Effects of overexpression of syndecan-1 in mesenchymal tumor cells

Abstract: BackgroundAll cells carry a transmembrane proteoglycan calledsyndecan. Syndecans influence many functions like cell migration, cell adhesionand cell proliferation and it is involved in cellular signaling andtumourigenesis. The common features of differentiation in twomesenchymal tumor cell types, malignant mesothelioma cells and fibrosarcoma cells,are connected to the synthesis of syndecans. By studying the overexpression ofsyndecan-1 we hope to discover new features of the syndecan-1 molecule that wecan add to the puzzle of mesenchymal tumors. Methods and findingsMalignant mesothelioma cells and fibrosarcoma cellswere cultured and transfected with full-length- and truncated syndecan-1 constructs.To detect the expression of syndecan-1 on RNA level Rt-Q-PCR was conductedfollowed by immunocytochemical analysis to establish the syndecan-1 expressionon protein level. The result showed a 2-7 fold increase of syndecan-1 in thetransfectants comparing to the control. The proliferation of transfectants was analyzedby cell proliferation assay and cell cycle analysis. All transfectants showed alower proliferation rate comparing to the controls and a slight increase inG0/G1 phase. Because of the high structural similarities ofsyndecan family members, I studied how overexpression of syndecan-1 affected theother syndecans using Rt-Q-PCR. Syndecan-2 and -4 were downregulated in thetransfectants carrying syndecan-1 ectodomain, whereas the truncated versionshad the opposite effect. The expression of syndecan-bound heparan sulfate wasstudied by FACS and indicated an upregulation for heparan sulfate whenmeasuring internal- and membrane bound syndecans simultanesly. ConclusionsIn this study I haveshown that overexpression of full-length syndecan-1 and the different truncatedvariants, had similar profound effects on mesenchymal cell proliferation. Syndecan-1also influences the other members of the syndecan family suggesting a complexregulation.