| 摘要: | 癌症是台灣過去三十年來，十大死因的第一位，其中肺癌是癌症死亡原因的第一位。抽菸已是確認的肺癌危險因子，但除了抽菸之外，其他因子可能造成肺癌病變，包括基因和病毒。人類乳突病毒(human papillomavirus, HPV)為子宮頸癌證實的致癌因子，其致病機轉主要是致癌蛋白E6抑制抑癌基因p53和致癌蛋白E7抑制抑癌基因Rb，持續性高危型人類乳突病毒型 (high-risk HPV)的感染和病人本身免疫力缺陷是導致子宮頸癌的重要因素。人類乳突病毒也被認為是頭頸癌的重要危險因子，主要的傳遞路徑可能是經由危險性行為導致口腔人類乳突病毒感染所導致，而且感染人類乳突病毒的頭頸癌患者具有較長的存活率。表皮生長因子受體(Epidermal growth factor receptor, EGFR)的訊號傳遞是癌化過程的重要路徑，表皮生長因子受體的過度表現常可見於肺癌組織。細胞膜上表皮生長因子受體和配體(ligand)接合後，會經由高基氏體、內質網，轉換位置到細胞核，影響轉錄因子進行轉錄作用，造成血管和細胞增生，導致癌病變。細胞核EGFR已在細胞株實驗中發現，為白金類藥物抗藥性是必要的因素，而且臨床上也證實為乳癌和卵巢癌患者的重要預後因子，因此細胞核表皮生長因子受體在癌症病人產生抗藥性的過程中，也具有決定性的影響。之前的研究證實，女性不抽菸的肺癌患者容易具有表皮生長因子受體基因突變型 (EGFR mutations)，且台灣地區曾有研究指出，人類乳突病毒感染容易發生在女性不抽菸的肺癌患者，而且表皮生長因子受體基因突變型可能導致表皮生長因子受體的過度表現。我的博士論文主要是研究人類乳突病毒在肺癌病變的角色，研究成果分成三個部份; 第一部分，我們已經證實，肺癌組織中確實存有人類乳突病毒，也發現感染人類乳突病毒的肺腺癌病患，具有較好的存活率，特別是接受白金化療藥物治療的那一組。第二部分，經由肺癌組織免疫化學染色，我們證實人類乳突病毒莢膜蛋白和細胞質表皮生長因子受體表現量有相關性; 人類乳突病毒16/18型致癌蛋白E6和細胞核表皮生長因子受體表現量，有明顯的關聯性，且致癌蛋白E6陽性的早期肺癌病患存活率較差。第三部分，經由細胞培養 (A431 cell line)實驗，我們發現了致癌蛋白16E5，會促使表皮生長因子受體核轉運輸， 致癌蛋白16E6會增加表皮生長因子受體蛋白總量，但磷酸化現象並不明顯，而致癌蛋白16E7和表皮生長因子受體蛋白具有交互作用。藥物測試的細胞實驗中，發現轉殖致癌蛋白16E5的癌細胞，對白金藥物的敏感性較差。所以，我們認為人類乳突病毒是可能導致肺細胞癌病變，人類乳突病毒在癌細胞造成的變化，可能是干擾了表皮上皮生長因子受體訊號傳遞的過程，仍需更多的分子機轉實驗加以證實。
In Taiwan, cancer is the leading cause of death in the past 30 years and lung cancer is the main cause of cancer death. Factors other than smoking might contribute to lung carcinogenesis, including genetics and viruses. Human papillomavirus is an identified factor for cervical carcinogenesis. The mechanisms have been proved due to HPV E6 oncoprotein suppressing p53 gene and HPV E7 oncoprotein suppressing Rb gene. Persistent high-risk HPV infection and defective host immunity might contribute to cervical carcinogenesis. HPV infections have also been an important risk factor for head-and-neck cancer and HPV positive oropharyngeal cancer patients have a better survival. The transmission route is thought due to high-risk sexual behavior, resulting in oral HPV infection. Epidermal growth factor receptor (EGFR) signaling plays a major pathway for carcinogenesis. EGFR overexpression is frequently found in lung cancer tissues. EGFR nuclear trafficking, from the cell membrane, Golgi apparatus, endothelial reticulum to the nucleus, causing angiogenesis and cell proliferation, appears to be involved in carcinogenesis. Nuclear EGFR has shown to be an important prognostic factor for ovarian and breast cancer, therefore, nuclear EGFR may have a determinate effect for treatment response. Previous papers have shown that the association between EGFR mutations and nonsmoking female lung cancer patients and HPV 16/18 infections have a higher prevalence in Taiwanese female lung cancer patients. My doctoral dissertation has investigated the role of HPV infections in lung cancer. There are three major results. In the first study, we have proved the presence of HPV in the lung cancer tissues and lung adenocarcinoma patients with HPV infections have a better survival. In the second study, we found that the correlation of HPV major capsid protein and cytoplasmic EGFR expression and the association between HPV 16E6/18E6 protein and nuclear EGFR protein in the lung carcinoma tissues. HPV 16E6/18E6 oncoprotein plays a determinant role for poor prognosis in early lung cancer patients. In the third study, we have found that HPV 16E5, HPV 16E6 and HPV 16E7 protein might interfere the EGFR nuclear trafficking and change the cancer behavior for an increase of nuclear phosphorylated EGFR protein in A431-16E5 cells, resulting in resistance of cisplatin administration, increased total nuclear EGFR protein in A431-16E6 cells, and the interaction between HPV 16E7 protein and EGFR protein. In conclusion, we thought that HPV might contribute to lung carcinogenesis and HPV 16E5, HPV 16E6 and HPV 16E7 might interfere the EGFR signaling pathway in A431 cell line. We need more molecular experiments to prove the mechanism for HPV induced lung carcinogenesis. |
