Immunologic detection of the cellular receptor for urokinase plasminogen activator.
The cellular receptor for urokinase plasminogen activator (uPA-R) is a monomeric phosphatidylinositol-linked glycoprotein (gp40-65) that may contribute to the invasive capacity of tumor and inflammatory cells by focusing the activity of urokinase (uPA) in converting plasminogen to plasmin, a serine protease capable of degrading extracellular matrix proteins. The further characterization of uPA-R has been facilitated by our recent development of a monoclonal antibody, anti-Mo3f, specific for uPA-R. This mAb bound to uPA-R expressed by phorbol myristate acetate-stimulated U-937 cells and by NIH-3T3 cells permanently transfected with uPA-R cDNA. In competitive binding assays, anti-Mo3f inhibited the binding of fluorescein-conjugated uPA ligand to uPA-R expressed by U-937 cells and uPA-R transfectants; conversely, preexposure of cells to saturating quantities of exogenous uPA partially blocked the subsequent binding of anti-Mo3f mAb to uPA-R. Anti-Mo3f mAb was employed as the capture reagent in an ELISA for the quantitation of soluble forms of uPA-R (derived from U-937 cells and recombinant uPA-R) which had a sensitivity of approximately 4-12 ng/ml. Anti-Mo3f mAb was also applied as a serologic probe for the detection of uPA-R expressed by human tumor tissues. By immunoperoxidase staining, anti-Mo3f demonstrated positive tumor cell staining in 4 of 16 breast and 7 of 31 prostate carcinomas in formalin-fixed, paraffin-embedded specimens. These data indicate that the anti-Mo3f mAb detects an epitope proximate to or within the ligand binding domain (domain 1) of uPA-R and may be useful as a tool for the serologic detection of uPA-R in soluble form or associated with human tumors.
Mizukami
I F
IF
Simpson Memorial Institute, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor 48109.
Garni-Wagner
B A
BA
DeAngelo
L M
LM
Liebert
M
M
Flint
A
A
Lawrence
D A
DA
Cohen
R L
RL
Todd
R F
RF
D016475:3T3 Cells / Q000737:chemistry / Q000648:ultrastructure; D000818:Animals; D000911:Antibodies, Monoclonal / Q000032:analysis; D001483:Base Sequence; D001667:Binding, Competitive; D001943:Breast Neoplasms / Q000737:chemistry / Q000648:ultrastructure; D005260:Female; D006801:Humans; D008024:Ligands; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D010960:Plasminogen Activators / Q000302:isolation & purification; D011471:Prostatic Neoplasms / Q000737:chemistry / Q000648:ultrastructure; D011956:Receptors, Cell Surface / Q000032:analysis* / Q000276:immunology; D055293:Receptors, Urokinase Plasminogen Activator; D014407:Tumor Cells, Cultured / Q000648:ultrastructure; D014568:Urokinase-Type Plasminogen Activator / Q000302:isolation & purification
D000911:Antibodies, Monoclonal; D008024:Ligands; C524898:PLAUR protein, human; C524899:Plaur protein, mouse; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator