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: Sumito Sato, Charlotte Kopitz, Bettina Grismayer, Nathalie Beaufort, Ute Reuning, Manfred Schmitt, Thomas Luther, Matthias Kotzsch, Achim Krüger, Viktor Magdolen
• Journal: Breast cancer research and treatment (Breast Cancer Res Treat) Vol. 127 Issue 3 Pg. 649-57 (Jun 2011) ISSN: 1573-7217 [Electronic] Netherlands
• PMID: 20635136 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• RNA, Messenger
• Receptors, Urokinase Plasminogen Activator

Topics

• Alternative Splicing
• Animals
• Blotting, Western
• Breast Neoplasms (genetics, metabolism, pathology)
• Cell Line, Tumor
• Cell Proliferation
• Enzyme-Linked Immunosorbent Assay
• Female
• Fluorescent Antibody Technique
• Humans
• Mice
• Neoplasm Invasiveness
• Neoplasm Metastasis
• Neoplasm Transplantation
• RNA, Messenger (genetics)
• Receptors, Urokinase Plasminogen Activator (genetics)
• Sequence Deletion