缺乏食管鳞状细胞癌（ESCC）免疫治疗的预测性生物标志物，免疫治疗抗药性仍然需要解决。长链非编码RNA（lncRNA）在ESCC免疫逃避和免疫治疗抗药性中的作用有待阐明。通过lncRNA测序和聚合酶链式反应法，鉴定了与肿瘤相关巨噬细胞上调的lncRNA以及在ESCC免疫治疗非反应者中高表达的外泌体lncRNA。利用CRISPR-Cas9技术探索了lncRNA的功能作用。进行了RNA pull-down、MS2标记的RNA亲和纯化（MS2-TRAP）和RNA结合蛋白免疫沉淀（RIP）实验，以鉴定lncRNA相关蛋白质和相关机制。在体内，建立了人源化PBMC（hu-PBMC）小鼠模型，评估特定lncRNA抑制剂的治疗反应及其与程序性细胞死亡蛋白1（PD-1）单克隆抗体（mAb）的联合治疗效果。采用单细胞测序、流式细胞术和多重荧光免疫组化等方法分析浸润肿瘤微环境的免疫细胞。我们发现了一个参与肿瘤免疫逃逸和免疫治疗抗药性的lncRNA。血浆外泌体中LINC02096（RIME）的高表达与PD-1 mAb治疗反应降低和预后差相关。从机制上讲，RIME结合混合血液系白血病蛋白-1（MLL1），预防ankyrin重复和SOCS盒含2（ASB2）介导的MLL1泛素化，提高MLL1的稳定性。RIME-MLL1增加了程序性死亡配体1（PD-L1）和吲哚胺2,3-双加氧酶1（IDO-1）启动子区域的H3K4me3水平，使肿瘤细胞中PD-L1/IDO-1的表达持续增加，抑制了CD8+T细胞的浸润和激活。huPBMC-NOG小鼠中的RIME降解显著抑制了肿瘤发展，并通过激活T细胞介导的抗肿瘤免疫，提高了PD-1 mAb治疗的有效性。本研究揭示了RIME-MLL1-H3K4me3轴在肿瘤免疫抑制中的关键作用。此外，RIME似乎是一种潜在的免疫治疗预后生物标志物，针对RIME的药物可能是克服免疫治疗抗药性并有益于ESCC患者的新治疗策略。 © 2023 The Authors. Clinical and Translational Medicine published by John Wiley & Sons Australia, Ltd on behalf of Shanghai Institute of Clinical Bioinformatics.

Predictive biomarkers for oesophageal squamous cell carcinoma (ESCC) immunotherapy are lacking, and immunotherapy resistance remains to be addressed. The role of long noncoding RNA (lncRNA) in ESCC immune escape and immunotherapy resistance remains to be elucidated.The tumour-associated macrophage-upregulated lncRNAs and the exosomal lncRNAs highly expressed in ESCC immunotherapy nonresponders were identified by lncRNA sequencing and polymerase chain reaction assays. CRISPR-Cas9 was used to explore the functional roles of the lncRNA. RNA pull-down, MS2-tagged RNA affinity purification (MS2-TRAP) and RNA-binding protein immunoprecipitation (RIP) were performed to identify lncRNA-associated proteins and related mechanisms. In vivo, the humanized PBMC (hu-PBMC) mouse model was established to assess the therapeutic responses of specific lncRNA inhibitors and their combination with programmed cell death protein 1 (PD-1) monoclonal antibody (mAb). Single-cell sequencing, flow cytometry, and multiplex fluorescent immunohistochemistry were used to analyze immune cells infiltrating the tumour microenvironment.We identified a lncRNA that is involved in tumour immune evasion and immunotherapy resistance. High LINC02096 (RIME) expression in plasma exosomes correlates with a reduced response to PD-1 mAb treatment and poor prognosis. Mechanistically, RIME binds to mixed lineage leukaemia protein-1 (MLL1) and prevents ankyrin repeat and SOCS box containing 2 (ASB2)-mediated MLL1 ubiquitination, improving the stability of MLL1. RIME-MLL1 increases H3K4me3 levels in the promoter regions of programmed death-ligand 1 (PD-L1) and indoleamine 2,3-dioxygenase 1 (IDO-1), constitutively increasing the expression of PD-L1/IDO-1 in tumour cells and inhibiting CD8+ T cells infiltration and activation. RIME depletion in huPBMC-NOG mice significantly represses tumour development and improves the effectiveness of PD-1 mAb treatment by activating T-cell-mediated antitumour immunity.This study reveals that the RIME-MLL1-H3K4me3 axis plays a critical role in tumour immunosuppression. Moreover, RIME appears to be a potential prognostic biomarker for immunotherapy and developing drugs that target RIME may be a new therapeutic strategy that overcomes immunotherapy resistance and benefits patients with ESCC.© 2023 The Authors. Clinical and Translational Medicine published by John Wiley & Sons Australia, Ltd on behalf of Shanghai Institute of Clinical Bioinformatics.