透過子宮內膜癌細胞DNA甲基化研究表觀基因的調控

Abstract

子宮內膜癌是在女性生殖器癌症中最常見的惡性腫瘤之一。根據國際衛生組織 (WHO) 在2014年提出的統計資料，全球每年新增超過30萬個病例，造成76,000人死亡。在美國估計2015年將超過54,870人被診斷出罹患子宮內膜癌，並可能會有10,170人因此而致命。近年來台灣每年約有1,200~1,500例新增的患者。目前的研究資料顯示，子宮內膜癌的發生是集合多種因素、多個基因變異間複雜的調控機制所累積產生的。雌激素 (estrogen) 的過度刺激，在目前認為是造成子宮內膜癌重要發病原因，而與其發生高度相關的基因包括PTEN抑癌基因、K-ras、tp53、MLH1、RASSF1A…等等。在臨床對子宮內膜癌早期診斷的分子指標物來說，普遍認為PTEN可作為早期診斷的指標，但是癌症發生的機制依然還不清楚。 DNA 甲基化和 microRNA 是細胞中非常重要的表徵基因學調節機制。DNA 甲基化是 DNA 化學修飾的一種，主要可以在不改變 DNA 的序列之下調控該基因的表現，通常在基因 promoter 的區域發生甲基化，可以造成基因沉默。microRNA 是真核生物中廣泛存在的一種 RNA 分子，長約21到23個核苷酸，它可藉由結合目標基因調節其他基因的表達。近年來，微晶片 (microarray) 以及高通量次世代定序技術 (NGS) 的快速發展，使研究者能夠在短時間內以少量的花費就可以偵測到所有基因的表現。因此本論文藉由分析公開的資料庫 (TCGA) 中子宮內膜癌的次世代定序以及微晶片資料結果，了解子宮內膜癌在癌化過程中受到 DNA 甲基化以及 microRNA 調控的影響。以期能建立子宮內膜癌的 microRNA 調控網路，並應用在其他的癌症上面，來加速相關癌症發展機制與治療藥物的研究。

Endometrial adenocarcinoma is the most frequently occurring female genital cancer. According to WHO statistics, there are over 320,000 new cases and causing 76,000 deaths in 2012. The American Cancer Society estimates endometrial cancer in the United States for 2015 are about 54,870 new cases of cancer of the body of the uterus will be diagnosed, and about 10,170 women will die from this disease. There are 1,200 to 1,500 new cases report in recent year in Taiwan and endometrial cancer is the second most common gynecologic cancer and its incidence and mortality increased rapidly in the past several decades. Emerging studying shows that endometrial cancer are characterized by multiple factors and a variety of genetic alterations. Estrogen level is playing an important role, and some related genes, PTEN, K-ras, TP53, MLH1, RASSF1A et al, are also highly correlated with endometrial cancer. Altered PTEN expression was taken as a diagnostic marker for the earliest endometrial cancer. Loss of PTEN function lead to up-regulation of PI3k/Akt/mTOR pathway which causes cell growth and p53 pathway can either be suppressed or activated in endometrial cancer, but the pathway were still unclear. DNA methylation and microRNA play important roles in epigenetic regulation. DNA methylation, a commonly occurring modification of human DNA, can affect the gene expression without change the sequence of the genome. Epigenetic gene silencing, which is associated with aberrant methylation of promoter DNA and transcriptional repression, is an important mechanism for the loss of gene function in cancer. MicroRNAs are small non-coding RNAs of 17~25 nucleotides sequences that function to regulate gene expression by interfering the post-transcriptional level. In recent years, high-throughput technology (microarray and NGS) progress rapidly, researcher can spend less money to detect all gene expressions in a short time. In this thesis, by analyzing endometrial cancer DNA methylation and gene expression data in the public repository database, TCGA, we dig out the cancer progress affected by DNA methylation and miRNA, and try to construct the regulatory network in endometrial cancer, and apply to other cancer. This valuable information is helpful in understanding DNA methylation and miRNA functions and provides knowledge to evaluate the therapeutic potential in clinical research.