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MRI-localized biopsies reveal subtype-specific differences in molecular and cellular composition at the margins of glioblastoma

ABSTRACT: We obtained radiographically-localized biopsies during glioma resection surgeries to sample the tumor core and margins from multiple glioma patients. We also procured fresh, non-neoplastic brain tissue specimens from multiple patients having procedures to relieve epilespy symptoms or to place shunts to treat normal pressure hydrocephalus. We then used RNA-Seq to compare expression patterns between geographically distinct regions of gliomas and computational deconvolution to estimate cell type-specific expression patterns in different disease subtypes.

ORGANISM(S): Homo sapiens

PROVIDER: GSE59612 | GEO | 2014/07/22

SECONDARY ACCESSION(S): PRJNA255754

REPOSITORIES: GEO

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Project description:The aim of this study is to provide an extended, retrospective validation of a previously described 4-gene signature (MMP1, COL4A1, P4HA2, and THBS2) predictive of oral carcinoma recurrence. We assessed an independent cohort including 245 histologically normal surgical margins from 62 patients with OSCC. Gene expression was determined using a color-coded probe assay for quantitative gene expression analysis. All margins and tumor blocks were cut (4-5µm tick) and stained with Hematoxylin-Eosin and tissues were subjected to needle microdissection using the stereo microscope Leica EZ4 (Leica Microsystems, Wetzlar, Germany) before RNA extraction, in order to isolate pure tumor or normal cell populations. RNA from FFPE samples was isolated using the RecoverAll Total Nucleic Acid Isolation kit (Ambion/Life Technologies, Carlsbad, CA, USA), following our previously reported protocol with modifications to improve RNA yield [PMID:23835716]. RNA was stored at -80ºC until RNA extraction and gene expression validation⁠. In addition, tumor tissues from the same patients were collected for further analysis (not in scope of the presented study). Probes were designed for the 4-gene signature (MMP1, COL4A1, P4HA2 and THBS2) and contained one capture probe linked to biotin and one reporter probe attached to a color-coded molecular tag for each gene sequence, according to the nCounterTM code-set design. RNA samples were randomized using a numerical ID and were then subjected to NanoString nCounterTM analysis by the Princess Margaret Genomics Centre (https://www.pmgenomics.ca), Toronto, ON, Canada. Patient samples were analyzed in two batches consisting of 125 and 152 margins tissue samples. The detailed protocol for mRNA transcript quantification analysis, including sample preparation, hybridization, detection and scanning followed the manufacturer’s recommendations and was described in [PMID: 21549012]. We used 400 ng of total RNA isolated from FFPE tissues for detection of probe signals. Raw data were analyzed using the nCounterTM digital analyzer software (http://www.nanostring.com/support/ncounter/) and gene expression levels were subjected to further bioinformatic and statistical analyses.

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MRI-localized biopsies reveal subtype-specific differences in molecular and cellular composition at the margins of glioblastoma

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