Carcinogenesis Advance Access published online on January 6, 2009
Carcinogenesis, doi:10.1093/carcin/bgp001
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Differential roles for membrane-bound and soluble Syndecan-1 (CD138) in breast cancer progression
Department of Gynecology and Obstetrics, University Hospital Münster, D-48149 Münster, Germany
1 Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
2 Agencourt Biosciences Corporation, Beverly, MA 01915, USA
3 Department of Medical Biochemistry and Microbiology, University of Uppsala, SE-751 23 Sweden
4 Department of Physiological Chemistry and Pathobiochemistry, University Hospital Münster, D-48149 Münster, Germany
5 Institute of Transfusion Medicine and Transplantation Immunology, University Hospital of Münster, D-48149 Münster, Germany
* To whom correspondence should be addressed. Tel: +49-251-83-56117, Fax: +49-251-83-55928, E-mail: martingotte{at}uni-muenster.de, Correspondence may also be addressed to George W. Yip, Tel: +65-6516-3206, Fax: +65-6778-7643, E-mail: georgeyip{at}nus.edu.sg
The heparan sulfate proteoglycan Syndecan-1 modulates cell proliferation, adhesion, migration, and angiogenesis. Proteinase-mediated shedding converts Syndecan-1 from a membrane-bound coreceptor into a soluble effector capable of binding the same ligands. In breast carcinomas, Syndecan-1 overexpression correlates with poor prognosis and an aggressive phenotype. To distinguish between the roles of membrane-bound and shed forms of Syndecan-1 in breast cancer progression, human MCF-7 breast cancer cells were stably transfected with plasmids overexpressing wild-type-, constitutively shed- and uncleavable forms of Syndecan-1. Overexpression of wild-type Syndecan-1 increased cell proliferation, whereas overexpression of constitutively shed Syndecan-1 decreased proliferation. FGF-2-mediated MAP kinase signalling was reduced following siRNA-mediated knockdown of Syndecan-1 expression. Constitutively membrane bound Syndecan-1 inhibited invasiveness, whereas soluble Syndecan-1 promoted invasion of MCF-7 cells into matrigel matrices. The latter effect was reversed by the MMP inhibitors N-isobutyl-N-(4-methoxyphenylsufonly) glycyl hydroxamic acid and TIMP-1. Affymetrix microarray analysis identified TIMP-1, Furin and uPAR as genes differentially regulated in soluble Syndecan-1 overexpressing cells. Endogenous TIMP-1 expression was reduced in cells overexpressing soluble Syndecan-1 and increased in those overexpressing the constitutively membrane-bound Syndecan-1. Moreover, E-cadherin protein expression was downregulated in cells overexpressing soluble Syndecan-1. Our results suggest that the soluble- and membrane-bound forms of Syndecan-1 play different roles at different stages of breast cancer progression. Proteolytic conversion of Syndecan-1 from a membrane-bound into a soluble molecule marks a switch from a proliferative to an invasive phenotype, with implications for breast cancer diagnostics and potential glycosaminoglycan-based therapies.
Received June 24, 2008; revised November 9, 2008; accepted December 21, 2008.