American scientists from the University of Texas Southwest Medical Center and the University of Chicago found in recent studies in animal experiments with mice that intestinal bacteria of certain species can positively influence the response to cancer immunotherapy and that this fact could save the lives of people who have cancer. The exact mechanisms still need to be clarified in detail. However, it is already clear that certain intestinal bacteria from the microbiome of mice or even humans can penetrate tumour cells and increase the effectiveness of immunotherapy, such as the intestinal microbe of the bifidobacterium type. Immunotherapy targets a very specific protein, the CD47 protein. The researchers have also found that non-responsive anti-CD47 tumours became responsive when cancer immunotherapy treatment was combined with bifidobacteria, because healthy intestinal bacteria of this type can not only positively influence the response to cancer immunotherapy, but can also generally ward off pathogens in the intestine. The exact mechanism of certain cancer therapies in interaction with the intestinal bacteria is also already known. The combination of antibodies from immunotherapy against the protein and the intestinal bacteria in conjunction with innate immunity is crucial. When the innate so-called STING immune signalling pathway is activated by the immigration of the bacteria into tumour cells, the production of immune signal molecules such as type 1 interferons is stimulated, which then activate immune cells that attack the tumour. The tumour is then destroyed. Only mice that can activate interferons also respond to the combined bacterial immunotherapy approach. Mice that did not have these intestinal bacteria did not show any reaction, but in animal experiments, the exchange of intestinal bacteria by oral or contact transmission – which is not yet clear – was successful if both groups of mice, those with intestinal bacteria and those without, were placed in the same cage. Antibiotics also prevent response to anti-CD47 therapy because these drugs kill healthy intestinal bacteria. Therefore antibiotics are contraindicated in cancer immunotherapy. However, the researchers recommend taking a probiotic because the analysis results suggest that this would improve anti-CD47 therapy.
