Immunohistochemical staining of EphB4 in prostate cancer samples. The expression of EphB4 in human prostate carcinomas was detected using immunohistochemical staining of formalin fixed, paraffin-embedded tissue samples. Images (20× magnification) of normal (panel 2) and diseased tissue (panel 4) from eight different patient samples are shown with a Haematoxylin/eosin stained consecutive section (panels 1 and 3). The Gleason score for each disease focus is shown in the top left-hand corner of the image of each tumour focus. A single sample that contained a focus of basal cell hyperplasia, two samples with well-differentiated adenocarcinoma, two samples of moderately differentiated adenocarcinoma and three samples of poorly differentiated adenocarcinoma are shown. The brown stain from the biotinylated secondary antibody indicates the EphB4 protein. Nuclei are stained with Harris haematoxylin and appear blue. Staining of normal tissues was either absent or weak and diffuse. Increased staining of the tumour tissue appeared to correlate with increased Gleason score. There was no cross-reactivity with the secondary antibody alone (result not shown).