Engineering the Brain Immune System for Tumor Therapy

描述（由申请人提供）：设计用于肿瘤治疗的脑免疫系统摘要脑多形性胶质母细胞瘤（GBM）通过浸润正常周围脑的胶质瘤细胞杀死，从而导致健康脑组织的移位和破坏。因此，即使是侵袭性手术切除也不能完全切除所有浸润细胞并提供长期存活。或者，免疫系统可以使用特异性免疫介导的归巢机制特异性靶向浸润肿瘤细胞。然而，由于大脑的免疫特权，即血脑屏障，缺乏适当的抗原呈递细胞（即，树突状细胞，DC），缺乏经典的淋巴流出通道，以及内源性免疫抑制剂的局部表达，即，转化生长因子β然而，实验和临床研究表明，免疫疗法可以有效地根除实验性GBM，并可用于开发人类脑肿瘤的新疗法。最近，我们已经表明，基因转移介导的脑免疫微环境的修饰诱导系统性抗肿瘤免疫应答。具体地，fms样酪氨酸激酶3配体（Flt 3L）的表达募集抗原呈递细胞（例如，树突状细胞（DC）转移到脑实质并进入肿瘤块。为了增加肿瘤抗原对DC的可用性，使用条件细胞毒性[单纯疱疹病毒1型胸苷激酶（TK）加更昔洛韦（GCV）]杀死肿瘤细胞。这种联合方法诱导肿瘤消退，持久的全身免疫记忆，以及具有大的同基因肿瘤的动物的长期存活。本提案中概述的实验的总体目标是定义参与这种抗GBM免疫应答的免疫细胞，确定脑DC的起源和功能活性，并阐明其诱导系统性长期抗肿瘤免疫能力的具体机制。我们的假设是Flt 3L和条件性细胞毒性将特定亚型的树突状细胞募集到脑中，即浆细胞样树突状细胞（pDC），这导致全身性抗肿瘤免疫应答。了解从大脑内部原位刺激这种免疫反应的机制将为最致命的人类癌症之一带来新的治疗方法。我们的方法的新奇在于我们响应Flt 3L的表达而特异性地将pDC募集到脑实质和肿瘤微环境的能力，这是一种实现从肿瘤块内原位引发针对GBM的全身免疫应答的方法。我们假设这将最大限度地产生对GBM抗原的有效抗GBM免疫应答。公共卫生相关性：多形性胶质母细胞瘤（GBM）是一种毁灭性的脑肿瘤，目前尚无治愈方法，在过去的30年里，患者的生存率没有显著改善。使用颅内脑肿瘤模型，我们已经表明，一种新的组合条件性细胞毒性/免疫刺激基因治疗消除了生长中的肿瘤，并诱导免疫记忆，保护动物免受肿瘤复发。此外，我们已经证明，任何不良副作用都是有限的，可逆的，没有长期的永久性负面后遗症。我们的目标是阐明介导这些效应的细胞机制，免疫细胞迁移到肿瘤微环境中，并为这种毁灭性的癌症设计新的治疗方法，这些方法将在I期临床试验中实施。

DESCRIPTION (provided by applicant): Engineering the Brain Immune System for Tumor Therapy Abstract Brain glioblastoma multiforme (GBM) kills through glioma cells that infiltrate normal surrounding brain, with consequent displacement and destruction of healthy brain tissue. Therefore, even aggressive surgical resection fails to excise completely all infiltrating cells and provide long term survival. Alternatively, the immune system could specifically target infiltrating tumor cells using specific immune mediated homing mechanisms. However, the immune system has reduced activity in the brain, due to the brain's immune privilege, i.e. the blood-brain barrier, a lack of proper antigen presenting cells (i.e., dendritic cells, DCs) in the healthy brain, absence of classical lymphatic outflow channels, and local expression of the endogenous immune inhibitors, i.e., transforming growth factor beta. Nevertheless, experimental and clinical studies have shown that immune-therapy can effectively eradicate experimental GBM, and can be harnessed to develop novel therapies for human brain tumors. Recently, we have shown that gene transfer mediated modification of the brain immune microenvironment induces systemic anti-tumor immune responses. Specifically, expression of fms-like tyrosine kinase 3 ligand (Flt3L) recruits antigen presenting cells (e.g., dendritic cells, DCs) to the brain parenchyma and into the tumor mass. To increase the availability of tumor antigens to the DCs, tumor cells are killed using conditional cytotoxicity [herpes simplex virus type 1 thymidine kinase (TK) plus ganciclovir (GCV)]. This combined approach induces tumor regression, long-lasting systemic immunological memory, and long-term survival in animals with large syngeneic tumors. The overall goals of the experiments outlined in this proposal are to define the immune cells involved in this anti-GBM immune response, determine the origin and functional activities of brain DCs, and elucidate the specific mechanism(s) underlying their ability to induce systemic long-term anti-tumor immunity. Our hypothesis is that Flt3L and conditional cytotoxicity recruit a specific subtype of dendritic cells to the brain, i.e. plasmacytoid dendritic cells (pDCs), which leads to a systemic anti-tumor immune response. Understanding the mechanisms that stimulate this immune response from within the brain in situ will lead to novel treatments for one of the deadliest human cancers. The novelty of our approach is our capacity to specifically recruit pDCs to the brain parenchyma and the tumor microenvironment in response to expression of Flt3L, an approach that achieves the priming of a systemic immune response against GBM from within the tumor mass in situ. We hypothesize that this will maximize the generation of an effective anti-GBM immune response to GBM antigens. PUBLIC HEALTH RELEVANCE: Gliobastoma multiforme (GBM) is a devastating brain tumor, for which there is no cure, and no significant improvements in patients' survival has occurred over the last 30 years. Using an intracranial brain tumor model we have shown that a novel combined conditional cytotoxic/immune-stimulatory gene therapy eliminates the growing tumor, and induces immunological memory which protects animals from tumor recurrence. Further, we have shown that any adverse side effects are limited, and reversible, with no long term permanent negative sequalae. We aim to elucidate the cellular mechanisms which mediate these effects, the migration of immune cells into the tumor microenvironment and devise novel therapeutic approaches for this devastating cancer which will be implemented in phase I clinical trials.