Colorectal cancer is one of the most common types of cancer in the Western world and a leading cause of cancer-related deaths. Age, diet and lifestyle are known risk factors. However, in most cases we still lack a precise understanding of what triggers the disease.
In recent years, researchers have increasingly turned their attention to the ecosystem of the gut – the vast community of bacteria, viruses and other microorganisms that live there.
Three questions for Flemming Damgaard about the study :
What did you investigate?
We investigated how gut bacteria may contribute to the development of colorectal cancer.
What is the most important finding?
We discovered a new and previously undescribed virus that infects gut bacteria in patients with colorectal cancer.
How could the results be used?
In the longer term, it may become possible to test for these viruses in stool samples to assess the risk of colorectal cancer and potentially improve prevention and treatment.
Now, researchers from the University of Southern Denmark and Odense University Hospital have discovered a previously undescribed virus in a common gut bacterium. The virus appears more frequently in patients with colorectal cancer.
A familiar bacterium – but an unsolved puzzle
For several years, one particular bacterium has been associated with colorectal cancer: Bacteroides fragilis.
The difficulty is that this bacterium is also present in the vast majority of healthy individuals.
– 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, says Flemming Damgaard, molecular biologist and PhD at the Department of Clinical Microbiology at Odense University Hospital and the University of Southern Denmark.
The researchers therefore decided to examine whether differences might exist within the bacterium itself.
They did.
A virus hidden inside the bacterium
In patients who later developed colorectal cancer, the bacterium far more often carried a specific virus – a virus that lives inside bacteria, known as a bacteriophage.
– 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, says Flemming Damgaard.
According to the researchers, the virus represents new types that have not previously been identified.
– It is not just the bacterium itself that seems interesting. It is the bacterium in interaction with the virus it carries, he explains.
The study demonstrates a statistical association between the virus and colorectal cancer, but it cannot determine whether the virus plays a direct role in the development of the disease.
– We do not yet know whether the virus is a contributing cause, or whether it is simply a sign that something else in the gut has changed, says Flemming Damgaard.
