头颈鳞癌CD24诱导新型CTLA-4+ ILC3亚群促进免疫逃逸的分子机制研究

The tumor microenvironment (TME) has a profound influence on the development of head and neck squamous cell carcinoma (HNSCC). A large number of immune cells present in TME and their signaling networks can regulate tumor immune escape. ILC3s are a novel identified group of innate lymphoid cells with acquired immune function, but its mechanisms in tumor are uncertain. Recently, with single-cell RNA sequencing of immune cells, we have discovered a new subgroup of ILC3s with high expression of CTLA-4 within HNSCC, which is positively correlated with CD24 expression and tumor malignancy. CD24-highly-expressed HNSCC induced by hypoxia can stimulate the expression of immune checkpoint molecule, CTLA-4, in ILC3s by CSF-1 secretion, thus resulting in tumor immune escape. The project aims to elucidate the immune characteristics, signal networks and immune escape promoting roles of CTLA-4+ ILC3s in the TME of HNSCC. Clinical specimens are also used to analyze expression of CTLA-4+ ILC3s and its correlation to the tumor microenvironment and cancer progression. This project will help to reveal new immune escape mechanisms of HNSCC and provide a new therapeutic target and strategies for HNSCC immunotherapy.

头颈鳞癌发生发展与肿瘤微环境密切相关，肿瘤内大量免疫细胞及其信号网络可以调控免疫逃逸。ILC3s是一群新近发现的具有获得性免疫功能的固有淋巴细胞，但其在肿瘤中的作用机制未明。我们通过免疫细胞单细胞测序发现，头颈鳞癌肿瘤组织存在一组高表达CTLA-4的ILC3s新亚群，与肿瘤组织中CD24表达及恶性程度呈正相关。低氧诱导肿瘤高表达CD24，继而分泌的CSF-1能促进ILC3s免疫检查点分子CTLA-4的表达增加并发挥肿瘤免疫抑制效应。本项目拟阐明头颈鳞癌肿瘤微环境中CTLA-4+ ILC3s产生及其免疫特征、信号网络组成及启动免疫逃逸的效应功能；进一步利用临床组织样本分析和验证CTLA-4+ ILC3s与抑制性免疫微环境及肿瘤临床特征的关系。本项目的实施将有助于揭示头颈鳞癌免疫逃逸的新机制，为寻找有效的临床靶标及免疫治疗策略提供新思路。

微环境与头颈鳞癌发生发展的关系尚不清。肿瘤内大量免疫细胞及其信号网络可以调控免疫逃逸。ILC3s是一群新近发现的具有获得性免疫功能的固有淋巴细胞，但其在肿瘤中的作用机制未明。本研究通过免疫细胞单细胞测序及临床样本验证显示头颈鳞癌中的CTLA-4+ ILC3s数量比癌旁正常组织明显增多，更倾向于出现淋巴结转移、远处转移、大的肿瘤直径和差的病理分级；体外共培养发现CTLA-4可促进头颈鳞癌细胞增殖、侵袭、转移；RNA-seq及KEGG PATHWAY分析结果显示CTLA-4+ ILC3s功能基因主要涉及PI3K-Akt信号通路；体外共培养实验及外泌体RNA-seq结果显示肿瘤来源外泌体（TDE）中circ_0041798可上调ILC3的CTLA-4表达。机制研究显示头颈鳞癌细胞通过释放外泌体circ_0041798吸附miR-195-5p，进而激活CTLA-4+ ILC3s的形成。头颈鳞癌细胞通过释放外泌体circ_0041798吸附miR-195-5p诱导微环境CTLA-4+ ILC3s亚群形成、激活PI3K-Akt信号通路促进头颈鳞癌的发生发展，本研究可为头颈鳞癌防治提供新思路。