结直肠癌通过外泌体miRNA调控微环境中巨噬细胞的机制研究

Cancer progression is closely associated with tumor microenvironment, and macrophage is a major kind of immune cell in the colorectal cancer (CRC) microenvironment. CRC cells could induce the M2 polarization of macrophage in their microenvironment and prompt tumor metastasis, but the detailed mechanisms remain unclear. MicroRNA (miRNA) is a universal mechanism of gene regulation; our and other studies revealed that tumor cells could regulate the functions of other cells by exsome-delivery miRNAs. Our recent data showed that some miRNAs were selectively packaged into the exosome of CRC cells and actively secreted into macrophage to induce M2 polarization. According to these data, we propose a hypothesis that CRC cells could regulate the anti-tumor effects of macrophage in the tumor microenvironment by exsome-delivery specific miRNAs, and finally promote tumor metastasis. Based on these new data, the present study will try to identify key miRNAs enriched in the CRC exosome, and the in vitro and in vivo assays as well as clinical samples analysis will be performed to study the regulation functions and pathways of exosome-delivery miRNAs secreted by CRC cells in macrophage. This study will reveal a new mechanism of immune escape that CRC cells regulate macrophage at the tumor microenvironment level, and provide theoretical data for the development and progression of CRC as well as new guidance and strategy for the therapy of CRC.

肿瘤进展与其所处特殊微环境密切相关；巨噬细胞是结直肠癌（CRC）微环境中的主要免疫细胞。CRC细胞可通过诱导微环境中巨噬细胞向M2型巨噬细胞极化，促进肿瘤转移，但具体机理不清。微小RNA(miRNA)是一种普遍的基因调控机制，本课题组及他人研究均揭示肿瘤细胞能通过外泌体miRNA调控其他细胞；我们进一步研究发现CRC外泌体富集某些miRNAs并可进入巨噬细胞，诱导其向M2极化。据此我们提出假说：CRC细胞能以外泌体为载体，分泌特定miRNAs调控微环境中巨噬细胞的活性，促进肿瘤转移。本项目拟在进一步鉴定CRC外泌体中富集的关键miRNAs的基础上，运用体、内外实验手段结合临床标本分析，研究这些外泌体miRNAs在巨噬细胞中的功能和调控的信号通路，从微环境角度揭示CRC通过调控巨噬细胞实现免疫逃逸的新机制，为CRC发生发展机制提供新的理论依据，并为CRC的治疗提供新的思路和策略。

肿瘤发生发展与其所处特殊微环境密切相关；巨噬细胞是结直肠癌（colorectal cancer, CRC）微环境中的主要免疫细胞。CRC细胞可通过诱导微环境中巨噬细胞向M2型巨噬细胞极化，促进肿瘤进展，但具体机理不清。本课题组前期研究及他人研究均揭示肿瘤细胞能通过外泌体微小RNA(microRNA,miRNA)调控其他细胞。在本项目的资助下，我们进一步研究发现CRC细胞可以分泌外泌体进入巨噬细胞，诱导其发生M2极化及表达更多PD-L1蛋白，进而抑制T细胞活性。通过高通量测序对CRC细胞及正常肠上皮细胞来源外泌体进行了miRNA表达谱分析，结合临床标本和体外细胞水平功能表型验证，发现外泌体miRNA-21-5p和miR-200a是CRC调控巨噬细胞功能的关键信号分子。进一步机制研究揭示了CRC外泌体miRNA-21-5p和miR-200a通过调控PTEN/AKT和SCOC1/STAT1通路，促进巨噬细胞M2极化和PD-L1的表达，从而抑制T细胞免疫，促进肿瘤生长。本课题创新性地从外泌体角度阐明CRC细胞通过miRNA这一关键表观遗传学信号分子实现对巨噬细胞的“驯化”，进而诱导产生免疫抑制性肿瘤微环境，促进肿瘤发生发展。研究结果有助于从肿瘤免疫微环境角度深入阐明CRC细胞诱导免疫逃逸的新机制，为CRC的发生发展机制提供新的理论依据，并为肿瘤的治疗提供新的思路和策略。