Effect of pharmacologic plasminogen activator inhibitor-1 inhibition on cell motility and tumor angiogenesis.
BACKGROUND
Plasminogen activator inhibitor-1 (PAI-1) is integrally involved in tumorigenesis by impacting on both proteolytic activity and cell migration during angiogenesis.


OBJECTIVE
We hypothesized that an orally active small molecule inhibitor of PAI-1 (PAI-039; tiplaxtinin) could affect smooth muscle cell (SMC) attachment and migration in vitro on a vitronectin matrix, and exhibit antiangiogenic activity in vivo.


METHODS
In vitro assays were used to assess the mechanism of inhibition of PAI-1 by PAI-039 using wild-type PAI-1 in the presence or absence of vitronectin and wild-type PAI-1 and specific PAI-1 mutants in SMC adhesion and migration assays. An in vivo tumor angiogenesis model was used to assess the effect of PAI-039 administration on neovascularization in a Matrigel implant.


RESULTS
PAI-039 dose-dependently inhibited soluble, but not vitronectin-bound, PAI-1. Cell adhesion assays using PAI-1 mutants unable to bind vitronectin (PAI-1K) or inactivate proteases (PAI-1R) further suggested that PAI-039 inactivated PAI-1 by binding near its vitronectin domain. In a tumor angiogenesis model, PAI-039 treatment of wild-type mice dose-dependently decreased hemoglobin concentration and endothelial cell staining within the Matrigel implant, indicating reduced angiogenesis, but exhibited no in vivo efficacy in PAI-1 null mice.


CONCLUSIONS
Administration of an orally active PAI-1 inhibitor prevented angiogenesis in a Matrigel implant. The lack of activity of PAI-039 against wild-type PAI-1 bound to vitronectin and PAI-1K suggests PAI-039 binding near the vitronectin-binding site. Our studies further substantiate a role for PAI-1 in cellular motility and tumor angiogenesis, and suggest for the first time that these effects can be modulated pharmacologically.
Leik
C E
CE
Department of Cardiovascular and Metabolic Diseases Research, Wyeth Research, Collegeville, PA, USA.
Su
E J
EJ
Nambi
P
P
Crandall
D L
DL
Lawrence
D A
DA
D020533:Angiogenesis Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D001011:Aorta; D002448:Cell Adhesion / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects*; D002478:Cells, Cultured; D003094:Collagen; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007210:Indoleacetic Acids / Q000494:pharmacology* / Q000627:therapeutic use; D007797:Laminin; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009154:Mutation; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D009369:Neoplasms / Q000098:blood supply / Q000188:drug therapy; D009389:Neovascularization, Pathologic / Q000378:metabolism / Q000517:prevention & control*; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011509:Proteoglycans; D019096:Vitronectin / Q000378:metabolism
D020533:Angiogenesis Inhibitors; D004338:Drug Combinations; D007210:Indoleacetic Acids; D007797:Laminin; D017395:Plasminogen Activator Inhibitor 1; D011509:Proteoglycans; D019096:Vitronectin; C488103:tiplaxtinin; C059485:matrigel; D003094:Collagen