MiR-155介导的肿瘤相关巨噬细胞重极化在结直肠癌发生发展中的作用机制研究

Tumor-associated macrophages (TAMs) are critical regulators of the tumor microenvironment and directly affect multiple steps in tumor development, including colorectal carcinoma(CRC). TAMs lose the potent of killing pathogens and tumor cells, further more, they produce many kinds of cytokines to promote tumor growth and contribute to the immune evasion. MicroRNAs (miRNAs) are small noncoding RNAs post-transcripionally control gene expression in many pathogenic and physiological processes, including immune system. Our recent studies have employed a low-density miRNA microarray assay and found that, miR-155 was the most down-regulated miRNA when the M1 phenotype transform to TAM. Overexpression of miR-155 could reprogram anti-in?ammatory, pro-tumorial M2 TAMs to pro-in?ammatory, antitumor M1 macrophages, and reduce IL-6 expression in the TAM. In addition, several studies demonstrated that IL-6 play important role in CRC progression and are most secreted by macrophages. Hence, the objectives of this work are to investigate whether miR-155 could increase the IL-6 secretion in CRC associated macrophages,then influence the IL-6 pathway and regulate the development and progression of CRC. In this study we try to find the molecular machnism that how TAM influence CRC progression from tumor microenvironment point. All these could provide a novel therapeutic approach for CRC treatment.

肿瘤相关巨噬细胞（TAM）是浸润肿瘤组织的主要免疫细胞，结直肠癌（CRC）中也不例外；TAM通过分泌各类因子促进肿瘤发生发展；微小RNA（miRNA）通过转录后调控影响几乎所有生物过程，包括免疫系统。申请人前期研究发现，miR-155下调与具有抗肿瘤活性的巨噬细胞向TAM的转化密切相关；高表达miR-155能使TAM重新获得抗肿瘤能力，并显著减少TAM分泌IL-6；而IL-6与CRC的发病机制密切相关，IL-6可通过旁分泌或自分泌的方式促进肿瘤发生发展，且IL-6主要来源于巨噬细胞。本项目拟在此基础上深入研究miR-155能否通过调控TAM IL-6的分泌，进而调节CRC细胞中IL-6信号通路，影响CRC的发生发展。该研究从肿瘤微环境着手，不仅从miRNA层面阐明TAM影响CRC发生发展的新分子机理，也为CRC的治疗提供了新策略。

肿瘤细胞对化疗的反应不仅取决于基因组的突变，同时也受其所处的微环境的影响。在多种肿瘤中，巨噬细胞的浸润通常与不良预后相关，包括结直肠癌。在本研究中，我们揭示了结直肠癌中的巨噬细胞与病人的耐药和生存相关。功能实验证明与结直肠癌细胞共培养后的巨噬细胞能通过分泌白介素-6来增加结直肠癌细胞对化疗药物的抵抗（5-氟尿嘧啶和奥沙利铂），而加入白介素-6的中和抗体后，这种对化疗抵抗的诱导被抑制了。巨噬细胞分泌的白介素-6能激活结直肠癌细胞中的IL-6R/STAT3通路，并且抑制肿瘤抑制因子miR-204-5p的表达。功能回复实验证实miR-204-5p是巨噬细胞诱导结直肠癌化疗抵抗的效应分子。另外，我们发现miR-155-5p在肿瘤相关巨噬细胞中显著下降，并通过靶向C/EBP-β激活了白介素-6。在肿瘤相关巨噬细胞中重新过表达miR-155-5p能逆转巨噬细胞引起的结直肠癌化疗抵抗。总之，我们的结果提示巨噬细胞中miR-155-5p/C/EBP-β/IL-6信号的失调能通过调控结直肠癌细胞中IL-6R/STAT3/miR-204-5p通路来诱导化疗抵抗。我们的研究揭示了基于结直肠癌肿瘤微环境的一种免疫细胞和肿瘤细胞交流的新方式。