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A gene signature in histologically normal surgical margins is predictive of oral carcinoma recurrence

ABSTRACT: Samples were prospectively collected from patients with histologically normal surgical resection margins. 96 tissue samples (histologically normal margins, oral carcinoma and adjacent normal tissues) from 24 patients comprised the training set. Our study design was guided by the hypothesis that the expression of genes present in oral squamous cell carcinoma (OSCC) but not in healthy oral tissues would be indicative of recurrence in advance of histological alteration. We used meta-analysis of five published microarray data sets (GEO accession GDS2520, Kuriakose et al. 2004; GDS1584, Toruner et al. 2004; GSE6791, Pyeon et al. 2007; GSE9844, Ye et al. 2008; and GSE10121, Sticht et al. 2008), in conjunction with the current training set, to identify genes reliably over-expressed in OSCC. This reduced gene set was used to train a risk model to predict recurrence based on over-expression of a subset of these genes in histologically normal surgical resection margins. Validation of the risk signature was performed using quantitative real-time reverse-transcription PCR in an independent set of 136 samples from an independent cohort of 30 patients. This was a case-only design involving a training set of 23 tumors and 73 margins from 24 patients with squamous cell carcinoma of the tongue.

ORGANISM(S): Homo sapiens

SUBMITTER: Waldron Levi

PROVIDER: S-ECPF-GEOD-31056 | biostudies-other |

REPOSITORIES: biostudies-other

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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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A gene signature in histologically normal surgical margins is predictive of oral carcinoma recurrence

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