檳榔鹼主要成份arecoline對人類表皮細胞之 致癌機轉的探討

The carcinogenic role of arecoline in human epithelial cells

蔡易珊(Yi-Shan Tsai)

指導教授 ： 鐘育志

共同指導教授 ： 林常申(Chang-Shen Lin)

高雄醫學大學/醫學院/醫學研究所/博士(2008年)

摘要

世界衛生組織國際癌症研究中心(IARC)在2004年公告檳榔是一級致癌物，且嚼食檳榔跟罹患口腔癌有高度相關。在台灣約有超過兩百萬嚼食檳榔者，檳榔對於口腔所造成的病理病兆已經被確立了，但是檳榔對於口腔的致癌分子機轉尚未被明顯地探討。在我們的研究中發現檳榔的主要成分檳榔素(arecoline) 透過抑制p53進一步抑制 DNA修復。我們利用??-H2AX的磷酸化現象，證實它造成DNA的損害。並且也證實檳榔素在KB、HEp-2 與293 細胞中處理24小時內均發現檳榔素啟動細胞DNA損害的訊息傳遞路徑，透過ATM、NBS1、Chk1、Chk2、p53和Cdc25C的磷酸化，導致細胞最後G2/M時期的停滯。同時我們也發現在紫外光照射後 DNA 的修復，在有檳榔素的存在下會明顯受到抑制。而且，p53的表現與其轉錄活性也明顯受到抑制。在分析臨床檢體有嚼食檳榔病人的口腔腫瘤組織發現p53 mRNA表現也是被抑制。因此本研究證實檳榔素造成的口腔上皮細胞的癌化機轉是透過抑制p53與p53參與的DNA修復所致。

關鍵字

檳榔 ； 檳榔素 ； DNA損害 ； DNA 修復 ； p53 ； 人類上表皮細胞

並列摘要

The International Agency for Research on Cancer (IARC) declared that areca nut was carcinogenic to human. Areca nut is the main component of betel quid (BQ), which is commonly consumed in Asia. Epidemiological studies have shown that BQ chewing is a predominant risk factor for oral and pharyngeal cancers. It has been known that areca nut is genotoxic to human epithelial cells. However, the molecular and cellular mechanisms underlying areca nut-associated genotoxicity are not fully understood. Here we showed that arecoline, a major alkaloid of areca nut, might contribute to oral carcinogenesis through inhibiting p53 and DNA repair. We found, on the biological aspect, that arecoline could induce ??-H2AX phosphorylation, a sensitive DNA damage marker, in KB, HEp-2, and 293 cells, suggesting that DNA damages were elicited by arecoline. This phenomenon was supported by the observations of arecoline-induced hyperphosphorylation of ATM, Nbs1, Chk1/2, p53, and Cdc25C, as well as G2/M cell cycle arrest, indicating that a cellular DNA damage response was activated. To explore the possible mechanism accounting for arecoline-elicited DNA damages, we found that arecoline could inhibit p53 by its expression and transactivation function. As a result, the expression of p53-regulated p21WAF1 and the p53-activated DNA repair were repressed by arecoline. Finally, we showed that p53 mRNA transcriptswere frequently downregulated in BQ-associated oral cancer, suggesting that arecoline-mediated p53 inhibition might play a role in BQ-associated tumorigenesis.

並列關鍵字

areca nut ； arecoline ； DNA damage response ； DNA repair ； p53 ； human epithelial cells

參考文獻

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