The role of TSPO in T cell immune control of glioblastoma

TSPO经常在胶质母细胞瘤（GBM）中过度表达，这是一种高度侵袭性但无法治愈的脑肿瘤，在炎症条件下通过TNF诱导。TSPO在GBMs中的表达与WHO分级、胶质瘤细胞增殖和患者预后不良呈正相关。然而，TSPO在GBM进展中的功能作用尚不清楚。我们认为TSPO调节了GBM的免疫控制。由于目前还没有研究TSPO在GBM抗肿瘤T细胞应答中的作用，也没有研究TSPO免疫调节作用的机制，因此本项目将重点研究TSPO在胶质母细胞瘤特异性细胞毒性效应T细胞对人GBM细胞的排斥反应中的作用。TSPO被其天然配体激活可以阻断白细胞介素（IL） 8的产生，IL - 8控制活性氧（ROS）水平，并导致对促凋亡炎症刺激的保护。另一方面，TSPO介导神经甾体的产生，可诱导炎性细胞因子如il - 6、肿瘤坏死因子（TNF）或il - 1。这些细胞因子对效应T细胞活性有不同的影响，因此可能在GBM的肿瘤免疫排斥调节中发挥关键但复杂的作用。因此，我们希望研究TSPO表达在GBM发展和治疗过程中对治疗抗性和免疫保护的影响。通过基因沉默和合成配体对TSPO活性的药理学调节，我们获得了初步数据，表明TSPO一方面在GBM细胞T细胞诱导的凋亡调节中发挥剂量依赖性作用，另一方面在肿瘤特异性T细胞的调控效应功能中发挥作用。这些发现表明，TSPO的药理学靶向可能代表了胶质母细胞瘤免疫治疗的潜在治疗选择。该项目建立在基因操作和TSPO配体的药理学干预上，使用一个大型亚型解剖的人类GBM组织样本代表小组（见项目A1）和来自患者及其自身肿瘤抗原特异性T细胞系的GBM祖细胞的原代培养。我们将建立GBM祖细胞中TSPO与T细胞排斥反应的整体相关性，确定TSPO如何调节GBM的炎症反应，研究TSPO在T细胞诱导的GBM祖细胞凋亡中的作用，表征TSPO对T细胞对GBM细胞反应的调节，研究TSPO对GBM浸润免疫细胞亚群的影响。因此，本项目不仅将提出TSPO参与GBM免疫控制的机制假设，而且将探索TSPO在GBM免疫治疗中的药理调节潜力。

TSPO is frequently overexpressed in glioblastoma (GBM), a highly aggressive yet incurable brain tumor, and is induced through TNF under conditions of inflammation. TSPO expression in GBMs positively correlates with WHO grade, glioma cell proliferation and poor prognosis of patients. However, the functional role of TSPO in GBM progression is far from being understood. We propose that TSPO regulates the immune control of GBM. Because neither the role of TSPO for anti-tumor T cell responses against GBM nor mechanisms underlying the immune-regulatory role of TSPO have been studied so far, the project focuses on the role of TSPO during the rejection of human GBM cells by glioblastoma-specific cytotoxic effector T cells. TSPO activation by its natural ligands can block the production of interleukin (IL) 8 which controls reactive oxygen species (ROS) levels and results in protection against pro-apoptotic inflammatory stimuli. On the other hand, TSPO mediates the production of neurosteroids which can induce inflammatory cytokines such as IL6, tumor necrosis factor (TNF) or IL1. Such cytokines exert differential effects on effector T cell activity and may therefore play a critical but complex role in the regulation of tumor-immune rejection in GBM. Therefore, we want to study the consequences of TSPO expression during GBM development and treatment both with regard to treatment resistance and immune protection. By genetic gene silencing and pharmacological modulation of TSPO activity with synthetic ligands we generated preliminary data suggesting that on the one hand TSPO plays a dose dependent role in the regulation of T cell induced apoptosis in GBM cells and on the other hand in orchestrating effector functions of tumor specific T cells. These findings suggest that pharmacological targeting of TSPO could represent a potential therapeutic option for immunotherapy of glioblastoma. The project builds up on genetic manipulation and pharmacological interventions with TSPO ligands using a large subtype-dissected representative panel of human GBM tissue samples (see project A1) and primary cultures of GBM progenitor cells from patients and their autologous tumor antigen specific T cell lines. We will establish the overall relevance of TSPO in GBM progenitor cells for their rejection by T cells, determine how TSPO modulates the inflammatory response of GBM, investigate the role of TSPO during T cell-induced apoptosis in GBM progenitor cells, characterize the regulation of T cell response against GBM cells by TSPO, and study the impact of TSPO on GBM infiltrating immune cell subsets.This project will thus not only develop mechanistic hypotheses of TSPO involvement in GBM immune control but also explore the potential of pharmacological TSPO modulation for GBM immunotherapy.