2003年台灣膀胱癌的發生率在癌症中已是第13位，尤其在南台灣的烏腳病流行區，膀胱癌的發生率及死亡率更高。根據流行病學的統計，發現烏腳病和飲水中含砷有密切關聯。膀胱癌細胞的惡性度與飲水中砷的含量也是成正比的。而重金屬砷更是已知的致癌因子，並且會造成各種疾病，如烏腳病、心血管疾病、皮膚癌及膀胱癌等。關於長期飲水中含砷造成膀胱癌確切的作用機轉及方式目前並不是十分清楚。為找出可能的致病機轉，我們首先以E7這個上皮細胞建立一個長期慢性砷暴露的模式:首先以濃度0.05 ppm 的砷加入培養液中，然後隨著時間增加提高砷的濃度大約8個星期，濃度到達細胞忍受的上限值 (0.4 ppm)。以0.4 ppm的砷經過2個星期的處理，將細胞收下進行遞減雜交，以挑出表現不一樣的基因。在反向實驗挑出的250個植株並將其中117個長片段進行定序。在確定得到的77基因經過分類後，分別與代謝、環境壓力、轉錄因子、蛋白質合成、DNA修補、細胞周期控制、離子通道、轉接蛋白等，還有一些則是目前還未知的基因或是功能尚不清楚的基因。此外, 我們也以生物資訊概念幫派找尋砷致癌的分子機轉. 透過文件搜尋分析，我們選擇了數個與砷相關的染色體，然後分析8q22.1-ter上的基因分布情形。 依照染色體缺失或染色體複製的位置挑出中與功能相符的2個基因，分別是NDRG1, LYNX1。其中18q21.1-ter 的MBD2也曾出現在反向的遞減雜交結果，而NDRG1則是出現在正向的遞減雜交結果中。此外我們也分析了一個新基因ITM1。RT-PCR分析這4個基因的RNA層級的變化，我們發現NDRG1在接受砷處理後的變化最明顯，並且與矩列陣及Real-Time PCR的結果相符。為了進一步了解NDRG1與砷誘發的膀胱癌是否有關係，先對NDRG1表現量低的細胞株J82進行暫時性轉殖， NDRG1過度表現會造成膀胱癌細胞快速生長的能力，似乎支持NDRG1的致癌基因的角色。以69例臨床檢體的初步觀察，NDRG1 在膀胱癌有59.4%的表現率，但是和癌症惡化的臨床指標初步沒有看到明顯地相關。由此一概念所進行的分析及研究，似乎可以成功地幫我們找到砷誘發的膀胱癌的可能分子機轉。至於NDRG1造成癌症的原因，未來將挑出穩定的轉殖細胞株以利之後的深入研究。

　Bladder cancer is ranked at the thirteenth important cancer in Taiwan. The incidence, as well as mortality, in the blackfoot disease-endemic areas of southern Taiwan is exceptionally high. The rationale to explain for this phenomenon is lacking, except for their association with arsenic in drinking water. This study was performed to elucidate the novel mechanisms of bladder carcinogenesis related to arsenic exposure in the blackfoot disease endemic area. We first established an in vitro model of chronic arsenic exposure in E7 uroepithelial cell lines starting from 0.05 ppm, current toxic threshold for drinking water, to 0.4 ppm over 8 weeks. Then E7 cells were maintained at 0.4ppm treatment for 2weeks for subsequent subtractive hybridization experiment. A total of 250 clones were harvested, and 117 of them were sent for sequencing. The 77 genes identified are related to metabolism, stress response, transcription factor, protein synthesis, cytoskeleton, DNA repair, cell cycle control, ion channel, and adaptor protein. Some of them are novel or unknown for their function. In addition, a bioinformatic algorithm was used to explore the molecular basis of arsenic-related carcinogenesis. This study focused on chromosome 8q22.1-ter. Among the predicted genes in 8q22.1-ter (NDRG1, LYNX1), 18q21.1-ter (MBD2) and a novel gene (ITM1), we proved that only NDRG1 fulfilled the criteria of oncogene proposed to be responsible for bladder tumorigenesis. In vitro experiment also supports the up-regulation of NDRG1 by arsenic. Preliminary screening demonstrated that over-expression of NDRG1 provides proliferative potential for human bladder cancer cells. There was a 59.4% (41/69) of NDRG1 expression rate in clinical cohort, but did not associate with aggressive indicators (grade, stage, size, and non-papillary) (p > 0.05, respectively). The significance of NDRG1 in cancer progression and the in vitro effects will be further investigated on transient or selected stable clones in the future.

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