Bacteria's Role in Colorectal Cancer

While many of the bacteria in our gut keep us healthy, some, like certain strains of E. coli, produce toxins that may lead to colorectal cancer also called CRC. Researchers discovered that this toxin causes mutational signatures in cells that line the colon, the same type found in colorectal tumor cells.

Typically CRC develops from polyps on large intestine walls and are accumulations of mutated cells. These polyps can become cancerous unless they're removed during a colonoscopy, when a doctor does so using a camera guided tube. Most of the E. coli in our colon are harmless but the pathogenic ones carry genes that encode a toxin called colibactin. Tumors of cancer patients have DNA with fifty mutational signatures, but does this toxin cause the mutations?

Using stem cells growing on a structure, researchers made mini-intestines that they then injected with toxin and non-toxin producing e. coli. After months of repeated injections, they found mutations in the mini intestines exposed to colibactin. Then they compared this mutational pattern to two thousand tumor samples from patients and five percent had the same pattern. This suggests that E.coli colibactin toxin may contribute to one in twenty bowel cancers.

We don't know yet if other bacteria and their toxins are linked to CRC, but this is a promising new lead in the fight against colorectal cancer.