Optimal Fixation Conditions and DNA Extraction Methods for MLPA Analysis on FFPE Tissue-Derived DNA

Objectives: Molecular genetic analysis of formalin-fixed, paraffin-embedded (FFPE) tissues is of great importance both for research and diagnostics. Multiplex ligation-dependent probe amplification (MLPA) is a widely used technique for gene copy number determination, and it has been successfully used for FFPE tissue-extracted DNA analysis. However, there have been no studies addressing the effect of tissue fixation procedures and DNA extraction methods on MLPA. This study therefore focuses on selecting optimal preanalytic conditions such as FFPE tissue preparation conditions and DNA extraction methods. Methods: Healthy tissues were fixed in buffered or nonbuffered formalin for 1 hour, 12 to 24 hours, or 48 to 60 hours at 4 °C or at room temperature. DNA extracted from differently fixed and subsequently paraffin-embedded tissues was used for MLPA. Four commercial DNA extraction kits and one in-house method were compared. Results: Tissues fixed for 12 to 24 hours in buffered formalin at room temperature produced DNA with the most optimal quality for MLPA. The in-house FFPE DNA extraction method was shown to perform as efficient as or even superior to other methods in terms of suitability for MLPA, time and cost-efficiency, and ease of performance. Conclusions: FFPE-extracted DNA is well suitable for MLPA analysis, given that optimal tissue fixation and DNA extraction methods are chosen.