In the effort of developing new immunotherapies, the sentinel node (SN) has proven a promising source from which to harness an effective antitumour T cell response. However, tumour immune escape, a process in which regulatory T cells (Tregs) play a central role, remains a major limiting factor. Therefore, there is a clear need to increase the knowledge of Treg function and signalling in sentinel nodes. Here, we set out to explore whether the proteome in SN‐resident T cells is altered by the tumour and to identify key proteins in SN T cell signalling, focusing on Tregs. Five patients with muscle‐invasive urothelial bladder cancer were prospectively included. Mass spectrometry was performed on two patients, with validation and functional studies being performed on three additional patients and four healthy donors. At cystectomy, SN, non‐SN lymph nodes and peripheral blood samples were collected from the patients and T cell subsets isolated through flow cytometry before downstream experiments. Proteomic analysis indicated that growth and immune signalling pathways are upregulated in SN‐resident Tregs. Furthermore, centrality analysis identified the cytokine IL‐16 to be central in the SN‐Treg signalling network. We show that tumour‐released factors, through activating caspase‐3, increase Treg IL‐16 processing into bioactive forms, reinforcing Treg suppressive capacity. In conclusion, we provide evidence that Tregs exposed to secreted factors from bladder tumours show increased immune and growth signalling and altered IL‐16 processing which translates to enhanced Treg suppressive function, indicating altered IL‐16 signalling as a novel tumour immune escape mechanism.

中文翻译：

---

前哨淋巴结调节性T细胞中的IL-16加工是膀胱癌免疫力的一个因素。

在开发新的免疫疗法的努力中，前哨淋巴结（SN）已被证明是一种有希望的来源，可从中利用有效的抗肿瘤T细胞反应。但是，肿瘤免疫逃逸仍然是主要的限制因素，而调节性T细胞（Tregs）发挥着重要作用。因此，显然需要增加前哨节点中Treg功能和信令的知识。在这里，我们着手探讨SN驻留T细胞中的蛋白质组是否被肿瘤改变，并着重于Tregs来确定SN T细胞信号传导中的关键蛋白。前瞻性纳入了5例肌肉浸润性膀胱尿路上皮癌患者。对两名患者进行了质谱分析，并对另外三名患者和四名健康供体进行了验证和功能研究。在膀胱切除术中，SN 从患者中收集非SN淋巴结和外周血样品，并在下游实验前通过流式细胞仪分离T细胞亚群。蛋白质组学分析表明，SN受体Tregs中的生长和免疫信号通路被上调。此外，集中性分析确定了细胞因子IL-16在SN-Treg信号网络中处于中心地位。我们表明，通过激活caspase-3释放的肿瘤因子会增加Treg IL-16加工成生物活性形式，从而增强Treg抑制能力。总之，我们提供的证据表明，暴露于膀胱肿瘤分泌因子的Tregs显示出增加的免疫和生长信号以及改变的IL-16加工过程，从而转化为增强的Treg抑制功能，这表明IL-16信号转导是一种新型的肿瘤免疫逃逸机制。