Colon cancer: intestinal bacteria promote tumor growth

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MunichResearchers have identified a previously unknown factor for the development of colon cancer: the intestinal flora. The scientists suspect that some bacteria may migrate into the intestinal wall and trigger fatal inflammatory processes there.

Colon cancer is the result of genetic mutations. They cause previously healthy cells to degenerate. At first they form harmless tumors called polyps. Sometimes these later develop into malignant tumors. Although such mutations can occur anywhere in the intestine, some types of colon cancer accumulate in specific passages of the digestive tract. From this it can be concluded that other, non-genetic factors are also involved in the development of the malignant ulcer.

Tumor-free despite bad genes

A New York research team has investigated what role intestinal bacteria could play in the development of colon cancer. They used an experiment with mice that were genetically programmed to develop colon cancer. They administered highly effective antibiotics to the animals that killed the bacteria in the intestines. As a result, the animals did not develop any polyps despite their genetic programming.

Bacteria in the intestinal wall

This indicates that bacteria are necessary for tumors to develop. As expected, polyps grew in some sections of the intestine in animals that were not given antibiotic therapy. The researchers suspect that bacteria migrate from the intestine into the tissue of the intestinal walls and trigger inflammatory reactions there. And that could encourage tumor growth. “Understanding the interplay between genetic mutations, intestinal bacteria and inflammatory processes could lead to new therapies against colon cancer,” says study director Sergio Lira from the Icahn School of Medicine at Mount Sinai in New York.

Lifestyle shapes the intestinal flora

However, further studies are necessary to clarify which intestinal bacteria are risky and how their number in the human intestine can be reduced. "In addition to genetic factors, there are a number of lifestyle factors that influence the risk of colon cancer," explains Lira. These include, for example, obesity and nutritional factors such as the consumption of red meat or high alcohol consumption. Since they can all affect the intestinal flora, this could be a possible mechanism that explains the connection between diet and cancer. (cf)

Source: Bongers, G., et al .: Interplay of host microbiota, genetic perturbations, and inflammation promotes local development of intestinal neoplasms in mice, 2014. J. Exp. Med. doi: 10.1084 / jem.20131587

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