Secretion of urokinase and metalloproteinase-9 induced by staurosporine is dependent on a tyrosine kinase pathway in mammary tumor cells.
Urokinase-type plasminogen activator (uPA) is a key serine protease involved in invasion and metastasis. We had shown that overproduction of uPA in tumor cells is controlled by a phospholipase D-protein kinase C-dependent pathway. Now we studied whether other signaling pathways participate in the regulation of constitutive uPA and metalloproteinase (MMP) overproduction in tumor cells. Staurosporine, a protein kinase inhibitor, stimulated uPA and MMP-9 secretion as measured by radial caseinolysis, zymography and Western blotting. Genistein, a specific tyrosine kinase inhibitor, reduced the constitutive and staurosporine-induced uPA and MMP-9 secretion. Interestingly, the phosphatase inhibitor vanadate stimulated uPA secretion. Verapamil, a calcium channel blocker, inhibited both endogenous and PMA-stimulated secretion of uPA but was unable to inhibit staurosporine-induced secretion. The alcohol n-butanol, a phospholipase D and protein kinase C inhibitor, besides inhibiting constitutive uPA secretion, blocked staurosporine-induced secretion. Our results suggest that constitutive and staurosporine-induced uPA and MMP-9 secretion by LM3 murine mammary tumor cells is controlled by an endogenous tyrosine kinase pathway and probably involves protein phosphatases. In addition, the staurosporine-induced signal regulating urokinase secretion is independent of extracellular calcium but dependent on phospholipase D.
Aguirre Ghiso
J A
JA
Research Area, Institute of Oncology Angel H. Roffo, University of Buenos Aires, Argentina. postmast@butnol.fmed.uba.ar
Farías
E F
EF
Alonso
D F
DF
Bal de Kier Joffé
E
E
D000818:Animals; D002118:Calcium / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D015674:Mammary Neoplasms, Animal / Q000201:enzymology*; D008666:Metalloendopeptidases / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D010960:Plasminogen Activators / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects; D014568:Urokinase-Type Plasminogen Activator / Q000187:drug effects* / Q000378:metabolism
D004791:Enzyme Inhibitors; D011505:Protein-Tyrosine Kinases; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator; D008666:Metalloendopeptidases; D019311:Staurosporine; D002118:Calcium