Is there a link between the oral microbiota and colorectal cancer?

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The composition of the oral microbiota can provide information about the presence of colorectal cancer or adenoma. Combined with data from the fecal microbiota, it could allow us to effectively detect these tumors.

 

Could it be possible to screen for colorectal cancer by analyzing oral and fecal microbiota? An Irish team examined the possibility of such a screening. Previous studies have already established a connection between fecal microbiota and colorectal cancer. Here, researchers analyzed the composition of the oral microbiota in order to prove a potential connection between dysbiosis and the presence of colorectal cancer or adenomatous polyps in the colon.

They took samples from the mouth, stool, and colonic mucosa of 99 patients with colorectal cancer, 32 patients with adenomatous polyps, and 103 control subjects. The results showed changes in the oral microbiota of subjects with cancer, which was true for at least 16 bacterial genera including Neisseria, Haemophilus, Parvimonas, Prevotella, Alloprevotella, Lachnoanaerobaculum, and Streptococcus. Furthermore, at least 12 bacterial genera are differentially represented in cases of adenoma. These differences, when added to the data from the fecal microbiota, allow for the identification of cases of colorectal cancer and adenoma compared to healthy subjects, with a sensitivity of 76% and 88% respectively. A test based on analyzing these microbiotas may result in very early detection, at pre-cancerous lesion stage.

These studies also indicate the presence of bacteria from the oral cavity in the colonic mucosa of patients with cancer. They form biofilms similar to those found in the mouth. These bacterial groups are associated with changes in the gene expression of mucosal cells, suggesting their involvement in cancer progression. Lastly, a high intestinal concentration of Lachnospiraceae was negatively correlated with a Western diet (low in fiber) and with the presence of oral bacteria in the colon, suggesting that certain bacteria play a protective role through diet.

 

Sources:

Flemer B et al. The oral microbiota in colorectal cancer is distinctive and predictive. Gut. 2017 Oct 7. pii: gutjnl-2017-314814.