Tumor cell-conditioned medium stimulates expression of the urokinase receptor in vascular endothelial cells.
We have previously reported that culture medium conditioned by human SK-Hep1 hepatoma cells or mouse S180 sarcoma cells induces in vitro angiogenesis and stimulates production of urokinase plasminogen activator (uPA) in vascular endothelial cells. These activities are mediated by a 3.5-10 kDa, heparin-binding peptide that upregulates endothelial cell expression of basic fibroblast growth factor (bFGF; Peverali et al., 1994, J. Cell. Physiol. 161:1-14.) We now report that SK-Hep 1 or S180 cell-conditioned medium rapidly induces a 4- to 5-fold increase in cell-bound uPA activity and in the high-affinity binding of 125I-prouPA to vascular endothelial cells. Ligand blotting and purification experiments show an equivalent increase in the synthesis of a cell surface protein corresponding to the endothelial cell uPA receptor (uPAR) on the basis of M, (45-50 kDa) and sensitivity to phosphatidylinositol-specific phospholipase C (PI-PLC). The tumor cell-conditioned media also upregulate uPAR mRNA levels in endothelial cells. Thus, the increase in uPA binding capacity of endothelial cells is mediated by an increased expression of uPAR. The uPAR-inducing activity of SK-Hep 1 or S180 cell-conditioned medium is not neutralized by antibodies to bFGF, and is associated with a peptide that has a M, higher than 10 kDa and no affinity for heparin. Therefore, it appears to be distinct from the bFGF/uPA-inducing factor secreted by the same cells, and from other heparin-binding cytokines that upregulate uPAR expression in endothelial cells.
Dipartimento di Genetica e Microbiologia, Università di Pavia, Italy.
G
G
Seghezzi
R
R
Marelli
S J
SJ
Mandriota
M L
ML
Nolli
R
R
Mazzieri
P
P
Mignatti
D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D015152:Blotting, Northern; D002417:Cattle; D002847:Chromatography, Agarose; D017077:Culture Media, Conditioned / Q000737:chemistry / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D004730:Endothelium, Vascular / Q000378:metabolism*; D005346:Fibroblast Growth Factors / Q000276:immunology; D006801:Humans; D051379:Mice; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D014407:Tumor Cells, Cultured; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism
D000906:Antibodies; D017077:Culture Media, Conditioned; C524898:PLAUR protein, human; C524899:Plaur protein, mouse; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D005346:Fibroblast Growth Factors; D014568:Urokinase-Type Plasminogen Activator