Emergence of invasive Escherichia coli pathobionts in gut microbiome promotes cancer stemness via targeting Hippo pathways.

Growing evidence suggests a pivotal role of the microbiome in tumorigenesis, extending beyond genetics. Apc(Min/+) mice exhibit reduced tumor load when housed in germ-free conditions. Nevertheless, how genetic factors shape microbiota and how dysbiosis fits into the genetic paradigm of intestinal carcinogenesis remain elusive. Epithelial stemness is regulated by Wnt/Apc/β-catenin pathway, whereas Apc mutations and Hippo signaling are associated with tumor growth. Invasive pathobionts emerge from microbiota as a result of epithelial barrier dysfunction. We hypothesize that the emergence of invasive pathobionts and dysbiosis of epithelial microbiota contribute to increased cancer stemness. The epithelial and fecal microbiota are longitudinally monitored in Apc(Min/+) and wild-type littermates born to wild-type surrogate dams. Segregation of epithelial microbiota between Apc(Min/+) and wild-type mice was observed as early as eight weeks after birth, whereas fecal microbiota diverged at 20 weeks of age. Epithelial dysbiosis and barrier defects were observed in Apc(Min/+) mice, characterized by intraepithelial Escherichia coli with invasive features. While antibiotic treatment reduced cancer burden, invasive E. coli infection promoted tumorsphere formation. Higher expression of Vgll3 and Tead4 (Hippo effectors) and Cd44 (a cancer stemness marker) was observed in bacteria-infected tumorspheres. Mechanistically, bacteria augmented epithelial clonogenicity by enhancing VGLL3/TEAD4-mediated CD44 promoter activity. Invasive E. coli genetic signatures were verified in 86% of human colorectal carcinoma specimens, and a positive correlation with TEAD4 expression was observed. In conclusion, Apc mutation drives the expansion of invasive pathobionts to promote cancer stemness via a VGLL3/TEAD4/CD44 axis. Bacteria-targeting interventions could be an alternative strategy for patients with hereditary tumors.