Role of hematopoietic microenvironment in plexiform neurofibroma progression

丛状神经纤维瘤是一种以致瘤雪旺细胞、炎性细胞、新生血管生成和细胞外基质改变为特征的复杂肿瘤。我们以前的工作提供了遗传、细胞和生化证据，表明NFL单倍体不足改变了肥大细胞中RAS活性和细胞命运，并且在小鼠模型中，cKit激活造血系统是启动丛状肿瘤形成所必需的。在这个应用中，我们建议建立这些观察，以确定c-kit如何介导其生物学效应的基础机制，并确定在临床上补充cKit介导的实验治疗的实验过程。我们将考察三个基本过程。首先，已知KIT激活与整合素信号合作，使髓系细胞能够附着在血管壁上，并从血液迁移到新出现的肿瘤。我们最近证实了NF1+/-肥大细胞 优先附着于α4beta1，这是一种在肥大细胞与内皮细胞黏附中起关键作用的整合素 在局部发炎的地方。我们假设Alpha4beta1在NF1+/-MAST的招募中是至关重要的 细胞到肿瘤微环境中促进局部肥大细胞的增殖和存活，并在 分泌促进新血管生成的分子。我们建议在体外和体内进行研究，以检验这一假设。其次，MMPs是一种分泌分子，可以促进预先形成的生长因子释放到循环中，并降解组织的细胞外基质，从而允许炎症细胞和间质细胞的入侵，导致肿瘤的进展。在初步研究中，我们检测到一种特定的基质金属蛋白酶优先表达和激活。提出了专门测试这种酶的作用的研究。最后，导致细胞外基质改变和新生血管生成的特定下游旁分泌信号尚不完全清楚。肿瘤相关的巨噬细胞被认为可以促进新生血管的生成和促进恶性肿瘤的生长。我们最近证实，在Krox20；NFL flx/-小鼠的外周血和神经纤维瘤中发现了大量的血管生成巨噬细胞。我们假设巨噬细胞募集及其在新血管生成中的作用是肥大细胞募集到肿瘤后的一个关键下游事件，因此，抑制这一活性的过程将阻止或延缓肿瘤的进展。为了验证这一假说，我们提出了采用迁移实验的方法。

Plexiform neurofibromas are complex tumors characterized by tumorigenic Schwann cells, inflammatory cells, neoangiogenesis and alterations of the extracellular matrix. Our previous work provided genetic, cellular, and biochemical evidence that haploinsufficiency of Nfl alters Ras activity and cell fates in mast cells and that ckit activation of the hematopoietic system is required in the initiation of plexiform tumor formation in a murine model. In this application, we propose to build oh these observations to identify the underpinning mechanisms of how c-kit mediates its biological effects, and to identify experimental processes that would complement ckit mediated experimental therapeutics in the clinic. Three basic processes will be examined. First, kit activation is known to cooperate with integrin signals in enabling myeloid cells to adhere to blood vessel walls and emigrate from the blood to the emerging tumor. We have recently established that Nf 1 +/- mast cells preferentially adhere to alpha4beta1, an integrin that has a key role in mast cell adhesion to endothelium and in local sites of inflammation. We hypothesize that alpha4beta1 is crucial in the recruitment of Nf1+/- mast cells to the tumor microenvironment in promoting local mast cell proliferation and survival, and in the secretion of molecules that promote neoangiogenesis. We propose studies to test this hypothesis in vitro and in vivo. Second, MMPs are secreted molecules that promote the release of preformed growth factors to the circulation and degrade the extracellular matrix of tissues allowing invasion of inflammatory and stromal cells leading to tumor progression. In preliminary studies we detect one specific MMP that is preferentially expressed and activated. Studies to specifically test the role of this protease are proposed. Finally, the specific downstream paracrine signals that lead to alterations of the extracellular matrix and neoangiogenesis are incompletely understood. Tumor-associated macrophages are known to enhance neoangiogenesis and facilitate malignant outgrowth. We recently established that large populations of angiogenic macrophages are found in peripheral blood and in the neurofibromas of Krox20; Nfl flox/- mice. We hypothesize that macrophage recruitment and their role in neoangiogenesis is a key downstream event following mast cell recruitment to the tumor and, therefore, processes that inhibit this activity will prevent or delay tumor progression. Adoptive transfer experiments are proposed to test this hypothesis.