肠道Weissella属细菌通过调控肠道微生物-胆汁酸-法尼酯X受体轴抑制肝细胞癌的机制研究

Targeting gut microbiota (GM) with probiotics is a hot research topic in the treatment of Hepatocellular carcinoma (HCC). The probiotics used for inhibiting HCC are less reported, and the mechanisms that probiotics modulate HCC are less studied as well. Our results showed that genus weissella in the gut of HCC patients had lower abundance than that of liver cirrhosis (LC) patients and was negatively correlated with tumor size. These indicates bacteria of genus weissella might be involved in regulating HCC progression. The lithocholic acid (LCA) and taurolithocholic acid (TLCA) in feces of HCC patients turned decreased and the later bile acid (BA) was positively with genus weissella. LCA and TLCA were positively related with expression of liver FGFR4 which could indicate the activity of intestinal farnesoid X receptor (FXR). Besides, the blood plasma inflammatory cytokines and pro-proliferation moleculars in liver tissue of HCC patients were increased. We speculates that the bacteria of genus weissella could modulate gut microbiota to change metabolism of bile acids (BAs), which activates the intestinal FXR to further block HCC progression. To test our speculation, we’ll establish orthopotic HCC models in intestinal Fxr-deficient mice and normal mice fed with the bacteria of genus weissella to characterize GM and BAs, and the role of FXR. The changed BA would be administered to the above HCC models to test which BAs rely on intestinal FXR to control HCC progression. Our results are expected to establish a causative mechanism axis between specific gut bacteria and HCC and to screen a probiotics for inhibiting HCC progression, which provides a “green” strategy for HCC treatment and has major medical, societal and economic impact.

益生菌靶向调控肠道微生物（GM）治疗肝细胞癌（HCC）是当前研究热点。能抑制HCC进展的益生菌报道很少，实验理论依据不足，限制了其应用。我们研究发现：HCC患者肠道Weissella属细菌(gW)丰度低于肝硬化患者，与瘤体负荷呈负相关；粪便中石胆酸（LCA）和甘氨石胆酸（TLCA）含量降低，与gW丰度呈正相关；LCA、TLCA与HCC肿瘤组织中肠法尼酯X受体（FXR）活性标志分子FGFR4表达呈正相关；伴随血浆促炎因子和肝脏促肿瘤分子表达增多。我们推测：gW通过调控GM-胆汁酸（BA）-肠FXR轴抑制HCC进展。接下来，拟用肠特异性敲除Fxr和正常小鼠构建肝原位HCC模型并灌喂gW，探究GM、BA变化规律及肠FXR的作用；筛选出的差异BA灌喂上述HCC小鼠，明确具体BA影响HCC进展对肠FXR的依赖情况。以期阐明特定肠道细菌与HCC因果关系机制轴，筛选出可用于HCC防治的益生菌。

肝细胞癌在我国发生率和死亡率高，更深层次的研究有助于推动肝细胞癌防治方面的发展。肠道微生物研究火热，明确与肝癌等肿瘤发展密切相关，但是研究依然不足。本项目我们从肠道细菌Weissella属和真菌两个层面探究肠道微生物对肝细胞癌的影响。首先，在细菌层面，基于临床样本16S rDNA测序数据显示了Weissella属菌在肝细胞癌患者的肠道丰度减少；而我们利用Weissella属代表菌株Weissella cibaria和肝细胞癌小鼠模型进行多次实验，结果显示W. cibaria不能抑制肿瘤进展，亦不能促进PD-1抗肿瘤效果。在真菌层面，基于临床样本ITS测序数据显示，与肝硬化患者比较，肝细胞癌患者肠道真菌多样性下降，且Candida albicans丰度显著增多；进一步的动物实验显示C. albicans异常定植能够促进肝细胞癌的进展且依赖肠炎症小体6，并改变了血浆代谢组。本项目的完成一定程度上为肝细胞癌的治疗提供了新的靶点和思路，丰富了肠道微生物与肿瘤关系研究领域内容，另一方面也提醒了临床和研究人员需要关注和思考临床现象与因果关系之间的差别。