Comparison of three methods for DNA extraction from paraffin-embedded tissues

DNA extraction from paraffin-embedded tissue (PET) is a critical step for many molecular techniques. Several protocols have been carried out for this objective according to the literature. In the present study, the performances of three DNA extraction methods from PET were compared to establish the optimal protocol for our laboratory. Ten lymph nodes from ten patients dying of AIDS were investigated. Histological and bacteriological studies were performed in lymph nodes samples. DNA was extracted using three methods: boiling for 20 minutes in distilled water (Method A); boiling for 30 minutes in 5% Chelex-100 resin solution (Method B) and a 4-hours lasting proteinase K digestion (Method C). PCR with specific sequence (IS 6110) were evaluated for the identification of Mycobacterium tuberculosis in PET. The DNA extract by the three methods was degraded. Statistical differences were observed when three DNA extraction methods were compared according to the purity of extracted DNA. Only with Methods B and C successful amplification was obtained. The last method (C) was the more time consuming of all. These results demonstrated that the Chelex-100 DNA extraction method (Method B), which uses a quelating resin, is useful as a routine method to achieve DNA extraction with good enough quality and quantity in a short period of time from PET. Method B is a good option in molecular pathology research.