Vascular Leukocytes influence the tumor microenvironment

描述(申请人提供)：PI之前的工作揭示了人和小鼠卵巢癌血管形成的新机制：β-防御素被证明大量招募CD45+CD11c+CCR6+髓系细胞到肿瘤微环境，在那里它们在体内被血管内皮生长因子转化为内皮样细胞，称为血管白细胞(VLCs)。VLC表达内皮细胞和树突状细胞前体的标志，并具有生理特性。我们的中心假设是，VLCs是CD11c+髓系细胞的特定谱系，在肿瘤形成过程中显著促进血管形成；因此，这些细胞可能是治疗癌症的重要和新的治疗靶点。这一假说基于以下观察：首先，从肿瘤标本中分离的小鼠和人类血管内皮细胞可以在血管生成条件下在体内产生可灌流的血管。其次，我们的结果表明，GFP标记的CD45+CD11c+细胞聚集在肿瘤血管内。第三，在合适的ITGAX-DTR-GFP小鼠模型中，CD11c+细胞的耗尽导致肿瘤生长显著减少。我们研究的长期目标是确定VLCs的确切来源及其参与肿瘤血管生成，以设计新的临床有效的癌症干预措施。在特定的目标1中，我们将确定具有血管生成潜力的白细胞的来源。小鼠的VLC将被耗尽，然后用混合了不同标记白细胞亚群的肿瘤攻击，使我们能够准确地确定哪个白细胞亚群(S)能够促进血管形成。具体目标2将评估肿瘤发展阶段，血管内皮细胞对肿瘤血管形成的贡献。我们建议用永久“标记的”VLC产生转基因小鼠，允许随着时间的推移容易地识别这个亚群，即使它们在内皮化过程中失去了它们的白细胞表型。具体目标3将评估VLC耗竭作为癌症治疗干预措施的有效性，重点是针对肿瘤微环境的抗VLC免疫毒素的有效性。这些努力将导致对肿瘤血管生成机制的新认识，并为更有效地靶向卵巢癌微环境提供基础，重点是在阻止肿瘤血管形成的同时触发有效的免疫反应。

DESCRIPTION (provided by applicant): The PI's previous work unveiled a novel mechanism of vascularization in human and mouse ovarian carcinoma: beta-defensins were shown to massively recruit CD45+CD11c+CCR6+ myeloid cells to the tumor microenvironment, where they were transformed by VEGF in vivo into endothelial-like cells, termed Vascular Leukocytes (VLCs). VLCs express markers - and have physiologic characteristics - of both endothelial cells and dendritic cell precursors. Our central hypothesis is that VLCs are a specific lineage of CD11c+ myeloid cells that significantly contributes to vascularization during tumor formation; as such, these cells may represent important and novel therapeutic targets in the treatment of cancer. This hypothesis is based on the following observations: First, mouse and human VLCs sorted from tumor specimens can create perfusable blood vessels in vivo under angiogenic conditions. Second, our results show that CD45+CD11c+ cells labelled with GFP accumulate within tumor blood vessels. Third, the depletion of CD11c+ cells in suitable ITGAX-DTR-GFP mouse model resulted in a dramatic decrease in tumor growth. The long-term objectives of our research are to determine the exact origin of VLCs and their involvement in tumor vasculogenesis, in order to design new clinically effective cancer interventions. In Specific Aim 1, we will determine the origin of leukocytes with vasculogenic potential. Mice will be depleted of VLCs, and then challenged with tumors admixed with different subsets of labelled leukocytes, enabling us to precisely define which leukocyte subset(s) are capable of contributing to vascularization. Specific Aim 2 will assess the stage in tumor development at which VLCs contribute to tumor vascularization. We propose to generate a transgenic mouse with permanently "tagged" VLCs, permitting the ready identification of this subset over time, even if they lose their leukocyte phenotype during the process of endothelialization. Specific Aim 3 will evaluate the effectiveness of VLC depletion as a therapeutic intervention in cancer, focusing on the efficacy of anti-VLC immunotoxins homed to the tumor microenvironment. These endeavours will lead to new insights into the mechanisms of tumor vasculogenesis and provide a basis for a more effective targeting of the ovarian cancer microenvironment, focused on triggering an effective immune response while impeding tumor vascularization.