Comprehensive analysis of faecal metagenomic and serum metabolism revealed the role of gut microbes and related metabolites in detecting colorectal lateral spreading tumours

Colorectal lateral spreading tumours (LST), early-stage lesions of colorectal cancer (CRC), are associated with gut microbiota dysbiosis. However, the functional alterations in gut microbiota and their metabolic pathways remain inadequately understood. This study employed propensity score matching to compare 35 LST patients with 35 healthy controls. Metagenomic and metabolomic analyses revealed notable differences in gut microbiota composition and metabolic pathways. LST patients exhibited a marked reduction in short-chain fatty acid (SCFA)-producing probiotics, such as <i>Roseburia</i>, <i>Clostridium</i>, and <i>Butyricicoccus sp-OF13-6</i>, alongside anti-inflammatory metabolites. In contrast, potential intestinal pathogens linked to inflammatory bowel disease (IBD), including <i>Escherichia</i> and <i>Citrobacter amalonaticus</i>, were significantly enriched. Orthogonal partial least squares discriminant analysis (OPLS-DA) highlighted significant metabolic disparities between the groups, with enrichment in pathways associated with cholesterol metabolism, choline metabolism in cancer, and amino acid metabolism - all relevant to cancer progression. Key biomarkers identified for LST included fumarate, succinate, glutamic acid, glycine, and L-aspartic acid, which were closely linked to these pathways. Functional studies demonstrated that these metabolites promoted the proliferation and invasion of HCT-116 and SW480 human colorectal cancer cells <i>in vitro</i>. Metagenomic and metabolomic analysis revealed a strong positive correlation between <i>Escherichia</i> and <i>Ruminococcus sp-AM41-2AC</i> abundance and the enriched pathways, whereas reductions in <i>Roseburia species</i>, including <i>Roseburia-OF03-24</i> and <i>Roseburia intestinalis_CAG13</i>-exhibited negative correlations. These results suggest that gut microbiota and metabolite alterations in LST contribute to intestinal inflammation and CRC development, underscoring their potential as biomarkers for early detection and therapeutic targets.