Toward efficient analysis of mutations in single cells from ethanol-fixed, paraffin-embedded, and immunohistochemically stained tissues.

Only a few studies have demonstrated successful molecular analysis after whole genome amplification using single cells dissected from paraffin-embedded tissues. The results in these studies were limited by low-amplification efficiency and high rates of allele dropout. In the present study, the amplification rate using a thoroughly modified primer extension and preamplification-PCR protocol was improved significantly for single cells microdissected from paraffin-embedded and immunohistochemically stained tissues. Tissue fixation with ethanol (85%) and the addition of 0.2 mmol/L EDTA helped to achieve an amplification rate between 67% (segments 200 to 400 bp) and 72% (segments <200 bp). Normal tissue sections were immunohistochemically double stained for overabundance of p53 protein and proliferating cell nuclear antigen. Microdissection of single cells was performed with a manual micromanipulator equipped with a Tungsten needle. Sequence analysis of the TP53 gene was performed after improved primer extension preamplification-PCR and multiplex PCR from single microdissected cells. The rate of allele dropout was at least 68%. These technical advances facilitate routine mutation analysis using a single cell or a few cells microdissected from routinely processed paraffin-embedded normal and tumor tissues. Allele dropout still represents a serious problem in single-cell mutation analysis, especially in samples with limited template DNA and prone to DNA damage.