eIF3d介导酸性微环境促进髓母细胞瘤细胞自噬及肿瘤转移的机制研究

Medulloblastoma is the most common type of primary malignant brain tumor in children. Unlike most brain tumors，medulloblastomas spread through the cerebrospinal fluid (CSF) and frequently metastasize to different locations in central nervous system (CNS), during which, the process of detachment and defulvium to CSF is the key event. This situation increases difficulties of clinical treatment. Therefore, investigation in underling mechanism and finding out the pivotal factor during this process will provide clues of diagnosis and management. Our previous work indicated possible ralation between eIF3d and metastatic medulloblastoma. Morever, eIF3d could be induced by acidic microenvironment, and lentivirus-mediate knock out further proved that eIF3d could modulate autophagy related proteins like LC3A/B. Thus, this project aims to: identify the association between expression level of eIF3d and medulloblastoma, and how it influences cell phenotype when acidic microenvironment is developed in the early stage; modulation of autophagy by eIF3d when induced by low pH; precise mechanism of autophagy-controlled phenotype including cell detachment and consequently gained-metastasis. By fixing these problems, we will gain comprehensive understanding of association from acidic microenvironment to tumor metastasis through autophagy, and identification of eIF3d as a key factor, and which will serve to develop promising clinical application.

髓母细胞瘤是儿童时期发病率极高的恶性脑肿瘤，目前临床治疗的难点在于肿瘤细胞失黏附脱落并随脑脊液播散，进而导致肿瘤在中枢神经系统内转移。因此，找出髓母细胞瘤转移进程的关键因素将有助于开发新的疾病诊断和治疗方法。通过前期研究，我们发现eIF3d与转移性髓母细胞瘤呈现相关性，酸性条件下其表达量上升；基因敲除实验证实了eIF3d可以调控LC3A/B等细胞自噬效用蛋白。本项目拟从分子、细胞、组织以及动物水平等多层次，研究髓母细胞瘤发展阶段的酸性微环境下，eIF3d与髓母细胞瘤细胞自噬的关联性和调节机制，以及其如何影响细胞的表型，并探讨由eIF3d介导的髓母细胞瘤自噬对细胞失粘附的影响以及其作用机制。本项目将通过对以上内容的研究，探讨酸性微环境对自噬的影响及其促进肿瘤细胞转移的分子机制，并确定该进程中关键因子eIF3d的作用，为临床诊断和治疗提供指导意义。

项目背景：在髓母细胞瘤（MB）中，伴MYC扩增的3型MB（G3-MB）患者常常预后较差，亟需新型有效疗法。作为该型肿瘤驱动和关键依赖基因，MYC已被证明是潜在治疗靶标。针对此类肿瘤，本项目研究旨在寻找靶向MYC翻译的新型有效的治疗策略。..主要研究内容：通过在MB肿瘤数据库中分析翻译起始复合物eIF4F的主要成员，EIF4A1被发现为伴MYC扩增的G3-MB的潜在治疗靶标。通过遗传学和药理学手段，我们利用多种患者来源的肿瘤模型在体内、体外加以证实并经蛋白印迹、实时定量PCR和质谱分析探索了内在机制。..重要结果和关键数据：MB肿瘤数据库分析显示，EIF4A1在G3-MB患者中表达水平较正常小脑显著上调，与MYC转录水平正相关，在伴MYC扩增的G3-MB细胞系中是一种重要的肿瘤依赖基因。借助CRISPR/Cas9技术或小分子抑制剂Silvestrol靶向EIF4A1，可通过阻滞增殖和诱导凋亡有效减缓多种伴MYC扩增的G3-MB临床前细胞模型的生长。机制上，抑制EIF4A1可在翻译水平有效干扰MYC表达，该抑制效果与细胞MYC蛋白水平正相关。对Silvestrol处理后细胞的全蛋白质组的质谱分析进一步揭示了受EIF4A1抑制影响的其它生物学功能与通路。..科学意义：本项目研究表明，通过抑制EIF4A1干扰MYC翻译可以成为治疗伴MYC扩增的G3-MB患者的潜在有效手段，为研发靶向药物提供科学的理论支持。