口腔上皮細胞長期暴露於檳榔素之癌幹性影響

由於嚼食檳榔的盛行，使得口腔癌為台灣男性癌症發生率及死亡率的第四位。百分之九十的口腔癌為鱗狀細胞癌，其特性為容易復發及轉移，而檳榔促使口腔癌腫瘤化之分子機制仍未知。癌幹細胞對於化學性化療及放射性療法具備阻抗性及導致癌細胞具有高度轉移力，而檳榔於癌幹細胞特性仍未闡明。本研究利用低劑量長時間將檳榔素暴露於口腔上皮細胞，發現口腔上皮長期暴露於檳榔素能增加癌幹細胞標記醛脫氫酶活性、幹細胞標記(Oct4, Nanog, and Sox2)及幹細胞球體形成率。口腔上皮細胞長期暴露於檳榔素之細胞移動性/侵襲性/細胞群落形成能力及活體腫瘤生成力會增強。微型RNA（microRNA，miRNA，miR）是一群約21-25 個核苷酸的內源性非編RNA，可透過抑制標靶基因調控癌幹細胞特性。利用微型RNA微矩陣分析發現長期暴露檳榔素口腔上皮細胞之microRNA-145(miR-145)表現量下降並驗證Oct4及Sox2為miR-145直接標靶基因。過度表現miR-145可反轉長期暴露於檳榔素誘發活體外及活體內腫瘤之生成力。本實驗結果提供檳榔促使口腔癌腫瘤化新模式，冀望能對檳榔嚼食習慣口腔癌病患之治療機制有所幫助。

Due to the popularity of areca use, oral cancer (OC) has become a prevalent disease in Taiwan. OC is currently the 4th most common cancer type and leading cancer mortality in male Taiwanese. Almost 90% of OC is classified as oral squamous cell carcinoma (OSCC), which is characterized by high recurrence and early metastasis. The mechanisms of areca nut induces OSCC tumorigenesis are not well understood. A subpopulation of cells called cancer stem cells (CSCs) possessing stemness properties was shown to enrich after therapy, resulting in the relapse and metastasis of tumors. The impact of areca nut exposure in cancer stemness remained unclear. In this study, low dosage long-term arecoline, a major areca nut alkaloid, treatment models (10 μg/mL, 90-days) in human oral epithelial (OE) cells were used. Long-term treatment of arecoline treatment was found to enhance the ALDH1 activity, stemness markers (Oct4, Nanog, and Sox2) expression, and sphere-forming property in oral epithelial cells. Moreover, long-term arecoline-stimulated OE cells up-regulated migration/cell invasiveness/anchorage independent growth and in vivo tumor growth by nude mice xenotransplantation assay. MicroRNAs (miRNAs)—highly conserved small RNA molecules that regulate CSCs properties depending on its main target genes. Using miRNA-microarray, arecoline down-regulated the expression of microRNA-145 (miR-145) and both Oct4 and Sox2 were identified as the novel targets of miR-145. miR-145 overexpression in long-term arecoline-treated OE cells was found to reduce their in vitro and in vivo tumorigenicity. This study hence attempts to provide novel insight into areca nut-induced carcinogenesis and new strategy for the treatment of OSCC patients with areca nut chewing.