title: Elevated urokinase-specific surface receptor expression is maintained through its interaction with urokinase plasminogen activator.
abstract: Urokinase plasminogen activator (uPA) and its receptor (uPAR) are overexpressed in various neoplasms, and play a key role in tumor progression and metastasis. In this study, we examined uPA and uPAR expression in a variety of human breast cancer cell lines and found that lines with elevated uPA expression also exhibited high uPAR expression, suggesting the possibility that uPA and uPAR are regulated in concert. To test this possibility, we introduced antisense uPA RNA and antisense uPAR RNA in MDA-MB-231 and BT-549 lines that express high levels of uPA and uPAR. Antisense uPA RNA not only downregulated uPA expression, but also greatly reduced uPAR expression in both lines. However, antisense uPAR RNA-reduced uPAR expression with no apparent inhibitory effect on the levels of uPA. These results indicate that expression of uPAR requires uPA but not vice versa. With a panel of uPA and uPAR monoclonal antibodies (mAbs), we observed that the mAbs disrupting uPA and uPAR interaction, rather than mAb inhibiting uPA protease activity, reduced uPAR expression. Moreover, adding soluble single chain uPA (scuPA) to MDA-MB-231 or BT-549 cells expressing antisense uPA mRNA-restored uPAR expression. These findings suggest that uPA dictates uPAR expression and that uPA binding to uPAR transmits signals for uPAR expression. Finally, we provided evidence that Fyn, a Src family kinase, is involved in uPA-induced uPAR expression.
authors.affiliation: Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA.
authors.forename: Chitladda
authors.initials: C
authors.lastname: Mahanivong
authors.forename: Jianqiang
authors.initials: J
authors.lastname: Yu
authors.forename: Shuang
authors.initials: S
authors.lastname: Huang
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000081247:CSK Tyrosine-Protein Kinase; D015536:Down-Regulation; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D015151:Immunoblotting; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051076:Proto-Oncogene Proteins c-fyn / Q000378:metabolism; D016372:RNA, Antisense / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; C524898:PLAUR protein, human; D017395:Plasminogen Activator Inhibitor 1; D011518:Proto-Oncogene Proteins; D016372:RNA, Antisense; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; C494957:FYN protein, human; D051076:Proto-Oncogene Proteins c-fyn; D019061:src-Family Kinases; C000631346:CSK protein, human; D014568:Urokinase-Type Plasminogen Activator