Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Transcription profiling of human primary colorectal cancers

ABSTRACT: Samples were taken from colorectal cancers in surgically resected specimens from 74 patients. The expression profiles were determined using Affymetrix Human Genome U133Plus 2.0 arrays. Our MSI/MSS classifer was applied to these samples. Experiment Overall Design: mRNA from 74 fresh-frozen primary colorectal tumour samples were extracted and hybridized to HG-U133Plus 2.0 expression arrays. The MAS5.0 procedure was used to make calls of expression. Data from each sample were quantile normalized with reference to a training set prior to application of our MSS/MSI classifier.

ORGANISM(S): Homo sapiens

SUBMITTER: Oliver Sieber

PROVIDER: E-GEOD-13067 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

DNA copy-number alterations underlie gene expression differences between microsatellite stable and unstable colorectal cancers.

Jorissen Robert N RN Lipton Lara L Gibbs Peter P Chapman Matthew M Desai Jayesh J Jones Ian T IT Yeatman Timothy J TJ East Philip P Tomlinson Ian P M IP Verspaget Hein W HW Aaltonen Lauri A LA Kruhøffer Mogens M Orntoft Torben F TF Andersen Claus Lindbjerg CL Sieber Oliver M OM

Clinical cancer research : an official journal of the American Association for Cancer Research 20081201 24

<h4>Purpose</h4>About 15% of colorectal cancers harbor microsatellite instability (MSI). MSI-associated gene expression changes have been identified in colorectal cancers, but little overlap exists between signatures hindering an assessment of overall consistency. Little is known about the causes and downstream effects of differential gene expression.<h4>Experimental design</h4>DNA microarray data on 89 MSI and 140 microsatellite-stable (MSS) colorectal cancers from this study and 58 MSI and 77 ...[more]

PMID: 19088021

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Project description:Samples were taken from colorectal cancers in surgically resected specimens in 33 colorectal cancer patients. The expression profiles were determined using Affymetrix Human Genome U133 Plus 2.0 arrays. Comparison between the sample groups allow to identify a set of discriminating genes that can be used for molecular markers for CIN phynotype Specimens from 33 consecutive stage II and stage III patients who had undergone surgical resection of CRC were studied. Patients with familial adenomatous polyposis and HNPCC were excluded from the study. Specimens from tumors and corresponding normal tissues in surgically resected specimens were snap-frozen in liquid nitrogen and stored at -80degreesC until use. Parallel tumor specimens were formalin fixed and paraffin embedded for histological examination. DNA and RNA was extracted from paired tumor and normal tissue using frozen samples. The patients provided written, informed consent to the collection of specimens, and the local Ethics Committee approved the study protocol. MSI and LOH phenotype analysis were done as follows; Using DNA, we performed the polymerase chain reaction (PCR) and determined the MSI status. In addition to five microsatellite markers recommended by the National Cancer Institute workshop, we also used TP53, D18S46, D18S363 and D18S474.9 We determined LOH status in non–MSI-high tumors, because LOH is rare in MSI-high tumors and also interpretation of LOH is difficult in MSI-high tumors. We defined LOH at each locus as a 50% reduction in the height of one of two allele peaks in tumor DNA relative to non-neoplastic control DNA. LOH was defined as present if any of the markers on the same chromosome show LOH. In order to evaluate the severity of chromosomal instability based on the actual frequency of LOH among evaluable loci, we defined the LOH Ratio (%) as: LOH Ratio (%) = Total number of chromosomes with LOH / Total number of chromosomes that could be evaluated for LOH × 100. Depending on the LOH Ratio, we classified tumors as having high levels of chromosomal instability (CIN-high) (33% < LOH Ratio < 100%) or low levels of chromosomal instability (CIN-low) (0% < LOH Ratio <33%). Furthermore, CIN-high tumors were divided into two subgroups; CIN-high (mild type) (33% < LOH Ratio < 75%) and CIN-high (severe type) (75% < LOH Ratio <100%).

Project description:Samples were taken from colorectal cancers in surgically resected specimens in 35 colorectal cancer patients. The expression profiles were determined using Affymetrix Human Genome U133 Plus 2.0 arrays. Comparison between the sample groups allow to identify a set of discriminating genes that can be used for molecular markers for CIN phynotype. Specimens from 35 consecutive stage II and stage III patients who had undergone surgical resection of CRC were studied. Patients with familial adenomatous polyposis and HNPCC were excluded from the study. Specimens from tumors and corresponding normal tissues in surgically resected specimens were snap-frozen in liquid nitrogen and stored at -80 ºC until use. Parallel tumor specimens were formalin fixed and paraffin embedded for histological examination. DNA and RNA was extracted from paired tumor and normal tissue using frozen samples. The patients provided written, informed consent to the collection of specimens, and the local Ethics Committee approved the study protocol. MSI and LOH phenotype analysis were done as follows; Using DNA, we performed the polymerase chain reaction (PCR) and determined the MSI status. In addition to five microsatellite markers recommended by the National Cancer Institute workshop, we also used TP53, D18S46, D18S363 and D18S474.9 We determined LOH status in non–MSI-high tumors, because LOH is rare in MSI-high tumors and also interpretation of LOH is difficult in MSI-high tumors. We defined LOH at each locus as a 50% reduction in the height of one of two allele peaks in tumor DNA relative to non-neoplastic control DNA. LOH was defined as present if any of the markers on the same chromosome show LOH. In order to evaluate the severity of chromosomal instability based on the actual frequency of LOH among evaluable loci, we defined the LOH Ratio (%) as: LOH Ratio (%) = Total number of chromosomes with LOH / Total number of chromosomes that could be evaluated for LOH × 100. Depending on the LOH Ratio, we classified tumors as having high levels of chromosomal instability (CIN-high) (33% < LOH Ratio < 100%) or low levels of chromosomal instability (CIN-low) (0% < LOH Ratio <33%). Furthermore, CIN-high tumors were divided into two subgroups; CIN-high (mild type) (33% < LOH Ratio < 75%) and CIN-high (severe type) (75% < LOH Ratio <100%).

Dataset Information

Transcription profiling of human primary colorectal cancers

Publications

DNA copy-number alterations underlie gene expression differences between microsatellite stable and unstable colorectal cancers.

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