TIMP3 啟動子甲基化與口腔癌轉移之相關性探討

在台灣，口腔癌排在十大癌症死因第五位且是常見的頭頸癌疾病之一，而原發腫瘤失去控制及淋巴結的轉移則是口腔癌病人死亡的主因。Tissue inhibitor of metalloproteinase-3 (TIMP3) 為 TIMP 家族的一員，當分泌之後會結合到細胞外基質並抑制腫瘤生長、血管新生、爬行及侵襲的能力。由過去文獻發現許多抑癌基因在癌症中都有甲基化的現象，但有關 TIMP3 甲基化在口腔癌的研究卻很少被提到，因此引起我們的興趣想探討 TIMP3 甲基化與基因表現在調控口腔癌轉移中所扮演的角色。首先利用 pyrosequencing 證實在口腔癌細胞株中，TIMP3 啟動子 CpG island 的甲基化程度比正常口腔細胞高，且 CpG island 的甲基化會影響轉錄因子 Sp1 與 TIMP3 啟動子結合而抑制 TIMP3 的表現。我們也證實 TIMP3 的表現主要是受到甲基轉移

Oral cancer is the most common head and neck malignancy, and the fifth leading cause of cancer deaths in Taiwan. Failure to control the primary cancer and lymph node metastasis are the main causes of death among patients. Tissue inhibitor of metalloproteinase-3 (TIMP3), a member of the TIMP family, is the only substance that can bind with the ECM and suppress cancer cell growth, angiogenesis, migration and invasion. However, little is known about whether abnormal expression and promoter methylation of TIMP3 facilitates oral cancer metastasis. In this study, DNA methylation of the TIMP3 CpG island were assessed using pyrosequecing. The results shown that TIMP3 CpG island methylation levels were higher in most oral cancer cell lines compared with normal cell lines. Furthermore, suppression of TIMP3 transcription by DNA methylation involves inhibition of transcription factor Sp1 binding to the TIMP3 promoter. Moreover, silencing of DNMT1 or DNMT3B increased expression of TIMP3. Functional analyses revealed that overexpression of TIMP3 reduced the migration and invasion in oral cancer cells and inhibited lymph node metastasis in vivo. TIMP3 also regulated epithelial–mesenchymal transition (EMT) by increasing expression levels of the epithelial markers (E-cadherin and ZO-1) and decreasing expression levels of the mesenchymal markers (snail, twist, vimentin and fibronectin). In conclusion, these results suggest that suppression of TIMP3 by DNA methylation contributes to oral cancer metastasis.