Targeting Translation Control in Malignant Glioma

描述（由申请人提供）：癌细胞表现出失控的生长和增殖，因为它们不适当地选择了聚集在翻译机制上并控制核糖体募集到mRNA的促有丝分裂信号传导途径。我们正在利用这一原理，以基因重组脊髓灰质炎病毒靶向胶质母细胞瘤（GBM）。常规的蛋白质合成是在mRNA上的典型5'帽结构处接合复杂蛋白质网络后开始的。某些编码关键生长、增殖和存活蛋白的mRNA可以通过以帽非依赖性方式直接募集核糖体亚基来逃避这种调控约束。有趣的是，这些mRNA启动翻译的基本机制与脊髓灰质炎病毒相同。通过对参与病毒翻译的脊髓灰质炎病毒RNA序列进行遗传操作，我们消除了正常CNS中的病毒复制能力，而不影响其对GBM的强细胞毒性。我们发现PVSRIPO的肿瘤细胞毒性是由MAPK信号决定的翻译机制，有利于在恶性肿瘤中的帽非依赖性翻译。我们的研究结果表明，这些信号的翻译因子可能参与细胞周期的调控，通过协调基因表达，通过选择性的翻译启动在有丝分裂。该项目旨在揭示帽独立翻译在癌症中的生理意义，阐明控制其活性的机制，并制定合理的策略来靶向癌症治疗。我们提出了三个具体的目标：1）揭示在有丝分裂过程中帽非依赖性翻译起始的生理作用和控制.我们将研究在有丝分裂过程中诱导帽非依赖性翻译的分子基础。2)阐明eIF4G调控的IRES介导的翻译机制。我们确定的信号转导途径，集中在中央支架的翻译装置和核糖体适配器，eIF4G。我们将研究调节eIF4G在帽非依赖性翻译起始中的作用的分子机制。3)确定增强胶质瘤细胞杀伤的策略，靶向诱导非帽依赖性翻译。抑制mTORC1会对翻译机制产生一系列影响，共同诱导癌细胞中的帽非依赖性翻译。我们将在动物胶质瘤模型中测试mTORC1抑制剂雷帕霉素与溶瘤脊髓灰质炎病毒的组合以协同增强肿瘤细胞杀伤。

DESCRIPTION (provided by applicant): Cancer cells exhibit deregulated growth and proliferation, because they inappropriately co-opt mitogenic signaling pathways that converge on translation machinery and control ribosome recruitment to mRNAs. We are exploiting this principle to target glioblastoma (GBM) with genetically recombinant poliovirus. Conventional protein synthesis is initiated upon engaging a complex protein network at the canonical 5' cap-structure on mRNAs. Certain mRNAs encoding critical growth, proliferation and survival proteins can evade this regulatory constraint by recruiting ribosomal subunits directly, in a cap-independent manner. Intriguingly, the basic mechanism employed by such mRNAs to initiate translation is shared by poliovirus. Through genetic manipulation of poliovirus RNA sequences involved in viral translation, we eliminated viral replication capacity in the normal CNS, without affecting its strong cytotoxicity for GBM. We discovered that PVSRIPO's tumor cytotoxicity is determined by MAPK signals to translation machinery that favor cap-independent translation in malignancy. Our findings suggest that such signals to translation factors may participate in cell cycle regulation by coordinating gene expression via alternative translation initiation during mitosis. This project aims to unravel the physiological significance of cap-independent translation in cancer, to elucidate mechanisms that control its activity and to develop rational strategies to target it for cancer therapy. We propose three Specific Aims: 1) Unravel the physiological role and control of cap- independent translation initiation during mitosis. We will investigate the molecular basis for induction of cap- independent translation during mitosis. 2) Elucidate the mechanism of IRES-mediated translation controlled by eIF4G. We identified signal transduction pathways that converge on the central scaffold of the translation apparatus and ribosome adaptor, eIF4G. We will study the molecular mechanisms regulating eIF4G¿s role in cap-independent translation initiation. 3) Identify strategies to enhance glioma cell killing throuh targeted induction of cap- independent translation. Inhibition of mTORC1 elicits a series of effects on translation machinery that jointly induce cap-independent translation in cancer cells. We will test combining the mTORC1 inhibitor rapamycin with oncolytic poliovirus to synergistically enhance tumor cell killing in an animal glioma model.