SELECTIVE EXPRESSION OF INDUCIBLE NITRIC-OXIDE SYNTHASE IN HUMAN PROSTATE CARCINOMA

BACKGROUND. Nitric oxide (NO) is synthesized by inducible nitric oxide synthase (iNOS) and plays an important role in tumor growth and angio genesis. NO generation by NOS also influences the cytotoxicity of macr ophages and tumor-induced immunosuppression. Before now, the expressio n of iNOS in prostate carcinoma tissue had not been determined. METHOD S. In this study, tissue sections from 16 patients with prostate carci noma were studied immunohistochemically and compared with tissue speci mens from 10 patients with benign hyperplasia. RESULTS. Positive iNOS immunostaining was detected in all sections from patients with prostat e carcinoma. The malignant epithelial cells were highly positive. The antibody against iNOS also marked round cells, which had the same cell shape as that observed for macrophages. These cells were located in s troma and epithelium adjacent to tumor islets. However, round cells in benign tissue stained negative for iNOS. None of the benign hyperplas ia specimens stained positive for iNOS immunohistochemically. CONCLUSI ONS. Prostate carcinoma tissue had a high iNOS content, whereas benign tissue did not. The authors suggest that epithelial iNOS expression c an be used as a specific immunohistochemical marker for prostate carci noma. NO generation by iNOS may play multiple roles in the development of this disease. (C) 1998 American Cancer Society.