多形性膠質母細胞瘤(glioblastoma multiforme; GBM)是成人腦部最常見和最具侵襲性的原發性腦腫瘤。為了增加患者生存的機率，尋找更有效的抗腦腫瘤治療方法至關重要。有文獻指出糖尿病的胰島素阻抗、高血糖或慢性發炎的作用機制都會影響癌症的發展，因此我們利用抗糖尿病的藥物組進行藥物篩選測試，預期找出有效抑制腦膠質瘤細胞的藥物。Darapladib (SB-480848)是一種Lp-PLA2的抑制劑，已知可用於治療動脈粥樣硬化。脂蛋白相關磷脂酶A2 (Lp-PLA2; PLA2G7基因)能作為心血管疾病中炎症的預測生物標誌物。有研究報告在小鼠腫瘤模型中，PLA2G7的缺乏可減少結腸腫瘤的形成，故我們進一步評估Darapladib對於腦瘤細胞之影響。本篇實驗發現，Darapladib能有效降低大鼠人類腦膠質瘤細胞的生長。利用LDH試劑、Annexin-V染色、PI染色以及JC-1染色並分別搭配ELISA、螢光顯微鏡與流式細胞儀分析，可觀察到Darapladib造成細胞凋亡和粒線體膜電位下降的現象。細胞因為Darapladib的作用有引起立即早期基因(IEGs) c-Fos基因的表現增加，並誘發C6細胞內ERK1/2磷酸化上升，但是卻抑制調控細胞存活的AKT路徑。我們更進一步利用離體腦組織切片培養系統確認在Darapladib處理植入腦組織切片的C6腦膠質瘤細胞的生長的確也受到抑制。總結以上研究結果，Darapladib可抑制腦膠質瘤生長並可能透過胞內粒線體功能下降促進細胞凋亡，Darapladib誘發ERK與IEGs活化，但抑制AKT細胞訊息傳遞路徑。

Glioblastoma Multiforme (GBM) is the most frequent and aggressive brain tumor in adults. To improve the patent’s survival rate, it is important to develop more effective treatment for anti-GBM. Lipoprotein-associated phospholipase A2 (Lp-PLA2) that is encoded by the PLA2G7 gene) serves as a predictive biomarker of sub-clinical inflammation in cardiovascular diseases. Evidence also shows that diabetes-related insulin resistance, hyperglycemia or chronic inflammation can influence the progression of cancers. Thus, several drugs collected in the Anti-Diabetic Compound Library were tested through the examination of C6 rat glioma cells. We found that Darapladib, a Lp-PLA2 inhibitor for treating atherosclerosis, was the inhibitory effect on glioma cell growth. The absence of PLA2G7 robustly decreased colon tumor formation in the mouse tumor model. Furthermore, we evaluated the effect of Darapladib on the growth of C6 rat glioma cells and human malignant glioma cell lines (U87 and U251). The results show that Darapladib effectively reduced the cell viability of rat and human glioma cell lines. By lactate dehydrogenase (LDH) assay, Annexin V staining, propidium iodide (PI) staining and JC-1 staining combined with ELISA, immunofluorescence and flow cytometric analysis, we indicated that Darapladib triggered apoptosis and mitochondrial membrane depolarization. Exposure of C6 cells to Darapladib upregulated immediate-early gene (IEG), c-Fos. Darapladib can increase phosphorylation of ERK1/2, whereas treatment with Darapladib reduced phosphorylation level of protein kinase B (PKB; AKT). The growth of C6 cells that were implanted into the ex vivo brain tissue slices was suppressed by Darapladib. In conclusion, these results demonstrate that Darapladib inhibits glioma growth via the induction of mitochondrial dysfunction, and suppressed AKT signaling transduction, but trigger an increased phosphorylation of ERK1/2.

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