Construction of a gut microbiota-gene-pathway network to reveal the molecular mechanisms underlying right- and left-sided colorectal cancer.

Aiming to reveal the molecular mechanisms involved in right- and left-sided colorectal cancer (CRC) development, CRC gene expression data and a microorganism atlas were downloaded from The Cancer Genome Atlas and The Cancer Microbiome Atlas, respectively. The R package was used to screen differentially expressed genes (DEGs) between right- and left-sided CRC samples and identify those related to prognosis, a correlation analysis was performed between DEGs and prognosis-related microbiota, and an interaction network was created using Cytoscape. Finally, a taxon set enrichment analysis of the microbiota was performed and a gene-genus-pathway network was constructed after GO and KEGG analyses. In total, 9 out of 1557 identified DEGs had a significant correlation with prognosis, whereas 3 out of 211 bacterial genera (Fusobacterium, Bacteroides, and Parabacteroides) showed a significant correlation with prognosis. DEGs were mainly enriched in the PPAR pathway and vitamin metabolic and transport processes. According to a taxon set enrichment analysis, the microbes in the integrated network were significantly abundant in 28 host-intrinsic, 2 host-extrinsic, and 1 environment taxon sets. This study provides new insights for understanding the molecular mechanisms of left- and right- CRC.