MIMP调控miR-21-Ras/MAPK通路抑制具核梭杆菌致肠上皮细胞癌变的机制研究

Recent studies have identified overrepresentation of Fusobacterium nucleatum in colorectal cancer tissues, but it is not yet clear whether this is pathogenic or an epiphenomenon.In our previous study, we have showed the key molecular mechanisms of prevention and treatment of intestinal inflammation and tumorigenesis through p38 MAPK signaling pathway using L.Plantarum Micro Integral Membrane Protein (MIMP).In addition, We have screened colorectal cancer(CRC) and matched normal tissue specimens using 16S rRNA sequencing and found marked over-representation of Fusobacterium nucleatum(Fn) sequences in tumors relative to control specimens. Moreover,we have verified that the overexpression of miR-21 in patients with ulcerative colitis impairs intestinal epithelial barrier function through targeting RhoB and miR-21 is involved in the regulation of colitis- associated colon cancer .Both of MIMP and miR-21 are involved in the Ras/MAPK sinaling pathway.On the basis of the preliminary results, we are seeking the clinical applications about Fn in CRC. We try to clarify the protective biological characteristics of the MIMP in the Fusobacterium nucleatum induced carcinogenesis via targeting mannose receptor and downregulating miR-21-Ras/MAPK signaling pathway through in vitro and in vivo experiments.Meanwhile, we are trying to explore the pathogenic role of Fn in patients with inflammatory bowel disease and CRC and AOM/DSS treated IL-10 knock-out or miR-21 knock-out mice model.The study may provide potential clinical applications in CRC prevention and therapy.

利用前期研究发现具核梭杆菌（Fn）在大肠癌(CRC)患者肠道粘膜、粪便中丰度显著增高及miR-21在炎症介导肿瘤机制中起关键作用的基础上，进一步明确Fn丰度在CRC不同病理阶段的临界阈值与规律性变化；利用基因沉默技术构建CRC细胞（miR-21敲除）和动物模型（miR-21敲除或IL-10敲除联合诱癌剂DSS/AOM）并进行体内外Fn干预实验，验证Fn丰度增高究竟是CRC的致病因素还是伴发现象，并阐明Fn致肠上皮细胞癌变的分子机制；分析前期研究发现的乳酸菌微小膜蛋白（MIMP）对感染Fn的CRC细胞和动物模型的保护作用，希望通过阐明MIMP与Fn竞争结肠上皮细胞甘露糖受体，抑制Fn对结肠上皮细胞的黏附，从而阻断miR-21-Ras/MAPK通路，发挥抗癌作用的分子机制，为将来利用Fn判断CRC发病风险和研发抗菌药物MIMP防治CRC提供理论基础。

大肠癌（colorectal cancer, CRC）是人类常见的恶性肿瘤之一，肠道微生物和CRC关联的发现推动了微生物致癌机制的研究，但机制尚不明确。为此，项目组开展以下一系列研究工作： 1. 基于前期发现大肠癌特征性致病菌-具核梭杆菌（fusobacterium nucleatum, Fn），开展针对Fn促癌分子机理的研究：首先临床样本验证发现Fn丰度与CRC患者的miR-21表达、T分期、淋巴浸润及Ki-67指数相关，预后分析提示Fn 高表达的患者总体生存期（Overall survival，OS）显著降低，当联合Fn和miR-21对患者生存期进行分析，发现Fn高丰度且miR-21高表达的患者其OS显著降低。在III/IV期CRC患者中，Fn为患者独立不良预后因素且与术后化疗效果显著相关。体内体外实验证明Fn通过经典TLR-4/MyD88/NF-κB通路影响miR-21表达，最终促进肠癌细胞的增殖和转移。2.自主研发微生态制剂MIMP并构建DSS诱导肠炎小鼠模型，发现其具有保护肠屏障、改善菌群紊乱及抑制炎症反应的作用。综上，这些研究结果进一步揭示肠道菌群在CRC发生发展中的关键作用，为通过微生态干预防治CRC提供重要理论基础。