Cobalt chloride (CoCl(2)) treatment of cells in vitro has been shown to induce cellular changes that are similar to those seen following hypoxia. To identify genes that are differentially expressed in response to treatment with CoCl(2), we compared the mRNA expression profiles of PC-3 cells that were treated with CoCl(2) with those of untreated PC-3 cells, using specific arbitrary primers and two anchored oligo(dT) primers provided in the ACP-based GeneFishing kits. The results of this study demonstrated that the puromycin-sensitive aminopeptidase (PSA) gene was downregulated in PC-3 cells that were treated with CoCl(2). This downregulation of PSA expression, in turn, suppressed the proliferation, migration, and invasion of PC-3 cells, as well as the secretion and expression of matrix metalloproteinase-9 (MMP-9).