Aminopeptidase N regulated by zinc in human prostate participates in tumorcell invasion

Aminopeptidase N (AP-N) degrades collagen type IV and is proposed to play a role in tumor invasion. However, the precise functions of AP-N in tumor ce lls and the relationship ofAP-N to prostate cancer remains unclear. In our study, we examined a possible role for zinc in the regulation of AP-N enzym atic activity in relation to tumor cell invasion in human prostate. AP-N pu rified from human prostate was irreversibly inhibited by low concentrations of zinc (Ki 11.2 muM) and bestatin. AP-N, which has zinc in the active cen ter, was also inhibited by the chelating agents, EDTA, a-phenanthroline and EGTA, EDTA was shown to remove zinc from the enzyme. When the effects of z inc and bestatin on invasion of PC-3 cells were investigated in vitro using a Transwell cell-culture chamber, zinc and bestatin effectively suppressed cell invasion into Matrigel at the concentration range of 50-100 muM. Thes e results strongly suggest that the suppression of PC-3 cell invasion by zi nc is based on the inhibition of AP-N activity by zinc. We also evaluated t he expression of AP-N to investigate the relationship with the progression of prostate disease in human cancerous prostate. AP-N was found to be locat ed at the cytoplasmic membranes of prostate gland epithelial cells and to b e expressed more in prostate cancer, while the expression of prostate-speci fic antigen (PSA), which is a useful marker for prostate cancer, was shown in normal and cancer tissues, suggesting that AP-N is potentially a good hi stological marker of prostate cancer. Thus, highly expressed AP-N in human cancerous prostate probably plays an important role in the invasion and met astasis of prostate cancer cells. (C) 2001 Wiley-Liss, Inc.