Simultaneous recovery of DNA and RNA from formalin-fixed paraffin-embedded tissue and application in epidemiologic studies.

Analysis of DNA, RNA, and protein extracted from tissue specimens in epidemiologic studies is useful for assessing etiologic heterogeneity, mechanisms of carcinogenesis, and biomarkers for prognosis and prediction of treatment responses. Fresh-frozen tissue samples may provide optimal quality nucleic acids, but pose multiple logistical considerations, including rapid access to tissues before histopathologic examination and specialized equipment for freezing, transport, and storage; in addition, morphology is often compromised. In contrast, formalin-fixed paraffin-embedded (FFPE) tissue samples, including enormous archives of existing specimens, represent a valuable source of retrospective biological material for epidemiologic research, although presenting different limitations compared with frozen samples. Recent efforts have made progress toward enhancing the utility of FFPE specimens for molecular analyses, including DNA studies, and increasingly for RNA and other macromolecules. Here, we report the method that we used to simultaneously recover DNA and RNA from FFPE tissue specimens with appreciable quantity and quality and discuss briefly the application of tumor markers in epidemiologic studies.