Differential regulation of gelatinase b and tissue‐type plasminogen activator expression in human bowes melanoma cells

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Abstract
A comparison of the production of tissue‐type plasminogen activator (t‐PA) and gelatinases A and B was made at the mRNA and protein levels in human Bowes melanoma cells treated with phorbol myristate acetate (PMA). Immunocytochemical analysis confirmed previous quantitative data on PMA‐mediated induction of t‐PA. It also showed that t‐PA immunoreactivity can be restrained to the local environment of the producing cell, most probably by interaction with extracellular matrix components. Zymographical analysis showed that gelatinase B protein was induced by PMA, whereas gelatinase A remained at the constitutive level. Protein kinase C (PKC) appeared to be involved in this regulation since, after PMA treatment (I) the PKC activity was found to be translocated from the cytosol to the particulate fraction of the cells and (2) addition of staurosporine and H‐7 blocked the gelatinase B increase. Northern‐blot hybridization showed a transient rise in t‐PA and gelatinase B mRNA levels whereas gelatinase A mRNA levels remained unchanged. When c‐fos and c‐jun mRNAs were investigated, only that of c‐fos was affected by PMA. Activation by PMA can be kinetically ordered as follows: translocation of PKC to the membrane fraction, transcription of the c‐fos gene and eclipsing of gelatinase B mRNA, increase in steady‐state mRNA levels of t‐PA and gelatinase B and, finally, secretion of t‐PA and gelatinase B glycoproteins. Our data also suggest that various proteases that are known to cooperate in the remodeling of the extracellular matrix can be differently regulated in one tumor‐cell type.