Endothelial Stem Cells in Tumor Vasculature

描述(由申请人提供)：肿瘤的生长和转移完全依赖于招募和维持功能性血管系统的能力。肿瘤新生血管的研究传统上集中在“血管生成”上，即从现有血管的增殖中生长出新的血管。最近有几项研究表明，肿瘤血管的一部分来自“血管生成”，即骨髓(BM)来源的循环内皮祖细胞(EPC)是肿瘤生长部位的家园，并有助于血管形成。血管内皮生长因子(VEGF)及其受体在包括肿瘤血管在内的正常和异常血管生成中起重要作用。然而，血管内皮生长因子及其受体在肿瘤血管生成中的作用以及导致EPC重新聚集到新生血管部位的因素尚不清楚。该方案的总体目标是研究内皮祖细胞分化的机制，并确定骨髓来源的内皮祖细胞在肿瘤新生血管形成过程中在多大程度上和通过哪些机制发挥血管生成作用。概述的实验旨在检验两个假设：1)血管内皮生长因子通过其招募和促进内皮祖细胞存活的能力，作为促血管生成细胞因子而促进肿瘤生长。2)培养扩增的人外周血来源的内皮祖细胞来源于单核细胞，并瞬时植入。这项建议的具体目的是：1)定量和定性地确定内皮祖细胞在体内肿瘤血管形成中的作用。具体地说，骨髓来源的血管系统的范围、分布和持久性是什么，这些参数是如何受到局部血管内皮生长因子的影响的？2)通过使用受体特异性抗体和在血管内皮细胞中过度表达血管内皮生长因子1，确定血管内皮生长因子-血管内皮生长因子受体1的相互作用是否介导了血管内皮细胞靶向体内肿瘤生长部位。3)比较骨髓祖细胞(CD34+/Lin-)和培养扩增的EPC在肿瘤血管生成中的归巢和持久性，并利用转基因小鼠模型确定EPC是否通过单核细胞中间体发生分化。建议的实验和培训计划是为了帮助我发展成为一名优秀的内科科学家。我希望对干细胞研究的重大贡献将导致建立一个成功的、独立的研究计划。

DESCRIPTION (provided by applicant): Tumor growth and metastasis are absolutely dependent on the ability to recruit and sustain a functional vasculature. The study of tumor neovascularization has focused traditionally on "angiogenesis," the growth of new vessels from proliferation of existing vessels. There have been several recent studies that indicate that portions of tumor vasculature are derived by "vasculogenesis," whereby bone marrow (BM)-derived circulating endothelial progenitor cells (EPCs) home to sites of tumor growth and contribute to blood vessel formation. Vascular Endothelial Growth Factor (VEGF) and its receptors play a fundamental role in normal and abnormal angiogenesis, including tumor vascularity. However, the role of VEGF and its receptors in tumor vasculogenesis and the factors responsible for EPC recruitment to sites of neovascularization are not yet known. The overall objective of this proposal is to study the mechanism of EPC differentiation and to determine to what extent and by which mechanisms BM-derived EPCs play a role in vasculogenesis during tumor neovascularization. The experiments outlined are designed to test two hypotheses: 1) VEGF promotes tumor growth by acting as a pro-vasculogenic cytokine via its ability to recruit and promote the survival of EPCs. 2) EPCs derived from culture expanded human peripheral blood are derived from monocytes and engraft transiently. The specific aims of this proposal are: 1) To determine quantitatively and qualitatively the contribution of EPCs to the development of tumor vasculature in vivo. Specifically, what are the extent, distribution and persistence of BM-derived vasculature and how are these parameters affected by local VEGF? 2) To determine if VEGF-VEGFR1 interactions mediate the targeting of EPCs to site of tumor growth in vivo by using receptor-specific antibodies and overexpressing VEGFR1 in EPCs. 3) To compare homing and persistence of BM-progenitor (CD34+/lin-) EPCs and culture-expanded EPCs in tumor vasculogenesis and to determine if EPC differentiation occurs through a monocyte intermediate using transgenic mouse models. The proposed experiments and training plan are designed to help me develop into an excellent physician scientist. I hope that significant contributions to the study of stem cells will result in the establishment of a successful, independent research program.