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Copy Number Data from Archival Leiomyosarcoma

ABSTRACT: 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.

ORGANISM(S): Homo sapiens

PROVIDER: GSE39663 | GEO | 2015/07/24

SECONDARY ACCESSION(S): PRJNA171373

REPOSITORIES: GEO

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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)].

Project description:This study was performed to evaluated RNA extraction and gene expression analysis of FFPE specimen stored for more than 20 years. Using long time stored FFPE material; large retrospective studies correlating molecular features with therapeutic response and clinical outcome, can be performed. Quantitative PCR (qPCR) was used to evaluate RNA extraction methods and to compare gene expression profiles of FFPE and fresh frozen (FF) tissue. Extracted RNA was subsequently subjected to microarray analysis and compared to qPCR data. The Ambion RecoverAll kit appears to be particularly suited for RNA extraction of long time stored FFPE tissues. Gene expression analysis using Affymetrix platform displayed a high degree of correlation for endogenous control genes comparing FF and FFPE tissues. We conclude that high quality gene expression signatures can be recognized using Affymetrix gene expression platform on FFPE tissue stored for more than 20 years. However, a general interpretation must be done with caution as different FFPE procedures have varying effects on RNA quality. Three RNA extraction methods from Roche (Basel, Switzerland), Ambion (Austin, TX, USA) and Qiagen (Hilden, Germany), designed for FFPE material was used. The methods were compared using qPCR. For the qPCR analysis, two different concentrations of input cDNA were used (20ng and 100ng) and 32 human endogenous control genes were examined. RNA from the Ambion FFPE kit was further analyzed by using microarray. Amplification of RNA prior to microarray analysis was performed using Nugen technologies (San Carlos, CA, USA). Nugen has developed amplification kits both for FFPE and FF materials: WT- ovation FFPE RNA amplification System V2 (Nugen FFPE), Ovation FF RNA Amplification System V2 (Nugen V2 FF) and Ovation FF Pico RNA Amplification System (Nugen PICO FF). The Nugen FFPE kit, designed for FFPE material was only used for FFPE tissue. The Nugen Pico FF kit, designed to target small amounts of FF RNA (>500 pg) and the Nugen V2 FF kit designed to target total FF RNA, were only used for FF tissue. Affymetrix standard amplification protocol (Affy FF) designed for FF RNA was also included as the standard method for amplification.

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Copy Number Data from Archival Leiomyosarcoma

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