DNA鹼基切除修復途徑之基因多型性與分化性甲狀腺癌之相關性

Association of Gene Polymorphisms in DNA Base-Excision Repair Pathway with Differentiated Thyroid Cancer

吳哲維(Che-Wei Wu)

指導教授 ： 郭文烈

高雄醫學大學/醫學院/醫學研究所/碩士(2008年)

https://doi.org/10.6832/KMU.2008.00065

摘要

目的：
大量研究證明, DNA鹼基切除修復途徑（base excision repair，BER）的單核苷酸多型性(single nucleotide polymorphisms, SNPs)，可以改變蛋白產物的DNA修復效能，進而影響個體之癌症易感性(susceptibility)。但目前文獻上並沒有太多關於BER途徑基因多型性與甲狀腺癌相關性的研究。本研究的目的即在探討BER途徑上五個關鍵基因包括：hOGG1 (human oxoguanine glycosylase 1)、MBD4 (methyl-CpG binding domain protein 4)、XRCC1(X-ray repair cross complementing group 1)、APE1 (apurinic/apyrymidinic endonuclease-1)及ADPRT (adenosine diphosphate ribosyl transferase)的基因多型性與分化性甲狀腺癌的罹病風險及其淋巴轉移之相關性。
研究方法：
我們設計一個病例對照研究，自高醫附設醫院選取無血緣關係之283名分化良好甲狀腺癌、以及293名健康對照個案，採取周邊血液後進行DNA萃取，之後使用real-time TaqMan PCR基因型定型(genotyping)法來檢測，包括：hOGG1-Ser326Cys、MBD4-Glu346Lys、XRCC1-Arg194Trp、XRCC1-Arg280His、XRCC1-Arg399Gln、APEX1-ASP148Glu及ADPRT-Val762Ala等5個BER基因上共7個常見的功能性nsSNPs，以Hardy-Weinberg equilibrium（HWE）平衡來檢驗各個SNP，並以多變向邏輯回歸來分析基因效應，藉此比較不同基因型與甲狀腺癌的罹病風險。也將病例進一步以頸部淋巴轉移的有無來做統計上的比較。
結果：
所偵測的基因型頻率分佈皆符合哈溫平衡 (Hardy-Weinberg equilibrium)。在XRCC1 Arg194Trp多型性中，我們發現相較於wild-type Arg/Arg基因型, variant homozygous Trp/Trp基因型有較高的罹病風險(ORadj: 1.83, 95%CI:1.01-3.23, p=0.045)，尤其合併頸部淋巴腺轉移更加顯著(ORadj of 4.42, CI:1.95-9.98, p=0.003)。變異型對偶基因194Trp自對照組、無淋巴腺轉移病患，至合併淋巴腺轉移病患的分佈亦呈現有意義上升趨勢(P-trend =0.003)。其餘6個SNPs的對偶基因及基因型頻率於疾病及對照組的分佈，在統計上都未達到顯著差異。XRCC1三個基因多型性的Hyplotype分析顯示，甲狀腺癌組與對照組間有顯著差異存在(P=0.04)，而且此差異主要來自合併淋巴腺轉移的病患族群(P=0.004)。在基因交互作用分析方面，我們發現XRCC1 Arg194Trp及ADPRT Val762Ala兩個多型性間，存在明顯之交互作用；當以合併XRCC1-194Arg/Arg及ADPRT-762Val/Val基因型作基準，帶有變異對偶基因之罹病風險呈現有意義上升趨勢，尤其當合併XRCC1-Trp/Trp及ADPRT-Ala/Ala時有3.28倍之甲狀腺癌罹病及9.68倍之合併頸部淋巴轉移風險。
結論：
實驗結果顯示BER途徑的基因多型性，可能與甲狀腺的罹病風險以及合併頸部淋巴轉移相關。尤其是XRCC1多型性，可能藉由本身的效應，或是藉由與ADPRT之交互作用，導致個體間DNA修復能力之差異，進而影響個體之癌症易感性。藉由辨認這些帶有風險的基因標記，可對分化性甲狀腺癌的致病機轉提供更進一步的了解，並且可於臨床應用，協助於制定更完整的治療策略。

關鍵字

DNA修復 ； 鹼基切除修復途徑之基因多型性 ； 甲狀腺癌 ； hOGG1基因 ； MBD4基因 ； XRCC1基因 ； APE1基因 ； ADPRT基因

並列摘要

Objectives/Hypothesis
DNA base excision repair (BER) pathway has been shown to be related with carcinogenesis. We hypothesized that functional polymorphisms of five BER genes, hOGG1 (human oxoguanine glycosylase 1), MBD4 (methyl-CpG binding domain protein 4), XRCC1 (X-ray repair cross complementing group 1), APE1 (apurinic/apyrymidinic endonuclease/redox effector-1) and ADPRT (adenosine diphosphate ribosyl transferase) confer a risk for differentiated thyroid carcinoma (DTC) and lymph node (LN) metastasis.
Methods
In a case–control study of 283 DTC cases and 293 controls, seven common non-synonymous single nucleotide polymorphisms (SNPs): Ser326Cys for hOGG1; Glu346Lys for MBD4; Arg194Trp, Arg280His, Arg399Gln for XRCC1; Asp148Glu for APE1, and Val762Ala for ADPRT were evaluated using the TaqMan 5' nuclease assay. Hardy-Weinberg equilibrium (HWE) was tested for each SNP, and genetic effects were evaluated by the x2- test and multiple logistic regression.
Results
We found all seven SNPs were in HWE. The 194Trp/Trp genotype of XRCC1 showed a significantly increased risk of DTC (ORadj: 1.83, 95%CI:1.01-3.23, p=0.045), especially in LN metastasis cases (ORadj of 4.42, CI:1.95-9.98, p=0.003). The other six SNPs did not show significant results. Haplotype analysis of XRCC1 polymorphisms yielded a significant result (P= 0.04), especially in LN metastasis cases (P= 0.004). Moreover, we found that XRCC1-194Trp and ADPRT-762Ala variants collectively contribute to an increased risk of the disease and LN metastasis, with the combined variant homozygous genotypes exhibiting the highest 3.28-fold risk for DTC and 9.68-fold risk for DTC with LN metastasis.
Conclusions
We conclude that the XRCC1 polymorphisms, especially the 194Trp allele may have an effect on thyroid cancer development.This variant can interact with ADPRT-762Ala variant to further substantially increase susceptibility to the disease and regional LN metastasis. Identifying these risk genetic markers could provide more insight into the DTC pathogenesis and may also provide information to develop better therapeutic strategies.

並列關鍵字

DNA repair ； BER polymorphism ； thyroid carcinoma ； hOGG1 gene ； MBD4 gene ； XRCC1 gene ； APE1 gene ； ADPRT gene

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