Steroid-induced epithelial-fibroblastic conversion associated with syndecan suppression in S115 mouse mammary tumor cells

Revisiting the Syndecans: Master Signaling Regulators with Prognostic and Targetable Therapeutic Values in Breast Carcinoma

Syndecans (SDC1 to 4), a family of cell surface heparan sulfate proteoglycans, are frequently expressed in mammalian tissues. SDCs are aberrantly expressed either on tumor or stromal cells, influencing cancer initiation and progression through their pleiotropic role in different signaling pathways relevant to proliferation, cell-matrix adhesion, migration, invasion, metastasis, cancer stemness, and angiogenesis. In this review, we discuss the key roles of SDCs in the pathogenesis of breast cancer, the most common malignancy in females worldwide, focusing on the prognostic significance and molecular regulators of SDC expression and localization in either breast tumor tissue or its microenvironmental cells and the SDC-dependent epithelial–mesenchymal transition program. This review also highlights the molecular mechanisms underlying the roles of SDCs in regulating breast cancer cell behavior via modulation of nuclear hormone receptor signaling, microRNA expression, and exosome biogenesis and functions, as well as summarizing the potential of SDCs as promising candidate targets for therapeutic strategies against breast cancer.

Prognostic and clinical significance of syndecan-1 in colorectal cancer: a meta-analysis

Background

Syndecan-1 plays a vital role in the suppression, transformation, and migration of several cancer types, including colorectal cancer (CRC). However, the prognostic and clinical significance of syndecan-1 in CRC remains conflicting. Therefore, we performed a meta-analysis to clarify this relationship.

Methods

A comprehensive literature search for relevant studies published up to December 2014 was performed using PubMed, EMBASE, and Ovid library database. The odds ratio (OR) and pooled hazard ratio (HR) with their 95 % confidence intervals (CI) were used to estimate the effects.

Results

Ten studies with 888 CRC patients were selected for evaluation. The results showed that syndecan-1 expression was lower in CRC tissue than in normal colorectal tissue (OR = 0.02, 95 % CI = 0.00–0.09), and lower in the advanced stage than in the early stage (OR = 2.24, 95 % CI = 1.14 − 4.42). Additionally, syndecan-1 expression was higher in well and moderately differentiated CRC than in poorly differentiated CRC (OR = 2.91, 95 % CI = 1.21–6.98); no significant difference was found in patients with or without lymph node metastasis (OR = 0.91, 95 % CI = 0.34–2.43) and distant metastasis (OR = 0.89, 95 % CI = 0.19-4.21). The pooled results showed that syndecan-1 expression was not associated with survival in CRC patients (HR = 0.93, 95 % CI = 0.86–1.01).

Conclusion

This meta-analysis indicated that loss of syndecan-1 expression is associated with CRC development, histological differentiation, and clinical stage, but not with lymph node metastasis and distant metastasis. In addition, these findings fail to support the prognostic significance of syndecan-1 in CRC.

Central serous chorioretinopathy in patients receiving exogenous testosterone therapy

PURPOSE

To report an association between central serous chorioretinopathy (CSCR) and exogenous testosterone therapy.

METHODS

This is a retrospective case series from two institutions. Patients who presented with fluorescein angiography and optical coherence tomography findings consistent with CSCR were included. All patients were concurrently being treated with exogenous testosterone therapy and lacked other known risk factors for CSCR.

RESULTS

Nine patients presented with CSCR after beginning exogenous testosterone therapy. Two patients stopped therapy with resolution of symptoms and subretinal fluid.

CONCLUSION

Exogenous testosterone may be an independent risk factor for the development of CSCR.

Association of heparan sulfate proteoglycans SDC1 and SDC4 polymorphisms with breast cancer in an Australian Caucasian population

Breast cancer is a common disease in both developing and developed countries with early identification and treatment improving prognosis and survival. Heparan sulfate proteoglycans (HSPGs) are key components of the extracellular matrix (ECM) that mediate cell adhesion, motility, proliferation, invasion and cell signalling. Members of the syndecan family of HSPGs have been identified to be involved in breast cancer progression through their varied interactions with a number of growth factors, ligands and receptors. Specifically, high expression levels of syndecan-1 (SDC1) have been demonstrated in more invasive breast tumours while elevated syndecan-4 (SDC4) levels have been identified to correspond with improved prognosis. With genetic changes in the syndecans and their association with breast cancers plausible, we examined two single nucleotide polymorphisms in SDC1 (rs1131351) and SDC4 (rs67068737) within an Australian Caucasian breast cancer case/control population. No association was found with SDC4 and breast cancer in our population. However, a significant association between SDC1 and breast cancer was identified in both our case/control population and in a replication cohort. When both populations were combined for analysis, this association became more significant (genotype, p = 0.0003; allele, p = 0.0001). This data suggests an increased risk of developing breast cancer associated with the presence of the C allele of the SDC1 rs1131351 single nucleotide polymorphism (SNP) and may provide a marker toward early breast cancer detection.

Syndecan-1 - A new piece in B-cell puzzle

Syndecans are transmembrane proteoglycans, with core proteins mainly decorated with heparan sulfate chains. Syndecan-1 is expressed in a tissue-, cell-and differentiation-specific manner. Its extra-cellular domain can bind via HS chains to matrix elements, to growth factors (especially "heparin-binding" proteins) and to certain biological agents. The ectodomain released by proteolysis can also be functionally active. The cytoplasmic domain can take part in signaling processes as well as in modifying cell shape. In hematopoietic cells syndecan-1 is expressed in normal pre-B-cells and plasma cells, as well as in plasmocytoid and lymphoplasmocytoid malignancies. According to our study syndecan-1 is expressed in B-CLL cells both in tissue environment and in circulation.

Inhibition of PDGF-B induction and cell growth by syndecan-1 involves the ubiquitin and SUMO-1 ligase, Topors

Syndecans are receptors for soluble ligands, including heparin-binding growth factors, and matrix proteins. However, intracellular targets of syndecan-1 (Sdc-1)-mediated signaling are not fully understood. A yeast two-hybrid protein interaction screening of a mouse embryo library identified the ubiquitin and SUMO-1 E3 ligase, Topors, as a novel ligand of the Sdc-1 cytoplasmic domain (S1CD), a finding confirmed by ligand blotting and co-precipitation with Sdc-1 from cell lysates. Deletion mutagenesis identified an 18-amino acid sequence of Topors required for the interaction with the S1CD. By immunohistochemistry, Topors and Sdc-1 co-localized near the cell periphery in normal murine mammary gland (NMuMG) cells in vitro and in mouse embryonic epithelia in vivo. Finally, siRNA-mediated knockdown of Topors demonstrated that Topors is a growth promoter for murine arterial smooth muscle cells and is required for the inhibitory effect of Sdc-1 on cell growth and platelet-derived growth factor-B induction. These data suggest a novel mechanism for the inhibitory effects of Sdc-1 on cell growth that involves the interaction between the cytoplasmic domain of Sdc-1 and the SUMO-1 E3 ligase, Topors.

Long pentraxin-3 inhibits FGF8b-dependent angiogenesis and growth of steroid hormone-regulated tumors

Fibroblast growth factor-8b (FGF8b) exerts nonredundant autocrine/paracrine functions in steroid hormone-regulated tumors. Previous observations had shown that the soluble pattern recognition receptor long pentraxin-3 (PTX3) is a natural selective antagonist for a restricted number of FGF family members, inhibiting FGF2 but not FGF1 and FGF4 activity. Here, we assessed the capacity of PTX3 to antagonize FGF8b and to inhibit the vascularization and growth of steroid hormone-regulated tumors. Surface plasmon resonance analysis shows that PTX3 binds FGF8b with high affinity (K(d) = 30-90 nmol/L). As a consequence, PTX3 prevents the binding of FGF8b to its receptors, inhibits FGF8b-driven ERK1/2 activation, cell proliferation, and chemotaxis in endothelial cells, and suppresses FGF8b-induced neovascularization in vivo. Also, PTX3 inhibits dihydrotestosterone (DHT)- and FGF8b-driven proliferation of androgen-regulated Shionogi 115 (S115) mouse breast tumor cells. Furthermore, DHT-treated, PTX3 overexpressing hPTX3_S115 cell transfectants show a reduced proliferation rate in vitro and a limited angiogenic activity in the chick embryo chorioallantoic membrane and murine s.c. Matrigel plug assays. Accordingly, hPTX3_S115 cells show a dramatic decrease of their tumorigenic activity when grafted in immunodeficient male mice. These results identify PTX3 as a novel FGF8b antagonist endowed with antiangiogenic and antineoplastic activity with possible implications for the therapy of hormonal tumors.

Association of loss of epithelial syndecan-1 with stage and local metastasis of colorectal adenocarcinomas: an immunohistochemical study of clinically annotated tumors

Background

Syndecan-1 is a transmembrane proteoglycan with important roles in cell-cell and cell-extracellular matrix adhesion and as a growth factor co-receptor. Syndecan-1 is highly expressed by normal epithelial cells and loss of expression has been associated with epithelial-mesenchymal transition and the transformed phenotype. Loss of epithelial syndecan-1 has been reported in human colorectal adenocarcinomas, but whether this has prognostic significance remains undecided. Here we have examined syndecan-1 expression and its potential prognostic value with reference to a clinically annotated tissue microarray for human colon adenocarcinomas.

Methods

Syndecan-1 expression was examined by immunohistochemistry of a tissue microarray containing cores from 158 colorectal adenocarcinomas and 15 adenomas linked to a Cleveland Clinic, IRB-approved database with a mean clinical follow-up of 38 months. The Kaplan-Meier method was used to analyze the relationship between syndecan-1 expression and patient survival. Potential correlations between syndecan-1 expression and the candidate prognostic biomarker fascin were examined.

Results

Syndecan-1 is expressed at the basolateral borders of normal colonic epithelial cells. On adenocarcinoma cells, syndecan-1 was present around cell membranes and in cytoplasm. In 87% of adenocarcinomas, syndecan-1 was decreased or absent; only 13% of patients had stained for syndecan-1 on more than 75% of tumor cells. Decreased syndecan-1 correlated with a higher TNM stage and lymph node metastasis and was more common in males (p = 0.042), but was not associated with age, tumor location or Ki67 index. Reduced tumor syndecan-1 staining also correlated with upregulation of stromal fascin (p = 0.016). Stromal syndecan-1 was observed in 16.6% of tumors. There was no difference in survival between patients with low or high levels of either tumor or stromal syndecan-1.

Conclusion

Syndecan-1 immunoreactivity was decreased in the majority of human colon adenocarcinomas in correlation with TNM stage and metastasis to local lymph nodes. In a small fraction of adenocarcinomas, syndecan-1 was upregulated in the local stroma. Syndecan-1 expression status did not correlate with patient survival outcomes. Combined analysis of syndecan-1 in relation to a potential prognostic biomarker, fascin, identified that loss of tumor syndecan-1 correlated significantly with strong stromal fascin staining.

Androgen receptor-mediated repression of novel target genes

BACKGROUND

The androgen receptor (AR) plays a pivotal role in prostate cancer (PCa) initiation and progression. To date, studies have focused disproportionately on androgen-stimulated genes such as prostate-specific antigen (PSA), while repressed genes have gained little attention, even though they too may be involved in regulating cell growth, differentiation, and apoptosis.

METHODS

ChIP Display was used to identify putative AR target genes in the ablation-resistant human PCa cell line, C4-2B. Quantitative real-time reverse transcription-PCR analysis was used to measure gene expression in cells subjected to dihydrotestosterone (DHT) timecourse and dose-response, as well as AR knock-down and bicalutamide-treatments.

RESULTS

We report on three genes, KIAA1217, CHRM1, and WBSCR28, which were newly identified in a screen for AR-occupied regions in C4-2B PCa cells, and which were repressed by treatment with DHT. AR knock-down resulted in increased KIAA1217, CHRM1, and WBSCR28 mRNA, indicating that, like PSA stimulation, AR represses these three genes even in the absence of added ligand. DHT decreased KIAA1217 and CHRM1 pre-mRNA levels, suggesting AR-mediated transcriptional inhibition. Cycloheximide attenuated DHT-mediated repression of CHRM1, suggesting the requirement of new protein synthesis. Furthermore, bicalutamide treatment did not mimic, but rather antagonized DHT-mediated KIAA1217 repression. Unlike the handful of androgen-repressed genes studied thus far, AR occupancy at KIAA1217, CHRM1, and WBSCR28 was mapped outside their respective 5'-promoter regions.

CONCLUSIONS

Many more genes likely share AR-mediated gene repression through distal regulatory elements. Further study of such targets and their transcriptional regulation may help explain the receptor's tumorigenicity in PCa.

Syndecan-1 regulates FGF8b responses in S115 mammary carcinoma cells

In murine mammary carcinoma cells Shionogi 115 (S115) testosterone induces phenotypical transformation which is largely due to expression of fibroblast growth factor (FGF) 8b. Concomitantly, the expression of the cell surface heparan sulfate proteoglycan syndecan-1 is down-regulated. However, if syndecan-1 expression is maintained by transfection with a testosterone-driven syndecan-1 construct, transformation does not occur. Here we have investigated how the down-regulation of syndecan-1 expression in testosterone-treated S115 cells and the high level of expression in syndecan-1 transfected cells influence the cellular responses toward FGF8b. Our results show that high level of syndecan-1 is associated with a decreased magnitude and duration of the FGF8b induced Erk phosphorylation. This effect was observed regardless whether the cells were stimulated directly with exogenous FGF8b or with testosterone to induce autocrine FGF8b production. Moreover, syndecan-1 transfected cells did not respond to FGF8b stimulation by increase in the intracellular free calcium, whereas untransfected cells displayed a rapid (10 s) induction. These data suggest that, in S115 cells, syndecan-1 acts as a modulator of FGF8b signaling that can limit cellular responses to FGF receptor activation. The decreased levels of syndecan-1 expression and upregulation of the FGF signaling system seen in many cancers may contribute to the proliferation of the malignant cells in vivo.

Altered expression of syndecan-1 in prostate cancer

Syndecan-1 is a cell surface heparan sulfate proteoglycan expressed by epithelial cells. It interacts with growth factors, matrix components, and other extracellular proteins, and is thought to be involved in processes such as cell growth, differentiation and adhesion. The expression of syndecan-1 appears generally downregulated in human carcinomas and in experimental cancer models, whereas transfectional expression of syndecan-1 in cultured cancer cells has been shown to inhibit their growth and other aspects of malignant behavior. These findings suggest that analysis of syndecan-1 expression might be of prognostic value in cancer diagnosis, and studies on some carcinomas indeed point to an inverse correlation between syndecan-1 expression and cancer prognosis. So far, little information has been available on the expression of syndecan-1 in human prostate and prostate disease. We have generated and characterized novel antibodies against syndecan-1 and applied them to immunohistochemical staining of specimens representing normal prostate as well as benign and malignant (n=23) prostate disease. The results indicate that syndecan-1 expression is altered but not uniformly absent in prostate cancer, which is in contrast to the expression of high-molecular-weight cytokeratins. The data initially suggest an inverse correlation between syndecan-1 expression and Gleason grade of the tumor, and warrant a larger study to assess the potential prognostic value of analysing syndecan-1 expression in prostate carcinoma.

Syndecans in tumor cell adhesion and signaling

Anchorage of cells to "heparin"--binding domains that are prevalent in extracellular matrix (ECM) components is thought to occur primarily through the syndecans, a four-member family of transmembrane heparan sulfate proteoglycans that communicate environmental cues from the ECM to the cytoskeleton and the signaling apparatus of the cell. Known activities of the syndecans trace to their highly conserved cytoplasmic domains and to their heparan sulfate chains, which can serve to regulate the signaling of growth factors and morphogens. However, several emerging studies point to critical roles for the syndecans' extracellular protein domains in tumor cell behavior to include cell adhesion and invasion. Although the mechanisms of these activities remain largely unknown, one possibility involves "co-receptor" interactions with integrins that may regulate integrin function and the cell adhesion-signaling phenotype. Thus, alterations in syndecan expression, leading to either overexpression or loss of expression, both of which take place in tumor cells, may have dramatic effects on tumor cell invasion.

Sulfated derivatives of Escherichia coli K5 polysaccharides as modulators of fibroblast growth factor signaling

Heparan sulfate (HS) proteoglycans are intimately involved in the regulation of fibroblast growth factor (FGF) signaling. HS and the related glycosaminoglycan heparin interact with FGFs and FGF receptors (FGFRs), and it is believed that both interactions are required for productive FGF signaling. Attempts to inhibit FGF activity have been made with modified heparin preparations, various heparin-like polysaccharide analogues and other polyanionic molecules, which may all act by interfering with the physiological HS-FGF-FGFR interactions on the cell surface. Here, we have studied the potential of sulfated derivatives of a bacterial polysaccharide (capsular polysaccharide from Escherichia coli K5 (K5PS)) in the modulation of FGF-heparin/HS interactions and FGF signaling. We demonstrate that O-sulfated and N,O-sulfated species of K5PS, with high degrees of sulfation, displaced FGF-1, FGF-2, and FGF-8b from heparin. However, only O-sulfated K5PS efficiently inhibited the FGF-induced proliferation of S115 mammary carcinoma cells and 3T3 fibroblasts, whereas N,O-sulfated K5PS had little or no inhibitory effect. Studies with CHO677 cells lacking endogenous HS, as well as with chlorate-treated S115 cells expressing undersulfated HS, indicated that whereas exogenously administered heparin and N,O-sulfated K5PS restored the cellular response toward FGF stimulation, O-sulfated K5PS was largely devoid of such stimulatory activity. Our data suggest that highly O-sulfated species of K5PS may be efficient inhibitors of FGF signaling.

Expression and characterization of minican, a recombinant syndecan-1 with extensively truncated core protein

Syndecan-1 is an integral membrane heparan sulfate/chondroitin sulfate proteoglycan, involved in the control of cell growth and differentiation. The biological activities of syndecan-1 involve interactions with a variety of extracellular ligands, such as growth factors and matrix components, that are mainly mediated by the heparan sulfate moieties. The expression of syndecan-1 is downregulated in various malignant tumors, and low levels of expression appear to correlate with poor prognosis of some cancer types. On the other hand, the extracellular portion of syndecan-1 (ectodomain) has been demonstrated to inhibit the proliferation of various cancer cells in culture, suggesting that proteoglycan-like molecules should be studied further with regard to their antitumor activities. We have expressed, in CHO cells, a truncated syndecan-1 ectodomain ("minican") harboring domains for glycosaminoglycan attachment and antibody recognition. Analysis of recombinant minican indicates that it shares some of the biochemical and biological characteristics attributed to syndecan-1 ectodomain. Minican was thus substituted with heparan sulfate chains and bound to extracellular matrix proteins as well as fibroblast growth factors. Notably, minican inhibited the proliferation of S115 mouse mammary carcinoma cells and the effect seemed to involve inhibition of the Ras/Erk signaling pathway. Our data suggest that recombinant syndecan-1 with a minimal protein component is biologically active. This information may provide useful in further design of proteoglycan-like antitumor molecules.

Heparan sulfate proteoglycans in invasion and metastasis

Because heparan sulfate proteoglycans mediate cell adhesion and control the activities of numerous growth and motility factors, they play a critical role in regulating the metastatic behavior of tumor cells. Due to their utilitarian nature, heparan sulfate proteoglycans may at times act as inhibitors of cell invasion and at other times as promoters of cell invasion, with their function being determined by their location (cell surface or extracellular matrix), the heparin-binding molecules they associate with, the presence of modifying enzymes (proteases, heparanases) and the precise structural characteristics of the proteoglycan. Also, the tissue type and pathophysiological state of the tumor influence proteogylcan function. This review summarizes our current knowledge of the role heparan sulfate proteoglycans play in regulating tumor cell metastasis, proposes mechanisms of how these molecules function and examines the potential for discovery of new therapeutic approaches designed to block metastatic cancer.

Testosterone-induced growth of S115 mouse mammary tumor cells is dependent on heparan sulfate

The androgen-induced proliferation of S115 mouse mammary tumor cells has been suggested to involve autocrinic fibroblast growth factor signaling. Heparan sulfate proteoglycans are required for fibroblast growth factor signaling, presumably due to their ability to alter binding of fibroblast growth factors to their receptors. We have investigated the role of heparan sulfate proteoglycans in the testosterone-induced proliferation of S115 cells. We demonstrate that when the cells are treated with sodium chlorate, which inhibits the sulfation of endogenous heparan sulfate proteoglycans, cell growth becomes dependent on exogenous heparin. The shortest heparin oligosaccharides supporting cell growth were octasaccharides, whereas dodecasaccharides were almost as effective as native heparin. The N-, 2-O-, and 6-O-sulfate groups of heparin were all required for full testosterone response. Treatment of S115 cells with chlorate or testosterone did not alter the expression of fibroblast growth factor receptors 1 or 3, whereas the expression of fibroblast growth factor receptor 2 was down-regulated. We have previously shown that overexpression of syndecan-1 heparan sulfate proteoglycan renders S115 cells insensitive to testosterone and now demonstrate that this effect can be overcome by sodium chlorate treatment in combination with exogenous heparin. Our results suggest that heparin-like molecules are intimately involved in the androgen-mediated proliferation of S115 cells.

Evidence for digenic inheritance in some cases of Antley-Bixler syndrome?

The Antley-Bixler syndrome has been thought to be caused by an autosomal recessive gene. However, patients with this phenotype have been reported with a new dominant mutation at the FGFR2 locus as well as in the offspring of mothers taking the antifungal agent fluconazole during early pregnancy. In addition to the craniosynostosis and joint ankylosis which are the clinical hallmarks of the condition, many patients, especially females, have genital abnormalities. We now report abnormalities of steroid biogenesis in seven of 16 patients with an Antley-Bixler phenotype. Additionally, we identify FGFR2 mutations in seven of these 16 patients, including one patient with abnormal steroidogenesis. These findings, suggesting that some cases of Antley-Bixler syndrome are the outcome of two distinct genetic events, allow a hypothesis to be formulated under which we may explain all the differing and seemingly contradictory circumstances in which the Antley-Bixler phenotype has been recognised.

Association of syndecan-1 with tumor grade and histology in primary invasive cervical carcinoma

OBJECTIVES

The expression of syndecan-1, a cell surface heparan sulfate proteoglycan, is reduced during malignant transformation of squamous cells. Studies on squamous cell carcinoma of the head and neck have shown that syndecan-1-positive tumors are associated with longer overall and recurrence-free survival. The purpose of this study was to analyze syndecan-1 expression in invasive cervical carcinoma and to examine the association of syndecan-1 expression with prognostic factors and overall survival.

METHODS

The study population consisted of 124 patients treated for primary invasive carcinoma of the uterine cervix at the Turku University Central Hospital during the years 1970-1988. The material consisted of 102 (82.3%) squamous cell carcinomas, 16 (12.9%) adenocarcinomas and 1 (0.8%) adenosquamous carcinoma, 1 (0.8%) small cell carcinoma, 1 (0. 8%) adenoid basal carcinoma, 1 (0.8%) carcinosarcoma, and 2 (1.6%) unclassified cervical carcinomas. Syndecan-1 expression was determined on paraffin-embedded tissue blocks using a human syndecan-1-specific monoclonal antibody B-B4 and immunohistochemistry. The expression of syndecan-1 was classified according to staining intensity as well as the percentage of positively stained tumor cells.

RESULTS

Staining intensity was strong in 44 (36%) samples, while 24 (19%) specimens remained syndecan-1-negative. In 49 (40%) samples, the percentage of syndecan-1-positive cells was >/=90%. Syndecan-1 expression, as determined by >/=50% positively stained tumor cells, was associated with the grade of differentiation (P = 0.03) and squamous histology (P < 0.001), but was not associated with clinical stage (P = 0.16) or disease-free survival (P = 0.86). Age (P = 0.003) and clinical stage (P < 0.001) were significant prognostic factors, but syndecan-1 expression determined neither by percentage of positively stained tumor cells nor by staining intensity was associated with the outcome.

CONCLUSIONS

In cervical carcinoma syndecan-1 is associated with histological differentiation grade and squamous histology, but does not predict clinical outcome.

Expression pattern alterations of syndecans and glypican-1 in normal and pathological trophoblast

Syndecans (syn-1, -2, -3, -4) and glypican-1 are proteoglycans expressed during development in association with changes in tissue organization and differentiation. They participate in the modulation of growth factor actions and in cell-cell and cell-matrix adhesion. The expression of syn-1, -2, -3, -4, and glypican-1 has been studied in normal human placenta and in gestational trophoblastic disease such as hydatidiform mole, invasive mole, and choriocarcinoma, using immunohistochemistry and western blots. Syndecan-3 was not expressed in normal or pathological tissues. During normal gestation, the other proteoglycans showed a specific staining pattern, which for some was modified during pregnancy. For instance, syn-1 was only expressed in syncytiotrophoblast; syn-4 was mainly localized in the villous and extravillous cytotrophoblast in the first trimester, whereas at term it was expressed in the syncytiotrophoblast. The most striking results are the altered expression patterns of syndecans and glypican-1 in pathological tissues. These proteoglycans showed a progressive decrease of immunostaining related to the increase of severity of trophoblastic disease, in particular in invasive mole and choriocarcinoma. In addition, dysregulation in the localization of the expression patterns was observed for syn-2 and -4. Because changes in syndecan expression enable cells to become more or less responsive to their micro-environment, the down-regulation and/or dysregulation of syndecans in relation to the degree of severity of trophoblastic diseases provides new insights into the progression of these pathologies.

Transcriptional regulation of Syndecan-1 expression by growth factors

Syndecan-1 is a prototype member of a family of transmembrane heparan sulfate proteoglycans. Syndecan-1 binds extracellular matrix components and fibroblast growth factors (FGFs) and modifies the function of FGFs. Syndecan-1 is constitutively expressed by several epithelial cells, but expression is also induced during many biological phenomena, such as tissue regeneration and the epithelial-mesenchymal interactions during organ development. Growth factors have been the prime candidates to induce syndecan-1 expression in these situations. In fibroblasts syndecan-1 is induced by FGF-2 and in keratinocytes by epidermal growth factor (EGF) and keratinocyte growth factor (KGF). The search for cis-acting elements regulating the growth factor-induced syndecan-1 expression has led to identification of a novel FGF-inducible response element (FiRE). FiRE is activated in fibroblasts and keratinocytes by the same growth factors that induce syndecan-1 expression in these cells. In adult tissues the activation of FiRE is restricted to migrating keratinocytes of healing wounds. The composition of the transcription factor binding to FiRE differs depending on the cell type and the activating growth factor. The FiRE provides a powerful tool for studies on growth factor specificity and regeneration of tissues. Moreover, it implies a novel transcriptional link that creates an FGF action-controlling autoregulatory loop between the heparan sulfate proteoglycans and the heparin-binding FGFs.

Differential regulation of syndecan expression by osteosarcoma cell lines in response to cytokines but not osteotropic hormones

Bone cells are regulated by interactions with both growth factors and components of the extracellular matrix (ECM). Syndecans are cell-surface heparan sulfate proteoglycans known to play a role in cell adhesion and migration, and binding of growth factors. This study was performed to investigate the expression of syndecans by osteoblasts. Reverse transcription-linked polymerase chain reaction (RT-PCR) and Northern analysis detected syndecan transcripts in the human osteosarcoma cell lines MG-63, TE-85, SaOS-2, and U2OS; human osteoblast-like cells; rat calvarial osteoblasts; and in human bone. Western blot analysis of proteoglycans from MG-63 and TE-85 cells detected multiple heparan sulfate proteoglycan core proteins consistent with syndecan expression. Regulation of syndecan-1, -2, and -4 expression was investigated in TE-85, MG-63, and SaOS-2 cells, in response to interleukin (IL)-1beta, and IL-6, parathyroid hormone [PTH(1-34)], and 1,25(OH)2-vitamin D3. Northern analysis demonstrated that in the osteosarcoma cell lines there was no regulation of syndecan transcript levels in response to PTH(1-34) or 1,25(OH)2-vitamin D3 for 24 or 48 h. In contrast, when MG-63 and SaOS-2 cells were incubated with IL-1beta (0.01-10 ng/mL) and IL-6 (0.1-50 ng/mL) there was a dose-dependent decrease in mRNA levels for syndecan-1 and -2 at 24 and 48 h, but in response to IL-1beta upregulation in the levels of syndecan-4 transcripts. In addition, Northern analysis was performed on RNA isolated from neonatal rat calvarial osteoblasts cultured under conditions that promote osteogenesis for 0, 5, 13, 21, and 35 days. Syndecan-1 expression was observed to decrease during the culture period, syndecan-2 transcript levels increased, and there appeared to be no overall change in syndecan-4 levels. Controlled expression of syndecans by cells of the osteoblast lineage may be important in the regulation of osteoblastic proliferation and differentiation.

Syndecan-1 expression suppresses the level of myeloma matrix metalloproteinase-9

ARH-77 human myeloma cells invade into type I collagen gels but become non-invasive when engineered to express syndecan-1, a heparan sulphate proteoglycan that promotes cell adhesion to collagen. To determine if syndecan-1 expression influences the activity of proteases that may facilitate invasion, we analysed media harvested from syndecan-1 expressing and non-expressing cells. High levels of a 92 kD gelatinase accumulated in serum-free growth medium of both parental and control-transfected ARH-77, but much less 92 kD gelatinase accumulated in the medium of ARH-77 transfectants expressing syndecan-1. The gelatinase was identified as matrix metalloproteinase (MMP)-9 because its activity was immunoprecipitated with a MMP-9-specific monoclonal antibody. Gelatinase activity and Western blot analyses revealed 2-3-fold less MMP-9 in medium from syndecan-1 transfected cells than in medium from parental cells. Decreased MMP-9 was not due to increased association of MMP-9 with cells expressing syndecan-1. An inverse correlation between the syndecan 1 level and the level of MMP-9 accumulation in the media was observed using a panel of ARH-77 transfectants expressing syndecan-1. Investigation of six unrelated human myeloma cell lines confirmed that high gelatinase levels were recovered from conditioned media of those that did not express syndecan-1 (ARH-77, Mer and Col) and one line that expressed a low level of syndecan-1 (RPMI-8226), but low gelatinase levels were recovered from media of lines that expressed high levels of syndecan-1 (ARK and clone 2+). Therefore syndecan-1 may play a dual role in inhibiting the metastasis of tumour cells by promoting cell adhesion to the extracellular matrix and suppressing the proteolytic activity needed for invasion.

Androgen regulation of prostate cancer cell FGF-1, FGF-2, and FGF-8: preferential down-regulation of FGF-2 transcripts

Using quantitative RT-PCR, we found that T1 rat prostate cancer cell relative FGF-1 transcript content was about 180-fold greater than that of FGF-2. This difference in transcript content was not representative of T1 cell relative FGF-1 and FGF-2 protein content which showed, at most, only a 4- to 5-fold greater FGF-1 content. Testosterone caused time-dependent down-regulation of prostate cancer cell FGF-2 transcript content without influencing either FGF-1 or FGF-8 transcript content or T1 cell proliferation. Moreover, testosterone-mediated down-regulation of prostate cancer cell FGF-2 transcripts did not result in a statistically significant change in 21.5 or 17.0 kD FGF-2 isoform content. By contrast, an approximately 20% statistically significant decrement in 19.5 kD FGF-2 isoform content was demonstrable following 24 h testosterone treatment. However, following 72 h testosterone treatment, T1 cell 19.5 kD FGF-2 isoform content was not statistically significantly different from that of control. It is probable that the modest and variable decrement in 19.5 kD isoform content is not physiologically significant and is attributable to artifact resulting from difficulty quantifying this minor component of the FGF-2 isoforms. Transient transfection analysis showed that androgen caused concentration-dependent increases in MMTV-LTR regulated expression of chloramphenicol acetyl transferase activity. Consequently, the failure of androgen to affect either T1 cell FGF-1 and FGF-8 transcript content or T1 cell proliferation could not be attributed to defective androgen receptor function. Moreover, the absence of a close relationship between T1 cell FGF-2 transcript and FGF-2 protein content implies that FGF-2 transcript content is not the dominant determinant of prostate cancer cell FGF-2 protein content. Testosterone-mediated down-regulation of prostate-cancer-cell gene expression may have significance for clinical management of human disease that is treated by androgen ablation. The possibility that such ablation may enhance aggressiveness of "androgen-independent" cells by selective upregulation of gene expression merits further consideration.

Regulated shedding of syndecan-1 and -4 ectodomains by thrombin and growth factor receptor activation

The syndecan family of transmembrane heparan sulfate proteoglycans is abundant on the surface of all adherent mammalian cells. Syndecans bind and modify the action of various growth factors/cytokines, proteases/antiproteases, cell adhesion molecules, and extracellular matrix components. Syndecan expression is highly regulated during wound repair, a process orchestrated by many of these effectors. Each syndecan ectodomain is shed constitutively by cultured cells, but the mechanism and significance of this shedding are not understood. Therefore, we examined (i) whether physiological agents active during wound repair influence syndecan shedding, and (ii) whether wound fluids contain shed syndecan ectodomains. Using SVEC4-10 endothelial cells we find that certain proteases and growth factors accelerate shedding of the syndecan-1 and -4 ectodomains. Protease-accelerated shedding is completely inhibited by serum-containing media. Thrombin activity is duplicated by the 14-amino acid thrombin receptor agonist peptide that directly activates the thrombin receptor and is not inhibited by serum. Epidermal growth factor family members accelerate shedding but FGF-2, platelet-derived growth factor-AB, transforming growth factor-beta, tumor necrosis factor-alpha, and vascular endothelial cell growth factor 165 do not. Shed ectodomains are soluble, stable in the conditioned medium, have the same size core proteins regardless whether shed at a basal rate, or accelerated by thrombin or epidermal growth factor-family members and are found in acute human dermal wound fluids. Thus, shedding is accelerated by activation of at least two distinct receptor classes, G protein-coupled (thrombin) and protein tyrosine kinase (epidermal growth factor). Proteases and growth factors active during wound repair can accelerate syndecan shedding from cell surfaces. Regulated shedding of syndecans suggests physiological roles for the soluble proteoglycan ectodomains.

Testosterone induces Ca2+ influx via non-genomic surface receptors in activated T cells

Using the Fura-2 method we investigated a possible direct action of testosterone on cytosolic free calcium of splenic T cells isolated from female C57BL/10 mice. Testosterone at physiological concentrations of 1-10 nM induces an increase in [Ca2+]i within seconds, which is due to Ca2+ influx and not to Ca2+ release from intracellular stores. In contrast, estradiol induces both Ca2+ influx and Ca2+ release. The testosterone-induced Ca2+ influx is mediated by Ni2+-blockable channels and is not inhibited by cyproterone, a blocker of the classical androgen receptor. Ca2+ influx can also be induced by testosterone conjugated to BSA which is impermeable to the plasma membrane. These data indicate a novel mode of direct action of testosterone on T cells which is not mediated through the classical androgen receptor response, but through unconventional plasma membrane receptors.

Inhibition of NFkappaB activity through maintenance of IkappaBalpha levels contributes to dihydrotestosterone-mediated repression of the interleukin-6 promoter

Androgens repress expression of many genes, yet the mechanism of this activity has remained elusive. The cytokine, interleukin-6, is active in a variety of biological systems, and its expression is repressed by androgens. Accordingly we dissected the mechanism of androgen's ability to inhibit interleukin-6 expression at the molecular level. In a series of co-transfection assays, we found that 5alpha-dihydrotestosterone, through the androgen receptor, repressed activation of the interleukin-6 promoter, in part, by inhibiting NFkappaB activity. It did not appear that 5alpha-dihydrotestosterone inhibited NFkappaB by activating the androgen receptor to compete for the NFkappaB response element as we could not detect androgen receptor binding to the IL-6 promoter by DNase I footprinting assay. However, by electrophoretic mobility shift assay we found that 5alpha-dihydrotestosterone repressed formation of NFkappaB middle dotNFkappaB response element complex formation. In LNCaP prostate carcinoma cells, 5alpha-dihydrotestosterone achieved this effect through maintenance of IkappaBalpha protein levels in the face of phorbol ester, a stimulus that results in IkappaBalpha degradation. Finally, we confirmed that IkappaBalpha inhibits NFkappaB-mediated activation of the interleukin-6 promoter. These data suggest that maintenance of IkappaBalpha levels may represent the first identified mechanism for androgen-mediated repression of a natural androgen-regulated gene.

Expression of avian glypican is developmentally regulated

An avian cDNA homologue of human and rat glypicans has been cloned from a stage 17 chicken heart cDNA library and used to analyze the distribution of this proteoglycan during development by Northern analysis and whole mount in situ hybridization. At stages 7-12, strong signals were detected in the cephalic region of the neural folds, rostral portion of paraxial mesoderm, and newly formed epithelial somites. At stages 20-25, strong expression was observed in the mantle zone of the telencephalon, the apical epidermal ridge and proximal region of developing limb. Transcripts also were found in the truncus arteriosus and arteriovenous-canal region of the heart, but not in the myocardium. This distribution pattern suggests that the avian glypican may be involved in the morphogenesis of limb, somite, heart, and brain. The expression of glypican also overlaps FGFs in limb bud, FGF receptors in heart and somite, and NGF receptors in forebrain. The affinity of heparan sulfate proteoglycans for growth factors and the distribution of the avian glypican are consistent with a role for this molecule in growth factor-mediated signals.

Syndecan-1 alterations during the tumorigenic progression of human colonic Caco-2 cells induced by human Ha-ras or polyoma middle T oncogenes

The products of ras and src proto-oncogenes are frequently activated in a constitutive state in human colorectal cancer. In this study we attempted to establish whether the tumorigenic progression induced by oncogenic activation of p21ras and pp60c-src in human colonic Caco-2 cells is associated with specific alterations of syndecan-1, a membrane-anchored proteoglycan playing a role in cell-matrix interaction and neoplastic growth control. To this end, we used Caco-2 cells made highly tumorigenic by transfection with an activated (Val 12) human Ha-ras gene or with the polyoma middle T (Py-MT) oncogene, a constitutive activator of pp60c-src tyrosine kinase activity. Compared with control vector-transfected Caco-2 cells, both oncogene-transfected cell lines (1) contained smaller amounts of membrane-anchored PGs; (2) exhibited decreased syndecan-1 expression at the protein but not the mRNA level; (3) synthesized 35S-labelled syndecan-1 with decreased specific activity; (4) produced a syndecan-1 ectodomain with a lower molecular mass and reduced GAG chain size and sulphation; and (5) expressed heparanase degradative activity. These results show that the dramatic activation of the tumorigenic potential induced by oncogenic p21ras or Py-MT/pp60c-src in Caco-2 cells is associated with marked alterations of syndecan-1 expression at the translational and post-translational levels.

Syndecans, signaling, and cell adhesion

Syndecans are transmembrane proteoglycans which can participate in diverse cell surface interactions, involving extracellular matrix macromolecules, growth factors, protease inhibitors, and even viral entry. Currently, all extracellular interactions are believed to be mediated by distinct structures within the heparan sulfate chains, leaving the roles of chondroitin sulfate chains and extracellular portion of the core proteins to be elucidated. Evidence that syndecans are a class of receptor involved in cell adhesion is mounting, and their small cytoplasmic domains may link with the microfilament cytoskeleton, thereby mediating signaling events. The molecular details are unknown, but the conservation of regions of syndecan cytoplasmic domains, and a strong tendency for homotypic association, support the idea that the ligand-induced clustering may be a discrete source of specific transmembrane signaling from matrix to cytoskeleton, as proposed for other classes of adhesion receptors.

Syndecan-1 expression in mammary epithelial tumor cells is E-cadherin-dependent

E-cadherin is a Ca(2+)-dependent cell-cell adhesion molecule, which is mainly expressed in epithelial cells. Recent studies have shown that E-cadherin has an important role as an invasion suppressor molecule in epithelial tumor cells. Syndecan-1 is a cell surface proteoglycan that has been implicated in a number of cellular functions including cell-cell adhesion, cell-matrix anchorage and growth factor presentation for signalling receptors. Its suppression has also been shown to be associated with malignant transformation of epithelial cells. In order to better understand the coordinated regulation of cell-cell and cell-matrix interactions during malignant transformation, we have studied the expression of syndecan-1 in malignant mammary tumor cells genetically manipulated for E-cadherin expression. In invasive NM-e-ras-MAC1 cells, where E-cadherin was partially downregulated by specific antisense RNA, syndecan-1 expression was suppressed. Furthermore, transfection of E-cadherin cDNA into invasive NM-f-ras-TD cells resulted in the upregulation of syndecan-1 expression in association with decreased invasiveness. In both cases, regulation of syndecan-1 occurred post-transcriptionally, since syndecan-1 mRNA levels remained unchanged. Instead, a translational regulation is suggested, since syndecan-1 core protein synthesis was E-cadherin dependent. Another cell adhesion protein, beta 1-integrin was not affected by E-cadherin expression. The data provide an example of coordinated changes in the expression of two cell adhesion molecules, syndecan-1 and E-cadherin during epithelial cell transformation.

Functional characterization of mouse syndecan-1 promoter

The members of the syndecan family are temporally and spatially expressed heparan sulfate proteoglycans of various tissues, where they mediate extracellular influences on cell morphology and behavior. Functional characterization of the mouse syndecan-1 promoter was carried out in order to elucidate the mechanisms involved in the maintenance of the high transcription levels of syndecan-1 gene in various epithelia. For that 9.5 kilobase pairs of the upstream region of mouse syndecan-1 gene were cloned, sequenced, and used to prepare chimaeric constructs with a reporter gene followed by transient or stable transfections into NMuMG cells, cultured either in the presence or absence of serum, the 2.5-kilobase pair promoter region resulted in the constitutive transcription activity, whereas in 3T3 cells the serum depletion decreased the promoter activity significantly. Deletion of the upstream sequences to -437 base pairs relative to the translation initiation site had little effect on this promoter activity. Further deletion to -365 base pairs removed three GT boxes and slightly increased the promoter activity, whereas the deletion of the next two GC boxes (to -326 base pair) reduced the promoter activity dramatically. All of the GC or GT box sequences bound the same set of Sp1-like nuclear protein in gel shift assays. Nuclear protein binding was also demonstrated around both of the most intense transcription initiation sites. Mutation of these regions separately resulted in total loss of transcription initiation from the deleted site and decreased the promoter activity in relation to the intensity of the abolished start site. This indicates that the transcription initiation of the syndecan-1 gene is directed through initiator-like elements directly overlapping the start sites, as shown for several TATA-less housekeeping and growth regulated genes. We assume that the constitutive high level gene expression in epithelial cells is achieved by the proximal promoter, which is controlled by members of Sp1 transcription factor family.

Experimental induction of epithelial-mesenchymal interconversions

Under some in vitro conditions, such as exposure to collagen, growth factors and related molecules, and agents affecting DNA methylation, a cell phenotype shift can be observed from an epithelial to a mesenchymal state of differentiation. The reverse process, a mesenchymal-to-epithelial conversion can likewise be obtained by certain experimental manipulations. In some instances the change is fully reversible by removing the inducer substances, but in others the conversion appears to be stable and irreversible. Only a partial modulation of the cell phenotype is often seen, but sometimes a complete switch to a new phenotype occurs, and morphological, biochemical and functional characteristics of the parent cells can be abrogated. In some in vivo models development of sarcomatous tumours can be seen in animals transplanted with several types of carcinoma, and it is possible that in some of these experiments an epithelial-to-mesenchymal conversion has occurred too. In normal embryonic development as well as in pathological lesions including tissue repair, tumour invasion, and some malignant biphasic tumours, changes similar to the ones observed in experimental epithelial-mesenchymal interconversion seem to take place. Therefore, it is conceivable that experimentally-induced phenotype conversions reflect an inherent potential of cells, and that under some experimental circumstances normally silent genetic programs for epithelial or mesenchymal differentiation are activated, thus recapitulating a phenomenon that occurs in physiopathological circumstances in vivo.

Expression of syndecan-1 changes during the differentiation of visceral and parietal endoderm from murine F9 teratocarcinoma cells

F9 teratocarcinoma stem cells treated with retinoic acid differentiate in suspension into embryoid bodies with an outer layer of visceral endoderm surrounding a core of largely undifferentiated cells. The visceral endoderm-containing embryoid bodies, when plated onto an extracellular matrix coating, give rise to parietal endoderm outgrowth. These in vitro cell cultures mimic both geometrically and biochemically the differentiation of visceral and parietal endoderm in the early mouse embryo and, thus, were used as a model system for the study of molecular and cellular mechanisms underlying the differentiation of the extraembryonic endoderm lineages. We have investigated the expression of syndecan-1, an integral membrane proteoglycan that binds to multiple components of the extracellular matrix and basic FGF, during visceral endoderm differentiation and parietal endoderm outgrowth. Syndecan-1 immunostaining is detected on all cell surfaces in the undifferentiated embryoid bodies and in the differentiating embryoid bodies prior to the formation of the visceral endoderm. Following the differentiation of visceral endoderm, syndecan-1 localizes predominantly to the basal surface of this epithelial layer, while syndecan-1 staining in the core of differentiated embryoid bodies is faint. Quantitation of cell associated syndecan-1 indicates that syndecan-1 is down-regulated during embryoid body differentiation. However, northern analysis shows that the amounts of steady-state syndecan-1 mRNA are the same in undifferentiated versus differentiated embryoid bodies, suggesting post-transcriptional regulation of syndecan-1 expression in the differentiating embryoid body. Analysis of syndecan-1 distribution in the outgrowth culture by immunofluorescence demonstrates that syndecan-1 is absent from the cell surface of parietal endoderm. However, a substantial amount of syndecan-1 is detected inside parietal endoderm cells. While all three cell types release syndecan-1 ectodomain into the culture medium, the parietal endoderm outgrowth releases more syndecan-1 ectodomain than the differentiated embryoid body. These data suggest that the post-transcriptional control and post-translational shedding of syndecan-1 from the cell surface are developmentally regulated during the differentiation of visceral to parietal endoderm and the migration of parietal endoderm.

Progression to steroid autonomy is accompanied by altered sensitivity to growth factors in S115 mouse mammary tumour cells

Progression to steroid autonomy is a major clinical problem in the treatment of steroid-sensitive tumours. Molecular mechanisms remain unknown but recent hypotheses imply a role for growth factors in this progression. Since S115 + A androgen-responsive mouse mammary tumour cells provide a model system to study this phenomenon in vitro, we have used this model to investigate growth factor gene expression and sensitivity during progression from a steroid sensitive to insensitive state. S115 + A androgen-responsive cells showed a positive proliferative response, morphological response and increased saturation density to various forms of fibroblast growth factor (FGF) and transforming growth factor beta (TGF beta) in both monolayer and suspension culture. A marked synergy was noted, however, between FGF and TGF beta in promoting growth in suspension culture. S115 + A cells possessed mRNA for both acidic FGF (aFGF) and TGF beta 1, both of which were increased by testosterone. Progression to androgen insensitivity was associated with a reversal of growth factor response such that all growth factor responses became generally inhibitory on growth of the unresponsive cells but with a particularly striking synergistic action between FGF and TGF beta 1 on inhibition of both monolayer and suspension growth. Levels of aFGF and TGF beta 1 mRNAs remained low in steroid-insensitive S115-A cells, indicating that loss of response was not associated with any constitutive upregulation of endogenous production of one of these growth factors. The scientific and clinical implications are discussed.

Loss of cell surface syndecan-1 causes epithelia to transform into anchorage-independent mesenchyme-like cells

Simple epithelial cells are polygonal in shape, polarized in an apical-basal orientation, and organized into closely adherent sheets, characteristics that result from a variety of cellular specializations and adhesive proteins. These characteristics are lost when the epithelia transform during embryogenesis into mesenchymal cells or after neoplasia into invasive carcinoma cells. Of the syndecan family of transmembrane heparan sulfate proteoglycans, simple epithelia produce predominantly syndecan-1, which is found at basolateral surfaces and within adhesive junctions. To elucidate the function of this syndecan-1, normal murine mammary gland epithelia were made deficient in syndecan-1 by transfection with an expression vector containing the syndecan-1 cDNA in the antisense configuration. Several independently derived clones of stable transfectants contained the antisense cDNA in their genome and expressed the antisense transcript. These grew either as epithelial islands of closely adherent polygonal cells, identical to both the parental cells and the vector-only control transfectants, or as individual elongated fusiform cells that invaded and migrated within collagen gels, like mesenchymal cells, but were anchorage-independent for growth. The clones that retained epithelial characteristics were moderately deficient in cell surface syndecan-1 (greater than 48% of control levels) but did not differ from control cells in expression of beta 1-integrins and E-cadherin, or in F-actin organization. However, the clones of fusiform cells were severely deficient in cell surface syndecan-1 (less than 12% of control levels) and showed rearranged beta 1-integrins, markedly reduced E-cadherin expression, and disorganized F-actin filaments, but retained mammary epithelial markers. Therefore, depleting epithelia of cell surface syndecan-1 alters cell morphology and organization, the arrangement and expression of adhesion molecules, and anchorage-dependent growth controls. Thus, cell surface syndecan-1 is required to maintain the normal phenotype of simple epithelia.

The effects of the neuN and neuT genes on differentiation and transformation of mammary epithelial cells

Overexpression of the proto-oncogene product, p185neuN, in a non-tumorigenic mammary epithelial line (31E) facilitates aspects of lactogenic differentiation. Formation of branching cords and induction of beta-casein synthesis by 31E cells normally require co-culture of these cells with fibroblasts, or the presence of collagen or fibronectin. In contrast, 31E cells expressing p185neuN spontaneously form branching cords when grown on tissue culture plastic and can synthesize beta-casein in the absence of exogenous substrates or feeder layers. Under these conditions, the cells deposit laminin and fibronectin, indicating a possible role for p185neuN in the deposition of extracellular matrix proteins. Overexpression of the corresponding oncogene product, p185neuT, has markedly different effects. Expression of p185neuT does not facilitate the formation of branching cords or the synthesis of beta-casein when grown on tissue culture plastic, although these cells do deposit laminin and fibronectin. Confocal microscopy indicates a significant difference in the distribution of laminin and fibronectin in 31E cells expressing p185neuT compared to those expressing p185neuN. The effects of p185neuN and p185neuT expression on cell transformation depend on cell type. Expression of both p185neuN and p185neuT increases anchorage-independent growth of 31E cells, but only p185neuT induces anchorage-independent growth of NIH 3T3 fibroblasts. This lineage specificity in the action of p185neuN may be related to observations that overexpression of p185c-erbB-2 (the human homologue of p185neuN) is only associated with the development of human epithelial cancers. The effects of p185neuN on laminin deposition by 31E cells may be relevant to the transforming ability of p185neuN, since laminin can induce anchorage-independent growth of mouse mammary cells. These results suggest that p185neuN and p185neuT could exert their effects on differentiation and transformation of mammary epithelial cells in part by promoting the deposition of extracellular matrix proteins.

Members of the syndecan family of heparan sulfate proteoglycans are expressed in distinct cell-, tissue-, and development-specific patterns

The syndecans are a gene family of four transmembrane heparan sulfate proteoglycans that bind, via their HS chains, diverse components of the cellular microenvironment. To evaluate the expression of the individual syndecans, we prepared cDNA probes to compare mRNA levels in various adult mouse tissues and cultured mouse cells representing various epithelial, fibroblastic, endothelial, and neural cell types and B cells at various stages of differentiation. We also prepared antibody probes to assess whether the extracellular domains of the individual syndecans are shed into the conditioned media of cultured cells. Our results show that all cells and tissues studied, except B-stem cells, express at least one syndecan family member; most cells and tissues express multiple syndecans. However, each syndecan family member is expressed selectively in cell-, tissue-, and development-specific patterns. The extracellular domain of all syndecan family members is shed as an intact proteoglycan. Thus, most, if not all, cells acquire a distinctive repertoire of the four syndecan family members as they differentiate, resulting in selective patterns of expression that likely reflect distinct functions.

Calcium regulation of heparan sulfate proteoglycans in breast cancer cells

Breast tumor cells have been shown to be responsive to calcium in that external calcium modifies cell calcium, shape and growth. In order to highlight some of the numerous mechanisms by which calcium is operating, we investigated its influence on the cell microenvironment and particularly its effect on membrane-associated heparan sulfate proteoglycans. The breast cancer cells MCF-7 were grown either at low (0.04 mM) or high (2.5 mM) calcium concentration. After 3 days of culture, cells were labeled with Na2(35)SO4 for 24 h and cell-associated proteoglycans extracted and purified. We showed that calcium enhances approximately twofold the synthesis of sulfated proteoglycans and, among these sulfated proteoglycans, chemical treatments indicated a specific two- to threefold increase of heparan sulfate proteoglycans. In view of the increasing implication of heparan sulfate proteoglycans in numerous mechanisms such as cell-cell contact, cell-matrix interactions and cell growth control, it appears that calcium may be a target for modulating metastatic and growth processes in breast tumor cells.

The cytoplasmic domain of syndecan-1 is not required for association with Triton X-100-insoluble material

Cell surface heparan sulfate proteoglycans such as syndecan-1 bind various extracellular matrix proteins and have been suggested to interact with the cytoskeleton. Such interactions are thought to be important for stabilizing cell morphology. Syndecan-1 resists extraction with Triton X-100. This insolubility was reported not to be affected by removal of the glycosaminoglycan chains, suggesting that the insolubility is not due to binding to the extracellular matrix, but rather to an association with the actin cytoskeleton (Rapraeger, A., Jalkanen, M. and Bernfield, M. (1986) J. Cell Biol. 103, 2683–2696). To examine further the interaction of syndecan-1 with the Triton X-100-insoluble residue, we expressed wild-type mouse syndecan-1 and a cytoplasmic deletion mutant (tail-less) in Chinese hamster ovary cells. We observed that both the wild-type and the tail-less syndecan-1 were partly insoluble in Triton X-100. The insolubility was not affected by increasing temperature (37 degrees C or 50 degrees C) or by cytochalasin D. Removal of the glycosaminoglycan chains from the ectodomain, however, resulted in complete Triton X-100 solubility, unlike previous reports. Syndecan-1 could also be released into the Triton X-100-soluble fraction by addition of heparin or heparan sulfate to the extraction medium. We conclude that the cytoplasmic domain of syndecan-1 is not responsible for Triton X-100 insolubility. Instead, our results indicate that Triton X-100 insolubility is caused by an interaction of syndecan-1 molecules with other cellular and/or extracellular molecules mediated by the heparan sulfate chains.

Immunohistochemical localization of syndecan-1 in normal and pathological human uterine cervix

Expression of syndecan-1, a cell surface proteoglycan that binds growth factors and extracellular matrix components, was studied in normal and pathological human uterine cervix using immunohistochemical methods. Normal cervical squamous epithelium showed positive staining for syndecan-1 in all cell layers, except the basal cell layer, whereas endocervical columnar epithelium stained weakly. In non-neoplastic reactive lesions, metaplastic squamous cells were positive for syndecan-1, whereas columnar cells showed weak or negative staining. In cervical condylomas, cells showing koilocytotic atypia were positive for syndecan-1. The progression of cervical intraepithelial neoplasia (CIN) grade I to grade III was associated with reduced syndecan-1 expression and localization of syndecan-1 to more superficial cell layers. In squamous cell carcinomas (SCCs), syndecan-1 expression correlated with histological differentiation, being absent from most poorly differentiated tumours. The results suggest that loss of syndecan-1 from atypical cells is an early event during cervical carcinogenesis and show a close association of syndecan-1 expression with preserved epithelial morphology and differentiation.

Translational suppression of syndecan-1 expression in Ha-ras transformed mouse mammary epithelial cells

A cell surface proteoglycan, syndecan-1, has been shown to participate in the maintenance of the epithelial cell morphology. A point mutated activated c-Ha-ras gene under the control of the glucocorticoid inducible MMTV-LTR promoter was transfected into the mouse mammary epithelial cell line, NOG-8. The NOG-8 ras cells were used to study changes in syndecan-1 expression during epithelial transformation. NOG-8 ras cells, when induced to express Ha-ras, transformed and formed foci in monolayer cultures and colonies in suspension cultures. Expression of syndecan-1 at the cell surface was markedly reduced in cells showing the transformed phenotype. The accumulation of newly synthesized core protein of syndecan-1 was suppressed in these cells, whereas mRNA levels remained unchanged. This novel finding indicates that syndecan-1 expression is translationally suppressed in the Ha-ras-transformed epithelial cells. Hence, syndecan-1 loss during epithelial transformation could take place without altering syndecan gene transcription and, on the other hand, could be one of the critical events involved in malignant transformation.

Epithelium-mesenchyme interconversion as example of epithelial plasticity

This review focuses on epithelium-mesenchymal transitions (EMT), defined as dynamic cell restructurations changing the epithelial state of differentiation into a mesenchymal phenotype. These transitions, known to occur during embryogenesis are also involved during some pathological events of adult life, such as wound repair and metastasis of cancer cells. Numerous studies of embryonic EMTs, found during some morphogenetic processes, have stressed the importance of intercellular and cell-matrix adhesive interactions as key elements regulating cell dissociation and acquisition of cell motility. On the other hand, in vitro studies indicate that growth factors, growth-factor related molecules and extracellular matrix components are involved in initiation of EMT. Therefore, the cellular targets of EMT-inducing molecules are likely to include molecules participating in cell adhesion systems.

"Trans-differentiation" from epidermal to mesenchymal/myogenic phenotype is associated with a drastic change in cell-cell and cell-matrix adhesion molecules

Cells of the human keratinocyte line HaCaT were shifted to a mesenchymal/myogenic phenotype (DTHMZ cells) by MyoD1 transfection, 5-aza-2' deoxycytidine treatment, and selection for reduced adhesion on plastic. Since this correlated with loss of stratification (inability to form a multilayered tissue), we determined the status of cell-cell and cell-matrix adhesion molecules involved in epidermal morphogenesis. Expression of desmosomal proteins (plakoglobin, desmoglein, desmoplakin) and uvomorulin was no longer detectable at the mRNA and protein level in the DTHMZ cells while both HaCaT cells and malignant variants (transfected with c-Ha-ras oncogene) expressed uvomorulin in vitro and in transplants in vivo, the latter even in invasively growing tumor nodules. Furthermore, HaCaT cells stained positive for the integrin subunits beta 1, alpha 2, alpha 3, and alpha 5, typical for cultured keratinocytes. In contrast, the putative fibronectin receptor alpha 5 beta 1, common also in fibroblasts, was the only integrin showing strong staining in DTHMZ cells. The integrin subunits alpha v and a6, clearly expressed at the mRNA level, weakly stained HaCaT cultures and led to a dotlike fluorescence in DTHMZ cells, possibly representing focal adhesion plaques. The respective integrin status correlated well with the growth behavior on different matrices. While HaCaT cells readily attached and proliferated on collagen (type I), fibronectin-coated, and laminin-coated collagen gels, DTHMZ cells formed monolayers only on fibronectin-coated collagen. This was, however, not sufficient to allow stratification in vivo. Altogether, the status of adhesion molecules in DTHMZ cells more likely reflects that seen in mesenchymal cells as compared to the pattern of keratinocytes displayed by HaCaT cells. Moreover, since the DTHMZ cells were clearly HaCaT descendants, the results support our hypothesis of a "trans-differentiation" process from an epidermal (HaCaT) to a mesenchymal/myogenic phenotype (DTHMZ).

Syndecan-1, a cell-surface proteoglycan, changes in size and abundance when keratinocytes stratify

In epidermis, keratinocytes in the basal cell layer differentiate, lose their attachment to the underlying extracellular matrix, and form extensive intercellular adhesions as they stratify. The alterations in cell-matrix and cell-cell adhesion required for keratinocyte stratification result from changes in the expression of numerous adhesion molecules. Syndecan-1, a member of a family of cell-surface proteoglycans, is known to bind cells to interstitial matrix. Syndecan-1 localizes to specific layers of mouse epidermal keratinocytes; its expression is modest in the basal layer, heavy in the suprabasal layers, but absent from the most superficial, terminally differentiated layers. This layer-specific difference suggests that syndecan-1 expression changes with keratinocyte differentiation. To assess this hypothesis, syndecan-1 expression was evaluated before and after calcium-induced stratification and differentiation. Cells growing as an unstratified monolayer express a higher molecular mass form of syndecan-1 than do stratified cells (modal relative mass of 160 kD versus 110 kD). This structural difference is due to larger and more heparan sulfate chains on syndecan-1 from monolayer cells. In addition, the amount of cell-surface syndecan-1 changes with stratification; stratified cultures show approximately 2.5 times more syndecan-1 per cell than do unstratified cultures, but do not significantly change the level of syndecan-1-specific mRNA. Thus, the structure and amount of syndecan-1 may be regulated to meet the changing adhesive requirements of stratifying keratinocytes.