Microbiota-derived metabolite landscapes modulate Fusobacterium fitness and colorectal cancer cell behaviour

Gut microbiota dysbiosis is increasingly viewed as a disruption of microbial metabolic functions rather than only a shift in microbial composition. Microbiota-derived metabolites not only shape microbial ecology but also directly influence surrounding host tissues by modulating epithelial cell signaling, inflammation, and tumor-associated processes. Among dysbiosis-associated microbes, Fusobacterium is consistently enriched in colorectal cancer (CRC) and contributes to tumor progression, yet the ecological factors regulating its expansion and interaction with host tissues remain unclear. Here, we investigated how microbiome-derived metabolite environments associated with healthy and dysbiotic microbial communities influence Fusobacterium fitness and colorectal epithelial cell behavior.

CRC-associated dysbiosis was generated using an orthotopic murine CRC model combined with antibiotic-induced microbiota perturbation. Gut microbial communities were profiled using 16 S rRNA gene sequencing. Metabolite-enriched supernatants derived from healthy gut microbiota, oral microbiota, dysbiotic microbiota and probiotic cultures were evaluated for their effects on CRC-associated bacteria and Fusobacterium sp. growth, adhesion and invasion. These metabolite supernatants were applied to colorectal cancer cells and their effects on viability (MTT assay), migration (scratch assay), apoptosis (Annexin V-FITC flow cytometry), and inflammatory signaling (Western blot analysis of inflammatory markers) were evaluated.

CRC-associated dysbiosis showed reduced microbial diversity with enrichment of opportunistic taxa including Fusobacterium and depletion of beneficial commensals such as Lactobacillus and Bifidobacterium. Metabolite-enriched supernatants from healthy gut and oral microbiota suppressed Fusobacterium growth by 55-65% and reduced bacterial adhesion and invasion in epithelial cells. In epithelial models, these metabolite environments reduced CRC viability to 60% of untreated control, with comparatively smaller effects observed in non-cancerous epithelial cells. They also inhibited cell migration, accompanied by suppression of inflammatory signaling pathways including IL-6, IL-1β, NF-κB, and HIF-1α. In contrast, conditioned media from dysbiotic cancer-microbiota interactions increased tumor cell viability to 120-140% of controls. These findings suggest an association between microbiota-derived metabolite landscapes, pathobiont fitness and epithelial responses under CRC-associated dysbiosis.