具核梭杆菌促进小鼠结肠肿瘤发生及其机制研究

Fusobacterium nucleatum Prompts Colonic Tumorigenesis in Mice and its Potential Mechanism

背景:越来越多的证据表明结直肠癌(CRC)与肠道菌群密切相关。近年研究显示具核梭杆菌在CRC发生中可能发挥重要作用,但具体作用机制尚不明确。目的:探讨具核梭杆菌与CRC发生的相关性及其可能作用机制。方法:选用野生型C57BL/6小鼠和肠道多发性腺瘤APC(Min/+)小鼠,分别予具核梭杆菌菌液灌胃、皮下注射致癌剂1,2-二甲基肼二盐酸盐(DMH)或两者联合等不同处理,观察结肠异常隐窝灶(ACF)(8周)或肿瘤(20周)生成情况。以Roche 454 GS FLX焦磷酸测序分析各组野生型C57BL/6小鼠肠道菌群结构,Bio-Plex ProTM技术检测肠黏膜免疫因子表达。结果:与无具核梭杆菌定植的DMH处理组野生型C57BL/6小鼠或APC(Min/+)小鼠相比,具核梭杆菌定植小鼠结肠内ACF或肿瘤数量显著增多(P<0.05)。具核梭杆菌定植小鼠肠道菌群结构改变明显,表现为蓝藻菌门含量减少,软皮菌门、疣微菌门含量增加(P均<0.05),肠黏膜肿瘤相关免疫因子IL-21、IL-22、IL-31、CD40L表达亦显著增高(P<0.05)。结论:具核梭杆菌在肠道定植可促进小鼠结肠肿瘤发生,其机制可能主要为引起肠道菌群失衡和调控肠黏膜肿瘤相关免疫因子表达。

Accumulating evidence links colorectal cancer （CRC） with the gut microbiota. Fusobacterium nucleatum （F. nucleatum） has been revealed to be involved in the development of CRC, however, the mechanism of F. nucleatum in mediating colorectal tumorigenesis is still poorly understood. Aims： To investigate the effect and potential mechanism of F. nucteatum on CRC. Methods ： Wild type C57BL/6 mice and APC （ Min/＋ ） mice characterized by multiple intestinal neoplasia were used in this animal study. After administered with F. nucleatum intragastrically and/or 1,2-dimethylhydrazine （DMH, a carcinogen） subcutaneously, the aberrant crypt foci （ACF） and colonic tumor were counted at 8th and 20th week, respectively. Structural alteration of intestinal microbiota and mucosal immune factors were detected in wild type C57BL/6 mice receiving different interventions by using Roche 454 GS FLX pyrosequencing and Bio- Plex ProTM cytokine assay, respectively. Results： In DMH-treated wild type C57BL/6 mice or APC （ Min/＋ ） mice, number of ACF and colonic tumor in those administered with F. nucleatum were significantly higher than those without （P 〈 O. 05 ）. F. nucleatum colonization significantly altered the lumen microbial structure, with decreased Cyanobacterium and increased Tenericutes and Verrucomicrobia （ P all 〈 0.05 ）. Furthermore, F. nucleatum up-regulated expressions of tumor-related immune factors in colonic mucosa, such as IL-21, IL-22, IL-31 and CIMOL （P 〈 0.05）. Conclusions： F. nucleatum colonization in intestine may prompt colonic tumorigenesis in mice via inducing intestinal dysbiosis and modulating tumor-related immune factors expression.