Gut microbiota and metabolite changes in metastatic colorectal cancer via 16S rRNA and metabolomics

Abstract

BACKGROUND

Distant metastasis causes most colorectal cancer (CRC) deaths. Gut microbiota (GM) dysbiosis and altered metabolites drive metastasis progression, serving as potential diagnostic biomarkers.

AIM

To investigate alterations in GM and metabolites between patients with non-metastatic and distant metastatic CRC.

METHODS

According to the inclusion criteria, fresh fecal samples were collected from 14 non-metastatic CRC patients and 15 distant metastatic CRC patients. We performed 16S rRNA sequencing to analyze the composition, diversity, and differential abundance of GM, along with predictive functional profiling of microbial communities. Additionally, all samples underwent liquid chromatography-mass spectrometry (LC-MS)-based untargeted metabolomic sequencing to identify metabolic changes and predict their biological functions.

RESULTS

The cohort comprised 16 non-metastatic CRC patients (designated as the S group) and 16 distant metastatic CRC patients (designated as the DZ group). Sequence analysis (16S rRNA) identified a total of 35016 operational taxonomic units (OTUs) across both groups (16886 OTUs in the S group; 16270 in the DZ group; 1860 shared between groups). Inter-group microbial diversity analysis revealed notable differences in the β-diversity group (P < 0.05). Comparative analysis of GM revealed significant taxonomic composition differences between groups (P < 0.05), with higher relative abundances of Butyricicoccus, Ruminococcus_1, Coprococcus_2 in the S group, Pyramidobacter, Christensenellaceae_R-7_group, and Romboutsia in the DZ group (all P < 0.05). Functional analysis of differential microbiota revealed predominant enrichment in metabolic pathways. LC-MS-based untargeted metabolomics detected 91 differential metabolites in both positive and negative ionization modes. GM-derived metabolites showed significant alterations in the DZ group. Kyoto Encyclopedia of Genes and Genomes and Human Metabolome Database analyses revealed associated pathways involving nucleic acids, organic heterocyclic compounds, alkaloids, lipids/lipid-like molecules, and nucleotides. These metabolites may function synergistically, as evidenced by positive correlations between diazoxide, hydroquinidine, aurapten, and triptophenolide. Differential metabolites were primarily involved in aminoacyl-tRNA biosynthesis, central carbon metabolism in cancer, phenylalanine metabolism, vitamin B6 metabolism, and protein digestion and absorption pathways.

CONCLUSION

GM and microbial metabolites differ significantly between CRC patients with distant metastasis and those without metastasis. Metabolites involved in nucleic acid, alkaloid, and lipid metabolism pathways potentially contribute to distant metastasis in CRC.

Keywords: Gut microbiota; Colorectal cancer; Untargeted metabolomics; 16S rRNA sequencing; Liquid chromatography-mass spectrometry

Core Tip: Colorectal cancer patients with different metastatic statuses exhibit distinct gut microbiota and metabolite profiles. These differences may contribute to cancer progression and metastasis, providing potential biomarkers for early diagnosis and therapeutic targets.