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Active BRAF-V600E is the key player in generation of a sessile serrated polyp-specific DNA methylation profile (Exome-seq data set)

ABSTRACT: Screening and surveillance of colorectal cancers (CRCs) using advanced colonoscopy technologies have significantly reduced the incidence and mortality rates of CRCs in recent years. However, a significant portion of CRCs are still remained undiagnosed, especially those involving sessile serrated adenomas/polyps (SSA/P), most likely due to their flat shape and the excessive amounts of secreted mucin that cover the polyps, making them invisible for colonoscopy. Here, a potential alternative solution is the application of molecular markers enabling unambiguous characterization of SSPs. However, full implementation of this strategy requires availability of robust markers which are still lacking. In this work by comprehensive molecular analysis of several malignant and normal samples at the genome, methylome and transcriptome levels we show that activating mutation of BRAF-V600E drives the generation of a unique SSP-specific DNA methylation profile. As the result a robust set of DNA methylation markers showing significant (~3 to 30 fold) increase in their methylation levels, exclusively in SSP samples, are introduced. These markers can be of important clinical relevance, especially in early diagnosis of SSPs using non-invasive approaches such as fecal DNA testing.

ORGANISM(S): Homo sapiens

PROVIDER: GSE110535 | GEO | 2018/04/09

REPOSITORIES: GEO

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Project description:Colorectal cancer often arises from adenomatous polyps. Polyps can grow and progress to cancer, but may also remain static in size, regress, or resolve. Prediciting which progress to cancer and which remain benign is difficult. We developed a long-lived murine model of colorectal cancer with tumors that can be followed by colonoscopy. Our aim was to assess whether these tumors have similar growth patterns and histologic fates to human colorectal polyps to identify features to aid in risk stratification of colonic tumors. Long-lived Apcin/+ mice were treated with 4% dextran sodium sulfate to promote colonic tumorigenesis. Tumor growth patterns were characterized by serial colonoscopy, and pathology was determined. Serial biopsies of tumors were obtained for immunohistochemistry and gene expression profiling by microarray analysis with Affymetrix Whole Genome array. Tumors (n=424) grew, remained static, regressed, or resolved over time with different relative frequencies. Newly developed tumors demonstrated dynamic growth patterns with higher rates of growth and resolution, while more established tumors tended to remain static in size. Colonic tumors were hyperplastic lesions (3%), adenomas (73%), intramucosal carcinomas (20%), or adenocarcinomas (3%). Differentially expressed genes between adenomas and intramucosal carcinomas were identified. We did not identify differentially expressed genes between early and late biopsies from the same tumor. This novel murine model of intestinal tumorigenesis develops colonic tumors that can be monitored by serial colonoscopy, mirror growth patterns seen in human colorectal polyps, and progress to colorectal cancer. Further characterization of cellular and molecular features are needed to determine which features can be used to risk-stratify polyps for progress to colorectal cancer and potentially guide prevention strategies. F1 (SWR x C57BL/6) Apcin/+ mice who had been given two treatments of 4% dextran sodium sulfate in drinking water at weaning underwent colonoscopy around 80 days of age. Those with distal colonic tumors amenable to biopsy had two biopsies taken at that time. Tumors were monitored by colonoscopy every 14 days. Every 28 days, two additional biopsies were taken of each tumor. This protocol was repeated until mice were moribund. Six tumors were removed after sacrifice. The earliest and latest biopsies of each tumor were selected for RNA extraction and Affymetrix hybridization.

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Active BRAF-V600E is the key player in generation of a sessile serrated polyp-specific DNA methylation profile (Exome-seq data set)

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