論文名稱:

DNA修復機轉與口腔黏膜癌化之關係

 

The Relationship Between DNA Repair Systems and Carcinogenesis in Oral Epithelium

研究生:

黃頌銜  Sung-Shian Huang

 

(以作者名查詢陽明大學館藏系統)

 

(以作者名查詢全國圖書書目資訊網)

指導教授:

楊世芳  Shih-Fang Yang

 

夏堪臺  Kan-Tai Hsia

        學位類別:

碩士

        學校名稱:

國立陽明大學

系所名稱:

口腔生物研究所

            學號:

39017006

          學年度:

91

          語文別:

中文

          出版年:

92

關鍵字:

DNA修復  DNA repair

 

口腔上皮細胞癌  oral squamous cell carcinoma

 

鹼基刪除修復  Base Excision Repair

 

酸錯誤配對刪除修復  Mismatch Repair

 

酸刪除修復  Nucleotide Excision Repair

 

雙股DNA斷裂修復  Double-Strand Breaks

全文說明:

電子全文

        論文頁數:

82

摘要:

    在維持生物體的存活與正常功能上,如何保持DNA的精確性與完整性極為重要,然而日常生活中卻有許多因素造成DNA傷害,如具基因毒性的物質(有內生性與外生性)、DNA複製時的核酸配對錯誤與DNA本身的化學結構不穩定造成的損傷等,當這些受損的DNA無法適時修補時,可能導致DNA複製或轉錄的異常、基因突變或產生細胞毒性導致細胞死亡,而且也可能會引起多種的先天遺傳疾病、老化及癌症等問題,為了解決這些問題在所有具核細胞中皆具有多種的機制可對受損DNA進行修復,維持DNA的精確性與完整性。

 

    DNA修補基因可藉由不同的機制對不同程度的DNA損害進行修復,雖然近來已有文獻指出,一些DNA修復蛋白可能參與多種DNA修復機制,不過一般可分為下列四種DNA修復機制:鹼基刪除修復(Base Excision Repair; BER),即對較小的DNA損傷(如鹼機的改變或缺損),進行修復;核苷酸錯誤配對刪除修復(Mismatch Repair MMR),即對複製時所產生的核苷酸配對錯誤或模板滑動造成的DNA損害進行修復;核苷酸刪除修復(Nucleotide Excision Repair; NER),即對因紫外線或有機化合物所造成的較大損傷進行修復;以及雙股DNA斷裂修復(Double-Strand Breaks; DSBs),即對雙股DNA斷裂進行修復,此機制又可分為同源染色體的重組與末端接合兩種主要路徑,對受損的DNA進行修復。

 

    在本研究的第一階段實驗中,作為提供在口腔癌方面的流病研究,與相關DNA修復機制基礎的第一步,本實驗一共觀察39個口腔癌樣本與27個正常組織樣本,經免疫組織染色處理後其DNA修復蛋白OGG1(BER)APE(BER)XPA(NER)hMSH2(MMR)hMLH1(MMR)ATM(HRR & NHEJ)RAD51 (HRR)的表現情形,結果發現在口腔癌樣本中以BER的修復路徑為主,而NERMMR也發現有升高的趨勢,在本研究中也發現檳榔子中主要成分檳榔素在濃度為200-800μM時對細胞活性有顯著的影響,然而以西方墨點法觀察以檳榔素處理後的細胞,其DNA修復蛋白的表現卻無明顯改變,這現象可能與處理細胞的時間有關。

 

    從本研究的結果可推測BERMMR修復機制可能是口腔中最主要的DNA修復機制。

 

    The maintenance of genome integrity and fidelity is essential for the proper function and survival of all organisms. This task is particularly daunting due to constant assault on the DNA by genotoxic agents (both endogenous and exogenous), nucleotide misincorporation during DNA replication, and the intrinsic biochemical instability of the DNA itself. Failure to repair DNA lesions may result in blockages of transcription and replication, mutagenesis, and/or cellular cytotoxicity. In humans, DNA damage has been shown to be involved in a variety of genetically inherited disorders, in aging, and in carcinogenesis. All eukaryotic cells have evolved a multifaceted response to counteract the potentially deleterious effects of DNA damage. For maintain the genome integrity and fidelity. DNA repair processes are classified into pathways responsible for repairing specific classes of DNA damage, although recent data indicated that some proteins function in multiple pathways. Base excision repair (BER) occurs through excision of a damaged region, followed by fill-in repair synthesis using the opposite strand as a template. Mismatch repair (MMR) operates on base mismatched and small loop-outs that arising during replication by misincorporation or slippage on the template strand. Nucleotide excision repair (NER) removes photoproducts from u.v. radiaton and bulky adducts from a multiple of chemicals. DNA double-strand breaks may be rectified by either homologous recombination repair (HRR) and nonhomologous end joining pathways (NHEJ) where both strands of the DNA duplex are damaged.

 

    As a step in providing a basis for epidemiology studies to relate DNA repair systems on oral cancer, this study initiate to investigate the main DNA repair genes in each system. A total of 39 patients with the diagnosis of oral cancer and 27 healthy controls were immunostained for protein expression of OGG1 (BER), APE (BER), XPA (NER), hMSH2 (MMR), hMLH1 (MMR), ATM (HRR & NHEJ), and RAD51 (HRR). The histopathological findings suggest that themain DNA repair pathway in oral cancer is BER; however, elevation of both NER and MMR was also found. This study also demonstrated that arecoline, a major pharmacologically active alkaloid of areca nut, affected the cell viability within 200-800μM. However, DNA repair systems in the arecoline treatment of cell culture were not significantly changed in western blotting. The negative biological significance in this assay may be correlated with time courses.

 

    In this study, we suggest that BER and MMR repair systems might be the major DNA repair system in oral tissue.