Regulation of plasminogen activator and plasminogen activator-inhibitor production by tissue culture cells: Evidence for independent induction and regulation

Effect of retinoic acid on human neuroblastoma: correlation between morphological differentiation and changes in plasminogen activator and inhibitor activity

The relationship between plasminogen activator (PA)/plasminogen activator inhibitor (PAI) activity and morphological differentiation was investigated in human neuroblastoma (NB) cells treated with retinoic acid (RA). Conditioned medium from nine NB cell lines and one closely related neuroepithelioma line was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and zymography. All NB cell lines were shown to secrete urokinase (UK)-type PA (mol. wt., 52 kDa), and all except two produced tissue PA (mol. wt., 65 kDa). Identification of the PAs was made based on molecular weight and sensitivity to inhibition by anti-UK and anti-tPA antibodies. Several cell lines expressed PA inhibitory molecules; two molecular-weight forms were observed (35 and 40 kDa) in different cell lines. Complex formation with [125]I-labelled proteases revealed specific binding with UK and trypsin but not thrombin, plasmin, or kallikrein. After treatment for 6 days with 1 microM RA, six of the cell lines exhibited an increase in cell-associated and/or secreted tPA activity, corresponding to morphological differentiation of the cells as manifested by extensive neurite outgrowth. A decrease in UK and UK-complex secretion was observed in several of these cell lines. Three cell lines exhibiting no detectable morphological alterations with RA treatment also showed no dramatic changes in PA/PAI activity. These results suggest that morphological differentiation of NB cells may be associated with alterations in the regulation of PA activity.

Treatment of mouse L-cells with phorbol myristate acetate induces the secretion of a plasminogen activator inhibitor which binds to human and mouse urokinase and human tissue plasminogen activator

1. Serum-free conditioned medium from L-cells or L-cells treated with the tumor-promotor phorbol myristate acetate (PMA) was analyzed for plasminogen activator (PA) and plasminogen activator inhibitor (PAI) activity. Conditioned medium from control or PMA-treated cells did not contain detectable PA activity when assayed by SDS-PAGE and zymography. 2. Conditioned medium from PMA-treated cells, but not control cells, contained a PAI of Mr = 40,000 da when assayed by reverse zymography. 3. The L-cell PAI formed SDS-stable complexes with purified human (homo sapiens) urokinase and tissue plasminogen activator, as well as, mouse (Mus musculus) urinary PA. 4. These results indicate that biochemical and immunological differences between human and mouse urokinase and human urokinase and human tissue plasminogen activator do not influence the interaction of the L-cell PAI with these enzymes.