Targeting Translation Control in Malignant Glioma

描述（由申请人提供）：癌细胞表现出不受调节的生长和增殖，因为它们不恰当地选择有丝分裂信号通路，这些信号通路聚集在翻译机制上，并控制核糖体向mrna的募集。我们正在利用这一原理用基因重组脊髓灰质炎病毒靶向胶质母细胞瘤（GBM）。传统的蛋白质合成是在mrna的典型5'帽结构上参与一个复杂的蛋白质网络时开始的。某些编码关键生长、增殖和存活蛋白的mrna可以通过直接募集核糖体亚基，以帽独立的方式逃避这种调节约束。有趣的是，这些mrna启动转译的基本机制与脊髓灰质炎病毒相同。通过基因操作参与病毒转译的脊髓灰质炎病毒RNA序列，我们消除了病毒在正常中枢神经系统中的复制能力，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，MAPK信号传递给翻译机制，在恶性肿瘤中有利于帽独立翻译。我们的研究结果表明，这些传递给翻译因子的信号可能在有丝分裂过程中通过替代翻译起始协调基因表达，从而参与细胞周期调节。本项目旨在揭示cap-independent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针对其进行癌症治疗。我们提出了三个具体目标：1)揭示有丝分裂过程中帽非依赖性翻译起始的生理作用和调控。我们将研究在有丝分裂过程中诱导帽无关翻译的分子基础。2)阐明eIF4G调控ires介导的翻译机制。我们确定了信号转导途径，这些信号转导途径聚集在翻译装置和核糖体接头的中心支架eIF4G上。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)确定通过靶向诱导帽无关翻译来增强胶质瘤细胞杀伤的策略。mTORC1的抑制引发了一系列对翻译机制的影响，这些影响共同诱导了癌细胞中帽非依赖性翻译。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性脊髓灰质炎病毒的联合作用，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. PUBLIC HEALTH RELEVANCE: Control over the synthesis of proteins is profoundly de-regulated in all cancers, due to abnormal activation of signaling pathways to the protein synthesis apparatus. We discovered an innovative strategy that exploits this fact for efficient tumor cell killing with a genetically recombinant poliovirus. This project aims to provide the scientific basis for upcoming clinical trials of our agent and elucidate basic mechanisms of de-regulated protein synthesis in cancer.