title: Comparing gene expression data from formalin-fixed, paraffin embedded tissues and qPCR with that from snap-frozen tissue and microarrays for modeling outcomes of patients with ovarian carcinoma.
abstract: BACKGROUND
  Previously, we have used clinical and gene expression data from The Cancer Genome Atlas (TCGA) to model a pathway-based index predicting outcomes in ovarian carcinoma. This data were obtained from snap-frozen tissue measured with the Affymetrix U133 platform. In the current study, we correlate the data used to model with data derived from TaqMan qPCR both snap frozen and paraffin embedded (FFPE) samples.
  
  
  METHODS
  To compare the effect of preservation methods on gene expression measured by qPCR, we assessed 18 patient and tumor sample matched snap-frozen and FFPE ovarian carcinoma samples. To compare gene measurement technologies, we correlated qPCR data from 10 patients with tumor sample matched snap-frozen ovarian carcinoma samples with the microarray data from TCGA. We normalized results to the average expression of three housekeeping genes. We scaled and centered the data for comparison to the Affymetrix output.
  
  
  RESULTS
  For the 18 specimens, gene expression data obtained from snap-frozen tissue correlated highly with that from FFPE samples in our TaqMan assay (r > 0.82). For the 10 duplicate TCGA specimens, the reported microarray data correlated well (r = 0.6) with our qPCR data, and ranges of expression along pathways were similar.
  
  
  CONCLUSIONS
  Gene expression data obtained by qPCR from FFPE serous ovarian carcinoma samples can be used to assess in the pathway-based predictive model. The normalization procedures described control variations in expression, and the range calculated along a specific pathway can be interpreted for a patient's risk profile.
authors.affiliation: Department of Obstetrics and Gynecology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226 USA.
authors.forename: William H
authors.initials: WH
authors.lastname: Bradley
authors.affiliation: Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, WI 53792 USA ; Current Address: Department of Biostatistics and Bioinformatics, Roswell Park Cancer Institute, Buffalo, NY USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Eng
authors.affiliation: Department of Pathology, Medical College of Wisconsin, Milwaukee, WI 53226 USA.
authors.forename: Min
authors.initials: M
authors.lastname: Le
authors.affiliation: Department of Pathology, Medical College of Wisconsin, Milwaukee, WI 53226 USA.
authors.forename: A Craig
authors.initials: AC
authors.lastname: Mackinnon
authors.affiliation: Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, WI 53792 USA.
authors.forename: Christina
authors.initials: C
authors.lastname: Kendziorski
authors.affiliation: Department of Obstetrics and Gynecology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226 USA.
authors.forename: Janet S
authors.initials: JS
authors.lastname: Rader