Markku Jalkanen

Syndecan-1: A New Prognostic Marker in Laryngeal Cancer

The cell adhesion molecule syndecan-1 expression is induced during keratinocyte differentiation and reduced during the formation of squamous cell carcinomas (SCCs). A significant correlation between decreased syndecan-1 expression in head and neck SCC measured from frozen sections with immuohistochemical methods and clinical outcome are reported. The clinical relevance of the cellular proliferation marker Ki-67 is controversial in SCC of the head and neck. The purpose of this study was to determine the expression of syndecan-1 and Ki-67 in SCC of the larynx and correlate the results with known prognostic factors and clinical outcome. Paraffin-embedded samples of 100 patients with laryngeal SCC (44 glottic, 36 supraglottic, 20 transglottic) treated at Turku University Central Hospital were re-examined and divided into four histological grades of differentiation, four grades of keratinisation, and four grades of 104-9 (syndecan-1) immunostaining. The mitotic index was analysed as the number of mitoses per volume corrected high power fields. The relative number of Ki-67 positive cells was evaluated. The patients mean age was 64 years and the 5-year survival was 69%. In univariate analysis, intermediate or strong staining for syndecan-1 was associated with higher overall survival than those tumours with no or little syndecan-1 expression (p = 0.048). Nodal status (p = 0.0001), tumour size (p = 0.0004) and localisation (p = 0.0008), general condition (p = 0.0001), histological grade (p = 0.02) and patient age (p = 0.03) correlated with overall survival whereas the Ki-67 index (p = 0.093), mitotic index (p = 0.23) and grade of keratinisation (p = 0.90) failed to do so. The results suggest that syndecan-1 could be a useful prognostic factor in SCC of the larynx.

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.

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.

Production and characterization of the extracellular domain of recombinant human fibroblast growth factor receptor 4.

Among the members of the fibroblast growth factor receptor family the FGFR4 has demonstrated strong dependence on heparin-like material for its activation by fibroblast growth factors. We have produced and characterized a recombinant human FGFR4 extracellular domain (FGFR4ed), in order to study its biochemical properties in isolated conditions. The FGFR4ed was expressed in an insect cell system and purified from the culture medium by Ni(2+)-affinity and gel filtration chromatography. Pure FGFR4ed was tested for FGF- and heparin-binding by covalent crosslinking experiments and by biosensor analysis. In solution, FGFR4ed formed complexes with acidic FGF (FGF-1) and basic FGF (FGF-2), both in the presence and absence of heparin. Immobilized FGFR4 also bound FGF-8 besides FGF-1 and FGF-2. Furthermore, heparin alone induced receptor oligomerization on the surface of the receptor coupled chip. Thus, the recombinant FGFR4ed revealed properties described for the cellular form of this receptor and can be used for interaction studies.

Extracellular matrix-dependent activation of syndecan-1 expression in keratinocyte growth factor-treated keratinocytes.

Syndecan-1 is a major heparan sulfate proteoglycan of the epidermis. Its expression is strongly induced in migrating and proliferating keratinocytes during wound healing and, on the other hand, diminished or lost in invasive squamous cell carcinoma. We have recently found in the syndecan-1 gene an enhancer (fibroblast growth factor-inducible response element (FiRE)) that activates gene expression in wound edge keratinocytes (Jaakkola, P., Kontusaari, S., Kauppi, T., Määttä, A., and Jalkanen, M. (1998)FASEB J. 12, 959–969). Now, we demonstrate that the activation of this enhancer by keratinocyte growth factor (KGF) is modulated by the components of the extracellular matrix (ECM). MCA-3D mouse immortal keratinocytes growing on fibrillar collagen failed to activate FiRE and subsequently to induce syndecan-1 in response to KGF. The same cells growing on fibronectin or laminin, however, increased FiRE-dependent reporter gene expression upon KGF treatment. The inhibition of the KGF induction by collagen appears to be specific for signaling to FiRE, as the increase in cell proliferation by KGF was not affected. The effect was selective to KGF, as EGF-induction was independent on ECM composition. Changes in the transcription factor binding were not involved in the differential activation of FiRE, as the levels and composition of the AP-1 complexes were unchanged. However, application of anisomycin, an activator of Jun amino-terminal kinase, resulted in a lower response in cells growing on collagen compared with fibronectin. These results indicate that the composition of ECM and availability of growth factors can play a role in the epidermal regulation of syndecan-1 expression and that FiRE is a novel target for gene regulation by the extracellular matrix.

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.