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MNK1 通路活性维持雷帕霉素治疗的神经胶质瘤中的蛋白质合成。

MNK1 pathway activity maintains protein synthesis in rapalog-treated gliomas.

出版信息

J Clin Invest. 2014 Feb;124(2):742-54. doi: 10.1172/JCI70198. Epub 2014 Jan 9.

Abstract

High levels of mammalian target of rapamycin complex 1 (mTORC1) activity in malignant gliomas promote tumor progression, suggesting that targeting mTORC1 has potential as a therapeutic strategy. Remarkably, clinical trials in patients with glioma revealed that rapamycin analogs (rapalogs) have limited efficacy, indicating activation of resistance mechanisms. Targeted depletion of MAPK-interacting Ser/Thr kinase 1 (MNK1) sensitizes glioma cells to the mTORC1 inhibitor rapamycin through an indistinct mechanism. Here, we analyzed how MNK1 and mTORC1 signaling pathways regulate the assembly of translation initiation complexes, using the cap analog m7GTP to enrich for initiation complexes in glioma cells followed by mass spectrometry-based quantitative proteomics. Association of eukaryotic translation initiation factor 4E (eIF4E) with eIF4E-binding protein 1 (4EBP1) was regulated by the mTORC1 pathway, whereas pharmacological blocking of MNK activity by CGP57380 or MNK1 knockdown, along with mTORC1 inhibition by RAD001, increased 4EBP1 binding to eIF4E. Furthermore, combined MNK1 and mTORC1 inhibition profoundly inhibited 4EBP1 phosphorylation at Ser65, protein synthesis and proliferation in glioma cells, and reduced tumor growth in an orthotopic glioblastoma (GBM) mouse model. Immunohistochemical analysis of GBM samples revealed increased 4EBP1 phosphorylation. Taken together, our data indicate that rapalog-activated MNK1 signaling promotes glioma growth through regulation of 4EBP1 and indicate a molecular cross-talk between the mTORC1 and MNK1 pathways that has potential to be exploited therapeutically.

摘要

哺乳动物雷帕霉素靶蛋白复合物 1(mTORC1)活性水平在恶性神经胶质瘤中升高,促进肿瘤进展,表明靶向 mTORC1 具有作为治疗策略的潜力。值得注意的是,在神经胶质瘤患者中的临床试验表明,雷帕霉素类似物(rapalogs)疗效有限,表明存在耐药机制的激活。MAPK 相互作用丝氨酸/苏氨酸激酶 1(MNK1)的靶向耗竭通过不明确的机制使神经胶质瘤细胞对 mTORC1 抑制剂雷帕霉素敏感。在这里,我们分析了 MNK1 和 mTORC1 信号通路如何调节翻译起始复合物的组装,使用帽类似物 m7GTP 在神经胶质瘤细胞中富集起始复合物,然后进行基于质谱的定量蛋白质组学分析。真核翻译起始因子 4E(eIF4E)与 eIF4E 结合蛋白 1(4EBP1)的结合受 mTORC1 途径调节,而通过 CGP57380 或 MNK1 敲低药理学阻断 MNK 活性,以及通过 RAD001 抑制 mTORC1,增加 4EBP1 与 eIF4E 的结合。此外,联合 MNK1 和 mTORC1 抑制可显著抑制神经胶质瘤细胞中 4EBP1 在 Ser65 的磷酸化、蛋白质合成和增殖,并减少原位神经胶质瘤(GBM)小鼠模型中的肿瘤生长。GBM 样本的免疫组织化学分析显示 4EBP1 磷酸化增加。总之,我们的数据表明,rapalog 激活的 MNK1 信号通过调节 4EBP1 促进神经胶质瘤的生长,并表明 mTORC1 和 MNK1 途径之间存在潜在的分子相互作用,具有治疗潜力。

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