Molecular and Cellular Pathogenesis of Pulmonary Langerhans Cell Histiocytosis

项目摘要。肺朗格汉斯细胞组织细胞增生症(PLCH)是一种罕见的间质性肺部疾病， 它几乎只发生在吸烟者中，存活时间的中位数是 12.5年。PLCH的特点是，Langerin+树突状细胞(DC)聚集，炎性病变， 结节形成和囊性重塑。最近，获得性BRAF(蛋白激酶)之间的因果联系 髓系/单核细胞系RAS通路突变与良性肿瘤发生 已有报道，在肺脏病变中发现了一种常见的BRAF(V600E)获得性突变 超过一半的PLCH患者。尽管这种因果联系是一项重要的突破，但 突变的组织细胞控制PLCH的启动和进展的机制尚不清楚。至 为了解决这一关键的知识鸿沟，我们开发了概括标志的临床前模型 PLCH的特点。我们发现，香烟烟雾(CS)暴露的小鼠表达了一种可诱导的 CD11c+细胞中的BRAFV600E突变表现为细支气管炎、结节形成和 空域扩大并伴有囊状结构。这些结构性变化是伴随着 通过DC动态平衡的改变，包括增加表达和对 趋化因子CCL20。此外，我们的数据表明，BRAFV600E依赖于多效性的生产 细胞因子CCL7是PLCH炎性损害的潜在驱动因素。最后，我们证明了 BRAF突变诱导DC衰老伴随非经典MHC配体上调 允许DC逃避免疫调节的清除。基于这些新颖的初步数据，我们 假设PLCH的发病机制是由BRAF突变和CS的组合启动的 暴露于放大CCL20介导的组织细胞聚集后，炎性细胞的招募 通过产生CCL7来发育细胞/结节，这一过程的放大通过 细胞毒性淋巴细胞上抑制受体配体的BRAF依赖性表达。我们将对此进行测试 有三个相互关联但又相互独立的特定目标的假设。我们预计可完成 研究将导致PLCH在概念上的新进展。虽然PLCH很少见，但我们认为临床前 模型将导致对BRAFV600E细胞在PLCH中的作用的深入了解。该模型提供了一个引人注目的 短期临床前研究和长期循证临床试验平台，以及 应该能够开发出一种威胁生命的肺部疾病的治疗方法。这个目标可能是 被认为是侵袭性的，但我们的研究发现了一种治疗淋巴管肌瘤病的有效方法 作为罕见肺部疾病联盟的一部分，我们小组正在进行有希望的临床试验， 直接证据表明，当自然界的线索丰富时，有效的治疗方法可以很快找到， 分子靶标是已知的，生物学上的可信度很高，患者社区组织得很好。

Project Summary. Pulmonary Langerhans Cell Histiocytosis (PLCH) is a rare interstitial lung disease, which occurs almost exclusively in cigarette smokers and has a median duration of survival from of of 12.5 years. PLCH is characterized by,Langerin+ dendritic cell (DC) accumulation, inflammatory lesions, nodule formation and cystic remodeling. Recently, a causative link between acquired BRAF (kinase in RAS pathway) mutations in the myeloid/monocyte lineage and the development of benign neoplasms has been reported, and a common, acquired mutation in BRAF (V600E) was found in lung lesions of more than half of PLCH patients. Although this causal link represents an important breakthrough, the mechanisms by which mutant histiocytes control the initiation and progression of PLCH are unknown. To address this critical knowledge gap, we have developed preclinical models that recapitulate hallmark features of PLCH. We show that cigarette smoke (CS) exposure of mice expressing an inducible BRAFV600E mutation in CD11c+ cells exhibit peribronchiolar inflammation, nodule formation, and airspace enlargement accompanied by cyst-like formations. These structural changes are accompanied by alterations in DC homeostasis, including increased expression of and responsiveness to the chemokine CCL20. Further, our data suggest the BRAFV600E-dependent production of the pleiotropic cytokine CCL7 is a potential driver of the inflammatory lesions in PLCH. Finally, we demonstrate that the BRAF mutation induces DC senescence accompanied by upregulation of non-classical MHC ligands that permit the DCs to evade immune-mediated clearance. Based on these novel preliminary data, we hypothesize that PLCH pathogenesis is initiated by a combination of BRAF mutations along with CS exposure to amplify CCL20 mediated histiocyte accumulation followed by the recruitment of inflammatory cells/nodule development via CCL7 production and the amplification of this process is preserved by BRAF-dependent expression of ligands for inhibitory receptors on cytotoxic lymphocytes. We will test this hypothesis with three inter-related, yet independent, Specific Aims. We expect the completion of the research will lead to new conceptual advances in PLCH. While PLCH is rare, we believe the preclinical model will lead to insights into the role of BRAFV600E cells in PLCH. This model provides a compelling platform for preclinical studies in the short term and evidence based clinical trials in the long term, and should enable the development of treatments of a life threatening pulmonary disease. This goal may be viewed as aggressive but the identification of an effective treatment for lymphanioleiomyomatosis by our group and promising clinical trials underway by our group as part of the Rare Lung Disease Consortium, are direct evidence that effective therapies can be found quickly when clues of nature are abundant, molecular targets are known, biological plausibility is high and patient communities are well organized.