鄰苯二甲酸二(2-乙基己基)酯對於肺腺癌之癌化過程影響探討

Abstract

肺癌為全球十大死因惡性腫瘤之一，在台灣發生率為所有惡性腫瘤中的第三名，死亡率則為為第一名，為威脅人民健康的重大疾病之一。肺癌可分為兩大類型：小細胞肺癌(small cell lung cancer)及非小細胞肺癌（non-small cell lung cancer, NSCLC），以非小細胞肺癌為大宗，約佔了85％的肺癌病患，其中又以肺腺癌(lung adenocarcinoma)佔NSCLC多數。造成肺腺癌的原因十分的複雜，環境汙染物、致癌基因的突變、遺傳等因素皆會影響肺腺癌的進程。 本篇研究的第一部分為探討環境汙染物-DEHP對於肺腺癌的影響，DEHP被發現與許多癌症的進程有關，但過去鮮少有探討塑化劑與肺腺癌關係的文獻。根據實驗結果，我們發現長期暴露DEHP會促使細胞轉移能力上升，在進一步利cDNA微陣列分析後發現DEHP會使調控細胞轉移、增生及黏附的基因表現量上升，其中一重要基因AGR2在過去的文獻研究中顯示與癌症進程有關，綜合以上的實驗結果，我們發現DEHP會促使AGR2表現量上升而使細胞轉移能力增強並提供DEHP影響肺癌的進程一分子機轉。 第二部分以代謝體學探討上皮生長因子(Epidermal growth factor receptor, EGFR)的突變對於肺腺癌細胞代謝之影響，並從中找出具代表此疾病的生物標記。L858R點突變為常見的EGFR突變形式。因此，針對EGFR所開發的藥物-酪胺酸激酶抑制劑(tyrosine kinase inhibitor, TKI)成為近年來治療肺腺癌的主流。然而，臨床上發現服用TKI後，病人會產生T790M的點突變會使得對EGFR-TKI治療產生抗藥性。因此，找出一生物標記作為診斷及用藥評估為一重要課題，我們利用代謝體學來分析此兩種EGFR突變小鼠肺癌組織中代謝途徑的差異，實驗結果顯示有二十個代謝物在EGFR突變小鼠肺臟中具顯著差異，且主要分布於糖解、檸檬酸循環、五碳糖循環、脂質代謝以及甲硫氨酸-回收途徑之中。我們建構出帶有EGFR突變的肺癌組織中其代謝體圖譜，並從中找出與細胞生長及癌症生成相關的代謝物如: spermine、hypoxanthine等。未來將會進一步分析病人血清來找出可以作為生物標記之代謝物。 根據本篇論文的研究顯示長期暴露DEHP會影響肺癌之進程，並利用代謝體學建立帶有EGFR突變的肺癌之代謝圖譜。

Lung cancer is the leading cause of cancer mortality in worldwide. According to the Taiwan cancer Statistics show that lung cancer mortality rate are the highest among all other cancer types. Three main types of lung cancer have been discovered: squamous lung cancer, small cell lung cancer and non-small cell lung cancer (NSCLC). Above all three types of lung cancer, 85% belongs to non-small cell lung cancers. Lung adenocarcinoma is the most common type of NSCLC. Many factors are known to increase the risk of cancer, including environmental toxins, oncogene mutation or inheritance, etc. The first part of our research is to investigate the effect of phthalates in lung adenocarcinoma cells. Phthalates (DEHP) incident in Taiwan was one of the most serious food safety issues that ever occurred. Exposure of the DEHP has been suggested to increase malignancy of many cancers in animal studies. But the relationship between DEHP and lung cancer was still unclear. According to our findings. Chronic DEHP exposure can enhance migration ability in CL1-0. Microarray analysis revealed that DEHP exposure influenced many genes related to cell metastasis、cell-adhesion and cell proliferation. We identified one important gene, anterior gradient homolog 2 (AGR2) that has been reported to play crucial roles in metastatic progression of cancer cells which might contribute to the mechanisms of DEHP-induced tumor progression. Herein, we provide possible mechanisms revealing how chronic DEHP exposure modulates lung adenocarcinoma progression. The second part of this study is to identify for potential metabolite biomarkers of lung cancer with EGFR mutations. L858R mutation in exon 21 of EGFR is the most common mutation in NSCLC. Lung cancer patients with activating EGFR mutations usually receive long term tyrosine kinase inhibitors treatment. However, a secondary mutation of T790M in EGFR would cause resistance to TKI treatment which leads to bad prognosis. Therefore, development of effective molecular biomarkers for early diagnosis becomes increasingly important in NSCLC patients. Transgenic engineered mice with Tet-on human EGFR T790M+L858R or EGFR L858R system were used to conditionally develop lung adenocarcinomas. Twenty metabolites were identified in lung tissue of EGFR mutant mice involving several key metabolic pathways such as glycolysis, tricarboxylic acid (TCA) cycle, fatty acids and methionine-salvage metabolism. Our metabolite profiling data also reveals several key metabolites such as spermine and hypoxanthine which are crucial in tumor progressions. Taken together, findings of this study suggest that DEHP might play crucial roles in lung adenocarcinoma progression. Furthermore, metabolite profile of lung cancer with EGFR mutation may provide potential therapeutic targets for lung cancer treatments.