Role of myeloid-derived suppressor cells in local and systemic immunosuppression in glioblastoma

胶质母细胞瘤（GBM）是最常见的原发性恶性脑肿瘤， 生存期长达20个月。男性GBM的发病率是女性的1.6倍， 疾病结果。目前处于临床试验阶段的免疫疗法在改善免疫功能方面取得了有限的成功。 患者结局。免疫抑制微环境促进肿瘤进展并限制抗肿瘤药物的产生。 肿瘤免疫应答可能是治疗抗性的基础。尽管骨髓源性的 抑制细胞（MDSC）在建立这种免疫抑制环境中起着关键作用， 单个MDSC亚群促进肿瘤发生和调节的机制仍然不清楚。 我们以前证明单核细胞MDSC（mMDSC）浸润男性肿瘤的比率较高， 临床前模型和患者样本。相比之下，粒细胞MDSC（gMDSC）在外周血中扩增。 在雌性动物模型中，gMDSC基因标记与不良预后相关 患者MDSC亚群的这种变化也告知了对氟达拉滨的性别特异性治疗反应， 抗IL-1β抗体在临床前模型中的应用最近，我们观察到mMDSC和gMDSC具有不同的 表观遗传景观，这也是由生物性别告知。虽然这突出了 表观遗传调控的MDSC亚群的活动，有有限的洞察机制驱动不同的MDSC 子集函数我们的初步结果表明，补体途径可能是这样的机制之一 作为补体成分，1 q（C1 q）在gMDSC中高度表达，并且在女性中升高。基于这些 根据观察，我们假设C1 q的表观遗传调控告知MDSC亚群的性别特异性行为 MDSC的表观遗传重编程将提高T细胞激活策略的功效。具体目标 1将检验MDSC亚群独特的表观遗传特征使其易受 可以与检查点调节剂组合的不同组蛋白修饰剂。子目标1A将审查 组蛋白赖氨酸脱甲基酶抑制剂在体外和体内对MDSC活性的功效，而Sub-Aim 1B将 尝试通过将先导抑制剂与抗PD-1、抗CTLA-1、抗CTLA-2、抗CTLA-3和抗CTLA-4组合来实现持久的抗肿瘤免疫应答。 4和抗OX 40。具体目标2将检验C1 q基因座在以下人群中差异可及的假设： 男性与女性MDSC亚组。子目标2A将使用ATAC-seq和CUT & RUN来评估表观遗传 基于差异组蛋白赖氨酸的补体蛋白和特异性组蛋白标记占有的景观 脱甲基酶表达谱。子目标2B将使用药理学抑制剂来检测以下药物的性别特异性效应： 组蛋白赖氨酸脱甲基酶对补体调节的影响。这些研究为发展 GBM免疫疗法的表观遗传修饰剂，通过解决抗肿瘤免疫的变化， 药物和确定靶向途径。这些结果广泛适用于其他癌症，并可能导致 先进的治疗机会和改善患者的结果。

PROJECT SUMMARY: Glioblastoma (GBM) is the most common primary malignant brain tumor, with a median survival of up to 20 months. Males have a 1.6-fold higher incidence of GBM compared to females and worse disease outcomes. Immunotherapies, which are currently in clinical trials, have had limited success in improving patient outcomes. An immunosuppressive microenvironment facilitating tumor progression and restricting anti- tumor immune response likely underlies therapeutic resistance. Although the accumulation of myeloid-derived suppressor cells (MDSCs) plays a critical role in the establishment of this immunosuppressive milieu, the mechanisms by which individual MDSC subsets promote tumorigenesis and are regulated remain poorly defined. We previously demonstrated that monocytic MDSCs (mMDSCs) infiltrated male tumors at higher rates in preclinical models and patient specimens. In contrast, granulocytic MDSCs (gMDSCs) expand in the peripheral circulation of female animal models and the gMDSC gene signature is associated with poor prognosis in female patients. This variation in MDSC subsets also informed sex-specific therapeutic responses to fludarabine and anti-IL-1β in preclinical models. More recently, we observed that mMDSCs and gMDSCs have a distinct epigenetic landscape, which is also informed by biological sex. While this highlights the potential role of epigenetic regulation of MDSC subset activity, there is limited insight into the mechanisms driving distinct MDSC subset functions. Our preliminary results suggested that the complement pathway could be one such mechanism as complement component 1q (C1q) was highly expressed by gMDSCs and elevated in females. Based on these observations, we hypothesize that epigenetic regulation of C1q informs sex-specific behavior of MDSC subsets and epigenetic reprogramming of MDSCs will improve the efficacy of T cell-activating strategies. Specific Aim 1 will test the hypothesis that the unique epigenetic signatures of MDSC subsets make them susceptible to different histone modifiers that can be combined with checkpoint modulators. Sub-Aim 1A will examine the efficacy of histone lysine demethylase inhibitors on MDSC activity in vitro and in vivo, while Sub-Aim 1B will attempt to achieve durable anti-tumor immune response by combining lead inhibitors with anti-PD-1, anti-CTLA- 4, and anti-OX40. Specific Aim 2 will test the hypothesis that the C1q locus is differentially accessible between male versus female MDSC subsets. Sub-Aim 2A will use ATAC-seq and CUT & RUN to evaluate the epigenetic landscape of complement proteins and specific histone mark occupancy based on the differential histone lysine demethylase expression profile. Sub Aim 2B will use pharmacological inhibitors to test the sex-specific effect of histone lysine demethylases on complement regulation. These studies lay the foundation for the development of epigenetic modifiers for GBM immunotherapies by addressing variations in anti-tumor immunity, repurposing drugs, and defining targetable pathways. These results are broadly applicable to other cancers and can lead to advanced treatment opportunities and improved patient outcomes.