Bacteroides fragilis Toxin Coordinates a Pro-carcinogenic Inflammatory Cascade via Targeting of Colonic Epithelial Cells

Cell Host Microbe. 2018 Feb 14;23(2):203-214.e5. doi: 10.1016/j.chom.2018.01.007. Epub 2018 Feb 1.

Abstract

Pro-carcinogenic bacteria have the potential to initiate and/or promote colon cancer, in part via immune mechanisms that are incompletely understood. Using ApcMin mice colonized with the human pathobiont enterotoxigenic Bacteroides fragilis (ETBF) as a model of microbe-induced colon tumorigenesis, we show that the Bacteroides fragilis toxin (BFT) triggers a pro-carcinogenic, multi-step inflammatory cascade requiring IL-17R, NF-κB, and Stat3 signaling in colonic epithelial cells (CECs). Although necessary, Stat3 activation in CECs is not sufficient to trigger ETBF colon tumorigenesis. Notably, IL-17-dependent NF-κB activation in CECs induces a proximal to distal mucosal gradient of C-X-C chemokines, including CXCL1, that mediates the recruitment of CXCR2-expressing polymorphonuclear immature myeloid cells with parallel onset of ETBF-mediated distal colon tumorigenesis. Thus, BFT induces a pro-carcinogenic signaling relay from the CEC to a mucosal Th17 response that results in selective NF-κB activation in distal colon CECs, which collectively triggers myeloid-cell-dependent distal colon tumorigenesis.

Keywords: Nf-κB; STAT-3; colorectal cancer; inflammation; mucosal immunology; myeloid cells.

MeSH terms

  • Adenomatous Polyposis Coli Protein / genetics
  • Animals
  • Bacterial Toxins / immunology*
  • Bacterial Toxins / metabolism
  • Bacteroides fragilis / immunology*
  • Bacteroides fragilis / pathogenicity
  • Carcinogenesis / pathology*
  • Cell Line, Tumor
  • Colon / cytology
  • Colon / immunology*
  • Colon / microbiology
  • Colorectal Neoplasms / etiology*
  • Colorectal Neoplasms / microbiology
  • Colorectal Neoplasms / pathology
  • Enzyme Activation / immunology
  • Epithelial Cells / immunology*
  • Female
  • Gene Deletion
  • HT29 Cells
  • Humans
  • Inflammation / immunology
  • Inflammation / microbiology
  • Interleukin-17 / genetics
  • Interleukin-17 / immunology*
  • Male
  • Metalloendopeptidases / immunology*
  • Metalloendopeptidases / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Myeloid Cells / immunology
  • Receptors, Interleukin-17 / genetics
  • Receptors, Interleukin-17 / immunology
  • Receptors, Interleukin-8B / genetics
  • STAT3 Transcription Factor / metabolism
  • Transcription Factor RelA / metabolism*

Substances

  • Adenomatous Polyposis Coli Protein
  • Bacterial Toxins
  • Il17a protein, mouse
  • Il17ra protein, mouse
  • Interleukin-17
  • Receptors, Interleukin-17
  • Receptors, Interleukin-8B
  • Rela protein, mouse
  • STAT3 Transcription Factor
  • Stat3 protein, mouse
  • Transcription Factor RelA
  • Bacteroides fragilis toxin
  • Metalloendopeptidases