Down-regulated expression of prostasin in high-grade or hormone-refractory human prostate cancers

BACKGROUND. We previously conducted a search for genes which are differentially expressed in hormone-refractory prostate cancers using cDNA-representational difference analysis (RDA). The prostasin gene was isolated as one showing down-regulation in hormone-refractory cancers. In the present study, linkage to the stage in prostate neoplasia was examined. METHODS. Prostasin expressions in 54 prostate cancer cases were examined by mRNA in situ hybridization and immunohistochemistry as well as by northern blot analysis. RESULTS. Expression levels of prostasin in hormone-refractory cancers were approximately one-sixth of those in organ-confined cancers by northern blotting. Glandular components in benign prostatic hyperplasia and high-grade prostatic intraepithelial neoplasias tended to exhibit mild to moderate and relatively strong intensities, respectively. Expression levels of both prostasin mRNA and protein were inversely correlated with histological differentiation but not associated with clinical stage of human prostate cancer. Almost all cases of metastatic and hormone-refractory cancers demonstrated down-regulation of prostasin expression. CONCLUSIONS. These results suggest that prostasin cannot be regarded as a prognostic indicator for human prostate cancer although it may be a useful marker for tumor differentiation. (C) 2002 Wiley-Liss, Inc.