Intestinal bacteria could support cancer therapy

Disruption of the intestinal flora may influence the effects of chemotherapy

27/11/2013

Intestinal bacteria may be helpful in the treatment of cancer. To this result, now American researchers have come in scientific experiments with mice. Thus, a disturbance of the intestinal flora - for example, by an antibiotic treatment - cause a chemotherapy loses its anti-tumor effect.

Intestinal flora plays a central role in the formation of the immune system
The gut of a healthy person is colonized by trillions of bacteria called as „natural intestinal flora“ be designated. This is not only involved in digestion and vitamin metabolism, but also plays a central role in the formation of the immune system in the intestine. But the intestinal flora can evidently do more, as a research team led by Giorgio Trinchieri and Romina Goldszmid from the laboratory of the „US National Cancer Institute“ In Frederick, Maryland, the bacteria may also help fight cancer.

„CpG oligonucleotides“ to support defense against cancer
Like the scientists in the trade magazine „Science“ In two studies with mice, they had an immunotherapy with so-called „CpG oligonucleotides“ tested, which are single-stranded synthetic DNA sections, by their relatively high proportion of „CpG motifs“ (CpG = cytosine-phosphate-guanine) to support the defense against cancer. This was also the case in the experiments - but only in the animals whose intestinal flora was healthy.

In tests with germ-free mice no positive effect
In the mice, however, were grown germ-free and therefore had no intact intestinal flora, showed in the tests no positive effect on the cancer defense. Even in the case of a previous antibiotic treatment, the attempt failed because it was the formation of endogenous signaling substances (cytokine) was blocked, which should activate the immune system and strengthen certain cancers. As a result, the mice's immune system was not strong enough to stop further growth of the tumors.

Many cancer patients receive antibiotic protection against infection
In further experiments, the researchers came to the conclusion that the effect of so-called „cytostatics“ is closely related to the intestinal flora. These are substances that prevent cell growth or cell division and are therefore used in particular in chemotherapy for the treatment of cancer. So it turned out that chemotherapy with the cytostatic „oxaliplatin“ had no positive effect, provided the intestine of the animals previously by antibiotic of microorganisms „cleaned“ - which is done in many cancer patients to protect against infections.

Disorders of the intestinal flora influence the reaction of the tumors
„We were able to show that disorders of the intestinal flora impair the response of the subcutaneous tumors to CpG oligonucleotide immunotherapy and platinum-based chemotherapy. In mice treated with antibiotics or germ-free, the tumor infiltrating cells responded inadequately to therapy resulting in lower cytokine production and less tumor killing following CpG oligonucleotide treatment and deficient production of reactive oxygen radicals and cytotoxicity following chemotherapy“, so the researchers in the abstract to their study.

French scientists come to similar conclusions
French scientists around Laurence Zitvogel from the Gustave Roussy Institute in Paris also came to similar conclusions. These had also dealt with in the context of animal experiments, first with inflammation of the mucous membrane of the gastrointestinal tract and the mouth or throat (mucosa), which is a common side effect of radiation with the cytostatic „cyclophosphamide“ occurs. As part of their investigation, the scientists discovered that the mucosal inflammation causes a disruption of the intestinal barrier, which causes individual bacteria to enter the bloodstream. If these then reach the lymph nodes, the immune defense is activated, which means that the bacteria - but also existing tumors - are combated. But even here it turned out that this effect could only be achieved if the intestinal flora of the animals had not been weakened by previous antibiotic therapy.

However, transferability to humans is still unclear
Whether or to what extent the results of the US and French researchers can be transferred to humans remains to be determined. But as opposed to cancer experts „Science“ emphasized that antibiotic treatment in cancer patients could negatively affect the effects of chemotherapy. Accordingly, further investigations should now follow. (No)