Adjunctive probiotic Lactobacillus rhamnosus Probio-M9 enhances the effect of anti-PD-1 antitumor therapy via regulating the gut microbiota damaged by antibiotics

To evaluate the role of probiotics in restoring the antibiotic-destroyed gut microbiota and efficacy of ICB therapies, we studied the effect of Lactobacillus rhamnosus Probio-M9 combined with anti-PD-1 on mouse colon cancer and the dynamic changes of gut microbiome by metagenome analyses. The results showed that the combination of Probio-M9 significantly improved tumor inhibition compared with ICB therapy alone in antibiotics treated mice, which could be attribute to the upregulated microbial diversity and increased abundance of beneficial bacteria such as Bifidobacterium pseudolongum, Parabacteroides distasonis and some species of Bacteroides after Probio-M9 supplemented. These changes of structure and composition in gut microbiota caused the alternation of microbiome function, of which the sugar degradation, vitamin and amino acid synthesis pathways were significantly enriched. Collectively, this study indicated that Probio-M9 enhanced the host's immunotherapeutic response by promoting the colonization of beneficial bacteria and improving intestinal function.