Improving gene expression analysis efficacy from formalin-fixed paraffin embedded tissues.

Abstract

Improving RNA isolation and cDNA synthesis techniques has emerged due to advancements in the knowledge of molecular basis of most diseases. This in turn increased the need of higher quantity and quality of the extracted genetic material to be used for a variety of diagnostic tests and experiments. The aim of the study was to compare three modified methods for RNA extraction from formalin-fixed paraffin embedded (FFPE) biopsied tissue and different cDNA synthesis strategies to facilitate study of gene expression. Compared RNA extraction methods were: lysis buffer, phenol-based extraction, and combination of both with concomitant use of silica-based spin columns. RNA quantity and purity were estimated spectrophotometrically. Different priming strategies for cDNA synthesis were applied: oligodT, combination of oligodT and random hexamer, and gene specific primer. Two-step RT-qPCR of ribosomal protein L37A on preamplified and non-preamplified cDNA templates was performed. The combination of lysis buffer with phenol based extraction gave higher RNA yield. By doing cDNA preamplification, the confidence of detection by qPCR was raised, and efficiency was improved. The preamplified template increased the sensitivity of analysis. Together, the combination of approaches improved substantially the reproducibility and validity of quantitative gene expression analyses from FFPE tissues.