Molecular Targeting of L1CAM to Inhibit Glioblastoma Stem Cell Invasion

描述(申请人提供)：多形性胶质母细胞瘤(GBM)是最具侵袭性和致命性的脑癌。尽管进行了积极的多模式治疗，但GBM的治疗仍然基本无效。这些致命癌症的根本问题是它们的高度浸润性和抗药性，导致肿瘤迅速复发。针对浸润性GBM细胞的改进治疗方法的发展需要对GBM侵袭和扩散的细胞和分子机制有新的认识。我们已经证明，与神经干细胞具有相似特性的GBM癌细胞亚群显示出更强的侵袭能力、血管生成潜力和治疗耐药性，这表明靶向这些GBM干细胞可能会显著改善治疗。我们的长期目标是开发针对GBM干细胞的新策略，以抑制GBM的侵袭，减少治疗阻力，防止肿瘤复发。在寻找GBM干细胞的潜在靶点时，我们发现L1CAM是GBM干细胞相对于非干细胞肿瘤细胞和神经前体细胞的一种差异表达的表面蛋白。通过shRNA靶向L1CAM可以有效地破坏神经球的形成，抑制肿瘤生长，并增加携带脑内GBM异种移植的小鼠的存活率。在初步研究中，我们发现L1CAM在体外显著降低了GBM干细胞的侵袭能力，并减少了三种侵袭相关蛋白(RhoC、组织蛋白L2和S100A4/Metastasin)的表达，提示L1CAM在介导GBM干细胞侵袭中起着关键作用，L1CAM可能是开发新的抗侵袭策略的关键靶点。根据我们的初步研究，我们假设L1CAM促进GBM干细胞的侵袭，体内靶向GBM干细胞的L1CAM抑制肿瘤侵袭。我们将通过以下三个具体目标来验证我们的假设并实现目标：1.通过在异种移植模型中可诱导的敲除来确定L1CAM在GBM干细胞侵袭中的作用；2.利用L1CAM封闭肽(L1HM06和L1HT08)来抑制GBM的侵袭和生长，从而建立针对GBM干细胞的治疗靶点；3.通过下游的过表达救援实验，确定L1CAM促进GBM干细胞侵袭的机制。我们将使用不同的分子和细胞方法以及生物发光成像技术等体内技术来追求这些特定的目标。这些研究将使我们能够评估L1CAM作为抗GBM干细胞侵袭的治疗靶点的潜力。我们期望这些拟议研究的结果将为未来开发治疗GBM和其他脑肿瘤的新方案奠定坚实的基础。

DESCRIPTION (provided by applicant): Glioblastoma multiforme (GBM) is the most invasive and lethal form of brain cancer. Despite aggressive multimodal therapy, the treatment of GBM remains largely ineffective. The fundamental problem of these fatal cancers is their highly infiltrative nature and resistant property that leads to rapid tumor recurrence. The development of improved therapies targeting the infiltrating GBM cells requires new insight into the cellular and molecular mechanisms underlying GBM invasion and dispersal. We have demonstrated that a sub-population of GBM cancer cells sharing similar properties with neural stem cells displays enhanced invasive capability, angiogenic potential and therapeutic resistance, suggesting that targeting these GBM stem cells may significantly improve the treatment. Our long-term goal is to develop novel strategies targeting GBM stem cells to inhibit GBM invasion, reduce therapeutic resistance and prevent tumor recurrence. In the search for potential targets specific for GBM stem cells, we identified L1CAM as a differentially elevated surface protein in GBM stem cells relative to non-stem tumor cells and neural progenitors. Targeting L1CAM by shRNA potently disrupts neurosphere formation, suppresses tumor growth and increases the survival of mice bearing intracranial GBM xenografts. In preliminary study, we found that L1CAM knockdown in vitro remarkably reduces invasive potential of GBM stem cells, and decreases expression of three invasion-associated proteins (RhoC, Cathepsin L2 and S100A4/Metastasin), suggesting that L1CAM plays a crucial role in mediating GBM stem cell invasion, and L1CAM may represent a critical target for developing a novel anti-invasion strategy. Based on our preliminary studies, we hypothesize that L1CAM promotes GBM stem cell invasion, and molecular targeting of L1CAM in GBM stem cells in vivo inhibits tumor invasion. We will test our hypothesis and accomplish the objectives by pursuing the following three specific aims: 1. Determine the role of L1CAM in GBM stem cell invasion in vivo through inducible knockdown in xenograft models; 2. Develop therapeutic targeting of GBM stem cells using L1CAM blocking peptides (L1HM06 and L1HT08) to suppress GBM invasion and growth; 3. Define the mechanisms by which L1CAM contributes to GBM stem cell invasion using downstream overexpression rescue experiments. We will pursue these specific aims using varied molecular and cellular approaches as well as in vivo techniques such as bioluminescent imaging technology. These studies will allow us to evaluate the potential of L1CAM as a therapeutic target against GBM stem cell invasion. We expect that the outcome from these proposed studies will lay a solid foundation for future development of new regimens for treatment of GBM and other brain tumors.