An innate immune checkpoint in cancer immunotherapy

我们的申请是一个试点项目，重点是消除癌症治疗的意外不良反应， 揭示了处于临床和临床前开发阶段的一类新型免疫治疗药物的健康风险。 受体酪氨酸激酶（RTK）基因Tyro 3、Axl和Mertk是新近鉴定的旁系同源基因， 称为“先天免疫检查点”。这类RTK的阻断正在作为免疫疗法开发中 可以增强抗肿瘤免疫反应。然而，在这里，我们提供了一些旁系同源的初步数据， 在脑中的星形胶质细胞和小胶质细胞中表达，并且对于维持 大脑健康和神经认知功能。具体来说，星形胶质细胞中Mertk和Axl功能的丧失并不 影响出生后早期脑发育（P45），但星形胶质细胞表达未折叠蛋白反应基因， 3月龄的小鼠，伴随着这些星形胶质细胞经历自发活化。9个月时 我们观察到脂褐素在大脑中的积累。虽然在学习和记忆任务中的表现 在3月龄和6月龄时是正常的，9月龄的小鼠在海马依赖性 学习和记忆。此外，我们还观察到，在阿尔茨海默氏症患者的小胶质细胞中，Axl的消融 疾病（AD）小鼠模型（5xFAD小鼠）加速了这些小鼠的学习和记忆缺陷。鉴于 这种新的知识的功能要求AXL和MERTK在大脑中，我们认为这是必要的， 全面研究靶向这些RTK的激酶活性是否会对神经认知产生不良影响。以来 激酶主要通过其酶活性磷酸化底物发挥作用，我们选择采用 这种方法首先。因此，我们的申请还包括开发一种新的资源- AXL激酶- 死亡或AxlKD小鼠。MertkKD已经在我们的实验室中可用。我们将使用这些小鼠模型， 研究靶向激酶功能在脑内稳态、学习和记忆中的作用。我们还将 在AD小鼠模型的背景下研究AXL功能。值得注意的是，我们的方法基本上是相同的 与用于生成初步数据的方法进行比较。包括在本研究中的同一组实验 初步数据将在MertkKD和/或AxlKD小鼠上进行。我们将在不同年龄段进行检测， 表征表型的年龄依赖性发作。观察到的脑组织学变化， MertkKD和/或AxlKD小鼠，沿着动物的行为变化，将不仅提供一种新的治疗方法， 了解MERTK和AXL激酶在大脑健康和神经认知功能，但也将提供 为基于AXL和/或MERTK的肿瘤免疫疗法开发脑排除疗法的基本原理。 激酶的非依赖性、支架功能也已被描述为存在。这一点将在 如果我们的研究未能揭示Axl基因敲除或Axl基因敲除所观察到的表型， 默特克

Our application is a pilot project focused on eliminating unexpected adverse effects of cancer therapeutics by uncovering health risk of a new class of immunotherapeutics that are in clinical and preclinical development. Receptor tyrosine kinase (RTK) genes Tyro3, Axl and Mertk are paralogs that have been newly characterized as “innate immune checkpoints”. The blockade of this class of RTKs is in development as immunotherapies that can boost anti-tumor immune response. However, here we provide preliminary data that some paralogs are expressed in astrocytes and microglia in the brain, and are functionally important for the maintenance of brain health and neurocognitive functions. Specifically, loss of function of Mertk and Axl in astrocytes did not affect early postnatal brain development (P45), but astrocytes expressed unfolded protein response-genes in mice by 3-months of age, concomitant with these astrocytes undergoing spontaneous activation. By 9-months of age, we observed lipofuscin accumulation in the brain. Although performance in learning and memory tasks was normal at 3- and 6-months of age, 9-month old mice displayed defects in hippocampus-dependent learning and memory. Furthermore, we also observed that ablation of Axl in microglia in an Alzheimer's Disease (AD) mouse model (5xFAD mouse) accelerated learning and memory defects in these mice. In light of this novel knowledge of the functional requirement AXL and MERTK in the brain, we believe it is imperative to fully investigate if targeting the kinase activity of these RTKs can have adverse neurocognitive effects. Since kinases primarily function through their enzymatic activity to phosphorylate substrates, we are choosing to take this approach first. Therefore, our application also includes the development of a new resource – AXL kinase- dead or AxlKD mouse. A MertkKD is already available in our laboratory. We will use these mouse models to investigate the effect of targeting kinase function in brain homeostasis, and learning and memory. We will also investigate AXL function in the context of an AD mouse model. Notably, our approach is essentially identical with the approach used to generate the preliminary data. The same set of experiments included in the preliminary data will be performed on MertkKD and/or AxlKD mice. We will perform the assays at various ages to characterize the age-dependent onset of the phenotypes. Observed histological changes in the brain in the MertkKD and/or AxlKD mice, along with behavioral changes in the animal, will not only provide a novel understanding of MERTK and AXL kinase in the brain health and neurocognitive function, but will also provide a rationale for developing brain-excluded therapeutics for AXL- and/or MERTK-based tumor immunotherapy. Kinase-independent, scaffold-functions of kinases have also been described to exist. This will be pursued in the future if our studies fail to reveal the phenotype observed with genetic knockout of Axl or that of Axl and Mertk.