Gut bacteria found to modulate response to cancer immunotherapy
Previous data have shown that certain species of intestinal bacteria not only help to regulate the immune function of the entire body, but also optimize the therapeutic effect of cancer immunotherapy drugs such as anti-PD-1/PD-L1 and anti-CTLA-4 drugs. The exact mechanism of how this works on the molecular level, however, has remained uncertain.
A recent study published in Science isolated three bacterial species that were shown to significantly enhanced the efficacy of immunotherapy drugs in mouse models of cancer. One intestinal bacterium in particular, Bifidobacterium psudolongum, was found to enhance immunotherapy response through the production of a substance (metabolite) called inosine. Due to decreased functioning of the gut barrier (the property of the intestinal lining to contain bowel contents while preserving the ability to absorb nutrients) during immunotherapy treatment, inosine was found to pass through the intestinal barrier and activate anti-tumour T cells, a specialized type of immune cell. This enabled the body to mount a more effective immune response and enhance the overall effectiveness of the immunotherapy treatment.The study findings identify a novel microbial metabolite – immune pathway that may be used in the future to develop adjuvant therapies that may be given in addition to immunotherapy to maximize effectiveness.
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