REGULATION OF MESOTHELIAL CELL MITOGENESIS BY ANTISENSE OLIGONUCLEOTIDES FOR THE UROKINASE RECEPTOR

The association of urokinase-type plasminogen activator (uPA) with its receptor (uPAR) influences various biologic functions, including cell migration, angiogenesis, differentiation, and wound healing. Expressi on of uPAR at the mesothelial surface could, therefore, influence cell ular responses in the pleural space, We found that a line of cultured human mesothelial cells (MeT5A) expressed specific and saturable bindi ng sites for uPA that increased on stimulation with PMA. Ligand blotti ng studies showed that the mesothelial receptor is a 50 kD protein sim ilar to that in other cell lines. Binding of active and intact, but no t amino terminal or low molecular weight fragment, uPA to mesothelial cells enhanced DNA synthesis and cell proliferation, and antibodies ag ainst either the active site of uPA or uPAR abrogated this effect. We reasoned that regulation of uPAR expression could control uPA-induced mitogenesis and tested this hypothesis with antisense oligonucleotides complementary to uPAR mRNA. Phosphorothioate-modified antisense oligo nucleotides inhibited uPA-mediated mesothelial cell proliferation in a concentration-dependent manner, These effects were associated with de creased binding of I-125-uPA and reduced expression of the uPAR gene p roduct. The results indicate that uPAR is involved in signal transduct ion pathways that control uPA-mediated mesothelial cell proliferation, a process implicated in the pathogenesis of mesothelial inflammation and pleural neoplasia. Antisense oligonucleotides to uPAR suppress mes othelial cell mitogenesis in vitro and offer a potential means of regu lating the process in vivo.