title: Overexpression of the urokinase receptor mRNA splice variant uPAR-del4/5 affects tumor-associated processes of breast cancer cells in vitro and in vivo.
abstract: uPAR, the three-domain membrane receptor of the serine protease urokinase, plays a crucial role in tumor growth and metastasis. Several mRNA splice variants of this receptor have been reported. One of these, uPAR-del4/5, lacking exons 4 and 5, and thus encoding a uPAR form lacking domain DII, is specifically overexpressed in breast cancer and represents a statistically independent prognostic factor for distant metastasis-free survival in breast cancer patients. The aim of the present study was to examine the molecular and cellular properties of the encoded uPAR-del4/5 protein. To investigate the impact of the uPAR-del4/5 overexpression on in vitro and in vivo aspects of tumor progression (e.g., proliferation, adhesion, invasion, metastatic seeding, and/or metastatic growth), we combined the analysis of transfected cancer cell lines with a murine xenograft tumor model. Increased expression of uPAR-del4/5 in human cancer cells led to reduced adhesion to several extracellular matrix proteins and decreased invasion through Matrigel, while cell proliferation was not affected in vitro. Moreover, invasion of uPAR-del4/5 overexpressing cells was not altered by addition of urokinase, while that of uPAR-wild-type overexpressing cells was drastically increased. Accordingly, we observed that, in contrast to uPAR-wild-type, uPAR-del4/5 does not interact with urokinase. On the other hand, when overexpressed in human breast cancer cells, uPAR-del4/5 distinctly impaired metastatic dissemination and growth in vivo. We demonstrate that the uPAR-del4/5 mRNA splice variant mediates tumor-relevant biological processes in vitro and in vivo. Our results thus illustrate how tumor-specific alternative splicing can distinctly impact the biology of the tumor.
authors.affiliation: Clinical Research Unit, Department of Obstetrics and Gynecology, Technical University Munich, Ismaninger Str. 22, 81675 Munich, Germany.
authors.forename: Sumito
authors.initials: S
authors.lastname: Sato
authors.forename: Charlotte
authors.initials: C
authors.lastname: Kopitz
authors.forename: Bettina
authors.initials: B
authors.lastname: Grismayer
authors.forename: Nathalie
authors.initials: N
authors.lastname: Beaufort
authors.forename: Ute
authors.initials: U
authors.lastname: Reuning
authors.forename: Manfred
authors.initials: M
authors.lastname: Schmitt
authors.forename: Thomas
authors.initials: T
authors.lastname: Luther
authors.forename: Matthias
authors.initials: M
authors.lastname: Kotzsch
authors.forename: Achim
authors.initials: A
authors.lastname: Krüger
authors.forename: Viktor
authors.initials: V
authors.lastname: Magdolen
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D051379:Mice; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D009368:Neoplasm Transplantation; D012333:RNA, Messenger / Q000235:genetics; D055293:Receptors, Urokinase Plasminogen Activator / Q000235:genetics*; D017384:Sequence Deletion
chemical_list: D012333:RNA, Messenger; D055293:Receptors, Urokinase Plasminogen Activator