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Inactivation of Irf1 causes susceptibility to colitis-associated colorectal cancer

ABSTRACT: The incidence of colorectal cancer (CRC) is increased in patients afflicted by inflammatory bowel diseases (IBD) The cellular and molecular mechanisms that link chronic inflammation of the gut and increased CRC susceptibility are poorly understood. Risk of IBD is strongly influenced by genetic factors, including the IBD5 locus (5q31), harboring the IRF1 gene. A cause to effect relationship between chronic inflammation and CRC, and a possible role of IRF1 were studied in Irf1-/- mutant mice in a model of colitis associated CRC (CA-CRC) induced by azoxymethane and the irritant dextran sulfate. Loss of Irf1 causes hyper-susceptibility to CA-CRC, with early onset and increased number of tumors leading to rapid lethality. Transcript profiling (RNA-seq) and immunostaining of colons shows heightened inflammation, enhanced crypt cells proliferation and reduced tissue repair in Irf1-/- mutants, and this prior to appearance of tumors. A considerable infiltration of leukocytes is seen at this early stage in Irf1-/- colons, this infiltrate being composed primarily of proinflammatory Gr1+ Cd11b+ myeloid cells, mast cells, and CD3+ lymphoid cells. Studies in bone marrow chimeras show that differential susceptibility to CA-CRC of Irf1-/- vs. B6 controls is fully transferable by hematopoietic cells. Studies in human datasets confirm that transcripts signatures seen in Irf1-/- mice in response to AOM/DSS are enriched in clinical specimens from patients with IBD and with CRC. In addition, IRF1 expression in the colon is significantly decreased in late stage CRC (stages 3, 4) associated with poorer prognosis. These studies suggest that partial or complete loss of IRF1 expression alters the type, number, and function of immune cells in situ in gut establishing microbial-driven chronic inflammation and possibly creating a tumor promoting environment.

ORGANISM(S): Mus musculus

PROVIDER: GSE116374 | GEO | 2019/10/31

REPOSITORIES: GEO

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Project description:Inflammatory bowel diseases (IBD) in humans are characterized by chronic inflammation and gastrointestinal tissue damage, caused by a combination of genetic and environmental factors. It has been largely documented that IBD frequently lead to colorectal cancers (CRC). The identification of causative factors of IBD is thus essential to understand CRC progression and develop therapeutical approaches. Models have been described in which molecular alterations are combined with inflammatory treatments in order to recapitulate IBD-associated CRC. Here, we describe a mouse line, Î±6fl/fl Villin-Cre, in which inactivation of the gene encoding the integrin alpha-6 subunit (ITGA6) specifically in the intestinal mucosa results into chronic inflammation and intestinal carcinogenesis. In these mice, the loss of integrin alpha-6 beta-4, a receptor mediating the attachment of epithelial cells to laminins, leads to epithelial detachment, hyperplasia, chronic inflammation, rectal prolapses, and ultimately adenocarcinomas. Alterations of differentiation affecting mucus secreting (goblet) cells as well as changes in expression of essential intestinal transcription factors were detected. Thus alpha-6 beta-4 integrin is a key factor for the maintenance of intestinal integrity and its loss may represent a risk factor for tumor progression associated with IBD. Transcriptome analysis of RNA from normal versus inflamed and carcinomatous rectal mucosa of Î±6 integrin deficient intestinal epithelium mice was performed. RNAs were prepared from 5 adenocarcinomas, which were macrodissected from the rectal prolapses and 4 flanking inflamed rectal mucosa of 53-80 week-old Î±6fl/fl Villin-Cre mice. RNAs from normal rectal mucosa were obtained by rectum scraping from 4 matched control animals. The transcriptome analysis was performed using the Affymetrix Mouse Gene 1.0 ST arrays. Images were processed using affymetrix GeneChipÂ® Command ConsoleÂ® Software (AGCC) (version 2.0) and numerical value were generated using Affymetrix Expression Consoleâ¢ Software (version 1.1).

Project description:PURPOSE: The goal of this study was to determine the gene expression networks regulated by tumor necrosis factor receptor 2 (TNFR2, or Tnfrsf1b) and to evaluate their potential bearing on immune cell subsets and inflammatory bowel disease (IBD). METHODS: mRNA-seq was performed on isolated distal colons from TNFR2-knockout and wildtype mice. Differentially expressed transcripts were compared to human ulcerative colitis microarray datasets on Gene Expression Omnibus and to mouse immunological expression datasets at the Immunological Genome Project. RESULTS: We identified 252 mouse transcripts whose expressions were significantly altered by the loss of TNFR2. The majority of these transcripts (228 of 252, ~90%) were downregulated in TNFR2-/- colons. TNFR2-regulated genes were able to positively discriminate between ulcerative colitis patients and healthy individuals with ~80% accuracy. Many TNFR2-regulated genes were also highly expressed in CD8+ T cells. CONCLUSIONS: Downregulation of TNFR2 is associated with a gene expression profile that is prominent in IBD and supportive of the role of CD8+ T cells in IBD pathogenesis. MANUSCRIPT ABSTRACT: Increased tumor necrosis factor (TNF) production has been associated with inflammatory bowel disease (IBD), and anti-TNF therapy is a common therapeutic for this patient population. However, the role of TNF or its receptors (TNFR1 and TNFR2) in the immunopathogenesis of inflammatory bowel disease (IBD) remains unclear. Here we report that TNFR2 is protective in spontaneous (IL-10 knockout) and chemically (azoxymethane/dextran sodium sulfate)-induced mouse models of colitis and colitis-associated cancer. Mechanistically, TNFR2-deficiency in hematopoietic cells significantly increased incidence and severity of colitis and colitis-associated cancer characterized by a selective expansion of CD8+ T cells. We identified TNFR2-regulated genes in the colon that were specific for CD8+ T cells, interacted with multiple IBD risk genes, and are important regulators of CD8+ T cell biology. TNFR2 regulated CD8+ T-cell-specific genes that act as genetic susceptibility modifiers for IBD to mitigate the development of a pro-colitogenic milieu. Antibody-mediated depletion of CD8+ T cells prevented colonic inflammation and significantly reduced pathology in IL10-/-/TNFR2-/- deficient mice. Furthermore, adoptive transfer of TNFR2-/- naïve CD8+ T cells resulted in more severe disease than with wildtype naïve CD8+ T cells. Our findings provide insight into the disease modifier role of TNFR2 in the immunopathogenesis of IBD through the modulation of CD8+ T cell responses and support future investigation of this therapeutic target, especially in the subset of IBD patients with CD8+ T-cell dysfunction. Total RNA from distal colons of 8 week-old male wildtype C57Bl/6 and TNFR2-/- mice (n=3 each) was isolated using the PureLink RNA kit (Ambion, Life Technologies). RNA samples were submitted to the Genomic Services Lab at the HudsonAlpha Institute for Biotechnology (Huntsville, AL) for multiplex library preparation, mRNA enrichment, and sequencing. Sequencing was performed to an average depth of 50M paired-end 50bp reads per sample (HiSeq, Illumina, San Diego, CA). Data files containing raw reads were aligned to the mouse genome using Tophat2/Bowtie2. Alignments were assembled into transcript representations with Cufflinks, and statistical tests for differential expression were performed with Cuffdiff 2. An adjusted P value < 0.05 (q<0.05) from the Cuffdiff 2 output was used as the cutoff for statistical significance.

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Inactivation of Irf1 causes susceptibility to colitis-associated colorectal cancer

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