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Tumor cell‐conditioned medium stimulates expression of the urokinase receptor in vascular endothelial cells
Author(s) -
Seghezzi Graziano,
Marelli Rosaria,
Mandriota Stefano J.,
Nolli Maria Luisa,
Mazzieri Roberta,
Mignatti Paolo
Publication year - 1996
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/(sici)1097-4652(199611)169:2<300::aid-jcp9>3.0.co;2-s
Subject(s) - urokinase receptor , endothelial stem cell , angiogenesis , basic fibroblast growth factor , cell culture , microbiology and biotechnology , biology , receptor , cell , chemistry , in vitro , growth factor , cancer research , biochemistry , genetics
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‐Hep1 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 125 I‐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‐Hep1 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. © 1996 Wiley‐Liss, Inc.