Defining a mechanism of LRP1B tumor suppression in glioblastoma

项目总结 胶质母细胞瘤是最常见的恶性脑瘤，5年存活率仅为5.0% 在多模式治疗后。胶质母细胞瘤细胞的高度侵袭性和浸润性使其复杂化 避免手术切除和局部化疗的治疗。因此，对 需要胶质母细胞瘤的增殖、迁移和侵袭机制来发展改进的治疗方法 并提高现有治疗方法的疗效。低密度脂蛋白受体相关蛋白1B (LRP1B)是一种大的内吞受体，被认为是最常见的缺失基因之一 跨越人类癌症。最近，LRP1B基因的缺失被证明与整体表现不佳密切相关 胶质母细胞瘤患者的存活率和无进展存活率较差。尽管它在人类中流行 对于癌症，LRP1B作为肿瘤抑制因子的机制(S)在很大程度上是未知的。一本出版的 我们实验室的研究表明，LRP1B经历了受调控的膜内蛋白分解，这一过程 涉及蛋白质的顺序蛋白分解，以释放可溶的胞外区和胞内区 域。LRP1B胞内结构域(LICD)定位于细胞核并抑制锚定。 自主成长。此外，LRP1B还被发现与参与Wnt信号转导的蛋白质相互作用 以及一些转录因子。初步研究发现LRP1B与LRP1B呈显著负相关 胶质母细胞瘤患者Wnt信号激活子和靶基因的表达 在这一支持下，该项目的中心假设是LRP1B的缺失促进了胶质母细胞瘤 通过增加Wnt信号的进展。我们的假设将在以下具体目标中得到检验。1) 确定LRP1B胞内结构域是否足以抑制胶质母细胞瘤的增殖和迁移。 2)明确LRP1B抑制细胞增殖和迁移的机制(S)。具体目标1将 研究LRP1B的胞内结构域并确定参与其功能的特定氨基酸序列 肿瘤抑制功能。为了补充这些研究，《特定目标2》将研究蛋白质和dna。 LRP1B胞内结构域的相互作用，并将量化全球蛋白质组和磷酸化的变化 发生在LRP1B表达时。总之，这些研究将使我们深入了解LRP1B 调节肿瘤抑制。这些目标将通过各种战略来实现，包括大规模 基于光谱的蛋白质组学、染色质免疫沉淀、下一代测序和分子 生物学技术。LRP1B的机制知识有可能使更好的治疗选择成为可能 并揭示合理药物设计的具体目标。此外，这些见解超出了胶质母细胞瘤的范畴。 治疗，考虑到人类癌症中LRP1B缺失的流行率以及LRP1B在 动脉粥样硬化和阿尔茨海默病。

PROJECT SUMMARY Glioblastoma is the most common form of malignant brain tumor, with a dismal 5-year survival rate of 5.0% after multimodal therapy. The highly aggressive and infiltrative properties of glioblastoma cells complicate treatment by evading surgical resection and local chemotherapies. Consequently, investigation into mechanisms of glioblastoma proliferation, migration and invasion are needed to develop improved therapeutics and increase the efficacy of current treatments. The low-density lipoprotein receptor-related protein 1B (LRP1B) is a large endocytic receptor that has been identified as one of the most commonly deleted genes across human cancers. Recently, deletion of LRP1B was shown to be significantly associated with poor overall survival and poor progression-free survival in glioblastoma patients. Despite its prevalence across human cancers, the mechanism(s) by which LRP1B acts as a tumor suppressor are largely unknown. A published study from our lab demonstrated that LRP1B undergoes regulated intramembrane proteolysis, a process that involves the sequential proteolysis of a protein to release a soluble extracellular domain and intracellular domain. The LRP1B intracellular domain (LICD) was found to localize to the nucleus and inhibit anchorage- independent growth. Additionally, LRP1B has been found to interact with proteins involved in Wnt signaling and a number of transcription factors. Preliminary studies have found strong negative correlations of LRP1B mRNA expression with the expression of Wnt signaling activators and target genes in glioblastoma patients. With this support, the central hypothesis of this project is that the deletion of LRP1B promotes glioblastoma progression through increased Wnt signaling. Our hypothesis will be tested in the following specific aims. 1) Determine if the LRP1B intracellular domain is sufficient to attenuate glioblastoma proliferation and migration. 2) Define the mechanism(s) by which LRP1B attenuates cellular proliferation and migration. Specific Aim 1 will investigate the LRP1B intracellular domain and define the specific amino acid sequences that contribute to its tumor suppressor function. To complement these studies, Specific Aim 2 will investigate the protein and DNA interactions of the LRP1B intracellular domain, and will quantify global proteomic and phosphorylation changes that occur upon LRP1B expression. Together these studies will give insight into mechanisms by which LRP1B mediates tumor suppression. These aims will be accomplished using a variety of strategies, including mass spectrometry-based proteomics, chromatin immunoprecipitation, next-generation sequencing and molecular biology techniques. Mechanistic knowledge of LRP1B has the potential to enable better therapeutic choices and reveal specific targets for rational drug design. Additionally, these insights reach beyond glioblastoma treatment, given the prevalence of LRP1B deletions across human cancers and the role of LRP1B in atherosclerosis and Alzheimer’s disease.