Background: Syndecans are a family of cell surface proteoglycans. In the bone marrow of multiple myeloma patients syndecan-1 is expressed only on the surface of malignant plasma cells. The aim of the study was to determine the soluble syndecan-1 levels in different plasma cell dyscrasias.

Methods: The serum concentration of soluble syndecan-1 was measured using human syndecan-1 enzyme-linked immunosorbent assay kit.

Results: Patients with multiple myeloma showed a significantly higher median serum syndecan-1 level than patients with plasmocytoma or monoclonal gammopathy of undetermined significance. Statistically significant differences were also observed among Salmon-Durie subgroups of 50 patients suffering from multiple myeloma. In addition to these findings a statistical correlation with other independent prognostic factors such as serum beta2-microglobulin level, monoclonal immunoglobulin concentration, and bone marrow plasma cell count could also be noted. A significant decrease in median serum syndecan level was observed in patients who responded to chemotherapy, whereas no change in the median syndecan-1 level could be observed in nonresponders.

Conclusions: These findings confirm the observation that high serum soluble syndecan-1 level is associated with a more advanced disease stage and is a strong independent indicator of poor prognosis. A diminished serum syndecan-1 reading as a result of chemotherapy may be a good indicator of favorable response to antitumor treatment.