Dysbiosis of human gut microbiome in young-onset colorectal cancer.

The incidence of sporadic young-onset colorectal cancer (yCRC) is increasing. A significant knowledge gap exists in the gut microbiota and its diagnostic value for yCRC patients. Through 16S rRNA gene sequencing, 728 samples are collected to identify microbial markers, and an independent cohort of 310 samples is used to validate the results. Furthermore, species-level and functional analysis are performed by metagenome sequencing using 200 samples. Gut microbial diversity is increased in yCRC. Flavonifractor plautii is an important bacterial species in yCRC, while genus Streptococcus contains the key phylotype in the old-onset colorectal cancer. Functional analysis reveals that yCRC has unique characteristics of bacterial metabolism characterized by the dominance of DNA binding and RNA-dependent DNA biosynthetic process. The random forest classifier model achieves a powerful classification potential. This study highlights the potential of the gut microbiota biomarkers as a promising non-invasive tool for the accurate detection and distinction of individuals with yCRC.