Mechanisms underlying BAI1/ADGRB1 negative regulation of glioblastoma mesenchymal transition and invasion.

项目摘要 恶性脑胶质瘤具有高度侵袭性和致命性，迫切需要新的治疗方法 肿瘤。胶质母细胞瘤(GBM)患者在确诊后1-2年内死亡，尽管目前的常规 治疗，包括手术、放疗和化疗。肿瘤复发的一个主要驱动力是浸润性 胶质瘤细胞进入邻近正常脑组织的性质，这是由间充质转录激活驱动的 程序。这种间充质转化是通过细胞外刺激细胞表面受体来激活的 生长因子如转化生长因子β1。本项目的总体目的是调查黏附的作用 G蛋白偶联受体B1(ADGRB1/BAI1)在间充质切换和侵袭中的作用 基底膜的相关机制及治疗方法。ADGRB1是一种特异性的孤儿黏附GPCR 在大脑中表达。我们先前发现ADGRB1在慢性阻塞性肺疾病患者中的表达显著降低。 通过表观遗传沉默，提示ADGRB1缺失可能促进肿瘤的形成。我们的新产品 初步数据显示，ADGRB1的低表达与胶质瘤的侵袭性和不良预后有关 病人。恢复ADGRB1在GBM细胞中的表达抑制培养中的间充质表型 和小鼠异种移植。我们的初步研究进一步提示ADGRB1可以抑制转化生长因子β1驱动的间质 在其第一个血栓反应蛋白1型重复序列(TSR1)中通过WxLWxLW基序进行转换。这一主题调解了 ADGRB1与潜在的转化生长因子β1复合体结合，阻止转化生长因子β1成熟。基于这些结果，我们 ADGRB1通过阻断转化生长因子β1介导的间质发挥脑肿瘤抑制作用的假说 用表观遗传疗法转换和恢复其表达将代表一种新治疗干预 对于GBM。为了验证我们的假设，我们提出了以下目标：(I)定义ADGRB1如何负向调节 间充质转化和胶质瘤侵袭，(Ii)决定BAI1如何拮抗转化生长因子β1前间充质 信号转导和(Iii)评价表观遗传恢复BAI1表达是否可以抑制脑胶质瘤细胞的侵袭 体外和体内，并提高术后生存。这些研究很重要，因为我们发现了一种特定的 抗转化生长因子β-1成熟和脑胶质瘤间充质的BAI1胞外区 开关，提供了一种新的机制来对抗这一可被利用的致癌途径 从治疗上讲。这些发现支持在癌症患者中针对这一新途径。 间充质转化。

Project Summary New therapies are urgently needed for patients with malignant gliomas, which are highly invasive and lethal brain tumors. Patients with glioblastoma (GBM) die within 1-2 years of diagnosis despite current conventional therapies, including surgery, radiation and chemotherapy. A major driver of tumor recurrence is the infiltrative nature of the glioma cells into adjacent normal brain, which is driven by activation of a mesenchymal transcription program. This mesenchymal transition is activated through extracellular stimulation of cell surface receptors by growth factors such as TGFβ1. The overall purpose of the present project is to investigate the role of adhesion G protein-coupled receptor B1 (ADGRB1/BAI1) in the mesenchymal switch and invasion, and explore new therapies for GBM based on the related mechanisms. ADGRB1 is an orphan adhesion GPCR specifically expressed in the brain. We previously showed that ADGRB1 expression is significantly reduced in patients with GBM through epigenetic silencing, suggesting that ADGRB1 loss may facilitate tumor formation. Our new preliminary data show that low ADGRB1 expression correlates with invasion and poor outcome in glioma patients. Restoration of ADGRB1 expression in GBM cells suppresses the mesenchymal phenotype in culture and mice xenografts. Our pilot studies further suggest ADGRB1 can inhibit TGFβ1-driven mesenchymal transition through a WxLWxLW motif in its first thrombospondin type 1 repeat (TSR1). This motif mediates ADGRB1 binding to the latent TGFβ1 complex and prevents TGFβ1 maturation. Based on these results, we hypothesize that ADGRB1 acts as a brain tumor suppressor by blocking the TGFβ1-mediated mesenchymal switch and that restoration of its expression with epigenetic therapy will represent a novel therapeutic intervention for GBM. To test our hypothesis, we propose the following aims: (i) define how ADGRB1 negatively regulates the mesenchymal transition and glioma invasion, (ii), determine how BAI1 antagonizes TGFβ1 pro-mesenchymal signaling and (iii) evaluate whether epigenetic restoration of BAI1 expression can inhibit glioma cell invasion in vitro and in vivo, and augment survival post-operation. These studies are important as we identified a specific region in the extracellular domain of BAI1 that antagonizes TGFβ1 maturation and the glioma mesenchymal switch, providing a new mechanism for antagonizing this oncogenic pathway that can be exploited therapeutically. These findings support targeting this new pathway in patients whose cancers are driven by mesenchymal transition.