Proteinase K Added to the Extraction Procedure Markedly Increases RNA Yield from Primary Breast Tumors for Use in Microarray Studies

Gene expression profiling by microarray technology has demonstrated the possibilities of biological separation, prognostication, and prediction (1)(2). In this study we demonstrate that the addition of proteinase K to the extraction procedure improves the yield of RNA from primary breast tumors, making the majority of samples eligible for array analysis by Qiagen RNeasy Minikit. In addition, we investigated whether the addition of proteinase K has any influence on the gene expression profile. The Qiagen RNeasy Mini protocol was used as described by the manufacturer (3)(4) for extraction of total RNA from 209 frozen primary breast tumors from women who had undergone surgery for breast cancer at Karolinska Hospital. The study was approved by an ethics committee at the hospital. Biopsies from the same tumors were extracted either with …