Role of activated protein C in facilitating basement membrane invasion by tumor cells.
The present study was undertaken to investigate the role of plasminogen activator inhibitor type 1 (PAI-1) and activated protein C (APC) in the regulation of tumor cell invasion. PAI-1 was purified in active form from conditioned medium of human umbilical vein endothelial cells under denaturing conditions (4 M guanidine-HCl). The purified inhibitor reacts with urokinase-type plasminogen activator (uPA) and APC. Two selected human lines, HOC-I (ovarian cancer cells) and SMT-ccl (choriocarcinoma cells), preferentially invaded through reconstituted basement membranes in an in vitro invasion assay using a modified Boyden chamber. The present study determined the efficacy of these two agents (PAI-1 and APC) used alone or in combination in inhibiting or facilitating tumor cell invasion. Active PAI-1 inhibited the tumor cell surface receptor-bound uPA activity. In an in vitro invasion assay, active PAI-1 reduced tumor cell invasive potential in a dose-dependent manner. When SMT-ccl cells saturated with uPA-PAI-1 complexes were treated with a 50-fold molar excess of APC, PAI-1-APC complex was demonstrated in conditioned medium, indicating that PAI-1 was dissociated from receptor-bound uPA on tumor cells and that tumor cell-associated uPA restored its enzymatic activity. Although APC alone had no effect on tumor cell invasion, the addition of APC to the cells saturated with uPA-PAI-1 complexes showed regeneration of tumor cell surface receptor-bound uPA activity and produced substantial and efficient invading effects. These data suggest that PAI-1 activity may be neutralized by APC or that APC may promote tumor cell invasion via inactivation of PAI-1 by formation of a stable PAI-1-APC complex. These observations suggest that APC may play a critical role in the initiation of a hematogenous metastatic process (extravasation step).
Kobayashi
H
H
Department of Obstetrics and Gynecology, Hamamatsu University School of Medicine, Shizuoka, Japan.
Moniwa
N
N
Gotoh
J
J
Sugimura
M
M
Terao
T
T
D001485:Basement Membrane / Q000737:chemistry / Q000473:pathology*; D002822:Choriocarcinoma / Q000473:pathology; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology; D009361:Neoplasm Invasiveness; D010051:Ovarian Neoplasms / Q000473:pathology; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D011486:Protein C / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000032:analysis / Q000378:metabolism; D055293:Receptors, Urokinase Plasminogen Activator; D014407:Tumor Cells, Cultured
C524898:PLAUR protein, human; D017395:Plasminogen Activator Inhibitor 1; D011486:Protein C; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator