| 摘要: | 自民國71年起，癌症一直高居我國十大死因的第一位，癌症的形成來自環境、飲食與生活習慣等各種因素，而癌症的治療方式有外科手術切除、局部放射線照射、以及使用抗癌藥物的化學治療，但治療效果與預後通常不盡理想，因此研發療效好且副作用少的抗癌藥物一直是新的藥物開發重點。表沒食子兒茶素沒食子酸酯（epigallocatechin gallate，EGCG）是綠茶中的成分之一，具有非常好的抗癌作用。然而，至今尚未有誘導對人類腎上腺癌細胞株（NCI-H295）產生凋亡作用與分子機制及EGCG信息傳遞的路徑的最新報告。本研究的目的是探討EGCG對NCI-H295細胞株的抗癌效果及分子機制。結果顯示，EGCG可抑制NCI-H295細胞之生長，且呈劑量和時間之依存性，對人類胚胎正常皮膚細胞株（Detroit 551）則具很低之毒性。
以20 ?慆的EGCG給與NCI-H295細胞後，流式細胞儀分析結果顯示在粒線體膜電位下降和細胞內游離Ca2+的濃度增加的作用具時間之依存性；西方墨點法檢測發現 Bcl-2、Bcl-xl、xIAP、cIAP和Hsp90等蛋白的表現量降低，而Bad、Bax、Fas/CD95、cytochrome c、Apaf-1、AIF、GADD153和caspase-3、-7、8與-9等蛋白的表現量則增加。實驗也證明EGCG可增加caspase-8、-9與-3的活性並具時間依存性；若預先以caspase-8、-9與-3的抑制劑處理，caspase-8、-9與-3三者之活性降低而細胞之存活率上升。
根據所有實驗結果，證實EGCG對人類腎上腺癌細胞株（NCI- H295）可經由caspase-dependent pathway和caspase-independent pathway誘導細胞凋亡，未來可開發為一個對正常細胞具低毒性的治療腎上腺癌的有效藥物。
Cancer has becoming the first of the ten major causes of death since 1982. There are many reasons such as surroundings, eating or life style will result in cancer. Nowadays, surgical resection, radiotherapy and chemotherapy is the major treatment. However, the effect of treatment and outcome are not perfect. Therefore, investigate an effective and fewer side effect anticancer drug is the task of top priority. (-)-Epigallocatechin-3-gallate (EGCG) is a major constituent of green tea, and has been identified as an excellent anti-cancer agent. Nevertheless, there are no reports to date about the molecular mechanisms and signal pathways of EGCG on the induction of apoptosis in human adrenal NCI-H295 cancer cells. The purpose of this study was to investigate the anti-cancer effect and molecular mechanisms of EGCG on human adrenal NCI-H295 cancer cells. The results showed that EGCG induced growth inhibition in a dose- and time-dependent manner. Beside, it exerts low cytotoxicity on Detroit 551 normal human embryonic skin cell. When NCI-H295 cells were treated with 20 ?嵱 EGCG, the mitochondrial membrane potential decreased and intracellular free Ca2+ increased in a time-dependent manner as analysed by flow cytometry. EGCG decreased the protein levels of Bcl-2, Bcl-xl, xIAP, cIAP and Hsp90, increased the protein expression of the Bad, Bax, Fas/CD95, cytochrome c, Apaf-1, AIF, GADD153 and caspase-3, -7,-8 and -9 as observed by Western blotting examination. EGCG promoted caspase-8, -9 and -3 activities in a time-dependent manner. However, cells pretreated with inhibitors of caspase-8, -9 and -3, led to a decrease in caspase-8, -9 and -3 activities and an increase in the percentage of viable cells. Based on the above findings, it was confirmed that EGCG could induce human adrenal NCI-H295 cancer cells apoptosis through caspase-dependent pathway and casepase-independent pathway. It may be a low cytotoxicity drug candidate for the treatment of human adrenal cancer in the future. |
