的表現與腫瘤的分化呈現顯著相關（p < 0.05），但與腫瘤分期無顯著差異；α-catenin的表現與腫瘤的分期之間呈現有意義的差異，但其表現量卻隨著腫瘤分期愈高而增加，然而與細胞的分化卻不具相關性；p120ctn在本研究中的表現與腫瘤的分期及細胞分化皆有顯著相關性；本研究再分析E-cadherin與α-catenin、β-cateninp及120ctn蛋白質表現的相關性，發現這些分子彼此之間不具任何顯著相關性；E-cadherin基因啟動子甲基化在本研究中被發現會影響mRNA的表現，而mRNA與E-cadherin蛋白的表現亦呈現有意義之相關性，因此直接分析E-cadherin基因啟動子甲基化與E-cadherin蛋白的表現，發現甲基化情形會影響E-cadherin蛋白質的表現量；但與臨床因子相比較並無任何相關性。
結論：本研究中，p120ctn與腫瘤分期及細胞分化的惡性度關係最密切。雖然有些結果與其他文獻的研究結果發現不盡然吻合，然而綜合大部分的研究，還是認為E-cadherin及其複合物可做為預測腫瘤潛在性轉移預後的因子，雖然仍無法取代目前病理組織學所採用的腫瘤分期、細胞分化的惡性度等分類。E-cadherin基因啟動子的甲基化研究讓我們對腫瘤轉移的病理生理學有更深的認識，並提供了早期偵測癌症的一種指標，以及發展去甲基製劑作為治療癌症的另類選擇。

關鍵字

E-cadherin ； catenin ； 甲基化

並列摘要

OBJECTIVE: Transitional cell carcinoma (TCC) of the urinary bladder is the ninth most common malignancy in the world. Bladder cancer is characterized by a diverse biological behavior, in which acquisition of the metastatic capacity is clinically most relevant. Although tumor grade and stage have been the cornerstones of predicting outcome for bladder cancer, a variety of tumor markers and prognostic factors have recently been used to study the progression of transitional cell malignancy. Recently, the role of cell adhesion molecule expression in tumor invasion and metastasis has received significant consideration as a potential indicator of the metastatic phenotype in a variety of epithelial malignancies. E-cadherin is the major cadherin molecule expressed by epithelial cells. Cadherin formed complexes with cytoplasmic proteins, called catenins, which comprise three molecules including α-, β-, γ- catenin and the armadillo repeat protein, p120ctn. The linkage of E-catenin and catenin is necessary for the formation of strong intercellular adhesion. Previous studies have demonstrated that decreased expression of E-cadherin is associated with high grade and advanced stage in malignancies. E-cadherin and catenin complexes have also been thought to be a predictor for occult or microscopic metastasis of TCC. Hypermethylation of E-cadherin gene promotor had been thought to play an important role for loss of expression and occurred in the early stage of cancer development. The objective of the study was to investigate the expression of E-cadherin and catenin complexes and the correlation with clinical and pathological parameters of bladder cancer. We also investigate the hypermethylation of E-cadherin gene promoter and correlate these results with E-cadherin mRNA, E-cadherin and pathological and clinical parameters.
RESULTS: From our studies, expression of E-cadherin was not related to tumor stage, but related to tumor grade (p < 0.05). Expression of α- catenin was high in higher tumor stage and not related to tumor grade. Correlation of expression of p120ctn with tumor stage and grade showed significantly difference. Correlation among E-cadherin, α-catenin, β-catenin and p120ctn did not show significantly difference. We also found hypermethylation of E-cadherin gene promoter was correlated with E-cadherin mRNA and E-cadherin protein. But hypermethylation of E-cadherin did not correlated with clinical and pathological parameters.
CONCLUSIONS: From our study, p120ctn was a better prognostic factor. Hypermethylation of E-cadherin gene promoter is also thought to be important for expression of E-cadherin and can be a predictor for early cancer. Work is in progress to establish whether normal expression of E-cadherin and catenin can be enhanced by gene transfer or biological therapy to induce a less invasive and metastatic phenotype.

並列關鍵字

E-cadherin ； catenin ； hypermethylation

參考文獻

Amling CL: Diagnosis and management of superficial bladder cancer. Curr Probl Cancer 2001;25(4):219-78.

Aono S, Nakagawa S, Reynolds AB, Takeichi M: p120(ctn) acts as an inhibitory regulator of cadherin function in colon carcinoma cells. J Cell Biol 1999;145(3):551-62.

Ashida K, Terada T, Kitamura Y, Kaibara N: Expression of E-cadherin, alpha-catenin, beta-catenin, and CD44 (standard and variant isoforms) in human cholangiocarcinoma: an immunohistochemical study. Hepatology 1998;27(4):974-82.

Barth AI, Nathke IS, Nelson WJ: Cadherins, catenins and APC protein: interplay between cytoskeletal complexes and signaling pathways. Curr Opin Cell Biol 1997;9(5):683-90.

Baylin SB, Herman JG: DNA hypermethylation in tumorigenesis: epigenetics joins genetics. Trends Genet 2000;16(4):168-74.