Mechanistic Target of Rapamycin (mTOR) Inhibition Synergizes with Reduced Internal Ribosome Entry Site (IRES)-mediated Translation of Cyclin D1 and c-MYC mRNAs to Treat Glioblastoma
Mechanistic Target of Rapamycin (mTOR) Inhibition Synergizes with Reduced Internal Ribosome Entry Site (IRES)-mediated Translation of Cyclin D1 and c-MYC mRNAs to Treat Glioblastoma
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DOI：
10.1074/jbc.m116.726927
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发表时间：
2016-07-01
影响因子：
4.8
通讯作者：
Gera, Joseph
中科院分区：
文献类型：
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作者：
Holmes, Brent;Lee, Jihye;Gera, Joseph
我们之前的工作已经证明，胶质母细胞瘤 (GBM) 肿瘤细胞中存在一种内在的 mRNA 特异性蛋白质合成挽救途径，该途径对雷帕霉素 (mTOR) 抑制剂的机械靶点具有抗性。面对整体 eIF-4E 介导的翻译抑制，这种内部核糖体进入位点 (IRES) 依赖性 mRNA 翻译起始途径的激活导致参与细胞周期进展的关键转录物的持续翻译。最近，我们鉴定了化合物 11 (C11)，这是一种能够抑制 c-MYC IRES 翻译的小分子，其结果是阻断必需的 c-MYC IRES 反式作用因子、异源核糖核蛋白 A1 与其 IRES 的相互作用。在这里，我们证明 C11 还可以阻断细胞周期蛋白 D1 IRES 依赖性启动，并在与雷帕霉素激酶抑制剂 PP242 的机制靶点组合时表现出协同抗 GBM 特性。研究了 C11 的结构-活性关系，并鉴定了 IRES-J007，其显示出改善的 IRES 依赖性起始阻断以及与 PP242 的协同抗 GBM 作用。 C11 和 IRES-J007 的机制研究揭示了抑制剂在异质核核糖核蛋白 A1 的 UP1 片段内的结合，对接分析表明靠近 RRM2 的小口袋作为潜在的结合位点。我们进一步证明，IRES-J007 和 PP242 的联合治疗显着降低了小鼠 GBM 异种移植物的肿瘤生长，并且联合抑制剂治疗显着降低了这些肿瘤中细胞周期蛋白 D1 和 c-MYC 转录物的 mRNA 翻译状态。这些数据支持联合使用 IRES-J007 和 PP242 在 GBM 中实现协同抗肿瘤反应。
Our previous work has demonstrated an intrinsic mRNA-specific protein synthesis salvage pathway operative in glioblastoma (GBM) tumor cells that is resistant to mechanistic target of rapamycin (mTOR) inhibitors. The activation of this internal ribosome entry site (IRES)-dependent mRNA translation initiation pathway results in continued translation of critical transcripts involved in cell cycle progression in the face of global eIF-4E-mediated translation inhibition. Recently we identified compound 11 (C11), a small molecule capable of inhibiting c-MYC IRES translation as a consequence of blocking the interaction of a requisite c-MYC IRES trans-acting factor, heterogeneous nuclear ribonucleoprotein A1, with its IRES. Here we demonstrate that C11 also blocks cyclin D1 IRES-dependent initiation and demonstrates synergistic anti-GBM properties when combined with the mechanistic target of rapamycin kinase inhibitor PP242. The structure-activity relationship of C11 was investigated and resulted in the identification of IRES-J007, which displayed improved IRES-dependent initiation blockade and synergistic anti-GBM effects with PP242. Mechanistic studies with C11 and IRES-J007 revealed binding of the inhibitors within the UP1 fragment of heterogeneous nuclear ribonucleoprotein A1, and docking analysis suggested a small pocket within close proximity to RRM2 as the potential binding site. We further demonstrate that co-therapy with IRES-J007 and PP242 significantly reduces tumor growth of GBM xenografts in mice and that combined inhibitor treatments markedly reduce the mRNA translational state of cyclin D1 and c-MYC transcripts in these tumors. These data support the combined use of IRES-J007 and PP242 to achieve synergistic antitumor responses in GBM.