Serum, plasma and paraffin-embedded tissues as sources of DNA for studying cancer susceptibility genes

The ability to isolate DNA from archived human serum, plasma andparaffin-embedded human tissues enhances opportunities to study breast,lung and other cancer risk factors. We report herein a simple and fastprotocol for the extraction of genomic DNA from these sources. Using aphenol-based extraction method, the recovery for DNA is quantitative andreproducible. DNA yields in serum (250 microl) were between 162 and 1060 ng(n = 18 subjects), in plasma (250 microl) were between 165 and 375 ng (n =5 subjects) and in embedded tissues (5-microm thick sections for ethanolfixed, and between 5- and 20-microm sections for formaldehyde fixation)were between 1 microg and 11.7 microg (n = 32 subjects). The extractionmethod was combined with newly designed PCR- based assays for cancersusceptibility marker genes such as CYP1A1 (exon 7), CYP2E1 (Dra1, Rsa1),GSTM1 and NAT2 [NAT2*5A (C481T), NAT2*6A (G590A), NAT2*7A (G857A)].Genotyping results from the serum and paraffin-embedded tissues comparedfavorably to results from archived freshly frozen tissues, whereconcordance was 98% for serum, 100% for ethanol-fixed embedded tissues, and97% for formaldehyde-fixed and paraffin-embedded tissues. This facilemethod will allow for the use of archived tissue samples of prospectivecohort and other studies where intact DNA was not previously available.