Gut Bacteria Are Possible Indicators of Colon Cancer Risk

Colorectal cancer (CRC), also known as bowel cancer, colon cancer, or rectal cancer, is the development of cancer from the colon or rectum. Signs and symptoms may include blood in the stool, a change in bowel movements, weight loss, and fatigue.

Colorectal cancer is a major health concern worldwide. Growing evidence for the role of the gut microbiota in the initiation of CRC has sparked interest in approaches that target these microorganisms. However, little is known about the composition and role of the microbiota associated with precancerous polyps.


A large team of medical scientists led by those at the University of Washington School of Medicine (Seattle, WA, USA) tracked 40 patients who had undergone routine colonoscopies and had biopsies taken near the polyps to identify bacteria present at relatively higher levels compared with those of patients who were polyp-free. All the patients were between the ages 50 and 75, and 60% were women. The team found distinct microbial signatures between patients with and without polyps and between polyp subtypes using sequencing and culturing techniques.

The investigators reportedly found a correlation between the common bacteria, non-enterotoxigenic Bacteroides fragilis recovered and the level of inflammatory cytokines in the mucosa adjacent to the polyp. Additional analysis revealed that B. fragilis from patients with polyps are bft-negative, activate NF-κB through Toll-like receptor 4, induce a pro-inflammatory response, and are enriched in genes associated with lipopolysaccharide (LPS) biosynthesis. They also found that the B. fragilis from patients with polyps differed in its ability to induce inflammation compared to the B. fragilis from polyp-free individuals.

William R. DePaolo, PhD, Associate Professor of Medicine and senior author of the study, said, “The whole idea is that most people look at advanced colorectal cancer and think of the microbiome, but it's hard to determine if the microbiome has changed and when it changed. What our data suggests is that, in order to survive within an environment where metabolic and inflammatory changes are occurring, a normally healthy gut and related bacteria may adapt in such a way that causes it to contribute to the inflammation rather than suppress it.”

Dr. DePaolo suggested that if a screening were available to test the microbes, before a polyp even appears, it could be a key factor to drive the rates of CRC down. The study was published on September 17, 2021, in the journal Cell Host & Microbe.

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University of Washington School of Medicine