Vascular Leukocytes Induce regulatory T cells (Treg) in Tumors

描述(申请人提供)：在我的实验室，我们最近发现了一种新的抗原提呈细胞亚群，它聚集在人和小鼠卵巢癌以及其他肿瘤中，我们将其命名为血管白细胞(VLCs)。血管内皮细胞具有血管生成能力，但也具有调节性抗原提呈细胞的特性。我们的数据表明，VLCs在肿瘤微环境中扩展Treg起着关键作用。我们假设这是通过两个互补的机制实现的，即(A)通过诱导和扩展，以及(B)通过招募Treg。我们的数据表明，血管内皮生长因子(VEGF)诱导肿瘤DC前体细胞产生VLC。我们的工作还首次表明，肿瘤血管内皮生长因子瘫痪了抗肿瘤效应的免疫机制。我们推测这是由VLC通过诱导Treg介导的，而通过阻断VEGF中和VLCs将加强针对Treg的治疗。我们将通过三个具体目标来检验这些假设。《特定目标-1》将了解VLC如何诱导Treg。我们将检验这一假设，即VLC是一种新的调节性DC亚型，可以诱导肿瘤特异性Treg。我们将在体外和体内系统地研究VLC诱导CD4+Treg的能力，并检测Treg的诱导是否是由于CD4+CD25+细胞的扩增和/或CD4+CD25-细胞的转化。我们还将测试Treg诱导是否依赖于细胞接触或MHC-II，以及肿瘤抗原特异性。最后，我们将研究阻断血管内皮生长因子是否能减弱VLC诱导的Treg。特定目标-2将决定VLC是否招募Treg。我们将测试这一假设，即VLC可以通过β-防御素和可能的其他趋化因子直接招募Treg。这是一种替代和互补的途径，VLCs可能通过它发挥其耐受功能来扩大肿瘤中的Treg。我们将检验这一假说，并揭示血管内皮生长因子和Treg通过趋化因子募集之间的联系。特异性AIM-3将评估VLC中和在Treg靶向治疗中的效果。我们将验证这样一种假设，即VLC构成了一个在肿瘤微环境中产生Treg的耐受性ARC平台。因此，我们假设，通过阻断血管内皮生长因子，中和VLC将减少Treg的产生，并将加强Treg的靶向治疗。我们将展示VLC是否在肿瘤内扩展Treg。此外，我们还将测试阻断血管内皮生长因子是否会降低肿瘤中VLC和Treg的频率；是否会通过抗DC25抗体来增强Treg耗竭治疗的疗效；以及是否会使抗肿瘤免疫反应得以协调。

DESCRIPTION (provided by applicant): In my laboratory, we have recently discovered a novel subset of antigen-presenting cells accumulating in human and murine ovarian cancer as well as other tumors, which we named "vascular leukocyte" (VLCs). VLCs are endowed with vasculogenic potential, but are also bestowed with properties of regulatory antigen- presenting cells. Our data suggest that VLCs play a critical role in expanding Treg in the tumor microenvironment. We hypothesize that this is accomplished through two complementary mechanisms, namely (a) through induction and expansion, and (b) through recruitment of Treg. Our data show that vascular endothelial growth factor (VEGF) induces the generation of VLCs from DC precursors in tumor. Our work also shows for the first time that tumor VEGF paralyzes antitumor effector immune mechanisms. We hypothesize that this is mediated by VLCs through induction of Treg, and that neutralization of VLCs through VEGF blockade will enhance therapies targeting Treg. We will test these hypotheses through three Specific Aims. Specific Aim-1 will understand how VLCs induce Treg. We will test the hypothesis that VLCs are a novel subtype of regulatory DCs which induce tumor-specific Treg. We will investigate systematically the ability of VLCs to induce CD4+ Treg in vitro and in vivo and examine whether Treg induction is due to expansion of CD4+ CD25+ cells and/or conversion of CD4+ CD25- cells. We will also test whether Treg induction is cell contact- or MHC-II dependent, and tumor antigen-specific. Finally, we will examine whether VEGF blockade attenuates Treg induction by VLCs. Specific Aim-2 will determine whether VLCs recruit Treg. We will test the hypothesis that VLCs can directly recruit Treg via beta-defensins, and possibly, other chemokines. This is an alternate and complementary pathway by which VLCs may exert their tolerogenic function to expand Treg in tumors. We will test this hypothesis and uncover the link between VEGF and Treg recruitment via chemokines. Specific Aim-3 will evaluate the effect of VLC neutralization on Treg targeting therapy. We will test the hypothesis that VLCs constitute a tolerogenic ARC platform that generates Treg within the tumor microenvironment. Thus, we hypothesize that VLC neutralization through VEGF blockade will attenuate generation of Treg and will enhance Treg targeting therapy. We will show whether VLCs expand Treg within the tumor. In addition, we will test whether VEGF blockade will decrease the frequency of VLCs and Treg in the tumor; enhance the efficacy of Treg depletion therapy through anti-DC25 antibody; and enable the orchestration of antitumor immune response.