Deciphering the role of Microglia in Glioblastoma

胶质母细胞瘤是最常见的脑部原发恶性肿瘤。全神经外科手术切除 胶质母细胞瘤是不可能的，肿瘤即使在切除、化疗和放疗后也总是会复发。 尽管对胶质母细胞瘤的生物学进行了广泛的研究，但护理标准并没有改变。 大约20年，从确诊到死亡的中位寿命仍然令人沮丧，大约15个月。这 强调了确定治疗这些毁灭性肿瘤的新靶点的必要性。 胶质母细胞瘤的特点是广泛的小胶质细胞渗入；主要居于先天免疫 大脑的细胞。然而，尽管存在大量的小胶质细胞，但它们未能控制肿瘤，似乎 促进肿瘤生长。小胶质细胞这种促肿瘤作用的确切机制(S)仍不完全 明白了。使用一种方法，允许我们选择性地识别和分离存在于脑内的小胶质细胞 肿瘤(与在同一大脑但在肿瘤外的那些)相比，我们确定了这些基因的转录本 用RNAseq技术在胶质母细胞瘤小鼠模型中检测胶质母细胞瘤相关小胶质细胞。我们发现 胶质母细胞瘤通过下调可能参与的通路重新编程小胶质细胞转录网络 识别和杀死肿瘤细胞。具体地说，我们发现Gami下调了：(A)基因 参与免疫感应和胶质母细胞瘤细胞的吞噬作用，以及(B)可能参与 直接杀死肿瘤。我们还发现，在Gami中观察到的大多数变化可能是由小胶质细胞驱动的 特定的路径。当我们分析来自人类胶质母细胞瘤患者的数据集时，我们获得了类似的发现。 在这一应用中，我们建议测试这些小胶质细胞的转录变化中的哪些是功能性的 三种临床前小鼠胶质母细胞瘤模型和共培养模型在调节肿瘤生长中的重要作用 患者来源的人胶质母细胞瘤和IPSC来源的小胶质细胞。我们还将确定准确的小胶质细胞 调节这些过程的途径。为了实现这一目标，我们提出了三个具体目标。在目标1中，我们将 确定Gami是否降低了识别和吞噬肿瘤细胞的功能能力，以及Gami对 这降低了肿瘤生长的能力。在目标2中，我们将确定Gami是否已减少功能容量以 杀灭肿瘤细胞，以及这种能力降低对肿瘤生长的影响。在目标3中，我们确定具体的 调节小胶质细胞感知和吞噬胶质母细胞瘤细胞的小胶质细胞通路，直接杀伤肿瘤 细胞，以及靶向这种途径是否会调节整个肿瘤的生长。我们的研究将提供证据证明 这些通路可以作为治疗这种毁灭性肿瘤的潜在有效靶点。

Glioblastomas are the most common primary malignant brain tumors. Total neurosurgical resection of glioblastomas is not possible, and tumors invariably recur even following resection, chemo- and radiotherapy. Despite extensive research into the biology of glioblastomas, there has been no change in the standard of care for ~20 years and the median lifespan from time of diagnosis to death remains dismal at ~15 months. This highlights the need for identifying new targets for therapy of these devastating tumors. Glioblastomas are characterized by extensive infiltration of microglia; the main resident innate immune cells of the brain. Yet, despite their large presence, microglia fail to keep the tumor in check and appear to promote tumor growth. The exact mechanism(s) of this pro-tumor role of microglia remain incompletely understood. Using an approach that allows us to selectively identify and isolate microglia present within the tumor (vs. those in the same brain but outside the tumor), we determined the transcriptomes of these Glioblastoma Associated Microglia (GAMi) by RNASeq in a murine model of glioblastoma. We found that glioblastomas reprogram microglial transcriptional networks by downregulating pathways potentially involved in recognizing and killing tumor cells. Specifically, we found that GAMi have downregulated: (a) genes potentially involved in immune sensing and phagocytosis of glioblastoma cells and (b) transcripts potentially involved in direct tumor killing. We also found that most of the changes observed in GAMi may be driven by a microglia specific pathway. We obtained similar findings when we analyzed datasets from human glioblastoma patients. In this application, we propose to test which of these microglial transcriptional changes are functionally important in regulating tumor growth using three preclinical mouse glioblastoma models and a co-culture model of patient-derived human glioblastoma and iPSC-derived microglia. We will also identify the precise microglial pathway that regulates these processes. To achieve this, we propose three specific aims. In aim 1, we will determine if GAMi have reduced functional capacity to recognize and phagocytose tumor cells, and the effect of such reduced capacity on tumor growth. In aim 2, we will determine if GAMi have reduced functional capacity to kill tumor cells, and the effect of such reduced capacity on tumor growth. In aim 3, we determine the specific microglial pathway that regulates microglial sensing and phagocytosis of glioblastoma cells, direct killing of tumor cells and whether targeting such pathway will regulate overall tumor growth. Our studies would provide proof of concept that these pathways can be used as potential effective targets for therapy of this devastating tumor.