星形胶质瘤恶性进展的LMO3分子机制研究

Astroglioma is the most common brain tumor with poor clinical outcome. Identification of new markers for cancers of astroglioma could be beneficial for the molecular diagnosis and target prognosis of glioma patients. LMO3(LIM only protein 3,LMO3),a new transcription regulator that was cloned by our group, plays a critical role in modulating the proliferation of astrocyte. However,the precise molecular mechanisms of its transcriptional regulation remain elusive. Our previous study found that in Glioblastoma multiforme (GBM), the upregulation of LMO3 was always accompanied by the downregulation of CIB1(Calcium-and integrin-binding protein,CIB), the interaction factor of LMO3 in cytoplasm. And the intracellular localization of LMO3 varied with the interaction with CIB1. CIB1 could inhibit LMO3-induced cell proliferation by interaction with LMO3 in cytoplasm. Therefore, we propose a hypothesis: LMO3 regulates astroglioma progression through the interaction with different molecules and shuttling between the nucleus and cytoplasm. The roles of LMO3 in regulating the proliferation of astroglioma were elucidated by overexpression or depletion of LMO3 and the mechanisms of LMO3-induced proliferation were demonstrated by chromatin immunoprecipitation sequencing (ChIP-seq).This study will shed light on the effect of LMO3 in the pathogenesis of malignant gliomas, and provide useful factor for identifying new target of glioma biotherapy.This study will also shed light on the relationgship between the changes of LMO3 and CIB1,the pathological charactors of astrogliomas, and the effect of LMO3.

星形胶质瘤是最常见的脑部肿瘤，患者预后不良。新的分子靶标的鉴定是胶质瘤分子诊断和靶向治疗的关键。我们发现的新转录调节因子LMO3可促进星形胶质细胞增殖，但其分子机制尚不清楚。我们前期发现，LMO3与其作用因子CIB1的表达随星形胶质瘤进展呈"此消彼长"的变化，且CIB1可与LMO3结合，影响LMO3的核定位，从而抑制细胞生长。据此我们提出假设：LMO3可在核质间穿梭，并通过与CIB1及其他分子的结合，调控星形胶质瘤的恶性进展。本项目从分子、细胞、组织以及动物水平等多方面，采用过表达、RNA干扰、PCR芯片、ChIP-seq等技术，阐明LMO3在星形胶质瘤增殖中的作用，探索CIB1调控LMO3的作用机制，筛选LMO3的核内下游靶分子，明确LMO3及相关因子表达变化与胶质瘤病理特征及预后的关系。预期结果将完善LMO3调控肿瘤发生的机制，并为胶质瘤的防治提供新的策略和治疗靶点。

LMO3属于仅有两个富含半胱氨酸的锌指样LIM结构域的LMOs转录调节因子家族，可以通过与其他转录因子形成多蛋白复合体，在肿瘤发生中发挥重要作用。我们的研究揭示了LMO3在胶质瘤中的新作用、可能的信号转导通路及其生物学意义和功能。研究发现LMO3在不同来源胶质瘤中的作用不同，可以促进或抑制胶质瘤细胞生长、增殖和迁移。通过TAP-MS筛选到47个LMO3新的相互作用蛋白，并验证了LMO3与ORCL1、MEK1/2、ARRB1、RHOA、LDB1、ZBTB34等蛋白的结合；实验发现LMO3通过OCRL1调节AKT1信号通路及其下游信号分子；由于LMO3可以与MEK-ERK信号通路分子ARRB1、MEK1/2结合，进一步研究表明LMO3通过调节MEK-ERK信号通路，抑制hEGF诱导的SHG44细胞增殖。LMO3及相互作用蛋白ARRB1、OCRL1、LDB1随胶质瘤恶性进展表达下调，LMO3高表达的患者生存期显著高于低表达患者。SHG44胶质瘤细胞裸鼠体内成瘤实验表明，LMO3高表达抑制胶质瘤的生长和增殖，提示LMO3是胶质瘤生长的负调控因子。我们的研究成果极大丰富了对 LMO3功能、相互作用蛋白、细胞信号转导机制的认识，补充完善了LMO3 调控肿瘤发生的作用和机制，为胶质瘤的防治提供了新的治疗靶点。