Endothelial Stem Cells in Tumor Vasculature

描述（申请人提供）：肿瘤的生长和转移完全依赖于血管的招募和维持功能的能力。传统上，肿瘤新生血管的研究主要集中在“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，肿瘤血管的一部分是由“血管生成”产生的，骨髓（BM）衍生的循环内皮祖细胞（EPCs）回到肿瘤生长的部位，并有助于血管的形成。血管内皮生长因子（VEGF）及其受体在正常和异常血管生成，包括肿瘤血管形成中起着重要作用。然而，VEGF及其受体在肿瘤血管形成中的作用以及负责EPC向新血管形成部位募集的因素尚不清楚。本提案的总体目标是研究EPC分化的机制，并确定在肿瘤新生血管形成过程中，bm来源的EPCs在多大程度上和通过何种机制在血管发生中发挥作用。上述实验旨在验证两个假设：1)VEGF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促进肿瘤生长。2)扩增培养的人外周血内皮祖细胞来源于单核细胞，可短暂移植。本提案的具体目的是：1)定量和定性地确定EPCs对体内肿瘤血管发育的贡献。具体来说，脑梗死衍生血管的范围、分布和持续性如何？这些参数如何受到局部VEGF的影响？2)通过受体特异性抗体和在EPCs中过表达VEGFR1，在体内确定VEGF-VEGFR1相互作用是否介导EPCs靶向肿瘤生长部位。3)比较bm祖细胞（CD34+/lin-） EPCs和培养扩增EPCs在肿瘤血管发生中的归巢和持久性，并利用转基因小鼠模型确定EPC分化是否通过单核细胞中间体发生。所提出的实验和训练计划旨在帮助我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.