闡明百里醌對口腔癌抑制癌幹性與致癌性的分子機制

口腔癌是台灣死亡率排名第五的惡性腫瘤，其中口腔鱗狀細胞癌（oral squamous cell carcinoma，OSCC）佔口腔癌罹患率90%。現今癌症治療已有顯著進展，但患者經常死於該疾病與併發症，在5年內的存活率不到50%。癌症幹細胞(cancer stem cells，CSCs)近年來被廣泛的研究，它具有自我更新的能力及高度轉移能力並與抗藥性相關，因此有文獻指出減少癌症幹細胞可以有效改善預後不良的現象。在眾多研究發現植物萃取的天然化合物可以標靶癌症幹細胞故本研究欲評估天然化合物百里醌（thymoquinone，TQ）對降低口腔癌幹細胞（oral carcinoma stem cells，OCSCs）的腫瘤幹性標記表達、細胞增殖能力、轉移能力和化學抗性的影響，並探討其分子作用機制。我們的研究結果顯示百里醌下調口腔癌細胞和口腔癌症幹細胞的癌症幹細胞標記ALDH1活性及CD44表達，並在幹細胞球體試驗中百里醌以濃度依賴性方式抑制口腔癌幹細胞的細胞存活和自我更新，以及抑制軟瓊脂細胞群落生成能力和細胞遷移。最重要的是百里醌改善傳統化療藥氟尿嘧啶(fluorouracil，5-FU)和順鉑(cisplatin)的化學敏感性。在機制方面發現百里醌藉由抑制Oct-4、SOX2、Nanog、Nestin與ABCG2表達降低癌幹性，還可以下調上皮間質轉化(epithelial-mesenchymal transition，EMT)的標記物ZEB1、Snail、Slug及Twist，降低口腔鱗狀細胞癌和口腔癌症幹細胞的轉移能力。基於上述，這項研究證明百里醌能標靶口腔癌症幹細胞，並作為化療藥物氟尿嘧啶或順鉑的輔助劑。

Oral cancer is the fifth mortality rate of malignant tumors in Taiwan and over 90% of oral cancer patients were oral squamous cell carcinoma (OSCC). Despite remarkable progress in cancer therapy, the prognosis of OSCC remains dismal because more than 50% of patients die of this disease within 5 years. Over the past decades, cancer stem cells (CSCs) have been extensively researched as it has the ability to self-renew, metastasize and is associated with the chemo-resistance. Therefore, the literature suggested that reduction of CSCs may be an effective approach to improve the poor prognosis. Various phytometabolites have been tested to target CSCs in numerous researches, and we selected the natural compound thymusquinone (TQ) in the current study. We aimed to evaluate its effects on reduction of the expression of cancer stemness markers, cell proliferation, metastatic and chemo-resistance of oral CSCs (OCSCs), as well as its molecular mechanism of action. Our results showed TQ treatment suppressed the expression levels of stemness markers ALDH+ and CD44+. In tumor sphere-formation test, TQ inhibited the cell survival and self-renewal of OCSCs in a dose-dependent manner. Besides, treatment of TQ downregulated the abilities of soft agar colony formation, migration. Most importantly, TQ improved the chemosensitivity of OCSCs to the traditional chemotherapy drugs 5-fluorouracil (5-FU) and cisplatin. As for the molecular mechanism, TQ repressed cancer stemness through inhibition of Oct-4, SOX2, Nanog, Nestin, ABCG2 expression and diminish the expression of various epithelial-mesenchymal transition (EMT) markers to reduce the ability of migration in OSCC cells and OCSCs. Collectively, this study suggested that TQ may target OCSCs and be used as an adjuvant to the chemotherapy drugs 5-FU or cisplatin.