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Updated: Sep 28, 2026

Conditional Knockdown of Gene Expression in Cancer Cell Lines to Study the Recruitment of Monocytes/Macrophages to the Tumor Microenvironment
Published on: November 23, 2017
Both u-PA inhibition and vitronectin binding by plasminogen activator inhibitor 1 regulate HT1080 fibrosarcoma cell
Michael Praus1, Désiré Collen, Robert D Gerard
1Center for Transgene Technology and Gene Therapy, Flanders Interuniversity Institute for Biotechnology, Katholieke Universiteit Leuven, Leuven, Belgium.
Abstract:
Overexpression of plasminogen activator inhibitor 1 (PAI-1) reduces tumor cell migration in vitro and metastasis in mice in vivo by mechanisms involving either inhibition of urokinase plasminogen activator (u-PA) activity or competition for an integrin binding site on vitronectin. To analyze the effects of PAI-1 on tumor cell migration in vitro and metastasis in vivo, recombinant adenoviral vectors expressing wild-type or mutant PAI-1 proteins were constructed. The mutant PAI-1 proteins were defective in either vitronectin binding (PAI-1(VN-)), plasminogen activator inhibition (PAI-1(INH-)) or both (PAI-1(VN-,INH-)). In vitro, migration of HT1080 human fibrosarcoma cells through a reconstituted extracellular matrix (ECM) was reduced 73% by overexpression of wild-type PAI-1 and 65% by PAI-1(VN-) compared with control virus-infected cells. Migration of cells infected by virus expressing either PAI-1(INH-) or PAI-1(VN-,INH-) was unaffected, indicating a requirement for plasminogen activator inhibitory activity. In vivo, however, only overexpression of wild-type PAI-1 reduced the burden of metastasis by 68% compared with the control group. This indicates that both u-PA inhibition and PAI-1 ECM interactions contribute to the mechanism of PAI-1-mediated regulation of cell migration.
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