Breakthrough in Understanding Gut Bacteria and Colon Cancer
Scientists have made a significant breakthrough in understanding how a common gut bacteria contributes to the development of colon cancer. This discovery could lead to new preventative treatments that protect the colon from early damage.
In 2009, a landmark study revealed that Bacteroides fragilis drives tumour formation by secreting a toxin that damages the lining of the colon, potentially leading to cancer. However, the exact mechanism by which this toxin attacks cells remained unclear until now.
A team of researchers from the United States has uncovered the missing link, offering hope for better detection and treatment of a disease that is on the rise among younger people. The toxic bacteria must first bind to a host receptor known as claudin-4 before it can cause damage.
“We’ve made several attempts over time to identify the receptor, so this is an exciting moment,” said Professor Cynthia Sears, lead author of the study from Johns Hopkins University School of Medicine. “Understanding how bacterial toxins work can open doors to new approaches for detection and therapy for associated diseases, including diarrhea, colorectal cancer and bloodstream infections.”
The discovery has already led to an intervention that successfully blocked the toxin’s effects in animal models. Now, researchers are working to replicate these results in humans.
The common gut bacteria is present in around 20 per cent of healthy individuals and has a powerful ability to trigger colon inflammation and tumour growth. Colorectal cancer claims over 17,000 lives each year in the UK alone. Rates in under 50s continue to climb, with a 75 per cent increase in under-24s since the 1990s.
Despite this alarming trend, scientists have yet to identify a single definitive cause. Poor diets, increasing obesity levels, and exposure to microplastics are thought to be major contributors. Colorectal cancer is often diagnosed at a late stage, when treatment is difficult, because it causes few symptoms early on—symptoms that are often mistaken for less serious conditions like irritable bowel syndrome (IBS).
The scientists hope their findings will pave the way for earlier detection and, one day, inform treatments for bacteria-associated diseases, including colon cancer.
Key Findings from the Study
The study, published in the journal Nature, tested thousands of genes to determine which ones affect cancer growth. Previous research found that the bacteria triggers chronic inflammation in the gut by attacking protein cells essential for maintaining the colon’s protective barrier.
However, the bacteria did not seem to be attaching itself directly to the protein. Some other elusive mechanism was at play. After ruling out thousands of potential genes involved, the researchers pinpointed claudin-4 as the culprit.
When they knocked out claudin-4 receptor cells, the bacteria had nothing to cling to, leaving the colon’s protective barrier untouched. “It took a while to validate the approach, but once we were able to the screen, claudin-4 was a clear, resounding top hit,” the researchers said. “That was an exciting moment.”
To confirm that the toxin and the receptor cells were physically locking together, the team looked at how the two organisms interacted in a test tube, providing the first physical evidence of the binding interaction.
They then created a dummy claudin-4 protein to see if they could prevent the toxin from binding to colon cells in mice. Results showed that, in mice treated with the dummy proteins, the bacteria bound to the decoys instead of claudin-4 receptor cells, protecting the mice from toxin-induced damage.
Future Research and Implications
The team is now exploring how to block the toxin in humans. This comes as a team of British researchers recently declared that obesity is a key factor in the rising rates of cancer among younger people in England.
There are 11 types of cancer, including bowel cancer, that are increasing among under 50s. Obesity is the only known behavioural risk factor that has been increasing in younger adults over the last two decades—while smoking, alcohol, and physical inactivity have all remained stable or in decline.
Maintaining a healthy weight has been shown to prevent around 20 per cent of bowel cancers. However, an imbalance in gut bacteria could also be behind the mysterious rise, experts say. Today’s youngsters have been exposed to more antibiotics than previous generations, making the gut microbiome more vulnerable to toxic invaders.
Diets high in ultra-processed foods may also play a role in the development of bowel cancer, fueling the growth of pro-inflammatory gut bacteria, which is thought to increase the risk of early-onset cancer.
