Differential expression of PSP94 in rat prostate lobes as demonstrated by an antibody against recombinant GST-PSP94

Prostate secretory protein (PSP94, 94 amino acids) is one of the most abund ant proteins secreted from the prostate. Its biological role is unknown and still controversial, although it is assumed to have the potential to be a biomarker and a suppressor of prostate cancer. In order to establish an ani mal model to further elucidate its biological role, we expressed the mature form of rat PSP94 in Escherichia coli, using a glutathione S-transferase ( GST) fusion expression vector; we generated a polyclonal rabbit antibody ag ainst the recombinant protein. The antibody specifically recognized recombi nant rat PSP94 and cross-reacted only very weakly with its human homologue. Using the characterized anti-rat PSP94 antibody, we found that PSP94 was l ocated primarily in rat prostate. Furthermore, PSP94 is present at differen t levels in different robes of rat prostate, With significant levels detect able only in the lateral robe (LP). In addition, the most abundant PSP94 ex pression was found in the prostate lobe secretions, and PSP94 levels in LP secretions were at least seven times higher than in secretions from the dor sal prostate (DP). The rat ventral prostate (VP) and other regions of the m ale accessory glands were found to be almost completely devoid of PSP94. Si nce most rat prostate dysplasia induced by steroid hormone treatment occurs only in dorsolateral prostate, prostate tissue-specific expression and the expression of PSP94 in dorsolateral, but not other, robes of the prostate suggest a potential role in prostate targeting and prostate cancer developm ent. (C) 1999 Wiley-Liss, Inc.