Tumour-associated and non-tumour-associated bacteria co-abundance groups in colorectal cancer

Background & aims Gut microbiota is closely related to the occurrence and development of colorectal cancer (CRC).

However, the differences in bacterial co-abundance groups (CAGs) between tumor tissue (TT) and normal tissue (NT), as well as their associations with clinical features, are needed to be clarified.

Methods Bacterial 16 S rRNA sequencing was performed by using TT samples and NT samples of 251 patients with colorectal cancer.

Microbial diversity, taxonomic characteristics, microbial composition, and functional pathways were compared between TT and NT.

Hierarchical clustering was used to construct CAGs.

Results Four CAGs were grouped in the hierarchical cluster analysis.

CAG 2, which was mainly comprised of pathogenic bacteria, was significantly enriched in TT samples (2.27% in TT vs. 0.78% in NT, p  < 0.0001).

CAG 4, which was mainly comprised of non-pathogenic bacteria, was significantly enriched in NT samples (0.62% in TT vs. 0.79% in NT, p  = 0.0004).

In addition, CAG 2 was also significantly associated with tumor microsatellite instability (13.2% in unstable vs. 2.0% in stable, p  = 0.016), and CAG 4 was positively correlated with the level of CA199 ( r  = 0.17, p  = 0.009).

Conclusions Our research will deepen our understanding of the interactions among multiple bacteria and offer insights into the potential mechanism of NT to TT transition.