具核梭杆菌感染激活IL-6/STAT3通路调控结直肠癌EMT及肿瘤干细胞形成

It has been suggested that bacterial dysbioses have been linked to colorectal cancer (CRC) and Fusobacterium nucleatum (Fn) is more abundant in CRC cases than controls. We also found that compared to normal mucosal biopsies, shifts in microbial composition were detected in tumer mucosal biopsies. A higher presence of Fn and a link between the abundance of Fn and disease progression step and tumor severity were found.Therefore, Fn played an important role in tumor initiation and progression,especially in tumor invasion and metastasis which were associateed with epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC). We found increases in EMT markers and CD44 when SW480 cells were co-cultured with Fn. Moreover, EMT-like cells showed a clearly higher expression of CD44. Therefore, it is possible that Fn generates cells with CSC via EMT-like changes. Genes downstream of interleukin-6/signal transducer and activator of transcription 3 (IL-6/STAT3) showed a clearly higher expression. It suggested IL-6/STAT3 played an important role in this progress. Hence, Fn stains which were isolated from human mucosal were cultivated and utilized. Markers of EMT, CSC and IL-6/STAT3 signaling pathway will be tested. We want to identify:1) Fn generates cells with CSC via EMT-like changes; 2) Fn regulates EMT-like changes and the formation of cancer stem cells through a novel IL6/Stat3 signaling pathway.This project will contribute to the etiology, diagnosis, treatment, and prevention of CRC.

具核梭杆菌(Fn)在结直肠癌(CRC)患者粘膜中大量增加已在多份研究中得到确认。本项目前期发现：Fn的增加与浸润深度及淋巴结转移正相关，提示Fn可能参与了CRC转移过程；将Fn与大肠癌细胞共培养后上皮间质化（EMT）相关蛋白及结肠癌干细胞（CSC）标志物CD44水平升高，且CD44升高主要发生在EMT细胞中，表明Fn感染可能通过EMT样作用产生CSC；基因芯片分析显示IL-6/STAT3通路相关靶基因表达水平升高，说明IL-6/STAT3通路可能在此过程中扮演重要角色。因此，本研究利用前期已从CRC组织中分离培养出的Fn菌株与肠癌细胞共培养，检测EMT、CSC及IL-6/STAT3通路标记物水平变化，旨在阐明: ①CRC时具核梭杆菌可通过EMT样作用产生CSC；②Fn感染可激活IL-6/STAT3信号通路调控EMT及CSC的产生。本项目研究将为结直肠癌的诊断、预防和治疗提供新思路.

结直肠癌（CRC）已成为一个严重危害人类健康的疾病，对其发生、发展以及治疗等的研究对改善民生具有重要战略意义。具核梭杆菌(Fn)是一种革兰阴性无芽孢专性厌氧菌，是广泛存在于人及多种动物消化道粘膜处的条件致病菌，其在CRC发生发展中的作用日益受到重视，我们前期研究已证实Fn的增加与浸润深度及淋巴结转移正相关。细胞间充质化（EMT）及肿瘤干细胞（CSC）与肿瘤转移的关系密切，前期结果表明Fn感染可导致细胞间充质化（EMT）发生，并引起肿瘤干细胞（CSC）标记物CD44升高。因此，本研究将Fn菌株与肠癌细胞共培养，通过检测细胞EMT、CSC及IL-6/STAT3通路标记物水平变化，探讨具核梭杆菌感染对结直肠癌EMT及CSC形成的调控，以及IL-6/STAT3通路在其中的作用，结果表明①CRC时具核梭杆菌感染可导致细胞出现EMT变化，EMT标记物Snail1、Vimentin、ZEB1水平升高，CSC标记物SOX2、OCT4 、c-MYC、ABCG2水平亦升高；②共培养后流式分选CD44 +细胞，其细胞干性标志：细胞增殖能力、体外分化能力、侵袭能力、形成克隆能力、体内致瘤能力都增强，且分选后细胞EMT标记物Snail1、Vimentin、ZEB1水平及CSC标记物SOX2、OCT4 、c-MYC、ABCG2水平升高；③Fn感染可导致IL-6/STAT3信号通路下游靶基因VEGF、Survivin、Bcl-2水平升高，抑制IL-6/STAT3通路后EMT标记物（Snail1、Vimentin、ZEB1）及CSC标记物（SOX2、OCT4 、c-MYC、ABCG2）水平下降。本项目证实了CRC时Fn感染可通过EMT样作用产生CSC，且IL-6/STAT3信号通路发挥调控作用，研究结果可为CRC的治疗提供新思路。