我校西南医院梁后杰教授和余松涛教授团队在《Signal Transduction and Targeted Therapy》发表研究成果——癌细胞来源乳酸激活巨
发布人:zhangyilin 发布时间:10/10/2020 9:27:00 AM  浏览次数:327次
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癌细胞来源乳酸激活巨噬细胞Ap-2α/Sirpα信号介导结肠癌免疫逃逸的机制研究

 

王筱姣、罗茜、陈川、梁后杰、余松涛

 

结肠癌是严重危害人类健康的重大疾病。由结肠癌导致的死亡率以高达9.2%比例在所有肿瘤中位列第二。结肠癌的恶性进展,是其死亡的主要原因,而癌细胞逃避了免疫监视,是癌细胞恶性进展的重要机制,因此探索结肠癌免疫逃逸的机制具有重要意义。肿瘤微环境的免疫状态是影响肿瘤进展的重要因素,近年来越来越多的研究关注结肠癌免疫微环境,并逐步将抑制免疫逃逸作为治疗手段。其中基于T细胞相关免疫治疗已在肿瘤治疗中崭露头角。而巨噬细胞作为天然免疫的第一线,在肿瘤及其治疗中的作用尚不清楚。

 

巨噬细胞表面受体直接影响其免疫吞噬功能。在骨髓中,巨噬细胞通过表达抑制受体蛋白Sirpα,结合其他细胞上“don’t eat me”信号分子CD47,抑制其免疫吞噬功能。而在肿瘤相关巨噬细胞(TAMs)中Sirpα的表达及作用机制尚不清楚。本研究在基于MC-38的异种移植模型中发现Sirpα在结肠癌的TAMs中表达并显著促进结肠癌进展。机制研究揭示,结肠癌细胞能分泌乳酸介导转录因子Ap-2a进入细胞核。染色质免疫沉淀(CHIP)试验证实入核后Ap-2α结合于Elk-1启动子的-1396 / -1391保守序列(GCCTGC)并启动其转录。而ELK-1可结合Sirpα启动子区域(CTTCCTACA (located at −229/−221) and CTTCCTCTC (located at −190/−182)),促进 TAMs 中 Sirpα的表达进而介导巨噬细胞与肿瘤间“don't eat me”信号的激活,促使肿瘤细胞逃避了巨噬细胞的吞噬。进一步特异性敲除巨噬细胞中的Ap-2a可显著增强TAM吞噬活性并抑制结肠癌进展。而当ELK-1高表达时上述效应则消失,并以Sirpα依赖的方式逆转TAMs的吞噬活性及结肠癌进展。同样,在肿瘤患者标本中ELK-1与Sirpα表达呈正相关,两者高表达预示了不良预后。并且利用流式细胞仪分析证实TAMS中Sirpα的蛋白水平随着肿瘤的进展而动态增加。

 

本研究结果揭示了结肠癌来源的乳酸诱导肿瘤微环境中肿瘤相关巨噬细胞的转录因子Ap-2α的核转位,Ap-2α入核后通过与Elk-1--Sirpα启动子区域结合而增强其转录表达,Sirpα与肿瘤细胞表面CD47结合后打开了巨噬细胞吞噬肿瘤的抑制性开关,从而促进肿瘤逃避TAMs吞噬的天然免疫监视的分子机制。本研究揭示了结肠癌免疫逃逸新机制,并为巨噬细胞性免疫治疗提供潜在靶点。

 

该研究成果于2020年04月发表于《Signal Transduction and Targeted Therapy》(IF=13.493)。陆军军医大学第一附属医院肿瘤科余松涛和梁后杰教授为该文共同通讯作者,王筱姣、罗茜和陈川为该文共同第一作者。该研究得到国家重点研发项目和国家自然科学基金等研究项目的资助。

 

附:英文摘要

The Ap-2α/Elk-1 axis regulates Sirpα-dependent tumor phagocytosis by tumor-associated macrophages in colorectal cancer

Xiaojiao Wang1, Xi Luo1, Chuan Chen2, Ye Tang3, Lian Li1, Banghui Mo1, Houjie Liang1 and Songtao Yu1

affiliations

1. Department of Oncology, Southwest Hospital, Army Medical University, 30 Gaotanyan Street, Chongqing 400038, People’s Republic of China;

2. Cancer Center, Daping Hospital and Research Institute of Surgery, Army Medical University, Chongqing 402560, People’s Republic of China and

3. Department of Oncology, Tong Liang District Hospital, Chongqing 402560, People’s Republic of China.

Correspondence: Houjie Liang (lianghoujie@sina.com) or Songtao Yu (songtaoyu@yahoo.com)

These authors contributed equally: Xiaojiao Wang, Xi Luo, Chuan Chen

PMID: 32296015

PMCID:PMC7156469

DOI: 10.1038/s41392-020-0124-z

 

Background: The inhibitory receptor signal regulatory protein-α (Sirpα) is a myeloid-specific immune checkpoint that engages the “don’t eat me” signal CD47, which is expressed on tumor and normal tissue cells. However, the profile and regulatory mechanism of Sirpα expression in tumor-associated macrophages (TAMs) are still not clear.

 

Methods:  Fluorescence-activated cell sorting (FACS) were performed to isolate cell,Immunofluorescence  staining verified the specificity of the primary antibody.Western blotting assays detected protein.ChIP assays were performed to study the interaction between the Elk-1 protein and Sirpα promoter DNA as well as between the AP-2α protein and Elk-1 promoter DNA in primary macrophages ( from mice or patients).

 

Results: The surface receptors of macrophages directly affect their immune phagocytic function.we showed that the nuclear translocation of Ap-2α in TAMs increased with tumor progression in MC-38 cell-based xenograft models,CRC cell-derived lactate induced the nuclear translocation of the transcription factor Ap-2α from the cytoplasm in TAMs. Ap-2α functioned as a transcription factor for Elk-1 by binding to the conserved element GCCTGC located at −1396/−1391 in the mouse Elk-1 promoter. Subsequently, the Elk-1 protein bound to two conserved sites, CTTCCTACA (located at −229/−221) and CTTCCTCTC (located at −190/−182), in the mouse Sirpα promoter and promoted Sirpα expression in TAMs. Functionally, the macrophage-specific knockout of Ap-2α notably promoted the phagocytic activity of TAMs and suppressed CRC progression, whereas these effects were prevented by the transgenic macrophage-specific expression of Elk-1, which regulated TAM phagocytosis and CRC development in a Sirpα-dependent manner.Furthermore, we showed that Elk-1 expression was positively correlated with Sirpα expression in TAMs and was associated with poor survival in CRC patients.

 

Conclusions: our findings revealed a novel mechanism through which CRC evades innate immune surveillance and provided potential targets for macrophage-based immunotherapy for CRC patients.

 

Keywords:Cancer microenvirment;Tumour immunology;Gastrointestinal cancer.

 

全文链接:https://doi.org/10.1038/s41392-020-0124-z

 


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