title: XR5967, a novel modulator of plasminogen activator inhibitor-1 activity, suppresses tumor cell invasion and angiogenesis in vitro.
abstract: Recent reports suggest that elevated levels of plasminogen activator inhibitor (PAI)-1 may contribute to tumor progression. We have recently shown that antibodies to PAI-1 block the invasive and migratory potential of human fibrosarcoma cells and suppress angiogenesis in vitro. Here we report the in vitro evaluation of a low-molecular-weight modulator of PAI-1, XR5967, on invasion, migration and angiogenesis. XR5967, a diketopiperazine, dose-dependently inhibited the activity of human and murine PAI-1, towards urokinase plasminogen activator (uPA), with IC50 values of 800 nM and 8.3 microM, respectively. This was confirmed by SDS-PAGE, revealing that XR5967 inhibited complex formation between PAI-1 and uPA. This suppression may be caused by XR5967 promoting insertion of the reactive center loop within PAI-1. XR5967 dose-dependently inhibited the invasion of human HT1080 fibrosarcoma cells through Matrigel. Their invasion was reduced by 57% (p<0.001) at 5 microM. HT1080 cell migration was inhibited in a similar manner, indicating that PAI-1 may play an additional role in invasion, which is distinct to its role in the regulation of proteolysis. The potential of XR5967 to inhibit the invasion/migration of human endothelial cells was investigated in an in vitro model of angiogenesis. In this model XR5967 reduced tubule formation by 77% at 5 microM (p<0.001), highlighting a crucial role for PAI-1 in angiogenesis. These data stress the importance of a balanced proteolysis in the processes of invasion, migration and angiogenesis. Our results support the clinical findings and indicate that modulation of PAI-1 activity, with low-molecular-weight inhibitor of PAI-1 activity, may be of therapeutic benefit for the treatment of cancer.
authors.affiliation: Xenova Ltd, Slough, Berkshire, UK. teresa.brooks@icr.ac.uk
authors.forename: Teresa D
authors.initials: TD
authors.lastname: Brooks
authors.forename: Shouming W
authors.initials: SW
authors.lastname: Wang
authors.forename: Nils
authors.initials: N
authors.lastname: Brünner
authors.forename: Peter A
authors.initials: PA
authors.lastname: Charlton
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D018920:Coculture Techniques; D004591:Electrophoresis, Polyacrylamide Gel; D042783:Endothelial Cells; D005456:Fluorescent Dyes; D006801:Humans; D015394:Molecular Structure; D010879:Piperazines / Q000494:pharmacology* / Q000627:therapeutic use; D017395:Plasminogen Activator Inhibitor 1 / Q000737:chemistry / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000378:metabolism*; D014568:Urokinase-Type Plasminogen Activator / Q000032:analysis / Q000737:chemistry / Q000378:metabolism
chemical_list: D020533:Angiogenesis Inhibitors; D000970:Antineoplastic Agents; D005456:Fluorescent Dyes; D010879:Piperazines; D017395:Plasminogen Activator Inhibitor 1; D015842:Serine Proteinase Inhibitors; C492576:XR 5967; D014568:Urokinase-Type Plasminogen Activator