頭頸癌患者血液中粒線體去氧核醣核酸的表現

Expression of the Mitochondrial DNA in the Peripheral Blood of Patients with Head and Neck Cancer

林巧峰(Frank Cheau-Feng Lin)

指導教授 ： 周明智

中山醫學大學/醫學院/醫學研究所/博士(2014年)

https://doi.org/10.6834/CSMU.2014.00154

摘要

背景 粒線體(mitochondria)是人類將三大營養素醣類，脂肪，蛋白質氧化為能量(Adenosine triphosphate, ATP)及水和二氧化碳的胞器。其失能可造成許多先天性疾病。人體細胞隨代謝反應的不同，有300-2000個粒線體。每個粒線體含有 2-10個拷貝的去氧核醣核酸(DNA)，每一個細胞約有1000-10000個拷貝的粒線體去氧核醣核酸(mtDNA)。因粒線體是去氧核醣核酸接近氧化還原反應最激烈的地方，且沒有組織體的保護，故容易遭到破壞。而增加粒線體去氧核醣核酸被認為是一種代償的機制。再者近期發現粒線體去氧核醣核酸的異常和各種癌症如食道癌，頭頸癌有關。

目的 探討血液中粒線體去氧核醣核酸拷貝數和頭頸癌之間的關係。

材料和方法 本研究共收集75位頭頸癌男性患者和80位無惡性腫瘤之男性對照組血液及臨床資料。以即時定量聚合酶鏈連鎖反應(RT-qPCR)方法檢測線粒體去氧核醣核酸的相對拷貝數。統計以t test 統計類別變項，ANCOVA統計連續變項。存活狀況以Keplan-Meire及對數等級(log rank)檢定統計，並以Cox比例風險比例模型( The Cox proportional hazard ratio models )找出影響存活的獨立因子。相對的粒線體去氧核醣核酸(mtDNA)拷貝數的診斷價值，則進行receiver operating characteristic (ROC)分析;並以Yoden's index找出最優臨界點。

結果 頭頸癌患者血液中之粒線體去氧核醣核酸拷貝數顯著高於對照組(中位數8.22 及 4.84，p<0.001 )。頭頸癌之粒線體去氧核醣核酸拷貝數與患者的存活率呈負相關(頭頸癌病人中相對拷貝數為最大四分位數以下或相等，和相對拷貝數為最大四分位數以上，兩組的存活時間之中位數分別是3.97及0.87年，p=0.011)。相對粒線體去氧核醣核酸(mtDNA)拷貝數> 17.55(第三個四分位數)，具有較高的淋巴結轉移(N)，遠處轉移(M)，和較後的癌症分期(p值分別為0018, 0.022, <0.001,及0.012)為頭頸癌死亡的預後因子。粒線體去氧核醣核酸相對拷貝數(p = 0.002.)及腫瘤遠處轉移(p<0.001)為兩個影響死亡的獨立因子。粒線體去氧核醣核酸拷貝數經檢定具有診斷的價值(AUC 0.710，p<0.001)，經Yoden's index找出粒線體去氧核醣核酸拷貝數之臨界點為11.1；靈敏度，特異性，陽性預測值（PPV）和陰性預測值（NPV）分別為44.0 ％，98.8 ％， 97.1％， 65.3 ％。

結論 本研究證實粒線體去氧核醣核酸拷貝數(mtDNA)的增加和頭頸癌之間的相關性，並與患者的存活有關。且證實血液中粒線體去氧核醣核酸拷貝數具頭頸癌的診斷價值。

關鍵字

粒線體去氧核醣核酸 ； 頭頸癌 ； 存活 ； 診斷

並列摘要

Background Mitochondrion is the powerhouse of the cells. It converts carbohydrate, fat, and protein into energy (ATP), water, and carbon dioxide. Diseases happen when mitochondrion loses its function. There are 300-1000 mitochondria for each cells varied with their metabolic status, and there are 2-10 copies of mitochondrial DNA (mtDNA) for each of the mitochondria. The number of copies of mtDNA of cells are around 1,000 to 10,000. The mtDNA is located near the sites that oxidation and reduction occur rigorously. Free radical are abound. Without the protection of the histone, the mtDNA are attacked frequently and are easily damaged. Unfortunately, there are no proofreading or repair mechanism for the mtDNA. Therefore mutation takes place more frequently than the nuclear DNA. The increase of the copy number of mtDNA are recognized as a compensatory mechanism to normalize the mtDNA. Anomalies in the mtDNA were associated with some cancers, such as esophageal cancer and head and neck cancer (HNC), which were reported recently. We design this study to examine the mtDNA copy number of the HNC.

Study purpose To investigate mtDNA copy number in HNC.

Material and methods The blood and clinical data of 75 HNC patients and 80 malignancy-free controls were collected. The mtDNA copy number were measured with real-time quantitative polymerase chain reaction (RT-qPCR).The categorical factors were compared using t-tests; the numerical factors with ANCOVA. The survivals were measured with Kaplan-Meier method with log-rank test. The independent survival factors were found out with the Cox proportional hazard ratio models. The diagnostic value of the mtDNA copy number for HNC was tested by the receiver operating characteristic (ROC) curve. The best cutoff value was found by the Yoden’s index.

Results The mtDNA copy number of the HNC patients was significant higher than the control (median 8.22 and 4.84, p<0.001). The mtDNA copy number was negatively correlated with the survival of HNC patients. The median survivals were 3.97 and 0.87 for mtDNA copy number of the HNC patients below and above the 3rd quarter, respectively. (P=0.011). The mtDNA copy number higher than the 3rd quarter, the higher N stage, the higher M stage, and the higher cancer stage (p= 0018, 0.022, <0.001, and 0.012, accordingly) were the poor prognostic factors. The mtDNA copy number (p=0.002) and distant metastasis (p<0.001) were the two independent factors for survival. The mtDNA copy number was tested to have diagnostic value (AUC 0.710，p<0.001) for HNC. The best cutoff value (Yoden’s index) was 11.1; the sensitivity, specificity, positive predict value, and negative predict value were 44.0%， 98.8％， 97.1％， and 65.3 ％ respectively.
Conclusion The mtDNA copy number was associated with HNC, and the survival of HNC patients. The mtDNA copy number also had diagnostic value for HNC.

並列關鍵字

mitochondrial DNA ； head and neck cancer ； survival ； diagnosis.

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