Certain gut bacteria can strengthen the immune system and, in experiments, slow the growth of tumors. This is shown by a successfully completed research project.
Certain gut bacteria can strengthen the immune system and, in experiments, slow the growth of tumors. This is shown by a successfully completed research project.
Certain gut bacteria can strengthen the immune system and, in experimental settings, slow tumor growth. This is demonstrated by a recently completed research project led by Prof. Dr. med. Michael Scharl from the Department of Gastroenterology and Hepatology at University Hospital Zurich (USZ).
The gut is a remarkably complex ecosystem composed of bacteria, fungi, and human cells. What particularly fascinates Prof. Scharl is the close connection between the gut and the immune system. “I am fascinated by how this micro-world functions and the crucial role it plays in our health,” says the gastroenterologist.
The goal of the research project was ambitious: to harness gut bacteria in ways that enhance the immune system’s ability to fight cancer cells. Previous studies had already shown that the composition of the gut microbiome can influence the effectiveness of immunotherapies. In earlier work, Scharl’s team identified specific bacteria—particularly members of the Clostridiales order—that activate immune responses and slow tumor growth in experimental models. Evidence from studies on fecal microbiota transfer, which involves transferring healthy gut flora, further supports this link.
Building on these findings, the project investigated whether combining Clostridiales bacteria with bifidobacteria could further enhance their antitumor effects. Bifidobacteria are beneficial gut microbes known to promote intestinal balance and support the growth of other helpful bacteria. “We wanted to see whether this combination would amplify the antitumor activity of Clostridiales,” explains Scharl.
Animal experiments confirmed this hypothesis: in mouse models of colorectal cancer, tumors grew more slowly, and increased numbers of immune cells infiltrated the tumor tissue when bifidobacteria were added.
The team also examined how individual bacterial species and microbial combinations affect immune and tumor cells in laboratory experiments and mouse models. One species in particular, Roseburia intestinalis, showed notable effects by modulating macrophages—immune cells involved in clearing cancer cells—making them more active in targeting tumors.
“Our long-term goal is to use bacteria as a natural complement to cancer therapy,” says Scharl. In the future, such treatments might be administered as capsules or liquid formulations. This research offers new hope for cancer patients and highlights the vast therapeutic potential hidden within the complex world of gut microbes.
Text: Danica Gröhlich, Fotos: Thomas Oehrli (visualcraft.ch)
KFS-5372-08-2021
