Abstract
The human tumor cell line HT-1080 was used as a model system to study the effects of transforming growth factor-beta (TGF beta) on polypeptide synthesis and proteolytic activity of malignant cells. Confluent cultures were exposed to TGF beta under serum-free conditions, and alterations in the production of proteins were examined by metabolic labeling and polypeptide analysis. TGF beta induced the synthesis and secretion of the Mr 47,000 endothelial type plasminogen activator inhibitor (PAI-1) as shown by reverse zymography, immunblotting, and immunoprecipitation analyses. TGF beta-induced PAI-1 was rapidly deposited in the growth substratum of the cells as shown by metabolic labeling and extraction of the cultures with sodium deoxycholate. Using pulse-chase experiments, we found a relatively fast turnover of substratum-associated PAI-1. Exogenously added urokinase released PAI-1 from the substratum even in the presence of the plasmin inhibitor aprotinin, suggesting a direct effect of urokinase. Immunoreactive complexes of higher molecular weight were subsequently detected in the medium. Epidermal growth factor, transforming growth factor-alpha, platelet-derived growth factor, and insulin did not elicit similar effects on the amount of PAI-1. TGF beta also inhibited the anchorage-independent growth of HT-1080 cells at the same concentrations at which it induced PAI-1. These results indicate that TGF beta can modulate the extracellular proteolytic activity of cultured cells by enhancing the secretion and deposition of PAI-1 into their microenvironment. It remains to be established whether TGF beta inhibition of anchorage-independent growth of these cells is associated with the induction of PAI-1.
Highlights
The human tumor cell line HT-1080 was used as a components
This matrix breakdownclearlyalsooccurs in model system to studythe effects of transforming vivo and is prominent in connectionwith maliggrowth factor+ (TGFB) on polypeptide synthesis and nant growth. proteolytic activity of malignant cells
Growth factors participate in the regulation of the proteolytic activity of cultured cells
Summary
From the $Department of Virology, University of Helsinki, Haartmaninkatu3, 002H90elsinki, Finland, the llDepartment of Cell Biology, New York UniversityMedical Center, New York, New York10016, and the IlDepartment of Cell Biology, Vanderbilt University Schoolof Medicine, Nashville, Tennessee37232. TGFB-induced PAI-1was rapidly deposited inthe growth substratum of the cells as shown by metabolic labeling and extraction of the cultures with sodium deoxycholate. TGFB inhibitethde anchorage-independent growth of HT-1080 cells at the same concentrations at which it induced PAI-1 TGFB can modulate the extracellularproteolytic activity of cultured cells by enhancing the secretion and deposition of PAI-1 into their microenvironment It remains to be established whether TGFB inhibition of anchorage-independent growth of these cells is associated with theinduction of PAI-1. We have studied here the effects of TGFP onthe production of a plasminogen activator inhibitor and the anchorage-independent growth of cultured HT-1080 tumor cells. The sodium deoxycholate extraction procedure yields a reproducible pattern of polypeptides consisting of both extracellular matrix proteins [36] and substratum-
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.