Vascular Leukocytes Induce regulatory T cells (Treg) in Tumors

描述（由申请人提供）：在我的实验室中，我们最近发现了一种新的抗原呈递细胞亚群，其在人类和小鼠卵巢癌以及其他肿瘤中积累，我们将其命名为“血管白细胞”（VLC）。VLC具有血管生成潜能，但也具有调节性抗原呈递细胞的特性。我们的数据表明，VLC在肿瘤微环境中扩展Treg中发挥关键作用。我们假设这是通过两种互补机制实现的，即（a）通过诱导和扩增，和（B）通过募集Treg。我们的数据显示，血管内皮生长因子（VEGF）诱导肿瘤中DC前体产生VLCs。我们的工作还首次表明肿瘤VEGF使抗肿瘤效应免疫机制瘫痪。我们假设这是由VLC通过诱导Treg介导的，并且通过VEGF阻断来中和VLC将增强靶向Treg的疗法。我们将通过三个具体目标来检验这些假设。具体目标-1将了解VLC如何诱导Treg。我们将测试的假设，VLCs是一种新的亚型的调节性树突状细胞诱导肿瘤特异性调节性T细胞。我们将系统地研究VLC在体外和体内诱导CD 4 + Treg的能力，并检查Treg诱导是否是由于CD 4 + CD 25+细胞的扩增和/或CD 4 + CD 25-细胞的转化。我们还将测试Treg诱导是否是细胞接触或MHC-II依赖性的，以及肿瘤抗原特异性的。最后，我们将检查VEGF阻断是否减弱VLC对Treg的诱导。特异性目标-2将决定VLC是否招募Treg。我们将检验VLCs可以通过β-防御素直接招募Treg的假设，可能还有其他趋化因子。这是一种替代和互补的途径，VLC可以通过该途径发挥其致耐受性功能以扩增肿瘤中的Treg。我们将测试这一假设，并揭示VEGF和Treg通过趋化因子募集之间的联系。Specific Aim-3将评估VLC中和对Treg靶向治疗的影响。我们将检验VLC构成在肿瘤微环境内产生Treg的致耐受性ARC平台的假设。因此，我们假设通过VEGF阻断的VLC中和将减弱Treg的产生并将增强Treg靶向治疗。我们将显示VLC是否在肿瘤内扩增Treg。此外，我们将测试VEGF阻断是否会降低肿瘤中VLC和Treg的频率;通过抗DC 25抗体增强Treg耗竭疗法的功效;以及能够协调抗肿瘤免疫应答。

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.