Fluorescence immuno-cytochemistry demonstrating expression and localization of androgen receptor (AR) at the cellular level. The cells were processed for immuno-cytochemistry as described in the materials and methods section. The red fluorescence demonstrates AR (panels A, C, E) or β-actin (panels B, D, F). The cells were counterstained with DAPI (blue) to reveal the nucleus. The red (antigen specific) and blue (nucleus) images were superimposed to demonstrate cellular localization of the antigen (AR or β-actin). Androgen receptor expression was localized primarily to the nucleus in LNCaP (panel E, AR+ve control) and DU145-Id4 (Panel A). In contrast, β-actin expression was primarily cytoplasmic (panels B, D, F). The AR expression in parental DU145 cells was not observed (panel C). Panels A and B: DU145-Id4, Panels C and D: DU145 and Panels E and F: LNCaP. The anti-AR and anti-β actin antibodies were highly specific and displayed no non-specific binding as determined by western blot analysis (e.g. Fig 7A). The photomicrographs (×200) are representative of at least 3 different experiments performed in replicates.