Macrophage-based Therapy and Immune Checkpoint Blockade for Glioblastoma

项目摘要 胶质母细胞瘤(Gbm)是最致命的原发脑肿瘤，预后差，对电流高度耐受。 治疗，包括免疫检查点阻断(ICB)，部分原因是免疫抑制 微环境。基底膜含有丰富的肿瘤相关巨噬细胞(TAM)，这些细胞是关键免疫细胞 肿瘤微环境中的细胞。因为大多数TAM是促进肿瘤的巨噬细胞 (pTAM，M2样)，促进恶性生长，促进治疗耐药，并调节免疫 抑制，将pTAM重新编程为肿瘤抑制巨噬细胞(STAM，M1样细胞)代表一种 前景看好的治疗策略。由于pTAM建立了免疫抑制微环境， 影响当前的免疫治疗，将pTAM重定向到STAM不仅激活巨噬细胞吞噬 但也可能重塑免疫微环境，以促进目前的ICB。要识别小的 可以将pTAM重新编程为STAM的分子，以促进胶质瘤细胞的巨噬细胞吞噬 设计了一种基于细胞的荧光筛选方法，使用GFP标记的IPSC来源的巨噬细胞和 表达番茄的胶质瘤细胞，包括胶质瘤干细胞(GSCs)，以发现候选药物和 相应的分子靶标。为此，我们发现了几种BACE1(β-Site)的特异性抑制剂 淀粉样前体蛋白裂解酶1可有效刺激巨噬细胞吞噬 包括GSC在内的胶质瘤细胞，并因此将BACE1确定为重新编程pTAM的治疗靶点 太棒了。我们证明了BACE1在人的GBM中由pTAM优先表达，并且是必需的 用于维持PTAM极化。重要的是，其抑制剂MK-8931对BACE1的药理抑制作用 (Verubecestat)有效地将pTAM重定向为STAM，并促进胶质瘤细胞的巨噬细胞吞噬 抑制GBM生长。此外，我们还发现，低剂量辐射(IR)对有显著的促进作用 侵袭与MK-8931治疗有协同作用，抑制GBM肿瘤生长。作为多个BACE1 包括最初为阿尔茨海默病开发的MK-8931在内的抑制剂已被证明是安全的 对于临床试验中的人类来说，将这些抑制物重新用于基于巨噬细胞的癌症治疗应该 直截了当，充满希望。因为大量的pTAM在很大程度上有助于免疫抑制 在微环境中，通过抑制BACE1将pTAM重新编程为STAM可能会重塑TME以 为当前的ICB提供便利。因此，我们假设将pTAM重新编程为STAM BACE1的药理抑制与当前的免疫检查点抑制协同改善 银屑病的治疗效果。我们将通过以下目标实现目标：(一) 评估将pTAM重新编程为STAM对GBM免疫微环境的影响；以及(2)我们 评价为主结合现代ICB治疗基底膜的疗效。结果是 将为未来的临床试验提供信息，以改进对GBM和潜在脑转移瘤的治疗。

Project Summary Glioblastoma (GBM), the most lethal primary brain tumor with poor prognosis, is highly resistant to current treatments, including immune checkpoint blockade (ICB) partially due to the immune suppressive microenvironment. GBM harbors abundant tumor-associated macrophages (TAMs) that are critical immune cells in the tumor microenvironment (TME). Because the majority of TAMs are tumor-promoting macrophages (pTAMs, M2-like) that augment malignant growth, promote therapeutic resistance, and mediate immune suppression, reprograming pTAMs into tumor-suppressive macrophages (sTAMs, M1-like) represents a promising therapeutic strategy. As pTAMs establish the immunosuppressive microenvironment that negatively impacts current immunotherapy, redirecting pTAMs into sTAMs not only activates macrophage phagocytosis of glioma cells but may also remodel the immune microenvironment to facilitate current ICB. To identify small molecules that can reprogram pTAMs into sTAMs to promote macrophage phagocytosis of glioma cells, we designed a cell-based fluorescent screening assay, using GFP-labeled iPSC-derived macrophages and tdTomato-expressing glioma cells including glioma stem cells (GSCs) to discover drug candidates and corresponding molecular targets. To this end, we found that several specific inhibitors of BACE1 (β-site amyloid precursor protein cleaving enzyme 1) could effectively stimulate macrophage phagocytosis to engulf glioma cells including GSCs, and thus identified BACE1 as a therapeutic target to reprogram pTAMs into sTAMs. We demonstrated that BACE1 is preferentially expressed by pTAMs in human GBMs and is required for maintaining pTAM polarization. Importantly, pharmacological inhibition of BACE1 by its inhibitor MK-8931 (Verubecestat) potently redirected pTAMs into sTAMs and promoted macrophage phagocytosis of glioma cells to inhibit GBM growth. Furthermore, we found that low doses of radiation (IR) markedly enhanced TAM infiltration and synergized with MK-8931 treatment to suppress GBM tumor growth. As several BACE1 inhibitors including MK-8931, initially developed for Alzheimer's disease, have been demonstrated to be safe for humans in clinical trials, repurposing these inhibitors for the macrophage-based cancer therapy should straightforward and promising. As abundant pTAMs largely contribute to the immune suppressive microenvironment, reprograming pTAMs into sTAMs through BACE1 inhibition may remodel the TME to facilitate current ICB. Thus, we hypothesize that reprograming pTAMs into sTAMs through pharmacological inhibition of BACE1 synergizes with current immune checkpoint inhibition to improve therapeutic efficacy for GBM. We will accomplish our objectives through the following aims: (1) We will assess the effect of reprograming pTAMs into sTAMs on the immune microenvironment in GBM; and (2) We evaluate the therapeutic impact of TAM-based therapy in combination with current ICB for GBM. The outcomes will inform future clinical trials to improve treatment for GBM and potentially brain metastases.