Single‐Cell <scp>RNA</scp> ‐Seq Reveals the Effect of Commensal Bacteria on the Multistep Development of Esophageal Cancer

Microbiomes within the tumor microenvironment (TME) are intricately linked to the modulation of cancer cell properties and the prognoses of various types of cancer, including esophageal squamous cell carcinoma (ESCC). However, their contribution to the onset and advancement of ESCC is still not fully elucidated. We adopted single-cell RNA sequencing to investigate the effects of esophageal commensal bacteria during the development of mice's spontaneous ESCCs. By analyzing the single-cell transcriptomes of 54,562 cells across different ESCC pathological stages, commensal bacteria were observed to display a cellular heterogeneous distribution in the ESCC TME. These bacteria were associated with the malignant transformation of epithelial cells and the formation of inflammatory fibroblasts, contributing to a chronic inflammatory microenvironment. However, after depriving commensal bacteria with an antibiotic cocktail (ABX), infiltrations of inflammatory fibroblasts and anti-bacteria macrophages were lower than those in the control H₂O group, while the infiltration of regulatory Cd4⁺ T (Treg) cells was higher. Interactions between inflammatory fibroblasts and Treg cells were intensified in the ABX group, which exacerbated the immunosuppressive state in the TME and developed more invasive carcinomas. This study demonstrates the significant role of commensal bacteria in ESCC tumorigenesis and sheds light on the potential clinical applications of adjusting commensal bacteria for the prevention and treatment of ESCC.