微環境酸化對於腫瘤細胞幹性維持之影響

Effects of Microenvironment Acidification on the Maintenance of Stemness in Cancer Cells

謝宛宜(Wan-Yi Shie)

指導教授 ： 郭生興

共同指導教授 ： 周涵怡(Han-Yi E. Chou)

國立臺灣大學/牙醫專業學院/口腔生物科學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.10366

摘要

腫瘤微環境是影響腫瘤幹性(stem ness)很重要的因子，而腫瘤環境酸化，是腫瘤微環境其中一個特性。在養分缺失的壓力下，腫瘤細胞往往轉向提高醣解作用，再從中間代謝物合成生存所需物質，這現象就是瓦式效應。但是大量走醣解作用會造成乳酸和氫離子產生，因此腫瘤必須強制性利用離子通道的排除，令腫瘤環境酸化。而微環境酸化已經被證實和腫瘤幹性維持有關，此外變成有幹性的腫瘤，是藉由Epigenetic改寫過程達成。而TIF1 β是一個轉錄的輔助因子，可以和HP1的結合或是其他轉錄因子結合，招喚Epigenetic 接受者影響染色質的組成調控基因表現，再加上TIF1β本身可以進行後轉譯修飾像是磷酸化。磷酸化的TIF1β的s473位子坐落在HP1結合區域的上游序列附近，被證實磷酸化S473位子會影響TIF1β和HP1的結合，影響到細胞分化。本文藉由組織免疫染色發現在口腔癌病人組織中TIF1β-S473的磷酸表現和腫瘤酸化有關。而在短期酸化細胞實驗，也發現TIF1β-S473的磷酸表現在惡性腫瘤裡比較多。此外在長期酸化處理下，邊緣細胞(side population)比率增加以及幹性相關蛋白表現和TIF1β-S473的磷酸表現下降有相關，並藉由螢光免疫染色的數據解釋在長期酸化處理下S473磷酸化，TIF1β在染色質的位子有了變動，跑去和幹性相關基因結合而使TIF1β不易被磷酸化。這些證據都暗示TIF1β-S473的磷酸化可能在癌幹細胞的幹性維持扮演重要腳色。因此進一步的研究是結合ENCODE資料庫，並用染色質免疫沉澱法，進行次世代定序法來驗證。探討在酸化時，s473磷酸化時會和那些轉錄因子、組蛋白酵素作用以及座落在哪段 DNA上，對於腫瘤的幹性研究和治療上有很大的幫助。

關鍵字

癌幹細胞 ； 幹性維持 ； TIF1β ； 酸化 ； 瓦式效應 ； ENCODE

並列摘要

The tumors microenvironment is the important factor for tumor stem ness. The acid stress is one of the characteristics of the tumor microenvironment. Under the pressure of the missing nutrients causes tumor to go glycolytic for growth. This phenomenon is Warburg effect .But it also product a lot of lactic acid and hydrogen ions, the tumor must be excluded by some ion channels. And then, this is reason why tumor environment is acid. Tumor microenvironment has been proven related with tumor stem-ness and the tumor becomes stem-ness tumor, which the rewriting process is by Epigenetic mechanism. Transcription intermediary factor 1(TIF1β) is a transcription intermediary factor which involved in epigenetic regulation and maintenance of pluripotency signal pathway. TIF1β can regulate chromatin remodeling and gene expression through the interaction with heterochromatin protein 1(HP1) and with other transcription factors. TIF1β also has post-translational modifications such as phosphorylation. The serine 473 residue of TIF1β seat is located upstream sequence of HP1 binding domain which has been confirmed that the phosphorylation of TIF1β-S473 form will interfere HP1 binding and finally affects cell differentiation and stem ness.
In this study, phosphorylation of TIF1β -S473 form expression is related with oral cancer patient by immunohistochemistry. Under short time acidification, the phosphorylation of TIF1β -S473 form expression has increased in malignant tumors. In addition, in the long-term acidification, the side population cells percentages have increased, but phosphorylation of TIF1β -S473 form expression is decreased. From here, immunofluorescence data explains long term acidification makes phosphorylation of TIF1β -S473 form, let TIF1β change chromatin site, interacting with stem ness-related genes and then TIF1β cans not be easy phosphorylation. These results suggest that phosphorylation of TIF1β -S473 form may play important role in regulating stem ness in cancer stem cells.
Further studies can combine with ENCODE (Encyclopedia of DNA Elements) data bank to find all functional elements in the human genome. And then use chromatin immune precipitation sequencing to do next-generation sequencing .By using two methods to verify that phosphorylation of TIF1β- S473 form in acidosis and in normal microenvironment which transcription factors and histone enzymes will interact with TIF1β? And on which genomics fragment? Taken together, if we understand the mechanism of TIF1β in maintain the stem ness, it can be a great development of cancer therapy.

並列關鍵字

Cancer stem cell ； TIF1β ； Stemness ； Warburg effect ； Acid stress ； ENCODE

參考文獻

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