Reversible Disruption of Cell-Matrix and Cell-Cell Interactions by Overexpression of Sialomucin Complex*
- From the Departments of ‡Cell Biology and Anatomy and§Biochemistry and Molecular Biology, University of Miami School of Medicine, Miami, Florida 33101
Abstract
Sialomucin complex (SMC) is a large, heterodimeric glycoprotein complex composed of mucin (ASGP-1) and transmembrane (ASGP-2) subunits and expressed abundantly on the cell surface of ascites 13762 rat mammary adenocarcinoma cells. We have isolated recombinant cDNAs containing different numbers of ASGP-1 mucin repeats, which can be expressed as protein products with variable lengths. To study the anti-adhesive effect of SMC, these cDNAs were transfected into human cancer cell lines. Using a tetracycline-responsive, inducible expression system, we demonstrated that the overexpression of SMC induces morphology changes, cell detachment, and cell-cell dissociation of transfected A375 human melanoma cells in culture. The transition between the adherent and suspension states of the cells is fully reversible and dependent on the SMC expression level. The anti-adhesion effect of SMC was further analyzed kinetically by measuring the cell adhesion of transfected A375 melanoma and MCF-7 breast cancer cell lines to fibronectin, laminin, and collagen IV, demonstrating that SMC disrupts integrin-mediated cell adhesion to extracellular matrix proteins. The degree of this anti-adhesion effect was dependent on the number of mucin repeats in the SMC molecule as well as the level of cell surface expression.
Footnotes
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↵* This research was supported in part by Grant CA 52498 from the National Institutes of Health, a grant from Amgen, Inc., and by Grant CA 14395 from the Sylvester Comprehensive Cancer Center.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵¶ To whom correspondence should be addressed: Dept. of Cell Biology and Anatomy (R-124), University of Miami School of Medicine, Miami, FL 33101. Tel.: 305-243-6512; Fax: 305-243-4431; E-mail:Kcarrawa{at}mednet.med.miami.edu.
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↵1 The abbreviations used are: SMC, sialomucin complex containing ASGP-1 and ASGP-2; ASGP, ascites sialoglycoprotein; RT-PCR, reverse transcription-polymerase chain reaction; PAGE, polyacrylamide gel electrophoresis; PBS, Dulbecco’s phosphate-buffered saline without calcium; mAb, monoclonal antibody; BSA, bovine serum albumin; ECM, extracellular matrix; kbp, kilobase pair(s).
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- Received September 29, 1997.
- Revision received October 8, 1997.
