口腔癌高居台灣地區最常發生的癌症前五位，更是國人男性死亡率增加最快的癌症之一。口腔癌細胞容易透過侵襲、轉移，導致病情快速惡化，而基質金屬蛋白?(Matrix metalloproteinases; MMPs) 的活性與癌細胞的轉移能力息息相關；因此，有效地抑制 MMPs 的作用極可能是遏止癌細胞轉移的重要策略。轉錄因子 FOXO1具有調節細胞週期與細胞凋亡等生理功能，而類黃酮物質之一的槲皮素具有抑制癌細胞生長的功效，但二者於口腔癌細胞轉移的作用和機制尚不明確；因此，本研究欲探索槲皮素抑制口腔癌細胞轉移的功效與轉錄因子 FOXO1 可能扮演的角色。研究結果顯示，槲皮素劑量性地 (0-20 μM) 抑制 HSC-3 與 FaDu 口腔癌細胞株的爬行與侵襲，伴隨著 FOXO1 表現量的增加，而 MMP-9 與 MMP-2 的表現量與活性，以及 HSC-3 在 3D matrigels 的細胞分支則明顯地減少。以 RNA 干擾術降低 FOXO1 表現量時，HSC-3 之爬行加速，MMP-9 與 MMP-2 的表現量與活性亦增加；過度表現 FOXO1 時，HSC-3 細胞的爬行與侵襲能力、以及 MMP-9 與 MMP-2 的表現量與活性則明顯減低。再者，高侵襲轉移口腔癌檢體的 FOXO1 mRNA 平均表現量顯著地低於正常組織，顯示 FOXO1 參與口腔癌細胞轉移的調節作用。FOXO1 siRNA 減弱槲皮素對於 MMP-9 與 MMP-2 的抑制功效，而 FOXO1 cDNA 則明顯地增強槲皮素對於 MMP-9、MMP-2及 HSC-3 細胞轉移與侵襲的抑制作用。綜合以上結果，槲皮素抑制口腔癌細胞轉移的功效，部分源自於 FOXO1 的調節作用。
Epidermal growth factor receptor (EGFR) gene is frequently overexpressed in oral squamous cell carcinoma (OSCC), which is often associated with unfavorable prognosis and poor survival. Oral cancer is one of the most common cancers in Taiwan, whose mortality rate increases significantly over the last decade. Earlier studies showed that enhanced activity of matrix metalloproteinases (MMPs) was correlated with cancer cell invasion; therefore, effectively suppressing could presumably prevent metastasis. Quercetin, one of the most common natural flavonoids, has been reported for its anti-tumor property, whereas the underlying mechanism in the suppression of oral cancer is unclear. Our previous work demonstrated that quercetin inhibited cell growth through FOXO1 transcription factor in EGFR-overexpressing oral cancer. In this study, we attempted to examine the anti-metastatic potential of FOXO1 in oral cancer, and investigate the role of FOXO1 in quercetin-induced suppression in cell invasion. Our results showed that quercetin dose-dependently suppressed cellular migration and invasion in EGFR-overexpressing HSC-3 and FaDu oral cancer cells. In HSC-3 cells, quercetin significantly inhibited cellular branching in 3D matrigels. In addition, quercetin down-regulated the expression and activity of MMP-9 and MMP-2 with a concomitant induction of FOXO1 activation. RNA interference-mediated depletion of FOXO1 enhanced migration as well as the expression and activity of MMP-9 and MMP-2 in HSC-3, whereas FOXO1 overexpression inhibited otherwise. Furthermore, FOXO1 knockdown reversed quercetin-reduced MMP-2 expression, whereas FOXO1 overexpression reinforced the anti-metastatic effect of quercetin. Analysis of FOXO1 expression in human oral cancer specimens revealed that FOXO1 levels were lower than those of normal tissue counterparts, further indicating that FOXO1 participates in metastasis in oral cancer. Taken together, our data indicate that quercetin is an effective anti-metastasis agent, and that FOXO1 is a crucial regulator in quercetin-induced suppression in invasive oral cancer.
