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Microbiota profiles in patients with colorectal cancer differ from healthy individuals
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Microbiota profiles associated with colorectal cancer were found to be different from those in individuals without colorectal cancer in a recent study. Moreover, bacterial clusters associated with colorectal cancer were found to be differentially correlated with mucosal gene-expression profiles.
“The heterogeneity of the CRC-associated microbiota identified could be exploited as a screening tool for individuals at greatest risk of developing CRC,” the researchers wrote.
The researchers prospectively examined fecal and mucosal samples from 59 patients who underwent surgery for CRC, 21 patients with polyps and 56 healthy controls. They used 16S rRNA amplicon sequencing to study colonic microbiota composition, and used real-time quantitative PCR to study the expression of specific host response genes.
Patients with CRC had significant differences in microbiota compared with the controls. However, the differences were not only in the cancerous tissue.
There were also differences found between distal and proximal cancers. Alistipes, Akkermansia, Halomonas and Shewanella were significantly more abundant in patients with rectal and distal cancer, while Faecalibacterium, Blautia and Clostridium were more abundant in patients with proximal cancer. Fecal microbiota was not fully reflected in the mucosal microbiota in patients with CRC.
“The differences in the microbiota of patients with proximal and distal cancers found here are an additional level of tumor-host heterogeneity,” the researchers wrote. “We identified a [co-abundance group] (Firmicutes Cluster 2), which was more often found to be increased in proximal cancers and associated with a gene expression profile more similar to the control cohort (and possibly a decreased TH17 response). In particular, the abundance of the Bacteroidetes Cluster 2 and Firmicutes Cluster 2 was negatively correlated with the expression of IL-17a and CCL20, a chemokine shown to promote cancer cell proliferation and migration and which binds to the TH17-cell receptor CCRC6.”
They also found that based on higher level structures of mucosal-associated bacterial co-abundance groups, patients with CRC can be stratified into groups, which resemble the previously formulated concept of enterotypes.
Co-abundance groups associated with CRC were differentially linked to the expression of host immunoinflammatory response genes.
“Distinct higher level structures in the microbiota can be employed to stratify individuals for their risk of presenting with CRC,” the researchers concluded. “Furthermore, CRC-associated microbiota is differentially correlated with distinct patterns of gene expression for host immunoinflammatory responses. Longitudinal studies are required to further assess the predictive value of the findings as biomarkers of disease risk.” – by Suzanne Reist
Disclosures: The researchers report no relevant financial disclosures.
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