臺灣博碩士論文加值系統

中文摘要（Chinese abstract）
在許多以動物為模式的實驗結果顯示：多食用豆類能減少腫瘤細胞的數目及發生，而genistein在豆類中具有很高的濃度，是已被認為具有抑制癌細胞生長的成分，但genistein如何降低細胞的存活率仍是大家關注的焦點。目前已知genistein是tyrosine kinase及topoisomeraseⅡ的抑制劑，能影響細胞的增生與分化及調控計畫性死亡（apoptosis）但在細胞週期上影響如何呢？首先，我們探討genistein是否對細胞具有細胞毒性且在細胞週期上是否會有影響，於是我們利用不同濃度的genistein處理RKO細胞，我們發現細胞的存活率會隨著藥物的濃度增加而降低，而以流式細胞儀來分析處理藥物後的細胞，發現處理genistein的細胞會停留在G2/M期，隨著藥物處理時間的增長，停留在G2/M期的細胞數目增多，同時我們也觀察到停留在G2/M期的細胞經過一段時間後便會恢復細胞週期的進行。因流式細胞儀無法分出細胞是停留在G2期或M期，我們以吉氏染劑（Giemsa stain）染色，發現細胞染色體濃縮聚集的數目並沒有因genistein的處理而增加，可知細胞為停留在G2期。且在處理genistein後，我們對細胞中cyclin B、cdc2的表現量及cyclin B/cdc2複合物的活性進行分析。實驗結果發現cyclin B、cdc2的表現量並沒有改變，但cyclin B/cdc2複合物的活性卻隨著genistein處理的時間增長而降低活性，由此結果更能佐證細胞是停留在G2期而導致無法順利進行細胞分裂，因而降低細胞增生的能力。我們知道當細胞停留在G2期可能對於游離輻射相當的敏感，於是我們觀察genistein及游離輻射的共同處理對細胞所造成的影響。首先，我們同時處理genistein及游離輻射， 8小時後進行clonogenic surivival assay及細胞週期的分析，顯示在照射的同時才處理genistein並不能顯著的增加細胞輻射敏感性，且細胞停留在G2期的數目並沒有增加。若在照射游離輻射前先處理genistein一段時間，發現細胞的存活率比單獨照射游離輻射時減少達2-4倍之多，可知前處理genistein可增加細胞的輻射敏感度。

英文摘要（English abstract）
Experiments in animal models of carcinogenesis suggest that soy consumption decreases tumor number and incidence. Genistein, an isoflavone which is present in soy at high concentrations, has been considered to be the primary antitumor constituent in soy. Up to now, studies on the biological effects of the genistein are quite limited. In this work, we investigated the biological responses of cells when exposed to genistein. First, we examined whether genistein could produce cytotoxic in cells. RKO cells were treated with various concentrations of genistein for 8 hours. We find out that dose-dependent cytotoxic effect and time-dependent cytotoxic effect were observed. Then we examined the effect of genistein on the cell cycle progression by flow cytometry. The results show that genistein induced G2/M arrest in RKO cells but it is reversal after several hours later. Since cells arrest in G2/M phase we investigated whether cyclin B and cdc2 level change and the cyclin B/cdc2 complex activity change after genistein treatment. It is found that cyclin B and cdc2 level were not affected by genistein. However, there is a time-dependent effect in cyclin B/cdc2 complex activity. It is concluded that genistein may block cell cycle progression at G2 phase of RKO cells.
To investigate whether the delay of G2 phase relates to the repair efficiency of cell damage, we therefore irradiated the genistein pretreated and co-treated cells and estimated the survival fraction. The results show that genistein more enhanced the radiosensitivity of pre-treated cells. But the G2 phase fraction of cells after treating both genisten and X-ray irradiation whatever pre-treated or co-treated were not enhanced.

內容（Contents）
中文摘要 （Chinese abstract）…………………….……..1
英文摘要 （English abstract）…………………….……...3
引言（Introduction）……………………………………..…5
材料與方法（Materials and Methods）…………………12
結果（Results）……………………………………………21
討論（Discussions）………………………………………29
參考文獻（References）………………………………… 35
附圖及附表（Figures and Tables）………………….…. 42

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