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.
Copyright © 2018 Elsevier Inc. All rights reserved.
MeSH terms
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Adenomatous Polyposis Coli Protein / genetics
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Animals
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Bacterial Toxins / immunology*
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Bacterial Toxins / metabolism
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Bacteroides fragilis / immunology*
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Bacteroides fragilis / pathogenicity
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Carcinogenesis / pathology*
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Cell Line, Tumor
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Colon / cytology
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Colon / immunology*
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Colon / microbiology
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Colorectal Neoplasms / etiology*
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Colorectal Neoplasms / microbiology
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Colorectal Neoplasms / pathology
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Enzyme Activation / immunology
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Epithelial Cells / immunology*
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Female
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Gene Deletion
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HT29 Cells
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Humans
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Inflammation / immunology
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Inflammation / microbiology
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Interleukin-17 / genetics
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Interleukin-17 / immunology*
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Male
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Metalloendopeptidases / immunology*
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Metalloendopeptidases / metabolism
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Mice
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Mice, Inbred C57BL
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Mice, Knockout
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Myeloid Cells / immunology
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Receptors, Interleukin-17 / genetics
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Receptors, Interleukin-17 / immunology
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Receptors, Interleukin-8B / genetics
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STAT3 Transcription Factor / metabolism
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Transcription Factor RelA / metabolism*
Substances
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Adenomatous Polyposis Coli Protein
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Bacterial Toxins
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Il17a protein, mouse
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Il17ra protein, mouse
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Interleukin-17
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Receptors, Interleukin-17
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Receptors, Interleukin-8B
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Rela protein, mouse
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STAT3 Transcription Factor
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Stat3 protein, mouse
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Transcription Factor RelA
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Bacteroides fragilis toxin
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Metalloendopeptidases