- 學位論文
探討Snail作為攝護腺癌復發預測因子及轉移治療標的之研究
Study the role of snail as a predictor of prostate cancer recurrence and therapeutic target of metastasis
摘要
據衛生署統計，西元二○一四年中華民國男性攝護腺癌的死亡率排名是男性癌症十大死亡原因的第七位。攝護腺癌患者主要的死亡原因是對於轉移性非雄激素依賴型攝護腺癌(androgen-independent prostate cancer, AIPC)的生長未能控制。 上皮間質轉化 (epithelial-mesenchymal transition, EMT)是一個癌細胞侵犯和轉移的過程，其特徵為和細胞間接附分子的喪失。Snail為上皮間質轉化的主要轉錄因子之一。然而它在攝護腺癌的角色並不清楚。 在研究的第一部份，我們發現在病理期數第二期之攝護腺癌病人腫瘤組織有較高的snail表現量與其術後復發有顯著相關；且可為單獨的預測因子。所以第二期的攝護腺癌病人且腫瘤組織有較高的snail表現量，應建議做術後的輔助治療來避免早期復發。 蛇床子素是從傳統中藥天然香豆素衍生物中提取出來，已知有許多研究，其中包括有抗發炎、抗氧化、抗過敏、抗骨質疏鬆、抗肝炎和抗癲癇的功能。它也涉及多種腫瘤抑制的功效，但蛇床子素對於非雄激素依賴型攝護腺癌的療效則是未知的。 在研究的第二部分，我們發現蛇床子素可以有效阻止癌細胞上皮間質轉化進而抑制非雄激素依賴型攝護腺癌細胞移動和侵犯的能力及在活體動物中抑制其轉移的能力。 機制探討方面，我們發現蛇床子素經由抑制TGF-β->Akt->MAPKs-> snail的訊號傳遞，減少snail和去氧核醣核酸 (DNA)的結合能力進而增加E-鈣黏蛋白(E-cadherin)表現而阻止了 EMT的進展。此外，攝護腺癌細胞在蛇床子素處理下亦可造成microRNA-23a-3p 的表現明顯下降。我們發現大量表現miRNA-23a-3p於癌細胞可明顯抑制其 E-cadherin 3'UTR 冷光報導基因系統的活性以及E-cadherin表現，進而降低了蛇床子素抑制癌細胞移行的能力。而直接抑制細胞中miRNA-23a-3p表現也可降低非雄激素依賴型攝護腺癌細胞侵犯的能力。 在臨床方面，病理期數後期（第三和四期）的攝護腺癌患者，其腫瘤組織snail表現量比病理期數早期(第II期)患者較高。且snail表現量較高的攝護腺癌患者其生存率亦較差。 綜合來說，我們發現蛇床子素可經由分子和表觀遺傳(epigenatic)調控方式來調節癌細胞上皮間質轉化能力，進而抑制腫瘤轉移的能力，藉此將可對攝護腺癌的治療提供新的曙光。
並列摘要
According to the statistics of Department of Health, R.O.C., the mortality rate ranks 7 among the top 10 cancers in 2014. The failure to control metastatic androgen-independent prostate cancer (AIPC) growth is the main cause of death in prostate cancer patients. Epithelial-mesenchymal transition (EMT) is a process by which cancer cells invade and migrate, and is characterized by loss of cell-cell adhesion molecules. Snail, a master transcription factor of EMT, however, its role in prostate cancer is not as widely reported. In the first study, we found that high snail image score was significantly correlated with worse recurrence-free survival in patients at stage T2 after radical prostatectomy. In patients with pathological localized prostate cancer and a high snail image score in cancer tissue, adjuvant therapy might be suggested to prevent early biochemical failure. Osthole, a natural coumarin derivative extracted from traditional Chinese medicines, is known to have many biological applications, including anti-inflammation, anti-oxidation, anti-allergic, anti-osteoporotic, anti-hepatitic, and antiseizure. It is also associated with multiple tumor-suppressing activities, but the effects of osthole on AIPC are largely unknown. In the second study, we found that treatment with osthole inhibited the migration/invasion of AIPC cells in vitro and metastasis in vivo by suppressing the EMT. Mechanistic investigations revealed a signal cascade, namely, osthole inhibiting TGF-β->Akt->MAPKs->snail, in which osthole reduced Snail-DNA-binging activity and upregulated E-cadherin expression and subsequently blocked EMT progression. Moreover, microR-23a-3p (miR-23a-3p) was predominantly downregulated after osthole treatment. Ectopic miR-23a-3p expression significantly suppressed E-cadherin 3' untranslated region (UTR) luciferase reporter activity and E-cadherin expression, and relieved the motility suppression imposed by osthole treatment. Furthermore, inhibition of miR-23a-3p in AIPC cells decreased the invasive abilities. Clinical samples indicated that snail was expressed at higher levels in patients with prostate cancer at advanced pathological stages (III and IV) compared to those at an early pathological stage (II). Higher snail expression levels were correlated with worse survival rates. Taken together, our results provide new insights into the role of osthole-induced molecular and epigenetic regulation in suppressing EMT-mediated tumor metastasis.