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  • 學位論文

蘆薈大黃素對於人類乳癌的作用及其機轉之研究

The Effects and Underlying Mechanisms of Aloe-Emodin on Human Breast Cancer

指導教授 : 廖雅芳 曾耀銘
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摘要


蘆薈大黃素(Aloe-Emodin,AE)來自蘆薈和大黃,屬於天然的蒽醌類,能夠在各種癌症中通過多種調節機制進行抗癌作用。本研究使用MCF-7乳腺癌細胞株進行實驗,解析蘆薈大黃素對於人類乳癌的作用及其機轉。MCF-7細胞株屬於賀爾蒙接受體陽性人類乳癌細胞,臨床上在治療賀爾蒙接受體陽性人類乳癌,抗賀爾蒙藥物泰莫西芬(Tamoxifen)扮演非常重要的角色,因此本研究以蘆薈大黃素合併泰莫西芬來研究乳癌的可能療效。結果顯示,在MCF-7細胞中泰莫西芬與蘆薈大黃素具有協同作用,可以明顯降低MCF-7細胞的存活率。在細胞凋亡路徑的分析方面,蘆薈大黃素可以誘導活性氧增加與降低細胞粒線體膜電位,可能有助於泰莫西芬促進MCF-7細胞的凋亡。針對細胞凋亡路徑相關蛋白表現,發現蘆薈大黃素聯合泰莫西芬處理可以調整Bcl-xl、Bim、Bax、cleavage caspase 7及PARP蛋白質的表現量,顯示蘆薈大黃素聯合泰莫西芬可以經由內因性路徑增強細胞凋亡的作用。此外,蘆薈大黃素能夠增進泰莫西芬所抑制ERα活化,以及加強泰莫西芬所抑制ERα陽性乳癌細胞的生長。在細胞增殖的路徑研究,發現在蘆薈大黃素與泰莫西芬處理後,與細胞增殖相關的Ras蛋白、ERK1/2蛋白和磷酸化ERK活性有明顯的降低,也發現在PI3K-Akt-mTOR信號傳導途徑內的PI3K和mTOR的磷酸化明顯降低,顯示蘆薈大黃素的抗癌機制在PI3K/mTOR途徑上扮演一個重要的角色。總結以上結果,蘆薈大黃素可以加強泰莫西芬對於雌激素接受體陽性乳癌細胞的治療效果主要經由兩大途徑:經由雌激素接受體途徑減少癌細胞的增殖作用為第一個途徑;經由加強細胞的凋亡作用為第二個途徑,藉由加強細胞凋亡途徑,減少癌細胞的存活。希望藉由本研究的基礎下,瞭解蘆薈大黃素對泰莫西芬誘導的化學敏感性中的重要性,以利增加癌症患者抗癌成功的機會。

並列摘要


Aloe-emodin (AE) derived from aloe vera and rhubarb, is a nature anthraquinone and exhibits anti-cancer activities via multiple regulatory mechanisms in various cancers. MCF-7 cancer cell was used in this study to analyze the effects and underlying mechanisms of Aloe-Emodin on human breast cancer. MCF-7 cell line belongs to hormone receptor positive human breast cancer. Tamoxifen, an anti-hormonal drug, plays an important role in the treatment of hormone-positive human breast cancer. Therefore, AE and Tamoxifen were used to explore the possible therapeutic effects of breast cancer and potential mechanisms in this study. We found that tamoxifen had synergistic effect with AE in MCF-7 cells. After combined with tamoxifen and AE, the survival rate of MCF-7 cells was reduced significantly. Besides, AE increased reactive oxygen species (ROS) and decreased the mitochondrial membrane potential and may contribute to the apoptosis of MCF-7 cells treated with tamoxifen. AE combined with tamoxifen in MCF-7 cells regulated the expression of Bcl-xl, Bim, Bax, cleavaged of Caspase 7 and poly ADP-ribose polymerase (PARP). It was shown that AE combined with tamoxifen could enhance apoptosis through the intrinsic pathway. Furthermore, AE promoted tamoxifen-inhibited the activation of ERα protein and the growth of ERα-positive breast cancer cells. After AE combined tamoxifen treatment, Ras protein, ERK1/2 protein, and phosphorylated ERK, PI3K and mTOR proteins were decreased in MCF-7 cells. Therefore, AE had a anti-cancer activity via PI3K/mTOR pathway. In conclusion, AE enhanced the therapeutic effect of tamoxifen on estrogen receptor-positive breast cancer cells via two pathways: the first was the reduction of cancer cells proliferation via the estrogen receptor pathway. The second was the induction of cell apoptosis. Under the basis of this study, we had finished the importance of AE in the chemosensitivity induced by tamoxifen to increase the chances of cancer resistance in cancer patients.

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