TY - JOUR
T1 - Elevated urokinase-type plasminogen activator receptor expression in a colon cancer cell line is due to a constitutively activated extracellular signal-regulated kinase-1-dependent signaling cascade
AU - Lengyel, E.
AU - Wang, H.
AU - Gum, R.
AU - Simon, C.
AU - Wang, Y.
AU - Boyd, D.
N1 - Funding Information:
This work was supported by National Institute of Health (R01DE10845 and R01CA58311) grants to DB and a fellowship to EL from the Deutsche Forschungsge-meinschaft (German Research Council Le 889/1-1). We are grateful for the outstanding technical assistance provided by Jose Juarez. We would like to express our appreciation to Dr Stephen Keyse (Imperial Cancer Research Fund, Ninewells Hospital, Dundee, Scotland) and Drs Jeff Frost/Melanie Cobb (Southwestern Medical Center, Dallas, Texas) for the CL100 expression vectors and ERK1/ERK2 mutant expression vectors respectively. We would like to express our thanks to Dr Ulf Rapp, Wurzburg, Germany and Dr Natalie Ahn for the Raf C4 and MEK expression vectors respectively. We are also grateful to Dr Steven Pelech (Kinetek Biotechnology Corp, Vancouver, Canada) for kindly providing the kinase-inactive ERK-GST fusion protein. We would like to thank Dr Alan Saltiel at Parke Davis, Ann Arbor, Michigan for providing the PD 098059.
PY - 1997
Y1 - 1997
N2 - The urokinase-type plasminogen activator receptor (u-PAR) facilitates extracellular matrix degradation in part by accelerating plasmin formation at the cell surface. We previously reported that u-PAR expression is elevated in colon cancer cell lines characterized by their in vitro invasive capacity. Since, u-PAR expression is increased by a variety of growth factors, which signal through the extracellular signal-regulated kinases 1 and 2 (ERK1/ERK2), we determined if these mitogen-activated protein kinases (MAPKs) regulate u-PAR expression in two cultured colon cancer cell lines. An in-gel kinase assay showed that ERK1 activity was considerably higher in RKO cells, which display ≤ 105 receptors/cell, than the GEO cells which have ≃ 104 urokinase receptors per cell. The expression of either an ERK-inactivating phosphatase (CL100), or a kinase-defective ERK1, decreased the activity of a u-PAR promoter-driven CAT reporter in RKO cells. Immune complex kinase assays indicated that the constitutive ERK1 activity in RKO cells was largely a result of an activated MEK1. Further, treatment of RKO cells with a specific inhibitor (PD 098059) of MEK1 activation, which diminished ERK1 activity, reduced the amount of urokinase specifically bound to the cell surface and this was associated with reduced laminin degradation. The expression of a dominant negative c-Raf-1 also reduced u-PAR promoter activity suggesting that MEK1 activation involved an activator at, or upstream, of this serine-threonine kinase. Transfection of the u-PAR-deficient GEO cells with a constitutively activated MEK1 expression construct upregulated u-PAR promoter activity. Similarly treatment of GEO cells with a phosphatase inhibitor (sodium vanadate) caused a dose-dependent increase in ERK1 activity which paralleled increased cell surface binding of urokinase. Taken together, these data suggest that elevated u-PAR expression, in at least a sub-population of colon cancer, is partly a consequence of a constitutively activated ERK-1-dependent signaling cascade.
AB - The urokinase-type plasminogen activator receptor (u-PAR) facilitates extracellular matrix degradation in part by accelerating plasmin formation at the cell surface. We previously reported that u-PAR expression is elevated in colon cancer cell lines characterized by their in vitro invasive capacity. Since, u-PAR expression is increased by a variety of growth factors, which signal through the extracellular signal-regulated kinases 1 and 2 (ERK1/ERK2), we determined if these mitogen-activated protein kinases (MAPKs) regulate u-PAR expression in two cultured colon cancer cell lines. An in-gel kinase assay showed that ERK1 activity was considerably higher in RKO cells, which display ≤ 105 receptors/cell, than the GEO cells which have ≃ 104 urokinase receptors per cell. The expression of either an ERK-inactivating phosphatase (CL100), or a kinase-defective ERK1, decreased the activity of a u-PAR promoter-driven CAT reporter in RKO cells. Immune complex kinase assays indicated that the constitutive ERK1 activity in RKO cells was largely a result of an activated MEK1. Further, treatment of RKO cells with a specific inhibitor (PD 098059) of MEK1 activation, which diminished ERK1 activity, reduced the amount of urokinase specifically bound to the cell surface and this was associated with reduced laminin degradation. The expression of a dominant negative c-Raf-1 also reduced u-PAR promoter activity suggesting that MEK1 activation involved an activator at, or upstream, of this serine-threonine kinase. Transfection of the u-PAR-deficient GEO cells with a constitutively activated MEK1 expression construct upregulated u-PAR promoter activity. Similarly treatment of GEO cells with a phosphatase inhibitor (sodium vanadate) caused a dose-dependent increase in ERK1 activity which paralleled increased cell surface binding of urokinase. Taken together, these data suggest that elevated u-PAR expression, in at least a sub-population of colon cancer, is partly a consequence of a constitutively activated ERK-1-dependent signaling cascade.
KW - Extracellular signal-regulated kinase
KW - Invasion
KW - Mitogen activted protein kinase
KW - Urokinase receptor
UR - http://www.scopus.com/inward/record.url?scp=0030996974&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0030996974&partnerID=8YFLogxK
U2 - 10.1038/sj.onc.1201098
DO - 10.1038/sj.onc.1201098
M3 - Article
C2 - 9191056
AN - SCOPUS:0030996974
SN - 0950-9232
VL - 14
SP - 2563
EP - 2573
JO - Oncogene
JF - Oncogene
IS - 21
ER -