Hidden Gut Virus Linked to Colon Cancer: New Discovery

Researchers from institutions in Denmark and Australia have identified a previously undescribed virus that may play a role in the development of colorectal cancer. The discovery focuses on a specific type of bacteriophage—a virus that infects bacteria—found within the gut microbiome of cancer patients.

The findings, published in the journal Communications Medicine, suggest that while certain bacteria are common in both healthy individuals and those with cancer, the presence of this hidden virus may be a distinguishing factor. This biological signal could have future implications for how the disease is screened.

The Paradox of Bacteroides fragilis

For several years, medical researchers have noted an association between colorectal cancer and a specific bacterium known as Bacteroides fragilis. However, this association presented a scientific paradox because B. Fragilis is also frequently found in the gut of healthy people.

Because the bacterium itself is a normal part of the gut ecosystem for many, researchers sought to determine if there was a crucial difference in the version of the bacterium found in individuals who develop cancer.

Flemming Damgaard, a medical doctor and PhD at the Department of Clinical Microbiology at Odense University Hospital and the University of Southern Denmark, noted the difficulty of this puzzle, stating: It has been a paradox that we repeatedly find the same bacterium in connection with colorectal cancer, while at the same time it is a completely normal part of the gut in healthy people.

Discovery of the Bacteriophage

By using genetic sequencing to analyze the gut bacteria of cancer patients in a large Danish population study, the research team discovered that in patients who developed colorectal cancer, B. Fragilis was far more likely to carry a specific, previously undescribed virus.

These viruses, called bacteriophages, live inside bacteria and hijack the cells to duplicate and spread. The researchers found that these specific viral patterns were closely linked to the bacteria found in patients with colorectal cancer.

To verify the initial findings, the team analyzed a larger cohort consisting of 877 people, including both those with and without colorectal cancer. This larger study confirmed the link, suggesting that viruses lurking within B. Fragilis may tip the scales toward the development of cancer.

Context of Colorectal Cancer Risk

Colorectal cancer is one of the most common forms of cancer in the developed and Western world and remains a leading cause of cancer-related deaths. While factors such as diet, lifestyle, and age are established risk factors, the precise triggers for the disease are often not fully understood in most cases.

In recent years, scientific attention has shifted toward the gut ecosystem, which comprises a vast community of microorganisms, including bacteria and viruses. This research adds to the understanding of how the microbiome contributes to the disease.

Implications for Future Research

The identification of this virus represents a new type of viral signal that had not been previously identified. By tracing these unusual viral patterns across patient samples from multiple countries, researchers believe they have uncovered a subtle biological marker.

The discovery provides a potential path forward for improving screening processes, as the presence of this specific bacteriophage may serve as a more precise indicator of cancer risk than the presence of the B. Fragilis bacterium alone.

We have discovered a virus that has not previously been described and which appears to be closely linked to the bacteria we find in patients with colorectal cancer.

Flemming Damgaard, Odense University Hospital