The mechanism how a common gut bacterium causes colon cancer has been uncovered by US scientists.
The researchers have found that a molecule produced by common gut bacteria Enterococcus faecalis activates signalling pathways associated with cancer cells.
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.
The researchers say that their findings suggest 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, they add.
"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.
The study is published in the October issue of the Journal of Medical Microbiology.