Most prostate cancer grows in a hormone-dependent manner. Most patients, however, show hormone-independent growth after several years of hormone therapy. The mechanism of hormone-refractory prostate cancer remains unknown. It is important, therefore, to identify gene(s) related to prostate cancer that are up- or downregulated. We studied differences in gene expression in pairs of prostate cancer and normal prostate tissue utilizing the differential display method. Expression of the identified gene was examined by RT-PCR and real time quantitative PCR (TaqMan-PCR) using 26 pairs of human prostate cancer and normal tissues. We identified a specific upregulated gene encoding a 55 kDa nuclear matrix protein (nmt55) in human prostate cancer. nmt55 gene expression in human prostate cancer tissue was higher (20/26 cases) than that in normal prostate tissue. Moreover, the relationship between nmt55 and androgen receptor (AR) expression showed a positive correlation. In another experiment, transcriptional activity of the prostate specific antigen (PSA) promoter was upregulated by nmt55 in 293 cells. nmt55 showed high expression in prostate cancer compared to normal tissue and its expression showed a positive correlation with AR expression. The PSA promoter was activated by nmt55 expression. These results suggest the possibility that nmt55 expression is related to hormone-dependency or -independence associated with the AR.
Copyright 2003 Wiley-Liss, Inc.