A two-step method for the extraction of high-quality RNA from endoscopic biopsies

The use of molecular techniques such as quantitative RT-PCR depends on the quality of cellular RNA. In particular, RNA extraction from endoscopic biopsies is difficult with respect to yield, and especially integrity. Endoscopic biopsies taken from the gastric antrum, corpus and duodenum were subjected to various RNA extraction protocols, and the RNA was used for quantitative RT-PCR. The subsequent use of two methods, (i) a phenol/chloroform extraction and (ii) a columnbased extraction method, resulted in a yield of 4.5 g total RNA per biopsy with reliable quality in 80% of samples. The quantitative RT-PCR analysis revealed that only RNA samples that clearly show both 18S and 28SRNA bands in agarose gel electrophoresis were suitable for quantitative RT-PCR as shown by expression of corpusspecific pepsinogen CmRNA and the duodenum-specific multidrug resistance protein-1 (mdr-1)mRNA. In partially degraded RNA, pepsinogen C, mdr-1, or beta-actin mRNAs were still detectable, but the quantitative determination gave inconsistent data. The twostep method described here is a suitable option for extracting high-quality RNA from endoscopic biopsies when other standard protocols fail.