幽門螺旋桿菌感染誘導之胃上皮細胞抗細胞凋亡分子分析與機制探討

Analysis of anti-apoptotic factors induced by Helicobacter pylori infection of gastric epithelial cells

劉宛欣(Wan-Hsin Liu)

指導教授 ： 周綠蘋教授

國立臺灣大學/醫學院/生物化學暨分子生物學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.02976

摘要

胃癌是世界上最常見的癌症之一。目前最受科學家注意的是幽門螺旋桿菌感染而造成的胃癌。儘管近年來有許多研究著重於幽門螺旋桿菌其致病機轉的探討，幽門螺旋桿菌導致胃癌發生的詳細機制卻仍還不是完全清楚。由先前的研究指出，幽門螺旋桿菌的寄生將會導致宿主胃部黏膜的發炎，由目前的研究顯示其主要原因之一是二號環氧化酶 (COX-2) 被幽門螺旋桿菌誘導表現所致。二號環氧酶為一製造前列腺素 PGE2 之酵素，除了參與發炎反應外，尚有研究指出，COX-2 以及 PGE2 可能參與抗細胞凋亡反應，然而 COX-2 及 PGE2 是如何參與或調控抗細胞凋亡反應目前尚不清楚。本論文利用幽門螺旋桿菌感染胃上皮細胞 AGS 確立幽門螺旋桿菌的感染可以促進抗細胞凋亡分子「存活素」的大量表現，並發現 COX-2 及 PGE2 均參與減少存活素泛素化之調控，為更進一步研究 COX-2 對存活素之調控，本論文以 shRNA 或者選擇性抑制 COX-2 之藥物 Celecoxib 處理幽門螺旋桿菌感染之 AGS，均有促使 AGS 中存活素下降之趨勢，證明，幽門螺旋桿菌確可以透過 COX-2 的表達以及其下游分子 PGE2 之產生來抑制存活素的泛素化，並減少其降解，因此 COX-2 可能是透過其和其下游分子 PGE2 之作用來穩定存活素，進而行使抗細胞凋亡之功能。除此之外，為了探討存活素是否確實在細胞質中行抗細胞凋亡反應，本論文更使用螢光顯微鏡觀察存活素在細胞中之位置，可觀察到處理幽門螺旋桿菌後，存活素確有自細胞核移至細胞質之現象，因此存活素可能在幽門螺旋桿菌感染後行使抗細胞凋亡之功能。本論文首度證明了幽門螺旋桿菌確有透過 COX-2 以及PGE2 來穩定存活素之現象，並證明了幽門螺旋桿菌可以透過引起存活素在細胞中位置之改變，因此可以產生抗細胞凋亡反應，進而導致胃癌產生。

關鍵字

幽門螺旋桿菌 ； 胃癌 ； COX-2 ； 存活素 ； 抗細胞凋亡

並列摘要

Gastric cancer is one of the most common cancers and Helicobracter pylori (H. pylori) infection has been widely accepted as a major factor of gastric cancer. Although many efforts have been made to study H. pylori, the exact mechanisms of gastric carcinogenesis induced by H. pylori remain unclear. Past studies have reported that H. pylori infection results in the over-expression of cyclooxygenase-2 (COX-2). It has been reported that both COX-2 and its downstream factor PGE2 may be involved in the regulation of anti-apoptosis, but the exact mechanisms is unclear. This thesis shows that H. pylori infection not only induces the over-expression of COX-2 but also results in the over-expression of anti-apoptotic factor, survivin, in gastric epithelial cells, AGS. In addition, both COX-2 and PGE2 stabilize survivin by decreasing the ubiquitination of survivin. Moreover, a significant decrease of the amount of survin is observed when either the shRNA of COX-2 or the selective COX-2 inhibitor, celecoxib, is used to inhibit the COX-2 induced by H. pylori infection. These results show that H. pylori infection can induce a great amount of survivin by over-expressing COX-2 and PGE2, which stabilize survivin. In addition, by using immunofluorescent microscopy to examine the location of survivin, it is observed that survivin translocates from nucleus to cytoplasm after H. pylori infection. This result implies that H. pylori can change the location of survivin so that survivin could execute anti-apoptosis. To my best knowledge, this is the first work that shows the infection of H. pylori induces a great amount of survivin, which is stabilized by COX-2 and PGE2, and induces the translocation of survivin.

並列關鍵字

Helicobacter pylori ； gastric cancer ； COX-2 ； survivin ； anti-apoptosis

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