Scientists identify bacteria that causes colon cancer

September 22nd, 2008 - 2:40 pm ICT by IANS  

Washington, Sep 22 (IANS) Scientists have identified a molecule produced by common gut bacterium that activates signalling pathways lined with colon cancer cells.”We wanted to investigate how colon cells respond to normal gut bacteria that can damage DNA, like E. faecalis,” said Mark Huycke of the Department of Veterans Affairs Medical Centre in Oklahoma.

“We found that superoxide from E. faecalis led to strong signalling in immune cells called macrophages (a type of white blood cell that ingests foreign material). 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.”

E faecalis is a normal gut bacterium. Unlike most gut bacteria, it can survive using two different types of metabolism: respiration and fermentation, reports Eurekalert.

When the bacteria use fermentation (without use of oxygen) they release by-products, one them being an oxygen molecule called superoxide, which can damage DNA and may play a role in the formation of colon tumours.

The team found that 42 genes in epithelial cells lining the gut are involved in the regulation of cell cycle, cell death and signalling based on the unique metabolism of E. faecalis.

This suggests that cells of the lining of 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 Huycke.

These findings are scheduled for publication in the October issue of the Journal of Medical Microbiology.

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