小鼠中microRNA-148a缺失改变肠道菌群平衡和加剧结直肠癌变的分子机制研究

Colorectal cancer seriously does harm to people's lives and health. Previously we have found that: miR-148a was identified to significantly inhibit colorectal cancer growth using high-content functional miRNA library screening; miR-148a downregulation correlated with human colorectal cancer patient clinical stages and survival; miR-148a promoter was highly methylated by a complex comprised of P65 and DNA methyltransferase 3 alpha (DNMT3A) in human colorectal cancer; miR-148a is widely expressed in the digestive tract epithelium and immune tissues; the miR-148a knockout mice were successfully constructed by homologous recombination; miR-148a-deficient mice were more susceptible to colitis and colitis-associated tumorigenesis; Cohousing experiments revealed that miR-148a deficiency altered gut microbiota balance. This project continues to further study whether miR-148a deficiency promotes the development of spontaneous colorectal and small intestine cancer and the targets and signal pathways regulated by miR-148a; to further study miR-148a deficiency altering gut microbiota balance and exacerbating colitis-associated tumorigenesis using series of modern experimental technology. It will clarify its roles in the prevention and treatment colorectal cancer through targeted intervention. This will reveal the molecular mechanism of miR-148a deficiency altering gut microbiota balance and exacerbating colorectal tumorigenesis, which will provide theoretical basis and new strategies for the prevention and treatment of these diseases.

结直肠癌严重危害人民生命健康。我们前期发现：功能微小RNA文库筛选到miR-148a抑制结直肠癌生长；miR-148a在结直肠癌表达下调与病人临床预后相关；P65招募DNMT3A升高miR-148a启动子甲基化而抑制其表达；miR-148a在肠上皮和免疫组织广泛表达；利用同源重组技术构建了miR-148a敲除小鼠，它的缺失增加DSS诱发结肠炎严重性和加剧AOM/DSS诱导结直肠癌变，并改变肠道菌群平衡。本项目应用现代实验技术进一步研究miR-148a缺失是否促进自发性结直肠和小肠肿瘤的形成及在结直肠癌变中它调控的靶基因及信号通路，它的缺失怎样改变肠道菌群平衡而调节结直肠癌变，并行防治研究。这将揭示miR-148a在调控肠道菌群平衡和结直肠癌变中的作用分子机理，为防治这类疾病提供坚实的理论基础和新策略。

结直肠癌严重威胁人类健康，其发病机制不清晰，一直无有效的治疗方案。1）我们发现miR-148a缺失激活NF-κB和STAT3促进肿瘤生长的相关信号通路而使小鼠更易患肠炎和肠癌变。miR-148a缺失促进ApcMin/+小鼠的肠细胞癌变。恢复miR-148a表达抑制自发性和化学物质诱导的肠细胞癌变。miR-148a在肠炎和结直肠癌病人中低表达，并与病人临床分期和生存相关。miR-148a抑制GP130、IL1R1 和 TNFR2等NF-κB和STAT3上游调控因子而阻断NF-κB和STAT3活化。P65和DNMT3A组成复合体介导miR-148a启动子高度甲基化而抑制它的转录。这有助于阐明肠炎和其相关肿瘤的发病机理，为防治这类疾病提供理论基础，结果发表在Cell Death & Differentiation上。 2）发现miR-148a缺失上调Cers5表达，进而促进神经酰胺合成。新合成的神经酰胺促进肠道菌群失调而促进AOM/DSS诱导性和ApcMin/+自发性肠癌的发生。机制上神经酰胺水平的增加与β-catenin活性和TLR4依赖性结直肠癌发生显著相关。进一步发现β-catenin直接结合SOAT1启动子而激活后者转录表达，进而诱导胆固醇酯化和肠癌发生。结直肠癌病人CERS5-TLR4-β-catenin-SOAT1信号轴表达异常。SOAT1抑制剂 (Avasimibe) 显著抑制AOM/DSS诱导和ApcMin/+自发性肠癌。这阐明了神经酰胺增加肠道菌群失调而依赖SOAT1胆固醇酯化来促进结直肠癌发生。未来用Avasimibe降低胆固醇酯化的治疗可能是肠癌有效的临床治疗策略，结果发表在JCI Insight上。在本项目资助下，共发表标注本基金的SCI论文11篇。总体而言，完成了各项预定的目标。