Sdc1 Expression Research Articles

Reduced migration, altered matrix and enhanced TGFβ1 signaling are signatures of mouse keratinocytes lacking Sdc1

We have reported previously that syndecan-1 (Sdc1)-null mice show delayed re-epithelialization after skin and corneal wounding. Here, we show that primary keratinocytes obtained from Sdc1-null mice and grown for 3-5 days in culture are more proliferative, more adherent and migrate more slowly than wt keratinocytes. However, the migration rates of Sdc1-null keratinocytes can be restored to wild-type levels by replating Sdc1-null keratinocytes onto tissue culture plates coated with fibronectin and collagen I, laminin (LN)-332 or onto the matrices produced by wild-type cells. Migration rates can also be restored by treating Sdc1-null keratinocytes with antibodies that block alpha6 or alphav integrin function, or with TGFbeta1. Antagonizing either beta1 integrin function using a function-blocking antibody or TGFbeta1 using a neutralizing antibody reduced wild-type keratinocyte migration more than Sdc1-null keratinocyte migration. Cultures of Sdc1-null keratinocytes accumulated less collagen than wild-type cultures but their matrices contained the same amount of LN-332. The Sdc1-null keratinocytes expressed similar total amounts of eight different integrin subunits but showed increased surface expression of alphavbeta6, alphavbeta8, and alpha6beta4 integrins compared with wild-type keratinocytes. Whereas wild-type keratinocytes increased their surface expression of alpha2beta1, alphavbeta6, alphavbeta8, and alpha6beta4 after treatment with TGFbeta1, Sdc1-null keratinocytes did not. Additional data from a dual-reporter assay and quantification of phosphorylated Smad2 show that TGFbeta1 signaling is constitutively elevated in Sdc1-null keratinocytes. Thus, our results identify TGFbeta1 signaling and Sdc1 expression as important factors regulating integrin surface expression, activity and migration in keratinocyte and provide new insight into the functions regulated by Sdc1.

Syndecan-1 expression by stromal fibroblasts promotes breast carcinoma growth in vivo and stimulates tumor angiogenesis

The induction of the cell surface heparan sulfate proteoglycan syndecan-1 (Sdc1) in stromal fibroblasts is observed in more than 70% of human breast carcinomas. Using a coculture model, we have recently shown that stromal cell-derived Sdc1 stimulates carcinoma cell proliferation in vitro, and that this activity requires Sdc1 glycanation. In the present study, we investigated the effect of stromal cell Sdc1 on breast carcinoma growth in vivo. MDA-MB-231 human breast carcinoma cells were inoculated into the flanks of athymic nude mice either alone, or as mixed suspensions with Sdc1-transfected or mock-transfected 3T3 mouse fibroblasts. The mixed tumors showed an intimate association between carcinoma cells and stromal fibroblasts and histologically closely resembled poorly differentiated human breast carcinomas. The presence of fibroblasts led to significantly accelerated tumor growth, which was further augmented (88% increase) by forced expression of stromal Sdc1. The hyperemic macroscopic appearance of tumors containing Sdc1-positive stromal cells contrasted with pale tumors developing in the presence of mock-transfected fibroblasts, which prompted us to examine tumor microvessels. Stromal Sdc1 expression was associated with a significantly elevated microvessel density (36% increase) and a larger vessel area (153% increase). To evaluate the relevance of this finding in human breast cancer, the relationship between stromal Sdc1 and tumor vascularity was also examined in a tissue array containing 207 human breast carcinoma samples. Similar to the xenografts, stromal Sdc1 expression correlated with both vessel density (P=0.013) and total vessel area (P=0.0026). In conclusion, stromal fibroblast-derived Sdc1 stimulates breast carcinoma growth and angiogenesis in vivo.

Induction of syndecan-1 expression in stromal fibroblasts promotes proliferation of human breast cancer cells.

Infiltrating carcinomas characteristically elicit a reactive stromal response, and accumulating evidence indicates that tumor stroma fibroblasts reciprocally promote tumor development and growth. The cell surface heparan sulfate proteoglycan, syndecan-1 (Sdc1), is thought to function as a coreceptor for growth factor and extracellular matrix interactions, and Sdc1 expression is induced in reactive stromal cells in both mice and man. Mice with a targeted mutation in Sdc1 show reduced tumor development in response to oncogene expression and altered responses to other pathological stimuli that are associated with the induction of stromal Sdc1. Here, we test the hypothesis that Sdc1 is required for the growth-promoting activities of reactive stroma. We found that when highly invasive carcinoma cells (MDA-MB-231) were placed in contact with mouse embryonic fibroblasts (MEFs) in a coculture model, Sdc1 expression was induced. Sdc1 was not induced by less invasive or normal cell lines (T47D and NMuMG). Furthermore, the growth of MDA-MB-231 cells was enhanced by 42% when cocultured with Sdc1+/+ MEFs compared with Sdc1-/- MEFs. When T47D cells were cocultured with fibroblasts that expressed transfected Sdc1, these Sdc1-positive fibroblasts stimulated growth of the breast epithelial cells by 85% compared with untransfected controls. The growth-promoting effect was completely abolished when fibroblasts were transfected with mutant Sdc1 lacking heparan sulfate attachment sites. In conclusion, we have demonstrated that a growth-promoting loop exists between breast cancer cells and their stroma that depends on the activity of glycanated Sdc1.