Society: AGA

In this session, you will learn about the advances in microbial biotransformation of drugs and this can impact clinical outcomes and adverse events.

Background: We identified that Catenibacterium is enriched in feces and liver tissues of hepatocellular carcinoma (HCC). We aimed to examine the role and mechanism of Catenibacterium mitsuokai (the only known species in genus Catenibacterium) in hepato-carcinogenesis.
Methods: The role of C. mitsuokai in HCC formation was evaluated in mice with orthotopic injection of mouse HCC cell lines (Hepa 1-6 and RIL175). The attachment ability of C. mitsuokai on tumor cells was evaluated by cell attachment assay and transmission electron microscopy (TEM). The functional bacteria surface protein and the hepatocyte receptor were identified by biotinylation-based far-western assay. The metabolites produced by C. mitsuokai in feces, portal vein serum and liver tumor tissue samples were identified by liquid chromatography-mass spectrometry. C. mitsuokai, its conditional medium, or candidate metabolites were co-cultured with human HCC cell lines (Hep3B, Huh7, PLC5) and normal hepatocyte cell line MIHA. C. mitsuokai associated the host gene expression was identified by PCR array.
Results: Oral gavage of C. mitsuokai significantly promoted HCC formation with increased tumor volume (P<0.05) and tumor weight (P<0.05) in two orthotopic mouse models. The gut barrier was also impaired by C. mitsuokai as indicated by increased intestinal permeability and down-regulated tight junction proteins Occludin and Claudin-3 and adherent protein E-cadherin. We confirmed that C. mitsuokai could colonize in mouse colon and liver tumors by fluorescence in situ hybridization (FISH). Mechanistically, C. mitsuokai had greater favorite to adhere to HCC cells compared to normal hepatocytes, of which, C. mitsuokai through its surface protein Gtrl1/RagA attached to the receptor of HCC cells. Moreover, both C. mitsuokai and its conditional medium significantly promoted the proliferation of HCC cells. Through integrated metabolomic analysis, quinolinic acid derived from C. mitsuokai was consistently increased in the feces, portal vein serum and HCC tissues of C. mitsuokai-treated mice. Quinolinic acid significantly promoted the proliferation of HCC cells. Quinolinic acid directly bund to and activated the tyrosine kinase receptor Tie2 on HCC cells. The phosphorylated Tie2 further stimulated the oncogenic PI3K/Akt signaling pathway, thereby promoting HCC development.
Conclusion: We demonstrated that C. mitsuokai is a novel pathogenic bacterium capable of promoting hepato-carcinogenesis. The enriched C. mitsuokai colonizes in the HCC tissue through its surface protein Gtrl1/RagA. C. mitsuokai derived quinolinic acid directly bund to Tie2 of hepatocytes to activate the PI3K/Akt oncogenic pathway therefore promoting hepatocarcinogenesis.

Introduction: Although Helicobacter pylori (H. pylori) has been known to be linked to gastric carcinogenesis, only the latest technical advances made it possible to evolve on the complex microbial architecture of the stomach mucosa that also includes Streptococcus, Prevotella and Fusobacterium etc. The impact of the microbial species on the clinical phenotype such as prognosis of gastric cancer patients is mostly unknown. In this study, we evaluated the link between tumoral and non-tumoral mucosal microbial community and prognosis of gastric cancer patients.

Materials and Methods: Surgically collected tissues specimen including paired tumorous specimen and adjacent non-tumorous gastric mucosa were available from 64 gastric cancer patients. Following DNA extraction, the region V1-V2 of the 16S rRNA gene was amplified by PCR and barcoded for high throughput sequencing using Illumina platform. The microbiome results were subsequently linked with clinical data, pathological characteristics and survival data for up to seven years. The cancer microbiome atlas (TCMA) data were used to validate the results.

Results: After normalization, roughly 5000 reads per sample were obtained and taxonomically annotated. In direct paired comparison between the microbial structure of the adjacent and tumorous tissues, only the abundance of H. pylori was significantly higher in non-tumorous tissues. Abundance of bacteria was associated with the overall survival of gastric cancer patients both in tumorous and non-tumorous tissues. In particular, increased abundance of Fusobacterium and Prevotella in tumorous, but not in non-tumorous tissues, was associated with worse prognosis (Kaplan-Mayer-Analysis p=0.0085 and p=0.04, respectively). Hazard ratio analysis revealed pathological staging and abundance of Fusobacterium as the main factors associated with worse prognosis in univariate and particular Fusobacterium in multivariate analysis (p=0.009). TCMA cohort was used to validate the analysis showing identical tread toward the worse prognosis in association with Fusobacterium. In depth bacterial network analysis revealed complex interactions between bacterial phylotype and especially a negative relationship between Helicobacter pylori and Fusobacterium nucleatum.

Conclusions: Mucosal microbial structure was associated with a prognosis of gastric cancer patents. As supported by testing and validations cohorts, abundance of Fusobacterium nucleatum needs to be considered as identifiable risk factor for worse prognosis and shorter overall survival.

Darja Nikitina

Appearances