Changes of intestinal microbiota in colorectal cancer and its potential ability to predict disease

Background：It is controversial whether colorectal cancer (CRC) impacts intestinal microbial alpha (α) diversity, and although some studies have suggested an association between intestinal microbiota and cancer risk, few have been used as a marker for CRC diagnosis. Methods：By searching PubMed and BioProject databases, we reanalysed published raw 16S ribosomal RNA (rRNA) gene sequences and metadata. We calculated α-diversity indices, screened the differentially enriched genera and species shared among different studies, identified potential CRC markers, and finally assessed the overall trend of these indices. Results：The pooled analysis showed that based on the fixed-effects model, α-diversity of the cancer group was lower than that of the non-cancer group, and there was significant heterogeneity. Heterogeneity was significantly reduced or eliminated when grouped by geographic region, study scope, and sequencing platform. We also found an association between gut microbiota and CRC. The genera Fusobacterium, Parvimonas, GemellaCampylobacter, and Peptostreptococcus were only enriched in the cancer group, while Faecalibacterium, Subdoligranulum, and Fusicatenibacter were dominant in the non-cancer group. At the same time, we also provide some evidence that Fusobacterium, Gemella, Faecalibacterium, and Subdoligranulum have diagnostic value in several studies and may be potential diagnostic markers of CRC. Conclusions： This analysis indicates an association between CRC and microbiota composition, and microbial markers could be used as diagnostic indicators of CRC. However, future studies should include more cohorts and wide sample sizes to identify the role of the different microbiota in CRC.