Gut bugs may spur development of bowel cancer

Microbes living in the gut may help drive the development of intestinal tumours, scientists have found.
Bowel cancer, also called colorectal cancer, results from a series of genetic changes (mutations) that cause healthy cells to become progressively cancerous, first forming early tumours called polyps that can eventually become malignant.
Although mutations can occur anywhere in the human intestine, certain types of colorectal cancer tend to develop in particular locations, suggesting that additional, nongenetic factors contribute to tumour growth and dictate where polyps appear.
Dr Sergio Lira and his team at the Icahn School of Medicine at Mount Sinai, New York, asked if gut microbes have a hand in tumour development.

The researchers had noticed previously that mice carrying polyp-causing mutations develop polyps only in a limited section of the intestine, despite the mutations being present in all cells along the intestine.
In the new study, they treated the mice with antibiotics to disrupt the populations of microbes living in their gut. This treatment prevented the formation of polyps, showing that bacteria are essential for early tumour development in this model.

The authors proposed that bacteria cross from the gut into the tissue of the intestinal wall, triggering inflammation that promotes tumour growth.
While further research is needed to confirm the identity of the cancer-promoting bacteria, the findings suggest it may be possible to reduce the risk of colorectal cancer in genetically susceptible individuals by removing certain types of gut bacteria.

"In addition to genetic changes, various lifestyle-related factors, such as obesity and diet, have been linked to colorectal cancer. Some of these lifestyle factors appear to affect the types of bacteria present in the gut," said Lira.
"Ultimately, understanding the interplay between genetic mutations, gut microbes, and inflammation may lead to novel diagnostics and therapies for intestinal cancer," Lira added.
The study was published in The Journal of Experimental Medicine.