The gut microbiota and colorectal lesions subtyped in adenoma-carcinoma sequence and serrated pathway

We examined the difference in diversity of the gut microbiota and in the abundance of individual bacteria among patients with colorectal lesions differentiated by adenoma-carcinoma sequence (AC) and serrated pathway (SE) and polyp-free controls.

This cross-sectional study analyzed data from the Oshima study, which enrolled residents aged 40-79 years of Izu Oshima, Japan, between 2015 and 2017. The participants answered a questionnaire, underwent a screening total colonoscopy, and provided a stool sample. Gut microbiota was assessed by sequencing 16S rRNA gene obtained from stool samples, and compared in terms of within-subject microbial diversity (α-diversity), dissimilarity between-subject microbial composition (β-diversity), and abundance of gut bacteria among 560 cases with AC, 76 with SE, and 480 controls without apparent colorectal lesions. We then estimated the differential abundance of gut microbiota using linear regression adjusted for potential confounders.

We found a difference in β-diversity and increased abundance of the genera Fusobacterium and its higher taxa up to the phylum level and genera Romboutsia, AY442821_g, and Tricibacter (all q < 0.10) in AC cases compared to controls. For SE cases, no clear difference in β-diversity or abundance of gut bacteria was observed. α-diversity did not differ among AC and SE cases and controls.

We found heterogeneity in the dissimilarity between-subject microbial composition and in the abundance of gut bacteria only in AC cases compared to controls. Our results suggest that the association of gut microbiota with colorectal cancer may vary by carcinogenesis pathway.