SOX9在口腔致癌機轉中扮演的角色

Abstract

流行病學研究指出，臺灣地區口腔癌發生與嚼檳榔有密切關係。目前，臺灣地區嚼檳榔人口已高達兩百多萬。根據衛生署癌症登記報告指出，口腔癌在臺灣男性十大癌症中死亡率與發生率皆位居第五位，口腔癌年增率也是臺灣地區年增率最高之癌症。SOX9 (Sry-related HMG box 9)一個參與在胚胎發育過程中很重要的轉錄因子，在許多組織分化中都需要受到SOX9的調控，SOX9在癌症中扮演的角色也逐漸受到重視，例如：肺癌、大腸癌、前列腺癌跟子宮頸癌。先前實驗室研究結果顯示，在口腔癌病患的組織切片中，SOX9的表現量隨著癌化的過程中有上升的趨勢，和患者的腫瘤大小、淋巴結轉移與否、癌症臨床分期有統計上相關。且為影響存活時間的獨立因子。但是其致病機轉到目前仍不明瞭。 本研究首先利用SOX9表現量較少的SAS細胞株送入帶有SOX9序列的質體，使其蛋白大量表現；另外，選擇SOX9表現量較多的Tw2.6細胞株利用shRNA干擾技術專一性抑制SOX9的表現。 結果發現隨著SOX9表現的增加，細胞移行的能力及侵犯的能力都會隨之提高，在專一性抑制Tw2.6細胞株SOX9的表現，則有相反的結果，並且都具有統計意義( p < 0.05 )，但細胞生長的能力卻不會受到影響。在原位接種SAS/SOX9腫瘤細胞的動物模式中,也可以發現SOX9的大量表現可以促使淋巴轉移的現象產生。從微陣列分析的數據中，本實驗挑選了一個被指出在癌細胞中與細胞移動及侵犯能力相關的蛋白Keratin19 (KRT19)，在Tw2.6專一性抑制SOX9的細胞株中，KRT19的表現量有增加的趨勢，我們另外送入專一性抑制KRT19的shRNA，發現當在Tw2.6/shSOX9細胞株中抑制KRT19的表現量，可以回復SOX9抑制後的細胞移行能力及侵犯能力。另外，我們也利用病人的組織切片去做了免疫組織染色，發現在臨床分期較低的病人，KRT19的表現量較多，而臨床分期較高的病人，KRT19的表現量較少，所以我們認為SOX9可能是透過KRT19來調控細胞移行與侵犯的能力。

Epidemiological studies have indicated that the oral cancer incidence in Taiwan is closely related to the habit of betel nut chewing. At present, the population of betel nut chewing has reach over two million in Taiwan. The mortality and incidence of oral cancer are ranked the fifth leading cancer in male, and the annual growth rate of oral cancer is also the highest in Taiwan. SOX9 (Sry-related HMG box 9) is an important transcription factor that plays important roles in embryogenesis and tissue differentiation. Previous studies showed that SOX-9 was significantly higher in oral cancer than that in normal oral mucosa. The expression of SOX-9 was correlated with advanced tumor stage, lymph node metastasis and short survival time. However, the role of SOX9 in oral cancer tumor progression is still unclear. In this study, SOX-9 over-expressed and shRNA stably-transfected cells were established to investigate migration/invasion ability in vitro and tumorigenesis and progression in vivo. We found that alterations in the SOX-9 level in OSCC cell lines positively modulated their invasive ability but not growth. Animal model also showed that SOX-9 overexpression had higher distant lymph node metastasis rate. Microarray analysis of gene expression in SOX-9 knockout TW2.6 cells identified dysregulation of many genes involved in metastasis. In particular, we knock-down KRT19 by shRNA and restored migration and invasion abilities in Tw2.6/shSOX9 cells. The KRT19 expression in OSCC specimens were examined by immunohistochemistry. KRT19 expression is higher in the patients with early stage, and lower in the patients with late stage. These results indicated that SOX9 influences cancer cell migration and invasion capacities through regulating KRT19.