Immunolocalisation of bone morphogenetic protein-6 in benign and malignant prostatic tissue: correlation with w situ hybridisation
Autzen P., Wilson Horne CH., Steward M., Henry L., Mclntosh GG., Robinson M., Robson C., Neal DE., Hamdy FC.
Bone morphogenetic proteins (BMPs) are able to induce bone formation in vivo. BMPs are known to be expressed in benign and malignant prostatic tissue, and preliminary studies have shown BMP-6 to be expressed only in advanced prostate cancer. The aims of this study were: 1] to localise BMP-6 protein in benign and malignant prostatic tissue using a novel anti-human BMP-6 antibody; and 2] to correlate immunolocalisation of BMP-6 with mRNA expression investigated by in situ hybridisation. Thirty-nine men were investigated Twenty men had metastatic disease, and eleven patients had disease confined to the prostate. Eight patients had benign prostatic hyperplasia (BPH). Tissue was formalin-fixed and paraffin embedded. Immunohistochemistry (IHC) was carried out using a monoclonal mouse anti-human BMP-6 antibody (Novocastra Laboratories, UK). For in situ hybridisation (ISH) RNA probes were generated from the human BMP-6 cDNA. mRNA was located in the cytoplasm of the malignant epithelial cells. The protein was mainly localised to the cytoplasm of epithelial cells, but in 3 cases the staining was nuclear. Nineteen of 20 patients with metastatic disease were positive for BMP-6 by ISH, 15 of the 20 were positive by IHC. In the localised cancers, 2 out of 11 showed positive signals by ISH and 7 out of the 11 were positive by IHC None of the BPH cases showed any evidence of BMP-6 expression by ISH, but 4 out of 8 cases were positive by IHC. The positive staining in BPH was limited to a few glands in each sample and was associated with histological evidence of inflammatory changes. BMP-6 mRNA and protein are located only within the prostatic epithelial cells. Wheras the mRNA was exclusively expressed in prostate cancers, the protein was detected in both benign and malignant cells. BMP-6 gene and protein expression appear to be associated with the presence of skeletal metastases in prostate cancer. To our knowledge, this is the first BMP-6 immunolocalisation study using and anti-human monoclonal antibody. Further studies are warranted to assess the potential value of BMP-6 immunostaining in prostate cancer.