Role of hematopoietic microenvironment in plexiform neurofibroma progression

丛状神经纤维瘤是一种复杂的肿瘤，其特征在于致瘤性雪旺细胞、炎性细胞、新血管生成和细胞外基质的改变。我们先前的工作提供了遗传、细胞和生化证据，表明Nfl的单倍不足改变肥大细胞中Ras活性和细胞命运，并且在小鼠模型中丛状肿瘤形成的起始中需要造血系统的ckit活化。在本申请中，我们建议通过这些观察来确定c-kit如何介导其生物学效应的基础机制，并确定将在临床中补充ckit介导的实验治疗的实验过程。将研究三个基本过程。首先，已知试剂盒激活与整合素信号合作，使骨髓细胞粘附于血管壁并从血液迁移到新出现的肿瘤。我们最近发现Nf 1 +/-肥大细胞 优先粘附于α 4 β 1，α 4 β 1是一种整合素，在肥大细胞粘附于内皮中起关键作用， 在局部炎症部位。我们假设α 4 β 1在Nf 1 +/-肥大细胞的募集中是至关重要的。 在促进局部肥大细胞增殖和存活方面， 促进新血管生成的分子的分泌。我们提出的研究，以测试这一假设在体外和体内。第二，MMP是分泌的分子，其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，从而允许炎性细胞和基质细胞侵入，导致肿瘤进展。在初步研究中，我们检测到一个特定的MMP，优先表达和激活。提出了专门测试这种蛋白酶作用的研究。最后，导致细胞外基质改变和新血管生成的特定下游旁分泌信号还不完全清楚。已知肿瘤相关巨噬细胞增强新血管生成并促进恶性生长。我们最近建立了大量的血管生成巨噬细胞被发现在外周血和神经纤维瘤的Krox 20; Nfl flox/-小鼠。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至肿瘤后的关键下游事件，因此，抑制这种活性的过程将阻止或延迟肿瘤进展。提出了连续迁移实验来验证这一假设。

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.