Newly Discovered Virus in Gut Bacteria Linked to Colorectal Cancer

A groundbreaking discovery by Danish scientists has revealed a previously unknown virus hiding inside common gut bacteria that may be linked to colorectal cancer. According to research published in Communications Medicine, patients with colorectal cancer were approximately twice as likely to harbor this virus within Bacteroides fragilis, a bacterium normally present in the human digestive system.

“These findings highlight the importance of the microorganisms in the gut and their relation to our health,” explained Dr. Flemming Damgaard, PhD, from the Department of Clinical Microbiology at Odense University Hospital and the University of Southern Denmark. “If we want to understand the full picture, we need to look deep into their genetic material.”

The connection between Bacteroides fragilis and colorectal cancer has been known for years, with the bacterium appearing more frequently in cancer patients. However, since most healthy people also carry these bacteria, researchers were puzzled about why they might be harmful in some cases but not others.

By examining subtle genetic differences within the bacteria, the research team made an unexpected discovery – a previously undocumented bacteriophage, which is a type of virus that infects bacteria rather than human cells.

“We were very surprised to find a whole virus inside the bacteria from the colorectal cancer patients,” Damgaard noted. “That was not something we expected when we started our study.”

The research team analyzed stool samples from 877 individuals across Europe, the United States and Asia. Their findings showed that colorectal cancer patients were approximately twice as likely to have traces of this virus compared to people without cancer.

Despite this strong statistical association, the researchers emphasize that the study does not prove the virus causes colorectal cancer. “The major limitation is that we still don’t know why the virus is linked to colorectal cancer,” said co-author Ulrik Stenz Justesen, who noted that further research is already underway.

The team is now conducting laboratory experiments and animal studies to determine whether the virus alters the bacterium’s behavior in ways that could influence cancer development. This research could potentially unlock new understanding about the complex relationship between microorganisms and human health.

The human body contains roughly as many microbial cells as human cells, underscoring the profound interconnection between microbes and human health. “Our understanding of [microbial cells] is still in its infancy,” Damgaard said. “There are many health-related discoveries to be made in the human microbiota.”

Colorectal cancer remains one of the leading causes of cancer-related deaths worldwide, according to the World Health Organization. Several high-profile deaths, including actors James Van Der Beek and Chadwick Boseman, have drawn increased attention to this disease’s impact across different age groups in recent years.

While diet and lifestyle factors contribute significantly to colorectal cancer risk, mounting evidence suggests the bacteria in our gut may also play a crucial role. Current screening methods include stool tests for occult blood and colonoscopies, but researchers suggest that future screening could potentially include tests for viral markers like those identified in this study.

The researchers point to cervical cancer as an instructive example of how identifying a viral cause can transform prevention efforts. After human papillomavirus (HPV) was linked to cervical cancer, vaccines were developed that significantly reduced new cases. While it’s premature to make direct comparisons, colorectal cancer screening and prevention strategies could eventually follow a similar path if a clear viral connection is confirmed.

“It is too early to act,” Damgaard cautioned. “We have a lot of hope, and that is what we want people to have at this point.”

This discovery represents a significant step forward in understanding the complex factors that may contribute to colorectal cancer, potentially opening new avenues for detection, prevention, and treatment of a disease that affects millions worldwide.