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Deletion of TNF in Winnie-ApcMin/+ mice reveals its protective role in the progression of colorectal cancer

ABSTRACT: To examine the effects of chronic, low-grade inflammation on the pathogenesis of colorectal cancer (CRC), we developed a novel murine model of colitis-associated cancer by crossing Winnie mice with ApcMin/+ mice thus combining the inflammatory background with a genetic predisposition to develop small intestinal polyposis, respectively. Winnie-ApcMin/+ mice showed early, spontaneous occurrence of colonic dysplastic lesions with a distinct molecular signature. Since TNF is a major clinical target for suppression of chronic intestinal inflammation, we investigated its impact on Winnie-ApcMin/+ model. Surprisingly, deletion of Tnf in Winnie-ApcMin/+ mice resulted in an initial reduction of dysplastic lesions at disease onset, but facilitated disease progression with a unique molecular footprint. Our results confirm that even a mild, but chronic, inflammation represents a crucial risk factor in individuals genetically-predisposed to CRC, and support a dual role for TNF in the onset vs. progression towards CRC.

ORGANISM(S): Mus musculus

PROVIDER: GSE138722 | GEO | 2021/12/31

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:Aberrant DNA methylation is frequently observed in colorectal cancer (CRC), but the underlying mechanisms and pathological consequences are poorly understood. Ten-Eleven Translocation (TET) dioxygenases and Thymine DNA Glycosylase (TDG) are involved in active DNA demethylation by generating and removing novel oxidized cytosine species. TET1 and TDG mutations, and alterations of the levels of oxidized cytosines have been identified in human CRC. To clarify the biological significance of the TET-TDG demethylation axis in intestinal tumorigenesis, we generated ApcMin mice that are devoid of Tet1 and/or Tdg, and characterized the methylome and transcriptome of intestinal adenomas by DREAM and RNA sequencing, respectively. Tet1-deficient and Tet1/Tdg-double heterozygous ApcMin adenomas manifested increased adenoma size and features of erosion or invasion, whereas an increased number (>30) of adenomas was found in Tdg-mutant ApcMin mice. Methylome analysis revealed progressive loss of global DNA hypomethylation in colonic adenomas from Tet1- and Tdg-deficient ApcMin mice, and hypermethylation of CpG islands in Tet1-deficient ApcMin mice. In addition, RNA sequencing showed upregulation of genes in inflammatory, immune and interferon response in Tet1- and Tdg-mutant colonic adenomas compared to control ApcMin adenomas. The corresponding 135-gene inflammatory signature separated human colonic adenocarcinomas into four groups, closely aligned with their microsatellite or chromosomal instability profile, and characterized by different levels of DNA methylation and DNMT1 expression levels that anti-correlated with TET1 expression levels. These findings demonstrate a novel mechanism of epigenetic regulation during intestinal tumorigenesis by which TET1-TDG-mediated active DNA demethylation decreases not only methylation levels, but also inflammatory/interferon/immune response, which impinges on the intrinsic features of genomic instability of the tumors. This study establishes a novel link, via inflammatory response, between epigenomic and genomic instability.

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Deletion of TNF in Winnie-ApcMin/+ mice reveals its protective role in the progression of colorectal cancer

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