薯蕷皂素抑制乳癌細胞增生之角色探討

Diosgenin是類固醇皂元（Steroidal sapogenin）的一種，結構與雌激素類似，文獻指出它具有抗發炎、降血脂的功能，且能抑制人類癌症細胞的增生，最後誘導凋亡的產生。我們用diosgenin處理乳癌細胞Hs 578T及MCF7，並探討其抑制乳癌細胞增生之機轉。結果發現diosgenin會造成乳癌細胞Hs 578T及MCF7的DNA產生損傷，其中包含了雙股斷裂。透過西方墨點法觀察到在diosgenin處理之下會活化chk1、p53及p21，進而抑制下游細胞週期蛋白cyclin D1、Cdk4，並使細胞週期停在G1時期。同時我們探討diosgenin是否會對DNA雙股斷裂修補系統中的非同源終端黏合修補(Non-homologous end-joining repair，以下簡稱NHEJ)產生影響。結果發現diosgenin不影響NHEJ系統中修補蛋白ku70及ku80的表現。另外，我們將作為抗癌藥物的蛋白質激酶C抑制劑UCN-01與diosgenin共同處理乳癌細胞，發現共同處理diosgenin與UCN-01會增加對乳癌細胞存活的抑制效果，且透過抑制cyclin D及cdk4使細胞週期停在G1時期。因此我們推測UCN-01與diosgenin可能具有協同作用去抑制乳癌細胞的增生，但詳細機轉我們仍不清楚。此外加入UCN-01會降低乳癌細胞株Hs 578T中NEHJ修補蛋白ku80的表現量，這是否與UCN-01及diosgenin的協同作用有關，仍需要進一步去透過實驗證實。

Diosgenin, a steroidal sapogenin, is similar to estrogen. It has been reported to have anti-inflammation and hypolipidemic effects, and it can inhibit proliferation and induce apoptosis in several human cancer cells. The mechanisms of anti-proliferation induced by diosgenin in breast cancer cell are not understood, we therefore treated breast cancer cell lines Hs578T and MCF7 with diosgenin. In our experiments, diosgenin caused DNA damages including double-strand break in breast cancer cell lines Hs578T and MCF7. We discovered that diosgenin reduced the expressions of cyclin D1 and Cdk4 protein, and induced G1 phase cell cycle arrest through activations of chk1, p53 and p21. We want to know whether diosgenin can affect non-homologous end-joining repair (NHEJ repair) when DNA double-strand break occurs. In outcome, diosgenin don’t influence the expressions of ku70 and ku80 in NHEJ enzymes. In addition, we add the protein kinase inhibitor (UCN-01) and diosgenin to treat breast cancer cell lines. This study suggests that breast cancer cells treated with diosgenin and UCN-01 reduced cell viability and induced G1 phase cell cycle arrest through the inhibition of cyclin D1 and cdk4. We infer that UCN-01 and diosgenin may have synergy to inhibit the proliferation of the breast cancer cells, but the detailed mechanisms are not understood. The addition of UCN-01 reduced the expression of ku80 in NHEJ enzyme in breast cancer cell Hs578T. That whether is related to synergy of UCN-01 and diosgenin still is needed to confirm.