Vascular Endothelial Growth Factor in Hematopoiesis in Cancer

描述(申请人提供)：血管内皮生长因子(VEGF)是一种由大多数人类实体肿瘤产生的促血管生成因子，是重要的造血调节因子。血管内皮生长因子信号在早期造血发育中起着至关重要的作用。然而，包括我们在内的最新数据显示，血管内皮生长因子作为免疫细胞分化的抑制因子，对树突状细胞(DC)和T细胞具有深远的影响。我们发现很大一部分血管内皮生长因子对DC的抑制作用是通过酪氨酸激酶非依赖性机制实现的。我们的初步数据表明，血管内皮生长因子受体1(VEGFR1)参与了这一过程。确定血管内皮生长因子免疫抑制作用的具体机制对于开发有效的治疗策略以纠正癌症的免疫是至关重要的。该项目的目标是研究该系统中抑制信号转导的机制和功能元件。大多数血管内皮生长因子配体或受体的扰动对胚胎的致死性使得对造血效应的遗传学研究变得更加困难。因此，我们开发了转基因小鼠胚胎干细胞可以分化为树突状细胞的体外系统。我们将使用敲除各种受体的小鼠ES细胞，并通过特定的受体突变进行转导，以确定每个受体及其亚域和信号伙伴在这一过程中的作用。我们的动物骨髓移植研究旨在阐明体内每个血管内皮生长因子受体及其酪氨酸激酶在DC功能障碍中的相对作用。我们推测，VEGFR1是DC失调的主要介导者，通过酪氨酸激酶依赖以外的机制转导其抑制信号的很大一部分，涉及膜旁区域、异源二聚体的形成或内化。我们将通过以下特定目的来测试这一点：1)研究VEGFR1非酪氨酸激酶亚域在体外DC分化和造血中的作用。2)研究VEGFR1酪氨酸磷酸化依赖信号在体外DC缺陷中的作用。3)评估各受体信号在体内介导血管内皮生长因子对DC发育的作用。了解血管内皮生长因子信号在造血细胞中的机制和作用，将有助于更深入地了解正常和病理性的造血，以及旨在改善免疫功能的潜在治疗干预措施，与癌症和免疫治疗具有高度的临床相关性。

DESCRIPTION (provided by applicant): Vascular Endothelial Growth Factor (VEGF), a pro-angiogenic factor produced by most human solid tumors is important modulator of hematopoiesis. VEGF signaling is crucial for early hematopoietic development. However, recent data including ours, revealed the role of VEGF as inhibitor of immune cell differentiation with profound effect on dendritic (DC) and T cells. We made an important observation that substantial part of VEGF inhibitory effect on DCs is mediated by tyrosine kinase-independent mechanism. Our preliminary data strongly implicate VEGF receptor 1 (VEGFR1) in this process. Identifying specific mechanisms of immunosuppressive effects of VEGF would be essential for the development of efficient therapeutic strategies aimed at immune correction in cancer. The goal of the proposed project is to investigate the mechanism and functional elements of inhibitory signal transduction in this system. The embryonic lethality of most perturbations of VEGF ligand or receptors makes genetic studies of hematopoietic effects more difficult. We have therefore developed in vitro system where genetically modified murine embryonic stem (ES) cells can be differentiated into DCs. We will use murine ES cells knocked out for various receptors and transduced with specific receptor mutants to determine the role of each receptor, their subdomains and signaling partners in this process. Our animal bone marrow transplant studies are designed to elucidate relative contribution of each VEGF receptor and their tyrosine kinases in DC dysfunction in vivo. We hypothesize that VEGFR1 being a major mediator of DC dysregulation transduces substantial part of its inhibitory signaling by mechanism other then tyrosine kinase-dependent, involving juxtamembrane domain, formation of heterodimers, or internalization. We will test this by the following specific aims: 1) Characterize the roles of VEGFR1 non-tyrosine kinase subdomains on DC differentiation and hematopoiesis in vitro. 2) Determine the role of VEGFR1 tyrosine phosphorylation dependent signaling in DC defects in vitro. 3) Assess the role of signaling by each VEGF receptors in mediating VEGF effects on DC development in vivo. Understanding the mechanism and effects of VEGF signaling in hematopoietic cells will lead to greater insight into normal and pathological hematopoiesis, and potential therapeutic interventions aimed at improvement of immune function and highly clinically relevant to cancer and immunotherapy.