Salmonella promote T cell-mediated anti-tumor immuno-therapy

B16 melanoma is widely used as an animal model to investigate the efficacy, mechanism and immune response of anti-tumor immuno-therapy. In this study, the anti-tumor efficacy was examined by using a Salmonella strain 7207, which cannot survive in the circulation system and aerobic tissues, but can thrived in the anaerobic environment of solid tumors. We found that Salmonella injection could significantly inhibited tumor growth in B16 tumor-bearing mice. Interestingly, injection of heat-killed Salmonella also showed comparable anti-tumor efficacy as alive Salmonella , with no bacteria detectable in the tumor and circulation system. In addition, both alive and heat-killed Salmonella could promote robust pro-inflammatory gene induction in bone marrow-derived macrophages and dendritic cells, and increased tumor-infiltrating IFN-g-producing cytotoxic T cells (CTL). Moreover, deletion of T cells abolished the anti-tumor effect by injecting of alive or heat-killed Salmonella in Rag1-deficient tumor-bearing mice, suggesting Salmonella -mediated anti-tumor effect is due to the cytotoxic function of CTL. Taken together, our study provides a new insight of the development of anti-tumor immuno-therapy, and a potential therapeutic strategy for B16 melanoma.