Investigating the Role of Intra-tumoral Streptococcus mitis in Gastric Cancer Progression: Insights into Tumor Microenvironment

Evidence increasingly implicates the intra tumoral microbiota in cancer, but the role of the microbiota in cancer progression is less understood. Here, using 16S rRNA sequencing, we identified a notable enrichment of tumor resident Streptococcus mitis in patients with gastric cancer. Based on the results of in vivo experiments, tumor tissue proteomics and serum cytokines analysis, we found that intra tumoral Streptococcus mitis can promote gastric cancer progression via inducing tumor immunosuppression. This might be mediated by its involvement in macrophage efferocytosis induction, leading to M2 polarization and changes in inflammatory cytokines expression, such as IL8. In summary, our results suggest that the intra tumoral microbiota, exemplified by Streptococcus mites, may promote the progression of gastric cancer, thereby emerging as potential therapeutic targets for this disease.