代謝酵素在肺癌發展與免疫治療的角色探討

The role of metabolic enzymes in lung cancer progression and immunotherapy

劉冠廷(Kuan-Ting Liu)

指導教授 ： 郭柏麟

高雄醫學大學/醫學院/臨床醫學研究所博士班/博士(2019年)

摘要

癌症近年來都是台灣的死亡原因第一位，而其中肺癌在我國是死亡率排名第一的癌症，所以肺癌相關的致病機轉及藥物治療研究是相當重要的。
Indoleamine 2,3-dioxygenase (IDO)是色胺酸代謝路徑的速率決定酵素，IDO的活化會造成免疫抑制並影響腫瘤預後。之前的研究發現給予IDO shRNA可以抑制腫瘤生長並增加腫瘤中的中性球浸潤，而這些腫瘤浸潤中性球的功能還不明。研究用LLC1肺癌模式用來研究中性球的功能，以肌肉注射IDO shRNA 或口服IDO抑制劑治療可延緩腫瘤生長並增加腫瘤中的中性球，腫瘤浸潤中性球同時表現高度的tumor necrosis factor-α 和transforming growth factor-β。此外，IDO shRNA治療誘發脾臟中細胞的interferon-γ 和tryptophan transfer RNA 表現，系統缺乏中性球會消除IDO shRNA造成的腫瘤治療效果並抑制脾臟中細胞的interferon-γ和tumor necrosis factor-α的表現。研究認為在IDO shRNA治療後出現的腫瘤相關的中性球出現抗腫瘤的表現型態。
過去研究發現部份脂質代謝酵素的表現和癌症相關。此次研究在PRECOG和Kaplan-Meier plotter 資料庫中找出 acyl-CoA thioesterase (ACOT)7、ACOT11、ACOT13、soluble carrier family 27 member A4 (SLC27A4) 和SLC27A5 的高表現和肺癌不良臨床預後相關。內質網是細胞胞器牽涉到許多種的生理活動，在腫瘤微環境中，會造成折疊異常蛋白質的堆積，這些堆積會導致內質網壓力及未折疊蛋白質反應。增強未折疊蛋白質反應訊號路徑反應也和許多種類的癌症有關，而內質網壓力對acyl-CoA 代謝酵素的影響還未十分了解。研究在public microarray database (GEO) 取得一組資料，其中ACOT7、ACOT11、SLC27A4和SLC27A5的表現和內質網壓力無關。相反的，部分酵素的表現下降。肺癌細胞株在經thapsigargin處置後脂肪酸吸收能力被抑制，但細胞內的活性氧化物量不受抑制，進行基因富集和調控元素分析找到可能的調控元素及肺癌在內質網壓力下反應的交互作用網路。

關鍵字

肺癌 ； 吲哚胺2,3-雙加氧酶中性球 ； 脂質代謝 ； 內質網壓力

並列摘要

Cancer is the leading cause of mortality and the lung cancer is the leading cancer in Taiwan. The researches in mechanism of carcinogenesis and cancer therapy are very important.
Indoleamine 2,3-dioxygenase (IDO) is a rate limiting enzyme in tryptophan-degrading pathways. IDO activity results in immune suppression and affect cancer prognosis. The previous studies demonstrate that delivery of short hairpin against IDO (IDO shRNA) suppresses tumor growth and increases neutrophils infiltration into tumor. However, the function of IDO shRNA-induced neutrophils is not clear. The LLC1 lung cancer model was used to investigate the role of these neutrophils. Intramuscular injection of IDO shRNA or IDO inhibitor treatment delayed tumor growth and both treatments increased neutrophil infiltration in tumor. Enriched tumor-infiltrating neutrophils expressed both high level of tumor necrosis factor-α and transforming growth factor -β. In addition, IDO shRNA treatment induced interferon-γ and tryptophan transfer RNA expression in splenocytes. Systematic depletion of neutrophils abolished the IDO shRNA-induced therapeutic effect and suppressed the levels of interferon-γ and tumor necrosis factor-α. In conclusion, these tumor-infiltrating neutrophils show antitumorigenic phenotype in spleen after IDO shRNA treatment in a murine lung cancer model.
Previous studies had revealed some lipid metabolism associated with cancer development. Evaluation of PRECOG and Kaplan-Meier plotter databases in the present study suggested that high expression of ACOT 7, ACOT11, ACOT13, SLC27A4 and SLC27A5 was associated with poor clinical outcomes. The endoplasmic reticulum (ER) is an organelle involved in various physiological processes. Acumulation of unfolded and misfolded proteins were found in a physiological tumor microenvironment. Such accumulation induces ER stress and unfolded protein responses (UPRs). Increased UPR signaling pathways are associated with multiple types of cancer. The influence of ER stress on acyl-CoA metabolic enzymes is not well understood. In the study, evaluation of a dataset from public microarray database (GEO) revealed expression levels of ACOT7, ACOT11, SLC27A4 and SLC27A5 were not altered after induction of ER stress. By contrast, expression of some enzymes was decreased. Fatty acid uptake capacity was suppressed in lung cancer cell lines after thapsigargin treatment but intracellular reactive oxygen species levels were not suppressed. Gene enrichment and regulatory element analysis were performed and found possible regulatory elements, and the interaction network involved in responses to ER stress in lung cancer.

並列關鍵字

lung cancer ； Indoleamine 2,3-dioxygenase ； neutrophil ； fatty acid ； endoplasmic reticulum stress

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