The role of endothelial progenitor cells in tumor growth and metastasis

描述(由申请人提供)：在这项建议中，我们探讨了在临床前模型系统中，骨髓(BM)来源的内皮祖细胞(EPC)在肿瘤发生和扩散中的作用。许多实验室已经证明，内皮祖细胞对于在原发肿瘤部位和转移灶形成完整的血管网络是必不可少的。因此，如果能够选择性地摧毁这些细胞，它们可能成为治疗干预的重要靶点。许多EPC标记物被许多不同类型的细胞共享，这阻碍了EPC的准确识别、分离和靶向。事实上，关于EPC的表型仍然存在争议，许多研究不仅质疑EPC的相对较低的贡献，而且质疑其在肿瘤新生血管形成中的意义。为了明确地阐明内皮祖细胞在肿瘤血管生成中的作用，理想情况下有必要唯一地定义这一群体，抑制其功能所必需的基因的活性，特异性地去除该群体，并证明这些细胞足以修复遗传模型中的血管生成缺陷。在这项建议中，我们利用了成人中Id1和VE-cadherin双阳性细胞定义EPC群体的事实。我们将在VE-cadherin内皮祖细胞中诱导Id1功能的丧失，并确定其对肿瘤生长的影响。将对VE-cadherin Id1细胞进行特定的消融。纯化的内皮祖细胞将用于挽救Id1基因敲除小鼠的血管生成缺陷。最后，内皮祖细胞特有的多肽将被用来向内皮祖细胞递送抑制性寡核苷酸，以测试我们识别的内皮祖细胞特异基因的功能意义。这些研究应该有助于阐明内皮祖细胞在肿瘤生物学中的作用，并为它们作为潜在的治疗策略在人类癌症管理中的靶向提供基础。 公共卫生相关性：在这项建议中，我们描述了一组特殊的细胞，这些细胞是在骨髓中产生的，对原发肿瘤部位和转移生长部位的功能性血管供应的形成是必不可少的。因此，如果这些细胞(称为“内皮祖细胞”或“内皮祖细胞”)能够选择性地被破坏，它们可能成为治疗干预的重要靶点。内皮祖细胞的准确鉴定、分离和靶向一直受到以下事实的阻碍：许多不同类型的细胞共享在其表面表达的用于鉴定的许多蛋白质(称为“标志物”)。在提出的实验中，我们概述了一种策略，通过使用两个标记的组合来绕过这个问题，我们展示了这两个标记唯一地识别EPC种群。使用一组基因工程小鼠品系，我们继续分离EPC群体，识别在其中特定表达的新基因，最后在原发和转移性肿瘤生长过程中摧毁这些细胞。在设计了一种在活体动物中抑制血管形成细胞内任何给定基因表达的策略后，我们建议将该策略调整为针对临床前小鼠癌症模型以及最终患者的EPC群体。这些实验可以导致靶向治疗的发展，可以减少原发肿瘤的生长和转移负担，希望延长侵袭性癌症患者的生命。

DESCRIPTION (provided by applicant): In this proposal we explore the role of bone marrow (BM) derived endothelial progenitor cells (EPCs) in development and spread of tumors in preclinical model systems. EPCs have been shown by a number of laboratories to be essential for the formation of an intact vascular network both at the primary tumor site and the metastatic niche. in As such these cells may be important targets for therapeutic intervention if they can be destroyed selectively. The precise identification, isolation and targeting of EPCs has been hindered by the fact that many EPC markers are shared by many different cell types. Indeed, controversies still exist about the EPC phenotype, and many studies have not only questioned the relatively low contribution, but also their significance in tumors neoangiogenesis. In order to definitively address the role of EPCs in tumor angiogenesis it is necessary ideally to uniquely define this population, inhibit the activity of genes essential for their function, ablate the population specifically and show that these cells are sufficient to rescue angiogenic defects in genetic models. In this proposal, we utilize the fact that Id1 and VE-cadherin double positive cells in the adult define the EPC population. We will induce loss of Id1 function in VE-cadherin+ EPCs and determine the consequence on tumor growth. Specific ablation of the VE-cadherin Id1+ cells will be performed. Purified EPCs will be used to rescue the angiogenic deficiency in the Id1 knockout mice. Finally, peptides which home specifically to EPCs will used to deliver inhibitory oligonucleotides to EPCs in order to test the functional significance of EPC-specific genes that we identify. These studies should help clarify the role of EPCs in tumor biology and provide a basis for their targeting as a potential therapeutic strategy in the management of human cancers. PUBLIC HEALTH RELEVANCE: In this proposal we characterize a specialized group of cells which are produced in the bone marrow in response to the growth of a tumor and are essential for the formation of a functional blood vessel supply both at the primary tumor site and at sites of metastatic growth. As such these cells (called "endothelial progenitor cells" or "EPCs") may be important targets for therapeutic intervention if they can be destroyed selectively. The precise identification, isolation and targeting of EPCs has been hindered by the fact that many of the proteins expressed on their surface used in their identification (called "markers") are shared by many different cell types. In the experiments being proposed we outline a strategy to circumvent this problem by using a combination of just two markers which we show uniquely identifies the EPC population. Using a set of genetically engineered mouse strains we go on to isolate the EPC population, identify new genes that are expressed specifically within them and, finally, destroy these cells during primary and metastatic tumor growth. Having devised a strategy to inhibit in living animals the expression of any given gene within blood vessel forming cells, we propose to adapt that strategy for targeting the EPC population in preclinical mouse models of cancer and ultimately in patients. These experiments can lead to the development of targeted therapies which can reduce primary tumor growth and metastatic burden with the hope of extending the lives of patients with aggressive cancers.