Cleavage of the urokinase receptor (uPAR) on oral cancer cells : regulation by transforming growth factor - beta 1 (TGF-beta 1) and potential effects on migration and invasion

• Main Authors: Magnussen, Synnove Norvoll, Hadler-Olsen, Elin, Costea, Daniela Elena, Berg, Eli, Jacobsen, Cristiane Cavalcanti, Mortensen, Bente, Salo, Tuula, Martinez-Zubiaurre, Inigo, Winberg, Jan-Olof, Uhlin-Hansen, Lars, Svineng, Gunbjorg
• Other Authors: Clinicum, Department of Oral and Maxillofacial Diseases
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2017
• Subjects: Urokinase plasminogen activator receptor (uPAR); Urokinase receptor; Transforming growth factor-beta1 (TGF-beta 1); Plasminogen; Plasmin; Cancer; Cell migration; Urokinase; Invasion; PLASMINOGEN-ACTIVATOR RECEPTOR; EPITHELIAL-MESENCHYMAL TRANSITION; LIGAND-BINDING DOMAIN; SMOOTH-MUSCLE-CELLS; BREAST-CANCER; TGF-BETA; IN-VITRO; MYOFIBROBLAST DIFFERENTIATION; TUMOR MICROENVIRONMENT; SOLUBLE RECEPTOR; 3122 Cancers; Arctic
• Online Access: http://hdl.handle.net/10138/190715

Background: Urokinase plasminogen activator (uPA) receptor (uPAR) is up-regulated at the invasive tumour front of human oral squamous cell carcinoma (OSCC), indicating a role for uPAR in tumour progression. We previously observed elevated expression of uPAR at the tumour-stroma interface in a mouse model for OSCC, which was associated with increased proteolytic activity. The tumour microenvironment regulated uPAR expression, as well as its glycosylation and cleavage. Both full-length- and cleaved uPAR (uPAR (II-III)) are involved in highly regulated processes such as cell signalling, proliferation, migration, stem cell mobilization and invasion. The aim of the current study was to analyse tumour associated factors and their effect on uPAR cleavage, and the potential implications for cell proliferation, migration and invasion. Methods: Mouse uPAR was stably overexpressed in the mouse OSCC cell line AT84. The ratio of full-length versus cleaved uPAR as analysed by Western blotting and its regulation was assessed by addition of different protease inhibitors and transforming growth factor - beta 1 (TGF-beta 1). The role of uPAR cleavage in cell proliferation and migration was analysed using real- time cell analysis and invasion was assessed using the myoma invasion model. Results: We found that when uPAR was overexpressed a proportion of the receptor was cleaved, thus the cells presented both full-length uPAR and uPAR (II-III). Cleavage was mainly performed by serine proteases and urokinase plasminogen activator (uPA) in particular. When the OSCC cells were stimulated with TGF-beta 1, the production of the uPA inhibitor PAI-1 was increased, resulting in a reduction of uPAR cleavage. By inhibiting cleavage of uPAR, cell migration was reduced, and by inhibiting uPA activity, invasion was reduced. We could also show that medium containing soluble uPAR (suPAR), and cleaved soluble uPAR (suPAR (II-III)), induced migration in OSCC cells with low endogenous levels of uPAR. Conclusions: These results show that soluble ...