Cucurbitacin I Induces Protective Autophagy in Glioblastoma in Vitro and in Vivo*
Cucurbitacin I Induces Protective Autophagy in Glioblastoma in Vitro and in Vivo*
复制标题
DOI：
10.1074/jbc.m113.528760
复制
发表时间：
2014-03
期刊：
影响因子：
--
通讯作者：
G. Yuan;Shaofeng Yan;H. Xue;Ping Zhang;Jintang Sun;Gang Li
中科院分区：
文献类型：
--
作者：
G. Yuan;Shaofeng Yan;H. Xue;Ping Zhang;Jintang Sun;Gang Li
背景：靶向阻断STAT 3可抑制恶性胶质瘤的生长和存活。结果：葫芦素I通过AMPK/mTOR/p70 S6 K通路诱导保护性自噬，下调HIF-1α表达。结论：自噬阻断可使胶质母细胞瘤对葫芦素I治疗敏感。意义：本研究为葫芦素I对胶质母细胞瘤的生物学和抗增殖活性提供了新的见解。迫切需要新的治疗途径来改善多形性胶质母细胞瘤（GBM）患者的结局。目前的研究表明，葫芦素I是JAK 2/STAT 3的天然选择性抑制剂，对多种癌细胞类型具有有效的抗癌作用。本研究表明葫芦素I可诱导细胞自噬和凋亡。GBM细胞暴露于葫芦素I通过激活bcl-2家族蛋白导致明显的凋亡性细胞死亡。用葫芦素I处理的细胞上调Beclin 1并触发自噬体形成和积累以及LC 3 I转化为LC 3 II。在葫芦素I诱导的自噬中，AMP活化蛋白激酶/哺乳动物雷帕霉素靶蛋白/p70 S6 K通路被激活，而PI 3 K/AKT通路未被激活，同时缺氧诱导因子1α水平降低。FG-4497诱导的低氧诱导因子1α稳定过表达可阻止葫芦素I诱导的自噬和bcl-2下调。Beclin 1的敲除或用自噬抑制剂3-甲基腺嘌呤处理也可以抑制葫芦素I诱导的自噬。免疫共沉淀实验表明，经葫芦素I处理后，Bcl-2与Beclin 1/hVps 34的相互作用明显减弱。此外，敲低beclin 1或用溶酶体抑制剂氯喹处理使癌细胞对葫芦素I诱导的凋亡敏感。最后，异种移植模型提供了葫芦素I诱导的细胞凋亡和自噬在体外发生的额外证据。我们的研究结果为葫芦素I介导的GBM细胞死亡的分子机制提供了新的见解，并可能为GBM患者提供有效的治疗。
Background: Targeting disruption of STAT3 results in inhibition of tumor growth and survival in malignant glioma. Results: Cucurbitacin I triggers protective autophagy through the AMPK/mTOR/p70S6K pathway and down-regulates HIF-1α. Conclusion: Autophagy blockade sensitizes glioblastoma to cucurbitacin I treatment. Significance: This study provides new insights into the biological and antiproliferative activities of cucurbitacin I against glioblastoma. There is an urgent need for new therapeutic avenues to improve the outcome of patients with glioblastoma multiforme (GBM). Current studies have suggested that cucurbitacin I, a natural selective inhibitor of JAK2/STAT3, has a potent anticancer effect on a variety of cancer cell types. This study showed that autophagy and apoptosis were induced by cucurbitacin I. Exposure of GBM cells to cucurbitacin I resulted in pronounced apoptotic cell death through activating bcl-2 family proteins. Cells treatment with cucurbitacin I up-regulated Beclin 1 and triggered autophagosome formation and accumulation as well as conversion of LC3I to LC3II. Activation of the AMP-activated protein kinase/mammalian target of rapamycin/p70S6K pathway, but not the PI3K/AKT pathway, occurred in autophagy induced by cucurbitacin I, which was accompanied by decreased hypoxia-inducible factor 1α. Stable overexpression of hypoxia-inducible factor 1α induced by FG-4497 prevented cucurbitacin I-induced autophagy and down-regulation of bcl-2. Knockdown of beclin 1 or treatment with the autophagy inhibitor 3-methyladenine also inhibited autophagy induced by cucurbitacin I. A coimmunoprecipitation assay showed that the interaction of Bcl-2 and Beclin 1/hVps34 decreased markedly in cells treated with cucurbitacin I. Furthermore, knockdown of beclin 1 or treatment with the lysosome inhibitor chloroquine sensitized cancer cells to cucurbitacin I-induced apoptosis. Finally, a xenograft model provided additional evidence for the occurrence of cucurbitacin I-induced apoptosis and autophagy in vitro. Our findings provide new insights into the molecular mechanisms underlying cucurbitacin I-mediated GBM cell death and may provide an efficacious therapy for patients harboring GBM.