Commensal Clostridiales strains mediate effective anti-cancer immune response against solid tumors

Despite overall success, the efficacy of T-cell checkpoint inhibitors is still limited to a minority of cancer patients. Recently, intestinal microbiota was found to critically modulate anti-cancer immunity and therapy response. Here, we identified certain members of the gut microbiota associated with a lower tumor burden in mouse models of colorectal cancer (CRC). Orally applied, a mix of four Clostridiales strains (CC4) prevented and even successfully treated CRC as stand-alone therapy. Interestingly, these commensal Clostridiales species were significantly reduced in colorectal cancer (CRC) patients compared to healthy controls. Our findings provide a strong preclinical foundation for exploring gut bacteria as novel stand-alone therapy against solid tumors.