Researchers from Johns Hopkins Medicine and collaborating institutions have identified the molecular mechanism by which a toxin produced by Bacteroides fragilis—a bacterium commonly found in the human gut—can damage the intestinal lining and promote colorectal cancer development. This discovery, published in Nature, represents a significant advance in our understanding of the relationship between the gut microbiome and cancer.
What did the researchers discover?
For more than 15 years, scientists have known that enterotoxigenic Bacteroides fragilis (ETBF) is associated with colorectal cancer. However, the exact mechanism remained unclear.
The new study found that:
The bacterial toxin BFT (Bacteroides fragilis toxin) first binds to a protein on intestinal cells called claudin-4.
This interaction allows the toxin to cleave E-cadherin, a critical protein responsible for maintaining the integrity of the intestinal barrier.
Disruption of this protective barrier promotes inflammation and creates conditions that may contribute to colorectal cancer development over time.
Why does this matter?
Understanding how a cancer-promoting bacterium damages healthy tissue is a crucial step toward developing:
- Targeted therapies that block the toxin before it injures the intestinal lining
- Biomarkers to identify individuals at higher risk
- Novel prevention strategies aimed at modifying harmful microbiome interactions rather than treating cancer after it develops
What patients should know
This research does not mean that all gut bacteria are harmful.
In fact, the vast majority of our gut microbiome supports digestion, immune function, and overall health. The findings relate specifically to toxin-producing strains of Bacteroides fragilis and represent early mechanistic research, not a new screening or treatment recommendation.
Current evidence-based measures to reduce colorectal cancer risk remain unchanged:
Participate in age-appropriate colorectal cancer screening. Eat a diet rich in fibre, fruits, vegetables, and whole grains. Maintain a healthy body weight and stay physically active. Avoid tobacco and limit alcohol consumption. Seek medical evaluation for persistent bowel habit changes, rectal bleeding, unexplained weight loss, or abdominal pain.
Takeaway
Cancer prevention increasingly extends beyond genetics and lifestyle—it also involves understanding the complex ecosystem of microorganisms that live within us.
This discovery is an important reminder that decoding the interaction between the gut microbiome and human cells may open new avenues for preventing colorectal cancer before it begins.
References
- White MT, et al. A pro-carcinogenic bacterial toxin binds claudin-4 to cleave E-cadherin. Nature. 2026.