Role of the collagen receptor LAIR-1 in glioma progression and the tumor immune microenvironment

摘要 高级别胶质瘤（HGG）是所有原发性脑肿瘤中最致命的。他们是无法治愈的， 在18-24个月之间。神经胶质瘤浸润肿瘤周围的健康脑组织。因此，即使这些 肿瘤不转移，患者因局部肿瘤复发而死亡。胶原蛋白是胶原蛋白的核心成分。 高级别胶质瘤的细胞外基质，并促进侵袭和肿瘤生长。它们如何做到这一点是复杂的， 而不是完全理解。胶原蛋白通过物理作用为细胞外基质提供结构刚度， 机制等除了物理机制外，胶原蛋白在生物化学上影响细胞内机制。 胶原蛋白通过与大量胶原蛋白受体相互作用来影响细胞内信号传导。这些受体 是：整联蛋白、盘状结构域受体DDR 1和DDR2、GPVI、MRC 2和LAIR-1。白细胞相关 免疫球蛋白样受体-1（LAIR- 1）是一种跨膜糖蛋白，其胞外段含有一个 单个免疫球蛋白样（IG样）结构域，其胞内片段具有两个免疫受体酪氨酸- 基于抑制基序（ITIM）。LAIR-1在T细胞、B细胞、自然杀伤（NK）细胞 巨噬细胞和其他免疫细胞。LAIR-1强烈抑制免疫细胞活化，从而减少 免疫反应。富含胶原蛋白的肿瘤，特别是胶原蛋白I和III激活CD 8 + T细胞中的LAIR-1， 降低T细胞介导的细胞毒性。因此，已经提出了在免疫细胞上激活LAIR-1作为免疫调节剂。 肿瘤抑制抗肿瘤免疫反应的机制。令人惊讶的是，我们发现LAIR-1也是 在神经胶质瘤细胞中表达。LAIR-1在其他实体瘤如宫颈癌、乳腺癌和肾癌中的表达 增加肿瘤的侵袭性。因此，我们推测LAIR-1可能通过直接影响胶质瘤的进展， 增加癌细胞的发病率，并通过抑制抗肿瘤细胞毒性免疫间接地 应答基因工程小鼠胶质瘤模型中的胶原蛋白敲除增加了中位 存活率和脑肿瘤内LAIR-1表达降低。因此，胶原蛋白可直接抑制抗胶质瘤 免疫反应，或影响胶质瘤细胞的恶性行为。因此，迫切需要一种机械的 了解LAIR-1如何通过浸润性免疫细胞或胶质瘤肿瘤细胞表达， 胶质瘤的进展和侵袭以及它如何重塑肿瘤免疫微环境。我们的长期目标 是了解细胞外肿瘤基质如何通过其胶原蛋白的表达影响肿瘤进展 和抗肿瘤免疫。我们在本申请中的总体目标是测试LAIR-1 LAIR-1在胶质瘤细胞中的表达增加了肿瘤进展（AIM 1），LAIR-1表达在调节胶质瘤细胞中的作用， 功能的浸润免疫细胞（AIM 2），并确定治疗潜力的抑制LAIR-1， 胶质瘤模型（AIM 3）。我们的中心假设是，LAIR-1发挥重要的病理作用，有助于 通过其在胶质瘤细胞和免疫细胞中的表达以及抑制LAIR-1来抑制胶质瘤进展 信号传导可能揭示HGG的新治疗靶点。

ABSTRACT High-grade gliomas (HGG) are the deadliest of all primary brain tumors. They are incurable and median survival is between 18-24 months. Gliomas infiltrate the healthy brain tissue surrounding the tumor. Thus, even if these tumors do not metastasize, patients die due to local tumor recurrence. Collagens are a central component of the extracellular matrix of high-grade gliomas, and promote invasion and tumor growth. How they do so is complex, and not fully understood. Collagen provides structural stiffness to the extracellular matrix, through physical mechanisms. In addition to physical mechanisms, biochemically collagen affects intracellular mechanisms. Collagen affects intracellular signaling by interacting with a large number of collagen receptors. These receptors are: integrins, discoidin domain receptors DDR1 and DDR2, GPVI, MRC2 and LAIR-1. Leukocyte-associated immunoglobulin-like receptor-1 (LAIR- 1) is a transmembrane glycoprotein, its extracellular segment contains a single immunoglobulin-like (Ig- like) domain, and its intracellular segment has two immuno- receptor tyrosine- based inhibitory motifs (ITIMs). LAIR-1 is strongly expressed on T cells, B cells, natural killer (NK) cells, macrophages and other immune cells. LAIR-1 strongly suppresses immune cell activation, thus reducing immune responses. Collagen-rich tumors, especially collagens I and III activate LAIR-1 in CD8+ T cells, and reduce T cell-mediated cytotoxicity. Thus, activation of LAIR-1 on immune cells has been proposed as a mechanism by which tumors inhibit antitumor immune responses. Surprisingly, we found that LAIR-1 is also expressed in glioma cells. Expression of LAIR-1 in other solid tumors, such as cervical, breast and kidney cancer increases tumor aggressiveness. Thus, we postulate that LAIR-1 could affect glioma progression by directly increasing the pathogenesis of cancer cells, and indirectly, by inhibiting the anti-tumor cytotoxic immune responses. Knockdown of collagen from genetically engineered mouse models of glioma increased median survival, and reduced LAIR-1 expression within brain tumors. Thus, collagen could directly inhibit anti-glioma immune responses, or affect the malignant behavior of glioma cells. There is thus a critical need for a mechanistic understanding of how LAIR-1 expressed by either infiltrating immune cells or glioma tumor cells contributes to glioma progression and invasion and how it remodels the tumor immune microenvironment. Our long-term goal is to understand how the extracellular tumor matrix, through its expression of collagen affects tumor progression and anti-tumor immunity. Our overall objectives in this application are to test the hypothesis that LAIR-1 expression in glioma cells increases tumor progression (AIM 1), the role of LAIR-1 expression in regulating the function of infiltrating immune cells (AIM 2), and determine the therapeutic potential of the inhibition of LAIR-1 in glioma models (AIM 3). Our central hypothesis is that LAIR-1 plays essential pathological roles that contribute to glioma progression through its expression in glioma cells and in immune cells and that inhibiting LAIR-1 signaling could uncover novel therapeutic targets for HGG.