One step procedure of PCR-DNA extraction from paraffin-embedded materials by Chelex-100.

The polymerase chain reaction (PCR) DNA amplification method is a powerful tool for the retrospective analysis of formalin-fixed and paraffin-embedded tissues.'-4 To utilize DNA from paraffin-embedded materials, several steps are required and may include transfers of DNA extracts to another container. In particular, the steps by xylene and ethanol need to remove paraffin from tissues for paraffin-embedded materials. These additional steps allow an increase in opportunities for cross-transfer of samples. Recently, it was reported that Chelexa-100 (Chelex; Bio-Rad, Richmond, VA, USA), which is a chelating resin and supplied commercially for the analysis of trace elements contained in soil, was used as a means of increasing the signal from the PCR amplification of small numbers of tissue culture cells and simplifying the pr~cedure.~ Stein and Raoult also reported the use of Chelex for paraffin-embedded tissues to detect bacterial DNA.6 Chelex was examined to detect ras oncogene in a small piece of biopsy. Samples used small pieces of 10 gastric biopsies from 10 patients with group Ill (so-called gastric adenoma) and were examined in the First Department of Pathology, Gifu University. All samples were fixed by 10% formalin and embedded conventionally in paraffin. The surface area of each sample was approximately 3-5mm2. All samples were cut from paraffin-embedded blocks into two sections of 6 pm thickness and then transferred to 1.5 mL microtubes. These were treated by three different procedures described as follows: first, as a conventional method, sections were deparaffinized with sequential washes of xylene and ethanol as described in previous dried and 100 pL of buffer (50 mmol/L