Origins of BRAF-mutant hematologic malignancies and their therapeutic resistance

摘要 虽然丝氨酸-苏氨酸激酶BRAF的激活突变发生在~8%的实体肿瘤中，但它们很少见 除毛细胞白血病(HCL)和全身性组织细胞增多症(SH)外，其他血液系统恶性肿瘤 朗格汉斯细胞组织细胞增生症与厄尔德海姆-切斯特病特定的BRAFV600E的存在 近100%的HCL患者和40%-60%的SH患者的突变为我们的理解提供了重要的见解 这些鲜为人知的疾病的病理生理学。BRAF靶向抑制剂的研究进展 或其下游介体治疗实体肿瘤已取得重大治疗进展，最近 这一范式已经在HCL和SH中得到应用。我们的跨学科团队利用了这些优势 BRAFV600E突变生物学和治疗学的进展 HCL起源于造血干细胞，并建立了基因准确的HCL小鼠模型。更多 最近，我们已经证实在造血干和祖细胞中存在BRAFV600E突变 在SH患者的细胞中，产生SH的小鼠模型，发现反复突变与 BRAFV600E在HCL和SH中的突变以及维莫拉非尼治疗HCL和SH的临床试验完成 病人。尽管我们的初步数据提供了大量证据表明HSPC有助于疾病 在HCL和SH中的发病机制都是通过它们获得BRAFV600E突变，目前还不清楚是如何发生的 这种常见的突变导致了这种表型和临床上不同的疾病的发展。 此外，尽管我们注意到HCL和SH患者表现出显著的临床反应 维莫拉非尼，我们已经开始确定维莫拉非尼在HCL中耐药的遗传机制，这为 我们有独一无二的机会来开发治疗这些疾病的下一线治疗策略 精神错乱。因此，这项提案的总体目标是描述 HCL和SH的发病机制，并利用这些信息来确定耐药突变的起源 在BRAF靶向治疗的背景下产生。我们假设BRAFV600E突变体所在的细胞 蛋白质是活跃的和/或协同突变的存在在决定疾病方面起着重要作用 对BRAF抑制的表型和反应。我们将在以下目标中解决这一假设：1)描述 BRAFV600E突变对造血功能的影响基于其活跃的细胞，2) 确定在HCL和SH中与BRAFV600E突变共存的突变星座，以及3) 确定BRAF抑制剂耐药的机制。该项目将提供一个全面的 描述导致HCL和SH的细胞起源和协同突变。此外，这一点 这项工作将描述血液系统恶性肿瘤中BRAF抑制剂耐药的机制--这一努力可能 对更多的BRAF突变癌症患者没有有效治疗的更广泛的益处 BRAF抑制剂。

Summary While activating mutations of the serine-threonine kinase BRAF occur in ~8% of solid tumors, they are rare among hematopoietic malignancies except in hairy cell leukemia (HCL) and the systemic histiocytoses (SH) Langerhans Cell Histiocytosis and Erdheim-Chester Disease. The presence of the specific BRAFV600E mutation in nearly 100% of HCL and 40-60% of SH patients has provided major insights into our understanding of the pathophysiology of these poorly understood diseases. The development of targeted inhibitors of BRAF or its downstream mediators to treat solid tumors has led to major therapeutic advances, and more recently this paradigm has been applied in HCL and SH. Our interdisciplinary team has taken advantage of these advances in BRAFV600E mutation biology and therapeutics and recently published its findings tracing the origin of HCL to the hematopoietic stem cell and developed genetically accurate murine models of HCL. More recently, we have confirmed the presence of the BRAFV600E mutation in hematopoietic stem and progenitor cells in SH patients, generated mouse models of SH, identified recurrent mutations co-existing with the BRAFV600E mutation in both HCL and SH, and completed clinical trials of vemurafenib for HCL and SH patients. Although our preliminary data provide substantial evidence that HSPCs contribute to disease pathogenesis in both HCL and SH through their acquisition of BRAFV600E mutations, it is not yet clear how this common mutation drives the development of such phenotypically and clinically distinct disorders. Moreover, although we have noted that HCL and SH patients exhibit remarkable clinical responses to vemurafenib, we have begun to identify genetic mechanisms of vemurafenib resistance in HCL, which provides us with the unique opportunity to develop the next line of therapeutic strategies in the treatment of these disorders. Thus, the overall goal of this proposal is to delineate the cellular and functional requirements for HCL and SH pathogenesis and to utilize this information to identify the origins of resistance mutations that arise in the context of BRAF targeted therapy. We hypothesize that the cell in which the BRAFV600E mutant protein is active and/or the presence of collaborating mutations play a major role in determining disease phenotype and response to BRAF inhibition. We will address this hypothesis in the following Aims: 1) Delineate the functional effects of the BRAFV600E mutation on hematopoiesis based on the cell in which it is active, 2) Identify the constellation of mutations co-existing with the BRAFV600E mutation in HCL and SH, and 3) Identify the mechanisms of BRAF inhibitor resistance. This project will provide a comprehensive characterization of the cellular origins and cooperating mutations that give rise to HCL and SH. Moreover, this work will delineate mechanisms of BRAF inhibitor resistance in hematopoietic malignancies - an effort that may have broader benefits to the larger population of BRAF-mutant cancer patients ineffectively treated with current BRAF inhibitors.