Characterization of the gut microbiota in patients with stage III colorectal cancer: A case-control study

To conduct a case-control study (pilot study) in Africa (Mali) in comparing the gut microbiota of patients with stage III colorectal cancer (CRC) using next-generation sequencing.

Shotgun sequencing was performed to characterize participants' fecal microbiota using Illumina's HiSeq platform. This case-control study involved newly diagnosed CRC patients (n = 23) prior to any treatment initiation, and unrelated healthy controls (n = 24) to elucidate their microbial diversity and relative abundance.

The findings revealed that the gut microbiota in CRC and in healthy were significantly distinctive according to the PERMANOVA test (R² = 0.132, P = 0.001), and the alpha-diversity was significantly lower in CRC. Beta-diversity, based on principal coordinate analysis, showed a distinct taxonomy between the CRC and the healthy. Levels of Pseudomonadota, Escherichia, Citrobacter freundii, Klebsiella sp. LTGPAF-6F, Escherichia albertii, Escherichia coli, Caudovirales, Apicomplexa, and Verrucomicrobiota populations were significantly elevated in CRC. The major metabolic pathways with higher relative abundance levels found in CRC compared to healthy were related to HEMESYN2-PWY: heme biosynthesis II (anaerobic), PWY-5154:L-arginine biosynthesis III (via N-acetyl-L-citrulline), FUC-RHAMCAT-PWY: superpathway of fucose and rhamnose degradation, ECASYN-PWY: enterobacterial common antigen biosynthesis, ENTBACSYN-PWY: enterobactin biosynthesis, and AEROBACTINSYN-PWY: aerobactin biosynthesis.

Distinct gut microbiome profiles between healthy and CRC were observed. In particular, the findings showed a significant reduction in microbial diversity in stage III CRC. This study provides initial metagenomic data on Malian patients with CRC. It will be used to create a larger cohort to better understand the relationship between CRC and the gut microbiota in the Malian CRC population.