DNA extraction from formalin-fixed, paraffin-embedded tissues: Protein digestion as a limiting step for retrieval of high-quality DNA

Several DNA extraction methods have been used for formalin-fixed, paraffin-embedded tissues, with variable results being reported regarding the suitability of DNA obtained from such sources to serve as template ill polymerase chain reaction (PCR)-based genetic analyses. We present a method routinely used for archival material in our laboratory that reliably yields DNA of sufficient quality for PCR studies, This method is based on extended proteinase K digestion (250 mu g/ml in an EDTA-free calcium-containing buffer supplemented with musset glycogen) followed by phenol-chloroform extraction. Agarose gel electrophoresis of both digestion buffer aliquots and PCR amplification of the beta-globin gene tested the suitability of the retrieved DNA for PCR amplification.