RNA in situ hybridization allows the detection of RNA transcripts directly on the tissue material under investigation (hence the name in situ). For this purpose, tumor sections are pretreated using a relatively complex procedure and then hybridized with a gene specific digoxigenin-labelled RNA probe. Excess probe is removed by stringent washing, the dioxigenin (a substance that only occurs in the plant kingdom and can therefore be detected with very high specificity) is detected by means of antibodies and visualized by means of a dye complex (BM Purple, Roche).
RNA in situ hybridization is particularly useful if no antibody is yet available for a new target gene, but the question has to be clarified whether this target gene is expressed in a specific cell type (e. g. tumor cells, epithelial cells).
RNA in situ hybridization with a gene specific probe (breast cancer section).
Left side: An expression in tumor cells (tissue area with large nuclei) is clearly visible.
Right: Hematoxylin-eosin (H/E) staining of a subsequent section. The H/E staining is the standard staining in histology.