The Involvement of Oral Pathogenic Bacteria, Fusobacterium nucleatum Subspecies animalis in the Pathogenesis of Human Esophageal Adenocarcinoma.

BACKGROUND AND AIMS: While esophageal microbiota is known to be altered in patients with esophageal adenocarcinoma (EAC), specific bacterial species contributing to the pathogenesis remain unclear. We aimed to identify bacteria associated with the pathogenesis of EAC and to investigate their potential role. METHODS: Microbiota in EAC tissues was explored by 16S-rRNA sequencing. The impact of intratumoral bacteria on tumor microenvironment was histologically evaluated. The influence by pathological bacteria on cancer cells was examined by the treatment of OE33 cell line with cultural supernatant of bacteria. RESULTS: Oral pathogenic bacteria previously reported to increase in colorectal cancer patients were detected in 7 out of 31 EAC patients and were associated with poor prognosis. Intratumoral bacterial infiltration was significantly accompanied with local neutrophil infiltration and nuclear positivity of NF-κB in cancer cells. Furthermore, the culture supernatant of Fusobacterium nucleatum applied to OE33 cells led to an upregulation of proinflammatory cytokine and chemokine genes that facilitate neutrophil migration. Notably, most of the F. nucleatum subspecies (spp.) present in the EAC tissues were identified as spp. animalis. The culture supernatant of spp. animalis induced significantly more reactive oxygen species-mediated DNA damage in EAC cells than spp. nucleatum, the most representative spp. of F. nucleatum, indicating the significance of spp. animalis rather than spp. nucleatum in the pathogenesis of EAC. CONCLUSION: Intratumoral microbiota, especially the infiltration of oral pathogenic bacteria such as F. nucleatum, has a profound impact on the tumor microenvironment of EAC. Spp. animalis was predominant among F. nucleatum in the EAC tissues and induced significant DNA damage in cancer cells.