Carcinogenesis Advance Access originally published online on January 6, 2009
Carcinogenesis 2009 30(3):397-407; 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 117597
2 Agencourt Biosciences Corporation, Beverly, MA 01915, USA
3 Department of Medical Biochemistry and Microbiology, The Biomedical Center University of Uppsala, PO Box 582, SE-751 23 Uppsala, Sweden
4 Department of Physiological Chemistry and Pathobiochemistry
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; Email: martingotte{at}uni-muenster.de
Correspondence may also be addressed to George W.Yip. Tel: +65 6516 3206; Fax: +65 6778 7643; Email: georgeyip{at}nus.edu.sg
The heparan sulfate proteoglycan syndecan-1 (Sdc1) modulates cell proliferation, adhesion, migration and angiogenesis. Proteinase-mediated shedding converts Sdc1 from a membrane-bound coreceptor into a soluble effector capable of binding the same ligands. In breast carcinomas, Sdc1 overexpression correlates with poor prognosis and an aggressive phenotype. To distinguish between the roles of membrane-bound and shed forms of Sdc1 in breast cancer progression, human MCF-7 breast cancer cells were stably transfected with plasmids overexpressing wild-type (WT), constitutively shed and uncleavable forms of Sdc1. Overexpression of WT Sdc1 increased cell proliferation, whereas overexpression of constitutively shed Sdc1 decreased proliferation. Fibroblast growth factor-2-mediated mitogen-activated protein kinase signaling was reduced following small-interfering RNA (siRNA)-mediated knockdown of Sdc1 expression. Constitutively, membrane-bound Sdc1 inhibited invasiveness, whereas soluble Sdc1 promoted invasion of MCF-7 cells into matrigel matrices. The latter effect was reversed by the matrix metalloproteinase inhibitors N-isobutyl-N-(4-methoxyphenylsufonyl) glycyl hydroxamic acid and tissue inhibitor of metalloproteinase (TIMP)-1. Affymetrix microarray analysis identified TIMP-1, Furin and urokinase-type plasminogen activator receptor as genes differentially regulated in soluble Sdc1-overexpressing cells. Endogenous TIMP-1 expression was reduced in cells overexpressing soluble Sdc1 and increased in those overexpressing the constitutively membrane-bound Sdc1. Moreover, E-cadherin protein expression was downregulated in cells overexpressing soluble Sdc1. Our results suggest that the soluble and membrane-bound forms of Sdc1 play different roles at different stages of breast cancer progression. Proteolytic conversion of Sdc1 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.
Abbreviations: ADAMs, a disintegrin and metalloproteinases; BSA, bovine serum albumin; FCS, fetal calf serum; FGF, fibroblast growth factor; HS, heparan sulfate; MAPK, mitogen-activated protein kinase; MMP, matrix metalloproteinase; mRNA, messenger RNA; PBS, phosphate-buffered saline; PCR, polymerase chain reaction; PE, phycoerythrin; PMA, phorbol myristate acetate; Sdc1, syndecan-1; siRNA, small-interfering RNA; TIMP, tissue inhibitor of metalloproteinase; uPAR, urokinase-type plasminogen activator receptor; WT, wild-type
Received June 24, 2008; revised November 9, 2008; accepted December 21, 2008.