- 學位論文
Nrf2-ARE調控抗氧化基因表現做為肺癌患者臨床預後因子之研究
The prognostic value of antioxidant gene expressions regulated by Nrf2-ARE pathway for lung cancer patients
摘要
Keap1在氧化壓力下會使Nrf2進入細胞核，結合至抗氧化基因的antioxidant response element (ARE)啟動抗氧化基因的轉錄活性以移除氧化壓力。因此天然物如何透過Nrf2-ARE路徑，達到化學預防致癌(chemoprevention)的分子機制是經常被研究的課題。已知肺腺癌之形成機制與慢性發炎有關，而慢性發炎大多經由ROS所引起，但是Nrf2-ARE路徑在肺腺癌的致腫瘤過程之相關性至今仍不清楚，急需瞭解是否Nrf2-ARE路徑發生變異而造成腺癌形成。因此本研究擬以免疫組織化學分析法瞭解Nrf2, Keap1, NQO1, GPx和MnSOD等蛋白在肺腫瘤組織中的表現，以及這些蛋白表現與肺癌患者的哪些臨床因子有關? 這些蛋白的表現是否與患者之預後有關能否做為肺癌患者之預後指標? 結果發現Keap1大多表現於腫瘤細胞之細胞質，當Nrf2蛋白表現於細胞核時，Keap1蛋白之表現比Nrf2不表現於細胞核時有較低之趨勢，但並沒有達到統計上之意義(P = 0.086)。同時亦發現Nrf2蛋白之表現與NQO1, GPx 和MnSOD三種抗氧化基因的表現都沒有相關性，這結果顯示在肺腫瘤組織中，Nrf2-ARE路徑在調控這三種抗氧化蛋白之角色可能較低。在臨床因子相關性分析上，不抽菸之肺癌患者之NQO1與GPx兩種抗氧化蛋白表現都較抽菸者高(P = 0.011 for NQO1; P = 0.001 for GPx)。同時Nrf2蛋白之表現在不抽菸者亦較抽菸者高(P = 0.028)。以上四種蛋白之表現與患者其他臨床因子都沒有統計上之相關性。在患者預後之分析上，本研究以單變項Log-rank分析發現Nrf2與MnSOD蛋白高表現者之預後似乎較表現者低者差(P = 0.062 for Nrf2; P = 0.004 for MnSOD)。進一步以Cox regression分析發現Nrf2和MnSOD之相對危險值與腫瘤期別幾乎相近(RR = 1.568 for Nrf2; RR = 1.691 for tumor stage; RR = 1.636 for MnSOD; RR = 1.512 for tumor stage)。因此Nrf2與MnSOD蛋白表現適合作為獨立的肺癌患者臨床預後因子。
並列摘要
Nrf2 nuclear translocation has been shown to be controlled by Keap1. Keap1-Nrf2 heterodimer was dissociated under oxidative stress and then Nrf2 translocated into nucleus and bound with antioxidant response element (ARE) to upregulate antioxidant genes, such as NQO1, GPx, and MnSOD. Lung adenocarcinoma tumorigenesis is considered to be associated with chronic inflammation and ROS is involved in lung inflammation. Therefore, aberrant Nrf2-ARE pathway could increase ROS production to cause lung adenocarcinoma development. In this study, immunohistochemistry was performed to evaluate Nrf2, Keap1, NQO1, GPx, and MnSOD protein expressions in lung tumors. The data would be provided to verify (1) whether the antioxidant protein expressions in lung tumors were regulated by Nrf2-ARE pathway? (2) the relationships between the five protein expressions and tumors’ clinical-pathological parameters, and (3) whether the protein expression could be act as an independent prognostic factor to predict patients’ survival? Our results indicated that Nrf2 protein expressed in nucleus of lung tumor cells was associated with lower Keap1 protein expression in cytoplasm of lung tumors, but it did not reach statistical significance (P = 0.086). Nrf2 protein expression was not associated with NQO1, GPx, and MnSOD protein expressions, suggesting that Nrf2-ARE pathway could play a minor role in the regulation of these antioxidant genes in lung tumors. In the relationships of these protein expressions with clinical-pathological parameters, Nrf2, NQO1 and GPx protein expressions in nonsmoking lung cancer patients were significantly higher than in smoking patients (P = 0.028 for Nrf2; P = 0.011 for NQO1; P = 0.001 for GPx), but not observed in other clinical parameters. In clinical prognostic value analysis, univariate analysis showed that patients with higher Nrf2 and MnSOD expressions had shorter survival time than those with lower Nrf2 and MnSOD, respectively (P = 0.062 for Nrf2; P = 0.004 for MnSOD). Moreover, Cox regression analysis indicated that RR value of Nrf2 and MnSOD was similar with RR of tumor stage (RR = 1.568 for Nrf2; RR = 1.691 for tumor stage; RR = 1.636 for MnSOD; RR = 1.512 for tumor stage), suggesting that both protein expressions in lung tumors can be act as an independent prognostic factor of lung cancer.