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Single cell changes in AAV-Ctrl or AAV-RSPO1-Fc treated intestinal adenoma cells from ApcMin/+ mice

ABSTRACT: We constructed AAV-vectors for systemic expression of a soluble RSPO1 protein in ApcMin/+ mice. We found that the RSPO1-Fc fusion protein suppresses the Wnt/ß-catenin signaling activity in intestinal adenomas and in adenoma-derived intestinal organoids ex vivo, but not in normal intestinal epithelial cells. In the Apc mutant cells, the RSPO1-Fc fusion protein activated the TGFß/SMAD signaling pathway to suppress several Wnt target genes and adenoma growth, which effect was rescued suppressed by the TGFß receptor kinase inhibitor SB-431542. Simultaneously, RSPO1-Fc induced proliferation of the normal intestinal stem cells, giving them a growth advantage over the mutant cells, which enabled the intestinal epithelium to eventually outgrow the adenoma cells. Prolonged systemic expression of AAV-RSPO1-Fc decreased significantly the number of the intestinal adenomas and improved the overall survival of ApcMin/+ mice. Thus RSPO1-Fc provides the normal intestinal epithelial cells a growth advantage when compared to the adenoma cells, which eventually leads to the extrusion of the adenomatous tissue. An attractive idea now is to exploit such differential response of normal vs. cancer cells in cancer therapy.

ORGANISM(S): Mus musculus

PROVIDER: GSE146138 | GEO | 2020/03/01

REPOSITORIES: GEO

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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.

Project description:Mouse models of intestinal crypt cell differentiation and tumorigenesis have been used to characterize the molecular mechanisms underlying both processes. DNA methylation is a key epigenetic mark and plays an important role in cell identity and differentiation programs and cancer. To get insights into the dynamics of cell differentiation and malignant transformation we have compared the DNA methylation profiles along the mouse small intestine crypt and early stages of carcinogenesis. Genome-scale analysis of DNA methylation together with microarray gene expression have been applied to compare intestinal crypt stem cells (EphB2positive), differentiated cells (EphB2negative), ApcMin/+ adenomas and the corresponding non-tumor adjacent tissue, together with small and large intestine samples and the colon cancer cell line CT26. Compared with late stages, small intestine crypt differentiation and early stages of carcinogenesis display few and relatively small changes in DNA methylation. Hypermethylated loci are largely shared by the two processes and affect the proximities of promoter and enhancer regions, with enrichment in genes regulated by PRC2 and associated with the intestinal stem cell signature. The hypermethylation is progressive, with minute levels in differentiated cells, as compared with intestinal stem cells, and reaching full methylation in advanced stages. Hypomethylation shows different signatures in differentiation and cancer and is already present in the non-tumor tissue adjacent to the adenomas in ApcMin/+mice, but at lower levels than advanced cancers. Taking into account the parallelisms between human and mouse intestinal carcinogenesis, this study provides a reference framework to interpret the alterations found in human cancer. We have analyzed ApcMin/+ adenomas and the corresponding non-tumor adjacent tissue, together with small and large intestine samples and the colon cancer cell line CT26. Samples were in triplicates, except for tissue adjacent to adenoma (in duplicates).

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Single cell changes in AAV-Ctrl or AAV-RSPO1-Fc treated intestinal adenoma cells from ApcMin/+ mice

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