Fusobacterium nucleatum interacts with cancer-associated fibroblasts to promote colorectal cancer.

Gut microbial species contribute to colorectal cancer (CRC) by interacting with tumor or immune cells, however if CRC-associated bacteria engage with stromal components of the tumor microenvironment remains unclear. Here, we report interaction between the CRC-associated bacterium Fusobacterium nucleatum and cancer-associated fibroblasts (CAFs), and show that F. nucleatum is present in the stromal compartment in murine CRC models in vivo and can attach to and invade CAFs. F. nucleatum-exposed CAFs exhibit a pronounced inflammatory-CAF (iCAF) phenotype, marked by elevated expression of established iCAF markers, secretion of pro-inflammatory cytokines such as CXCL1, IL-6 and IL-8, generation of reactive oxygen species (ROS), and an increased metabolic activity. In co-culture experiments, the interaction of cancer cells with F. nucleatum-stimulated CAFs enhances invasion, a finding further validated in vivo. Altogether, our results point to a role for the tumor microbiome in CRC progression by remodeling the tumor microenvironment through its influence on cancer-associated fibroblasts, suggesting novel therapeutic strategies for targeting CRC.