- 學位論文
益生菌之益源質抑制大腸癌細胞株HCT116生長之機制探討
Tumor-suppressive Effects of Biogenic on HCT116 Human Colorectal Cancer Cells
摘要
近年研究發現，大腸癌病患的腸道菌出現生態失衡的狀態，因此可以得知腸道菌與大腸癌的發展有著密切的關連，此外，許多乳酸菌(Lactobacillus)的益源質(Biogenics)已被證實能夠抑制大腸癌細胞的生長，但目前尚未有研究探討同樣為益生菌的酵母菌對於大腸癌的影響。因此本研究欲尋找一種能夠抑制大腸癌細胞生長的益源質-酵母菌萃取物，並進一步探討其中詳細的機制。在本研究中，找出了一種酵母菌萃取物能夠抑制人類大腸癌細胞株HCT116的生長，並將其命名為YE。本研究發現，YE藉由增加活性氧物質 (Reactive oxygen species, ROS)的產生以及耗盡麩胱甘肽還原酵素 (Glutathione, GSH)以增加細胞內的氧化壓力，促進鈣離子流入細胞中，導致粒線體受損而釋放出細胞色素c (Cytochrome c)，並活化下游凋亡蛋白酶-9, -3 (Caspase -9, -3)，使細胞走向細胞凋亡 (Apoptosis)，然而，此路徑可被鈣離子螯合劑-EDTA所抑制。另外，本研究也發現，YE所造成的氧化壓力也會活化Beclin 1蛋白，並增加酸性囊狀胞器(Acidic vesicular organelles, AVOs)的產生，進而引起大腸癌細胞HCT116走向細胞自噬 (Autophagy)。本研究證實，YE同時引起大腸癌細胞HCT116走向鈣離子依賴型細胞凋亡 (Ca2+-dependent mitochondrial apoptosis)以及Beclin 1蛋白所調節的細胞自噬 (Beclin-1-mediated autophagy)。
並列摘要
Recent research has shown that intestinal microflora was changed in colorectal cancer patients suggesting intestinal microflora closely related to the occurrence of colorectal cancer. Besides, some biogenics, which derive from Lactobacillus strains have been demonstrated that have tumor-suppressive effects on colorectal cancer cells. However, there is currently no research on the effects of Saccharomyces on colorectal cancer; thus, this study set out to ascertain a specific biogenic, yeast extract, that has tumor-suppressive effects and further to investigate the underlying mechanisms involved. In this study, an extract derives from Saccharomyces, which is identified and named YE, which has cytotoxicity to HCT116 human colorectal cancer cells. Furthermore, underlying mechanisms were explored. The results showed that YE treatment caused oxidative stress by increased reactive oxygen species (ROS) production and glutathione (GSH) depletion. Afterwards, Ca2+ influx was induced then resulting in an increased [Ca2+]i, which further increased ROS production and caused mitochondrial dysfunction accompanied by the release of cytochrome c, and then triggered a cascade of downstream caspase activation that led to DNA fragmentation followed by apoptotic cell death. However, this pathway could be suppressed by addition of EDTA. Apart from apoptosis, the excessive ROS production also activated Beclin 1, which promoted both apoptosis and autophagy process by activating caspase 9 and increasing the formation of acidic vesicular organelles (AVOs). In conclusion, YE treatment caused cell death in human colorectal carcinoma cell line HCT116 through Ca2+-dependent mitochondrial apoptosis and Beclin-1-mediated autophagy.