Neuropilin-1 as mediator for Vascular Endothelial Growth Factor (VEGF)-dependent T cell migration

最近，我们已经确定了CD4+CD25+调节性T细胞（Treg）高度表达的Neuropilin-1 （Nrp-1）的作用，作为Treg肿瘤浸润的介质，以响应肿瘤源性血管内皮生长因子（VEGF）。与野生型（WT）小鼠相比，T细胞特异性消融Nrp-1表达的转基因小鼠表现出肿瘤生长和进展的极大降低。这种表型与抗肿瘤免疫反应的强烈增加和肿瘤组织中Foxp3+ Tregs数量的显著减少有关。此外，消融肿瘤产生的VEGF同样导致肿瘤内Foxp3+ Tregs数量减少，免疫反应增加，肿瘤生长受损。根据这些结果，我们得出结论，Nrp-1引导Tregs进入肿瘤组织，从而达到VEGF，因此代表了治疗癌症干预的一个有希望的目标。在目前的提案中，我们的目的是了解Nrp-1/ VEGF依赖的T细胞迁移是肿瘤特异性机制还是也参与特定自身免疫性疾病的其他炎症免疫反应。此外，我们的目标是剖析这一机制是否可以转化为T效应细胞，引导它们直接进入产生VEGF的肿瘤组织，从而提高抗肿瘤免疫反应。我们的初步数据表明，异位表达Nrp-1的T效应细胞有助于有效的抗肿瘤免疫应答，因为在转基因小鼠品系（CD4-Nrp-1）中，T细胞特异性过表达Nrp-1会损害肿瘤生长。为了详细研究这一点，更重要的是开发一种新的免疫治疗策略（引导T效应细胞进入肿瘤），我们的目标是在naïve CD4+和CD8+ T细胞以及体外分化的CD8+细胞毒性淋巴细胞（ctl）、CD4+ Th1细胞和CD4+ Th17细胞中过表达Nrp-1，并分析其对小鼠肿瘤生长的预防和治疗作用。在概念验证的基础上，我们希望在未来的项目中将我们的发现转化为人体系统，从而开发出一种新的免疫治疗方法（将T效应细胞引导到肿瘤组织中），以改善抗肿瘤免疫反应。

Most recently, we have identified the role of Neuropilin-1 (Nrp-1), that is highly expressed by CD4+CD25+ regulatory T cells (Tregs), as a mediator for Treg tumor infiltration in response to tumor-derived Vascular Endothelial Growth Factor (VEGF). Transgenic mice with T cell-specific ablation in Nrp-1 expression exhibit a tremendously reduced tumor growth and progression in contrast to wildtype (WT) mice. This phenotype is associated with a strong increase in the anti-tumor immune response and strikingly significant reduced numbers of Foxp3+ Tregs within the tumor tissue. In addition, ablation of tumor-produced VEGF likewise leads to decreased numbers of Foxp3+ Tregs within the tumor, an increased immune response and impaired tumor growth. From these results we conclude that Nrp-1 guides Tregs into the tumor tissue towards VEGF, and therefore represents a promising target for therapeutic interventions for the treatment of cancer. In the present proposal we aim to understand whether the Nrp-1/ VEGF dependent T cell migration is a tumor-specific mechanism or also involved in other inflammatory immune responses in particular autoimmune diseases. Moreover, we aim to dissect whether this mechanism can be translated to T effector cells for guiding them directly into VEGF producing tumor tissues to improve anti-tumor immune responses. Our preliminary data suggest that T effector cells that ectopically express Nrp-1 contribute to an effective anti-tumor immune response as T cell-specific over-expression of Nrp-1 in a transgenic mouse line (CD4-Nrp-1) impairs tumor growth. To study this in detail and more importantly to develop a new immunotherapeutic strategy (guiding T effector cells to tumors), we aim to over-express Nrp-1 in naïve CD4+ and CD8+ T cells as well as in in vitro differentiated CD8+ cytotoxic lymphocytes (CTLs), CD4+ Th1 cells and CD4+ Th17 cells and analyze their prophylactic and also therapeutic effect on tumor growth in mice. Upon proof of concept we would like to translate our findings to the human system in future projects and thereby develop a new immunotherapeutic approach (directing T effector cells into tumor tissues) for improving anti-tumor immune responses.