Identification of a gene expression signature in colorectal adenocarcinoma in comparison with colorectal adenoma
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ABSTRACT:
ORGANISM(S): Homo sapiens
SUBMITTER: Laurent Corcos
PROVIDER: E-GEOD-50115 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:Approximately two decades ago, Vogelstein and Fearon proposed the adenoma-carcinoma sequence of sporadic CRC development and illustrated the accumulation of genetic alterations during the stepwise progression, thereby providing a guideline for clinical practice. Although the detection and excision of precancerous lesions could prevent colorectal cancer and reduce mortality, 6% of adenomas will ultimately develop into colorectal cancer. Thus, this genetic model for colorectal tumorigenesis may not completely reflect the complex essence of the disease and whether the mode of initiation of the events in the multistep progression affects the outcome of CRC is still unknown. In this study, mRNA and miRNA expression profiling was performed with human colorectal tissues, including normal mucosa, adenoma and adenocarcinoma. Then, an integrated approach was adopted to establish the regulatory interaction networks that were correlated with colorectal carcinogenesis. Finally, a 55-gene signature whose expression was down-regulated in precancerous lesions compared to normal tissue was identified as a potential early indicator of CRC survival. The results suggested that genes related to immunity and homeostasis played a critical role in protection against adenoma initiation and that the altered molecular events that influence colorectal cancer prognosis may be set in an early, precancerous stage. Four types of human colorectal tissues were selected by colonoscopic resection or colorectal surgery, including 12 normal mucosae, 21 low-grade adenomas (mild or moderate atypical hyperplasia), 30 high-grade adenomas (severe atypical hyperplasia or carcinoma in situ) and 25 adenocarcinomas. Gene expression profiling analysis of these samples was performed using Agilent 4x44K human whole genome gene expression microarray (G4112F).
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Project description:Genetic and epigenetic alterations are a fundamental aspect of colorectal cancer formation. There is considerable heterogeneity between colorectal cancers regarding the mutations and methylated genes they carry, and this heterogeneity may arise early in the polyp-cancer sequence. However, our understanding of the epigenetic alterations and gene mutations in colon adenomas and their relation to colorectal cancer is incomplete. Thus, we have assessed the methylome in normal colon mucosa, tubular adenomas, and colorectal adenocarcinomas and have determined the relationship of these findings between adenomas and cancer in the colon. Genome-wide alterations in DNA methylation were found in the normal colon mucosa adjacent to colorectal cancer, tubular adenomas, and colorectal cancer. Three subgroups of CRCs and two subgroups of adenomas were identified on the basis of their DNA methylation patterns. The adenomas separated into a high-frequency methylation class (Adenoma-H) and a low-frequency methylation class. The adenoma-H polyps have a methylated DNA signature similar to non-CIMP CRCs, whereas those of the Adenoma-L class have a similar methylation pattern to normal colon mucosa. The CpGs that account for these signatures are located in intragenic/intergenic regions, which suggests that these two groups of adenomas arise from different stem cell populations. We conducted genome-wide array-based studies and comprehensive data analyses of aberrantly methylated loci in 41 normal colon samples, 42 colon adenomas, and 64 colorectal cancers. Supplementary file 'GSE48684_Matrix_signal_intensities_1.txt.gz': includes the unmethylated and methylated signal intensities from Samples GSM1183439-GSM1183561. Supplementary file 'GSE48684_Matrix_signal_intensities_2.txt.gz': includes the unmethylated and methylated signal intensities from Samples GSM1235135-GSM1235158.
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