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Stress in the gut microbiota promotes tumor growth
Cell stress in combination with changes in the intestinal flora drives tumor growth in the large intestine. A German research team comes to this unexpected result when examining intestinal bacteria. This finding is completely new. So far, scientists have assumed that intestinal bacteria in combination with cell stress are only involved in the development of inflammatory bowel diseases.
The microbiota in the intestine (intestinal flora) is involved in tumor growth in the large intestine. The team led by Professor Dirk Haller at the Technical University of Munich (TUM) comes to this astonishing conclusion in a study on intestinal bacteria. The results were recently published in the journal "Gastroenterology".
New triggering factors identified from colon cancer
The team actually wanted to learn more about the development of intestinal inflammation. "With our study, we originally wanted to clarify what contribution bacteria in the intestine have to the development of intestinal inflammation," reports Professor Haller from the Chair of Nutrition and Immunology at the Weihenstephan Science Center at TUM. Then the researchers came across an unexpected result.
Cell stress and an altered intestinal flora drive tumor growth
"In combination with an altered microbiota in the large intestine, cell stress drives tumor growth," the TUM experts explain in a press release on the study results. These are previously unknown factors in the development of colon cancer.
Tumor growth without inflammatory reactions
"However, the surprising result for us was that changes in the microbial ecosystem (microbiota) together with stress in the intestinal cells lead to the development of tumors," says Professor Haller. The researchers were only able to observe this phenomenon in the large intestine - without any inflammatory reactions.
How does cell stress develop in the intestine?
As the TUM experts report, a certain protein (transcription factor ATF6) regulates and activates the stress in the cells. In the case of diseases, both the duration and the intensity of this stress activation are increased. "However, it is not cell stress alone that leads to tumor growth, but the cooperation between stress and microbiota that favors cancer growth," emphasizes Haller.
Course of the study
The researchers gained their insights on the mouse model. Mice that live under sterile, i.e. germ-free, conditions have no intestinal flora. In the first step, the researchers activated the transcription factor ATF6, which caused stress activation in the intestinal mucosa (intestinal epithelium). The team was unable to find any defective changes. It was only when they returned the intestinal flora to the animals that the rodent developed cancer in the colon.
The Koch postulates provided the evidence
Using the Henle-Koch postulates, the researchers were able to prove that microorganisms in the intestine are involved in the development of colon cancer. The postulates are a recognized method of checking whether certain microorganisms can be correctly referred to as pathogens.
In collaboration with the Klinikum rechts der Isar, the team checked the results based on data from 541 colon cancer patients. The scientists found that patients with a significantly higher proportion of the protein transcription factor ATF6 also had a significantly higher relapse rate.
A new marker for colon cancer?
"In certain patients, the ATF6 protein could serve as a diagnostic marker for an increased risk of colon cancer," summarizes Professor Haller. Thereby, therapy could be started early. Microbial therapy is also conceivable. However, one must first find out more about the composition of the bacteria. However, one thing was made clear by the study: "Chronic inflammation has no influence on the development of cancer in the large intestine," said the TUM experts.
Healthy intestinal flora is so important
The study underlines the importance of healthy intestinal flora for our health. It provides good protection against illnesses and health problems. If the delicate balance is disturbed, for example by drugs such as antibiotics, an intestinal cleansing can help to build up the intestinal flora. (vb)