Modulation of the Gut Microbiota Alters the Tumor-Suppressive Efficacy of Tim-3 Pathway Blockade in a Bacterial Species- and Host Factor-Dependent Manner
Abstract Background T cell immunoglobulin and mucin domain-containing protein-3 (Tim-3) is an immune checkpoint molecule and a potential target for anti-cancer therapy. Alterations in the tumor-suppressive efficacy of immunotherapy due to gut microbiota disturbance have been reported; however, the influence of gut microbiota on the efficacy of Tim-3 blockade is yet to be investigated. In this study, we examined whether gut microbiota manipulation altered the anti-tumor efficacy of Tim-3 blockade. The gut microbiota was manipulated by the administration of antibiotics and oral gavage of bacteria to mice. Results Alterations in the gut microbiome were analyzed by 16S rRNA gene sequencing. Gut dysbiosis triggered by antibiotics attenuated the anti-tumor efficacy of Tim-3 blockade in both C57BL/6 and BALB/c mouse strains. Anti-tumor efficacy was restored via gut microbiota manipulation through oral gavage of fecal bacteria even as antibiotic administration continued. In the case of oral gavage of Enterococcus hirae or Lactobacillus johnsonii, the transferred bacterial species and host mouse strain were critical in determining the anti-tumor efficacy of Tim-3 blockade. Furthermore, oral bacterial gavage did not increase alpha diversity of the gut microbiota in antibiotics-treated mice but did alter microbiome composition, which was associated with restoration of anti-tumor efficacy of Tim-3 blockade. Conclusions Our results highlight the importance of the gut microbiota in anti-cancer immunotherapy responsiveness and indicate that gut microbiota modulation may increase the efficacy of immunotherapy when concomitantly administered with antibiotics. The administered bacterial species and host factors should be considered so as to benefit from gut microbiota modulation.