Gene expression analysis of lung cancer using long time stored formalin-fixed and paraffin embedded (FFPE) tissue

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.

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