“The gut microbiome is linked to various physiological functions associated with colon cancer,” explain Patrick Schloss, Grace Chen and Joseph Zackular, authors of a recent study published in mBio. “We wanted to determine whether changes in the gut microbiome are actively driving tumorigenesis or just a collateral effect of this process,” they add.

To answer this question, the researchers used a mouse model of inflammation-associated colorectal cancer. Next-generation sequencing of the 16S rRNA gene was used to show how changes in the gut microbial community were associated with the development of tumours. Tumour-bearing mice had enrichment of Bacteroides, Odoribacter and Akkermansia genera and decreases of Prevotellaceae and Porphyromonadaceae family members when compared with healthy mice.

Germ-free mice were then colonized with microbiota from either healthy or tumour-bearing mice. An increased number and size of tumours developed in mice that received microbiota from tumour-bearing mice. “Finally, we used a broad-spectrum antibiotic cocktail to alter the microbiome of conventional mice, and these mice developed few, if any, tumours,” describe Schloss, Chen and Zackular.

These findings indicate that a causal link exists between dysbiosis of the gut microbiota and colon tumorigenesis. Therefore, the researchers conclude that manipulating the microbiota composition is a potential strategy to prevent colorectal cancer development.

Zackular et al. are now investigating therapies—including diet, probiotics and prebiotics—that would modulate the gut microbiota to prevent or limit colorectal cancer progression.