Diversity and modulation of plasminogen activator activity in human prostate carcinoma cell lines

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Abstract
Baseline cellular plasminogen activator (PA) activity, and the cellular proteins responsible for variations in PA activity were evaluated in three human prostate carcinoma cell lines. Net PA activity in the cell lines PC‐3, DU‐145, and LNCaP was measured using a plasminogen‐dependent fibrin lysis assay. These three cell lines were then analyzed to determine the specific protein(s) responsible for differences in PA activity. mRNA and protein levels of cellular urinary PA (uPA), tissue PA (tPA), PA inhibitor 1 (PAI1), PA inhibitor 2 (PAI2), and uPA receptor (uPAr) were measured using Northern analysis and ELISA assays. Net cellular PA activity in the three cell lines varied over a 3‐fold range (PC3 > DU145 > LNCaP). Net PA activity in the fibrinolysis assay demonstrated a direct correlation with mRNA transcript levels of uPA, tPA, PAI1, and uPAr (PC‐3 > DU‐145 > LNCaP). uPA protein was identified in both the PC‐3 and the DU‐145 lines. tPA, PAI1, and PAI2 proteins were identified only in PC‐3 cells. In general, cellular protein levels correlated with mRNA levels. These findings demonstrate that prostate carcinoma cell lines vary in their net PA activity. This variability results from both qualitative and quantitative differences in the cellular expression of PA regulatory proteins.