Streptococcus gallolyticus supernatant promotes macrophage M2 polarization and regulates the IL-17 pathway in the oncogenesis of colorectal cancer

Colorectal cancer (CRC) is a highly prevalent malignant tumor worldwide, and emerging evidence suggests that the gut microbiota plays a crucial role in its development. Streptococcus gallolyticus ( Sg ) is a gut commensal bacterium that can also act as an opportunistic pathogen in association with CRC. In this study, it was found that the detection rate of Sg was higher in CRC tissues and the high burden of Sg was correlated with tumor location. Moreover, the researchers demonstrated that Sg supernatant could promote the proliferation of CRC cells, increase tumor burden in AOM/DSS-induced mice, exacerbate inflammatory response, and promote M2 polarization of macrophages. The aforementioned effects may be related to the IL-17 pathway, as revealed by RNA-seq analysis. Overall, these findings suggest a potential role of Sg in the pathogenesis of CRC, and targeting its supernatant may represent a promising approach for the prevention and treatment of CRC.