US scientists found that a common bacterium found in the gut could play a role in the development of colon cancer by producing a fermentation byproduct that damages DNA and affects signalling pathways used by colon cancer cells and the immune system.
The study was the work of Professor Mark Huycke of the Department of Veterans Affairs Medical Center, Oklahoma City, and is to be published in the October 1st issue of the Journal of Medical Microbiology.
Our bodies contain more bacteria than the total number of people that have ever walked on our planet. In fact, bacteria in the colon outnumber the cells of the body, and while scientists are discovering more and more complex relationships between them, for several decades they have suspected that gut bacteria play a role in the formation of sporadic cancer.
One such bacterium is a normal gut microbe called Enterococcus faecalis which survives using two different types of metabolism: respiration and fermentation. When it ferments it releases an oxygen compound called “superoxide” that damages DNA.
Huycke said in a press statement:
“We wanted to investigate how colon cells respond to normal gut bacteria that can damage DNA, like E. faecalis.”
“We found that superoxide from E. faecalis led to strong signalling in immune cells called macrophages. It also altered the way some cells in the gut grew and divided and even increased the productivity of genes that are associated with cancer,” he added.
Huycke and colleagues found that signals from E. faecalis affected the activity of 42 genes that are involved in the regulation of the lifecycle and death of the epithelial cells that line the gut.
They suspect E. faecalis may have developed new ways of triggering colon cells to become cancerous, which happens when the bacterium is in fermentation mode and rapidly affects the lining of the colon.
Cancer in the gut almost always starts in the colon where billions of bacteria are in contact with the cells of the lining. The bacterial communities are extremely complex, making it very difficult to study their interaction with tissue cells. This study is one of the first to unravel such a relationship.
“Our findings are among the first to explore mechanisms by which normal gut bacteria damage DNA and alter gene regulation in the colon that might lead to cancer,” said Huycke.
“This research puts into perspective the complexity of the effects normal gut bacteria can have on the health of an individual,” he added.
Other experts suggest E.faecalis may not be the only candidate for triggering colon cancer.
One who spoke to BBC News, Dr Barry Campbell, a gut microbiologist at the University of Liverpool in the UK, said there are likely to be others; for instance, he and his colleagues are investigating a type of E. coli in just such a manner. He also said there are “many other factors involved, such as genetics and environment”.
“Dichotomous metabolism of Enterococcus faecalis induced by haematin starvation modulates colonic gene expression.”
T. D. Allen, D. R. Moore, X. Wang, V. Casu, R. May, M. R. Lerner, C. Houchen, D. J. Brackett and M. M. Huycke.
J Med Microbiol 57: 1193-1204, October 1, 2008.
Source: Society for General Microbiology, BBC News.
Written by: Catharine Paddock, PhD