Microbes may reveal colon cancer mutations

BALTIMORE — Microbes can reveal which mutations drive colon cancer, a new study suggests.

By examining bacteria growing alongside 44 colon cancer tumors and 44 healthy tissue samples, researchers have determined that particular mixes of microbes are associated with both the number and types of DNA mutations the cancer carries.

Colon tumors with more mutations had a more diverse mix of bacteria, or microbiome, than did tumors with few mutations, Ran Blekhman of the University of Minnesota, Twin Cities, reported October 9 at the annual meeting of the American Society of Human Genetics. And certain bacteria were more likely to be found growing next to cancer cells carrying specific mutations. For instance, the presence of Fusobacterium was associated with tumors harboring mutations in the APC gene, Blekhman and colleagues found. Microbe analysis predicted with 70 to 80 accuracy when researchers would find mutations in five of 11 genes examined.

Mutations may create different environments, or niches, for bacteria to grow in, Blekhman said. Tumors with mutations that cause their cells to take in more of the sugar glucose (most cells’ favorite energy source) were associated with bacteria that turned on genes that could help the microbes get energy from other sources. The researchers don’t yet know whether the bacteria change in response to the cancer, or if the microbe alterations somehow promote growth of cells carrying certain mutations.

Right now, researchers only have data to show that bacteria growing close to the tumor are associated with particular mutation patterns. But if tumor mutations affect the makeup of the microbiome throughout the intestines, stool samples could one day be used as a screening test for colon cancer.