口腔組織中BPDE鍵結物表現量可作為口腔癌危險生物指標

BPDE-like DNA Adduct level in Oral Tissue May Act as a Risk Biomarker of Oral Cancer

周英一(Ying-Yi Chou)

指導教授 ： 何全城

中山醫學大學/口腔醫學院/牙醫學系碩士班/碩士(2014年)

https://doi.org/10.6834/CSMU.2014.00022

摘要

背景: 過去在的研究顯示口腔癌患者腫瘤組織中的PAH-related DNA鍵結物含量與吸菸有關。但這些研究並沒有針對香菸裡所含的特殊致癌物成分做進一步分析，本研究的目的在了解BPDE (7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene)–DNA 鍵結物在台灣地區口腔癌疾病發展所扮演的角色。
實驗設計:本研究共收集158 口腔癌患者及64 非癌症控制組分析兩組間對於香菸暴露形成DNA 鍵結物的感受性是否不同。BPDE–DNA鍵結物是以免疫組織化學染色法(Immunohistochemistry ) 及酵素免疫分析法( ELISA; enzymelinked immunosorbent assay) 進行分析。
結果: 本研究結果顯示BPDE–DNA鍵結物含量與性別、抽菸與否、是否吃檳榔及是否飲酒呈統計上的正相關。BPDE–DNA鍵結物含量與glutathione S-transferase M1 (GSTM1) 基因多型性有關但與cytochrome P-4501A1 (CYP1A1)無關。患者組織中的BPDE–DNA鍵結物含量大於34.03 adducts/108 nucleotides時相較於小於 34.03 adducts/108 nucleotides者有 9.936倍罹患口腔癌的風險( p < 0.001)。
結論: 本研究結果推測患者本身的基因多型性及致癌物暴露可能增加口腔癌疾病發展的風險。

關鍵字

口腔癌 ； 危險因子 ； DNA 鍵結物

並列摘要

Both genetic and environmental factors contribute to the development of oral cancers. Approximately 90% of oral cancers are squamous cell carcinomas. Major risk factors include the use of tobacco products, betel nut chewing, and alcohol consumption.1–3 Tobacco smoke components include polycyclic aromatic hydrocarbons (PAHs), aromatic amines, and N-nitrosamines, all of which are potent carcinogens.4
It has been shown that the increased level of tobacco-related carcinogen DNA adducts is a risk factor for smoking related oral cancer development.5–7 Benzo[a]pyrene (BaP) is an important carcinogen in cigarette smoke. BaP is made up of polycyclic aromatic hydrocarbons (PAHs) and has been found to cause p53 mutations and then tumorigenesis. BaP 7,8-diol 9,10-epoxide (BPDE) is an ultimate metabolite of BaP, which attacks deoxyguanosine to form a BPDE-N2–dG adduct which results in p53 mutations. The mutation hotspots of p53 in human lung tumours (codons 154, 157, 158, 245, 248, and 273) are caused by the BPDE-N2–dG adduct.8 Thus, an evaluation of DNA adducts induced by BaP and other PAHs is a suitable marker for cancer risk. BaP is oxidized by a series of well-characterized enzymes such as cytochrome p450 1A1, 2C9, and 3A4.9,10 A thymine/cytosine point mutation in the MspI restriction site of CYP1A1 has been reported to result in increased enzyme activity.11 The CYP1A1 MspI polymorphism has been linked to susceptibility for smoking-related cancers, such as oral, colon, breast, and lung cancers.12–14 Not only cytochrome P450 but other enzymes, such as glutathione s-transferase M1 (GSTM1) have been shown to be involved in BaP metabolism.15–17 GSTM1 has also been shown to be polymorphic. A deletion is responsible for the existence of a null allele associated with the lack of expression of a functional protein.18,19 The polymorphic GSTM1 null genotype has been found in 20–50% of populations of various ethnic origins, and this genotype has been correlated with the risk for various tobacco-related cancers.20–23 Therefore, the genetic polymorphisms of the CYP1A1 and GSTM1 genes may contribute to BPDE-like DNA adduct formation in oral cancer.
In this study, we examined the BPDE–DNA adduct levels in oral tissue from oral cancer patients and non-cancer controls using ELISA and immunohistochemistry. This study was done to understand the role of BPDE–DNA adducts in oral cancer and to determine whether BaP is the major contributor in DNA damage from cigarette exposure. The CYP1A1 and GSTM1 polymorphisms were also analysed to verify the effects of the genotype of both genes on the formation of DNA adducts in oral tissue.

並列關鍵字

oral cancer ； risk factor ； DNA adducts

參考文獻

1. Ko YC, Huang YL, Lee CH, Chen MJ, Lin LM, Tsai CC. Betel quid chewing: cigarette smoking and alcohol consumption related to oral cancer in Taiwan. Journal of Oral Pathology and Medicine 1995;24(10):450–3.

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5. Hsu TM, Zhang YJ, Santella RM. Immunoperoxidase quantitation of 4-aminobiphenyl- and polycyclic aromatic hydrocarbon–DNA adducts in exfoliated oral and urothelial cells of smokers and nonsmokers. Cancer Epidemiology Biomarkers and Prevention 1997;6(3):193–9.

7. Besarati Nia A, van Straaten HW, Godschalk RW, Van Zandwijk N, Balm AJ, Kleinjans JC, et al. Immunoperoxidase detection of polycyclic aromatic hydrocarbon–DNA adducts in mouth floor and buccal mucosa cells of smokers and nonsmokers. Environmental and Molecular Mutagenesis 2000;36(2):127–33.