March 6 (UPI) -- The list of benefits of "good bacteria" in the digestive tract keeps growing.
A study led by researchers at the University of Texas Southwestern Medical Center and University of Chicago, and published Friday in the Journal of Experimental Medicine, shows that bacteria that live in the gut can accumulate in tumors and improve the effectiveness of drug treatment.
The results, based on experiments in mice, suggest that treating cancer patients with Bifidobacteria -- a type of bacteria that is often found in the gastrointestinal tract of people who are healthy -- might boost their response to CD47 immunotherapy, an anti-cancer treatment that is currently being evaluated in several clinical trials.
"Our results open a new avenue for clinical investigations into the effects of bacteria within tumors and may help explain why some cancer patients fail to respond to immunotherapy," co-author Ralph R. Weichselbaum, co-director of The Ludwig Center for Metastasis Research at the University of Chicago, said in a press release.
CD47 is a protein expressed on the surface of many cancer cells, and inhibiting this protein can allow the immune system to attack and destroy tumors. Antibodies targeting CD47 are currently being tested in clinical trials for a wide variety of cancers.
However, studies with laboratory mice have so far yielded mixed results. Some mice seem to respond to anti-CD47 treatment, while others do not.
In general, Weichselbaum and his colleagues found that mice with tumors that normally respond to anti-CD47 treatment failed to respond if their gut bacteria were killed off by a cocktail of antibiotics. In contrast, anti-CD47 treatment became more effective in mice that are usually non-responsive when these animals were supplemented with Bifidobacteria.
In addition, they noted that Bifidobacteria also migrate into tumors, where they appear to activate an immune signaling pathway called the stimulation of interferon genes pathway. This also bolsters the immune system and, when combined with anti-CD47 treatment, activated immune cells can attack and destroy the surrounding tumor.
Bifidobacteria have previously been shown to benefit patients with ulcerative colitis and other similar conditions.
"Our study demonstrates that a specific member of the gut microbial population enhances the anti-tumor efficacy of anti-CD47 by colonizing the tumor," said Yang-Xin Fu, a professor of immunology and pathology at the University of Texas Southwestern Medical Center. "Administration of specific bacterial species or their engineered progenies may be a novel and effective strategy to modulate various anti-tumor immunotherapies."