Restoration of TGF-β regulation of plasminogen activator inhibitor-1 in Smad3-restituted human choriocarcinoma cells

Abstract

Proliferation, migration, and invasiveness of the normal placental extravillous trophoblast (EVT) cells are negatively regulated by transforming growth factor-β (TGF-β), whereas malignant EVT (JAR and JEG-3 choriocarcinoma) cells are resistant to TGF-β. These malignant cells were found to have lost the expression of Smad3. Present study examined whether Smad3 restitution in JAR cells could restore TGF-β response. We produced a stable Smad3 cDNA-transfected clone (JAR-smad3/c) which exhibited further upregulation of Smad3 in the presence of TGF-β1. Since anti-invasive effects of TGF-β in the normal EVT cells were shown to be mediated in part by plasminogen activator inhibitor-1 (PAI-1) and urokinase-type plasminogen activator (uPA), we compared the expression of PAI-1 and uPA in the normal EVT, JAR, and JAR-smad3/c cells in the presence or absence of TGF-β1. The basal levels of PAI-1 mRNA and secreted PAI-1 and uPA proteins were found to be very low in JAR and JAR-smad3/c cells, as compared to the normal EVT cells. However, TGF-β1 upregulated PAI-1 and downregulated uPA in JAR-smad3/c cells, but not in JAR cells. Thus, resistance of choriocarcinoma cells to anti-invasive effects of TGF-β may, at least in part, be due to loss of Smad3 expression.