Unknown,Transcriptomics,Genomics,Proteomics

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Preparation of archival formalin-fixed paraffin-embedded mouse liver samples for use with the Agilent gene expression microarray platform

ABSTRACT: For decades, formalin-fixing and paraffin embedding (FFPE) has been routinely used to preserve tissue samples for histological analysis.M-BM- Global gene expression analysis of these archival tissues has the potential to greatly advance research attempting to link perturbations in molecular pathways to disease outcome. We investigated 16-year-old FFPE mouse liver samples treated with phenobarbital and created a protocol for their analysis using Agilent gene expression arrays. Despite low quality RNA, archival phenobarbital samples exhibited strong induction of the positive control genes CYP2b9 and CYP2b10 by RT-PCR. We hybridized Universal Linkage SystemM-bM-^@M-^Slabelled cDNA libraries to 8x60K Agilent gene expression arrays. We compared one- and two-colour microarray experiments and tested the effects of increasing the amount of cDNA loaded. Canonical gene responders to phenobarbital treatment were measurably induced under each experimental condition (however increasing cDNA input also increased the array background signal). Individual genes were validated by RT-PCR and literature searches, and pathway analysis demonstrated that 9/10 top canonical pathways were consistent across experiments. These analyses suggested that future experiments should be done in duplicate to identify and eliminate false positive genes. We conclude that FFPE samples can be used for meaningful and reproducible gene expression and pathway analyses using microarrays. Phenobarbital-exposed mice (n=3) versus Control mice (n= 3)

ORGANISM(S): Mus musculus

SUBMITTER: Anna Jackson

PROVIDER: E-GEOD-40990 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Soft tissue sarcomas (STS) often present a significant diagnostic challenge as many STS bear histologic resemblance, but are known to have very different clinical and biologic characteristics. Some STS subtypes are characterized by specific genetic abnormalities and this has helped in their classification, diagnosis and even treatment. However, a large majority of STS have no known specific genetic aberrations even though they almost always have highly aberrant karyotypes. We therefore hypothesize that the latter subgroup of STS bear genetic abnormalities that are sub-type specific, but as yet unidentified. High-resolution mapping of copy number aberrations in cancer genomes is a valuable way of identifying recurrent genomic changes that could be of pathogenetic significance. Traditionally, this has been done using high quality DNA obtained from fresh frozen tissue or cells and archived tissue is generally regarded as unsuitable because of the degradative effects of formalin fixation on DNA. Utility of archival tumour material for such molecular genetic analysis is vital, especially for rare cancers like STS but recent efforts to accomplish this have produced variable results. We therefore set out, in addition to optimize a protocol for obtaining genomic copy number data from formalin-fixed, paraffin-embedded (FFPE) STS material that is comparable to that from fresh frozen (FF) material. Microarray-based Comparative Genomic Hybridization (aCGH), a high- resolution, genome-wide method was used to identify somatic copy number aberrations (SCNAs) in primary STS samples (fresh frozen and archival FFPE), using an optimized protocol for labeling DNA. Findings were confirmed using Conventional Cytogenetics and Fluorescence in-situ Hybridization (FISH). Data obtained from paired samples (FF and FFPE) of the same tumours showed similar results and array results were consistently of good quality. On-going analysis of the recurrent SCNAs in combination with expression data and clinical correlates may serve to identify specific patterns that can serve as diagnostic markers, characterize subgroups with prognostic implication or identify potential therapeutic targets. To identify common CNAs among LMS fresh and FFPE. 25 samples in total: 22 individual FFPE cases; 3 cases also obtained fresh. Reference DNA was obtained from same patient when possible, otherwise commercial genomic DNA was used [Promega® UK with Cat Nos. G1471 (male) and G1521 (female)].

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Preparation of archival formalin-fixed paraffin-embedded mouse liver samples for use with the Agilent gene expression microarray platform

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