J Cell Biol 102 : 1235-41 ( 1986)
Abstract
The effect of tumor promoters and growth factors on the synthesis of urokinase and urokinase mRNA in human carcinoma cells has been investigated .
In urokinase-producing human carcinoma cells ( A1251 ) , a -40-fold increase in urokinase mRNA level is obtained after treatment with 10 nM phorbol myristate acetate ( PMA ) , a smaller effect ( two- to fourfold ) with 2 ng/ml platelet-derived growth factor ( PDGF ) and no effect with epidermal growth factor ( EGF ) ( up to 50 nM ) .
After treatment with PMA , urokinase mRNA level increases already at 30 min peaking 2-4 h thereafter .
Cell line A431 , which has an abnormally high number of EGF receptors , shows the same response to PMA , but also responds to EGF ( two- to fourfold increase in mRNA ) .
The kinetics are similar to those of A1251 .
Nuclear transcription experiments show that the PMA-induced increase in urokinase mRNA is due to increased synthesis .
The protein synthesis inhibitor , cycloheximide ( 10 micrograms/ml ) , also increases the level of urokinase mRNA .
When both cycloheximide and PMA are used , super-induction is observed .
This result may indicate that a short-lived protein negatively regulates the level of urokinase .
The different efficiency of the effectors ( PMA and PDGF better than EGF ) and their kinetics , as well as the effect of cycloheximide on urokinase mRNA synthesis , ( a ) are reminiscent of the effect of PDGF and PMA on competence phase genes ( Kelly , K. , B.H. Cochran , C.D. Stiles , and P. Leder , 1983 , Cell , 35 : 603-610 ) , ( b ) demonstrate that the synthesis of urokinase is part of the early cellular response to these factors , and ( c ) provide a preliminary insight in the overproduction of urokinase by primary malignant tumors and transformed cells in culture .