肺癌細胞膜異位表達三磷酸腺苷合成酶阻斷後的分子機制探討

肺癌是全球癌症相關類別死因的首要原因。現行的標靶治療雖然能提供顯著的臨床反應、提升治療效果、且具有較少的副作用，但是這些標把藥物的治療效果仍然是有限的。因為多數患者隨著時間會對藥物產生耐藥性，導致癌症的復發或惡化。因此，尋找新的治療標靶分子可能可以達到這項未達治療標準的醫療需求。據報導發現粒線體F1Fo型三磷酸腺苷合酶會異位表達在癌細胞的細胞膜上，但其位於此處的功能尚不清楚。本研究中，我們發現表面型三磷酸腺苷合成酶和電子傳遞鏈皆於細胞膜上的呈現塊狀的分佈，這對於維持癌細胞增殖是相當重要的。應用表面型三磷酸腺苷合成酶抑制黃綠青黴素能夠誘導的細胞週期阻滯和抑制肺癌細胞的增殖及細胞的非貼附性生長。透過蛋白質體圖譜分析，我們發現黃綠青黴素的處理能誘導細胞發生未折疊蛋白反應以及轉譯起始因子eIF2α蛋白的磷酸化，進而觸發細胞生長的抑制作用。黃綠青黴素造成的eIF2α蛋白磷酸化可以透過降低PERK的表現、以及活性氧清除劑半胱氨酸所回復，建立了黃綠青黴素的處理會大量誘導活性氧分子的產生，透過PERK及eIF2α蛋白磷酸化而造成蛋白質轉譯的下降而導致細胞生長停滯的關係。因此，未折疊蛋白反應啟動和活性氧分子上升能互相正向加強，因此開啟了一個正向回饋迴路進而強化細胞生長的抑制。我們的研究結果釐清了表面型三磷酸腺苷合成酶在肺癌細胞的細胞膜的分子功能，並且進一步探討了其作為癌症治療上的潛力。

關鍵字

表面型三磷酸腺苷合成酶；未折疊蛋白反應；蛋白質體學；肺腺癌；黃綠青黴素

並列摘要

Lung cancer is the leading cause of cancer-related death worldwide. Although targeted therapies can initiate dramatic clinical responses and offer significant therapeutic benefits and fewer side effects, the effectiveness of targeted therapies is currently limited because the majority of patients develop resistance over time, resulting in a relapse or worsening of the cancer. Thus, discovery of novel therapeutic markers might achieve the unmet clinical need. Ectopic expression of the mitochondrial F1Fo-ATP synthase on the plasma membrane has been reported to occur in cancer but whether it exerts a functional role in this setting remains unclear. Here we show that ectopic ATP synthase and the electron transport chain exist in a punctuated distribution on the plasma membrane of lung adenocarcinoma cells where it is critical to support cancer cell proliferation. Applying ATP synthase inhibitor citreoviridin induced cell cycle arrest and inhibited proliferation and anchorage-independent growth of lung cancer cells. Analysis of protein expression profiles after citreoviridin treatment suggested this compound induced the unfolded protein response (UPR) associated with phosphorylation of the translation initiation factor 2α (eIF2α), triggering cell growth inhibition. Citreoviridin-enhanced eIF2α phosphorylation could be reversed by siRNA-mediated attenuation of the UPR kinase PERK combined with treatment with the antioxidant N-acetylcysteine, establishing that reactive oxygen species (ROS) boost UPR after citreoviridin treatment. Thus, a coordinate elevation of UPR and ROS initiates a positive feedback loop that convergently blocks cell proliferation. Our findings reveal a molecular function for ectopic ATP synthase on the plasma membrane in lung cancer cells and prompt further study of its inhibition as a potential therapeutic application.

並列關鍵字

ectopic ATP synthase ； unfolded protein response ； proteomics ； lung adenocarcinoma ； citreoviridin

參考文獻

1. Ferlay, J. et al. Estimates of worldwide burden of cancer in 2008: GLOBOCAN 2008. International Journal of Cancer 127, 2893-2917 (2010).

2. Jemal, A., Siegel, R., Xu, J. & Ward, E. Cancer statistics, 2010. CA: a Cancer Journal for Clinicians 60, 277-300 (2010).

5. Ding, L. et al. Somatic mutations affect key pathways in lung adenocarcinoma. Nature 455, 1069-1075 (2008).

6. Weir, B.A. et al. Characterizing the cancer genome in lung adenocarcinoma. Nature 450 (2007).

7. Paez, J.G. et al. EGFR mutations in lung cancer: correlation with clinical response to gefitinib therapy. Science Signalling 304, 1497 (2004).

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肺癌細胞膜異位表達三磷酸腺苷合成酶阻斷後的分子機制探討

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