Cancer-causing gut bacteria exposed

Sep 22, 2008

Normal gut bacteria are thought to be involved in colon cancer but the exact mechanisms have remained unknown. Now, scientists from the USA have discovered that a molecule produced by a common gut bacterium activates signalling pathways that are associated with cancer cells. The research, published in the October issue of the Journal of Medical Microbiology, sheds light on the way gut bacteria can cause colon cancer.

There are more bacteria in our bodies than there ever have been people on the Earth. In fact, there are more bacteria in the colon than there are human cells in our bodies. Most of the bacteria in our guts are harmless and many are beneficial to our health. However, for several decades scientists have thought that some microbes living in the gut may play a role in the formation of sporadic colorectal cancer.

Enterococcus faecalis is a normal gut bacterium. Unlike most gut bacteria, it can survive using two different types of metabolism: respiration and fermentation. When the bacteria use fermentation they release by-products. One of these is a kind of oxygen molecule called superoxide, which can damage DNA and may play a role in the formation of colon tumours.

"We wanted to investigate how colon cells respond to normal gut bacteria that can damage DNA, like E. faecalis," said Professor Mark Huycke from the Department of Veterans Affairs Medical Center in Olklahoma City, USA. "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."

The team found that 42 genes in epithelial cells in the gut are involved in the regulation of the cell cycle, cell death and signalling based on the unique metabolism of E. faecalis. This suggests that cells of the lining of the colon are rapidly affected when E. faecalis switches to fermentation. It also indicates that E. faecalis may have developed novel mechanisms to encourage colon cells to turn cancerous.

Intestinal cancers occur almost exclusively in the colon where billions of bacteria are in contact with the gut surface. For years scientists have tried to identify links between gut bacteria and people who are at risk of colon cancer. This has been made difficult by the enormous complexity of the microbial communities in the intestine.

"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 Professor Huycke. "This research puts n to perspective the complexity of the effects normal gut bacteria can have on the health of an individual."

Source: Society for General Microbiology

Explore further: New family of small RNAs boosts cell proliferation in cancer

Related Stories

Viruses: You've heard the bad—here's the good

Apr 30, 2015

"The word, virus, connotes morbidity and mortality, but that bad reputation is not universally deserved," said Marilyn Roossinck, PhD, Professor of Plant Pathology and Environmental Microbiology and Biology at the Pennsylvania ...

Artificial intestine helps fight bad gut bacteria

Feb 24, 2011

(PhysOrg.com) -- Cornell professor John March is attempting to transform bacteria in our gut into disease-fighting machines. Now, thanks to two members of his research team, he has a powerful new tool to help ...

Baboon friends swap gut germs

Mar 16, 2015

The warm soft folds of the intestines are teeming with thousands of species of bacteria. Collectively known as the gut microbiome, these microbes help break down food, synthesize vitamins, regulate weight ...

Protection of the mouse gut by mucus depends on microbes

Dec 18, 2014

The quality of the colon mucus in mice depends on the composition of gut microbiota, reports a Swedish-Norwegian team of researchers from the University of Gothenburg and the Norwegian University of Life Sciences in Oslo. ...

Recommended for you

Researchers confirm gene p73's role in tumor growth

14 hours ago

A team of researchers at National Cancer Centre Singapore (NCCS) and Singapore General Hospital (SGH) has determined dual functionality gene p73, in both the promotion and suppression in tumour growth. The NCCS team also ...

Researchers define unique group of high-risk lymphoma patients

17 hours ago

The goal for many cancer patients is to reach the five-year, disease-free mark, but new research from UR Medicine's Wilmot Cancer Institute suggests that two years might be a more practical survival goal for people with follicular ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.