Microbiomics: Novel Biomarkers of Colorectal Cancer Diagnosis and Prognosis

With colorectal cancer (CRC) accounting for over 1.9 million new cases and 930,000 deaths globally in 2020, there is a critical need for innovative indicators to forecast disease advancement and therapeutic outcomes. The gut microbiome has emerged as a fertile area for discovering such diagnostic and prognostic signals. This narrative review collected current evidence on intestinal microorganisms and their metabolic products as candidate markers for CRC control. Intestinal communities influence malignancy through diverse mechanisms, including metabolic shifts, immune modulation, inflammation, proliferation/apoptosis regulation, genotoxicity, and mucosal barrier disruption. Pathogenic species, such as Fusobacterium nucleatum and enterotoxigenic Bacteroides fragilis, facilitate tumorigenesis via FadA-mediated signaling and Th17/IL-17 responses. In contrast, beneficial taxa like Faecalibacterium prausnitzii and Akkermansia muciniphila provide protective effects through short chain fatty acid production. Macrophage phenotype physiological equilibrium is altered and inflammatory status fluctuates under the former. Metabolically, hydrogen sulfide damages mitochondrial DNA and secondary bile acids stimulate cellular proliferation. While 16S rRNA sequencing and shotgun metagenomics are established detection strategies, innovative platforms like organoids and gene arrays remain in the exploratory stage. Clinical data indicates that F. nucleatum aligns with advanced tumor stage, and its combined detection with colibactin-producing E. coli achieves high sensitivity for early-stage screening. Additionally, A. muciniphila levels can anticipate the efficacy of PD-1 blockade immunotherapy. Microbiota-derived tools represent a transformative direction in oncology. Future research must focus on standardizing protocols and validating multi-marker panels to enhance clinical translation.