Gut microbial β-glucuronidases and their role in the microbiome-metabolite axis in colorectal cancer

Colorectal cancer (CRC) development involves microbial and metabolic dysbiosis, with gut microbial β-glucuronidases (gmGUSs) potentially impacting carcinogenesis through de-glucuronidation of diverse important molecules. Here, we identify 550 gmGUSs from a public cohort, employing 114 alignment references, three structural domains, and seven conserved residues. Stage-specific shifts include enrichment of mini-Loop2 (a category defined by two active site-adjacent loop regions) and species-level gmGUS dysregulation (e.g., Bacteroides cellulosilyticus) in CRC. GUS biomarkers display modest efficacy in classifying CRC and adenoma patients from controls, though with limited generalizability, and in predicting CRC outcomes (AUCs > 0.8). Taxonomic and metabolic association analyses highlight microbe-gmGUS-metabolite (MGM) axis perturbations, including increased Alistipes and Fusobacterium, enriched mucin and flavonoid degraders, as well as amino acid and vitamin metabolism alterations linked to CRC progression. In vitro enzyme assays show that the identified gmGUSs possess differential substrate activities. Furthermore, RNA-seq of HCT116 cells co-cultured with BC.G3 (one of the differential gmGUSs from B. cellulosilyticus) reveals upregulation of RNA transcription, DNA replication, and protein folding, shedding preliminary light on its potential effects in CRC progression. Here, we define disturbance of MGM axis in colorectal tumorigenesis and offer potential early diagnostic biomarkers and therapeutic targets for CRC.