Targeting Translation Control in Malignant Glioma

描述(申请人提供)：癌细胞表现出不受调控的生长和增殖，因为它们不适当地选择了聚合在翻译机制上的有丝分裂信号通路，并控制核糖体向mRNAs的募集。我们正在利用这一原理通过基因重组脊髓灰质炎病毒来靶向胶质母细胞瘤(GBM)。传统的蛋白质合成是在mRNAs上典型的5‘帽结构与复杂的蛋白质网络结合时开始的。某些编码关键生长、增殖和生存蛋白的mRNAs可以通过以帽不依赖的方式直接招募核糖体亚基来逃避这一调控限制。耐人寻味的是，这种mRNAs启动翻译的基本机制与脊髓灰质炎病毒相同。通过对病毒翻译过程中涉及的脊髓灰质炎病毒RNA序列的遗传操作，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的强烈细胞毒性。我们发现PVSRIPO的肿瘤细胞毒性是由MAPK信号决定的，翻译机制倾向于在恶性肿瘤中进行帽非依赖性翻译。我们的发现表明，翻译因子的这种信号可能通过在有丝分裂过程中通过选择性翻译启动来协调基因表达，从而参与细胞周期调节。本项目旨在揭示帽非依赖性翻译在癌症中的生理学意义，阐明控制其活性的机制，并开发合理的策略将其用于癌症治疗。我们提出了三个具体的目标：1)解开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非依赖性翻译的分子基础。2)阐明eIF4G调控IRES介导的翻译机制。我们确定了聚集在翻译装置和核糖体适配器eIF4G的中央支架上的信号转导通路。我们将研究调控eIF4G、S在帽非依赖性翻译启动中作用的分子机制。3)确定通过靶向诱导帽非依赖性翻译来增强胶质瘤细胞杀伤的策略。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。我们将测试mTORC1抑制剂雷帕霉素与溶瘤脊髓灰质炎病毒的结合，以协同增强动物胶质瘤模型中的肿瘤细胞杀伤。

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.