沒食子酸透過誘發細胞週期停止與細胞凋亡抑制乳腺癌細胞生長

根據衛生署統計，國人十大死因中惡性腫瘤位於第一，而乳癌在女性癌症死亡統計排行第四位，可見乳癌對於女性國人的壽命是很嚴重的問題。造成乳癌死亡的主要因素，是由於乳癌細胞的生長快速且具有高度的轉移(High metastasis)特性，因此開發相關的抑制癌症藥物與治療乳癌方法一直是相當重要的課題。沒食子酸(gallic acid, GA)是一種普遍存在且含量豐富的多酚，已被證實有抗氧化能力、抗腫瘤能力、抗病毒、抗細胞突變等功能。然而，目前對於沒食子酸是否能影響人類乳腺癌細胞的機制仍有未清楚之處。因此本論文擬從細胞實驗研究觀察沒食子酸對於不同惡性程度的乳腺癌細胞的效應，並進一步研究其作用之分子機制。實驗結果發現，經過24、48小時不同濃度的沒食子酸處理，可發現沒食子酸明顯地誘發乳腺癌細胞株MDA-MB-231與HS 578T細胞株形態上的改變，並可以降低細胞的存活率。接著利用流式細胞儀檢測發現沒食子酸對人類乳腺癌細胞會使細胞週期停滯在G0/G1 期。利用西方墨點法分析蛋白表現量，發現沒食子酸處理會增加調控細胞週期蛋白Cyclin D與CDK 4的蛋白表現量，同時會抑制Cyclin E/CDK 2、Cyclin A/CDK 2的蛋白表現量。進一步實驗結果顯示沒食子酸處理會造成抑制細胞週期蛋白p21Cip1與 p27kip1的蛋白表現量增加。此外，利用西方墨點法進行凋亡相關蛋白表現量的分析結果顯示，沒食子酸處理會導致Bax、Caspase-3的蛋白表現量增加，再利用TUNEL assay也發現凋亡細胞有顯著地增加。綜合上述研究結果，顯示沒食子酸可以抑制人類乳腺癌細胞增生，誘發人類乳腺癌細胞的細胞週期停滯於G0/G1 期和誘發細胞凋亡。因此，沒食子酸對於抑制乳癌的快速生長應有一定的幫助。

Breast cancer is the most frequent neoplasm in women worldwidely. Moreover, the etiology of breast cancer involves a complex interplay of genetic, hormonal, and probably dietary factors. Therefore, investigation of new anti-cancer drugs and therapies is in great need for breast cancer patients. Gallic acid (3,4,5-trihydroxybenzoic acid, GA), an abundant phenolic compound in various natural products, including tea leaves, green tea, grapes, blueberry, has been reported to possess anti-tumoral activity. In this study, we aimed to investigate the anti-cancer effects of GA on breast carcinomas and the underlying mechanisms. Our results revealed that GA siginificantly inhibited cell proliferation and induced apoptosis of breast caner cell lines MDA-MB-231 and HS 578T by using MTT assay and flow cytometry analysis. In addition, GA treatment also induced apoptosis of the 2 breast carcinomas basing on increased sub-G1 phase and DNA fragmentation using flow cytometry analysis and TUNEL assay. Further investigation revealed that GA increased up-regulated protein level of negative cell cycle regulators, p21Cip1 and p27kip1. In conclusion, these findings indicate that GA inhibits cell proliferation, leads to cell cycle arrest at G0/G1 phase and induces apoptosis, which may attribute to up-regulation of p21Cip1 and p27kip1, suggesting that GA should be beneficial to treatment of human breast cancer.