Elevated levels of shed syndecan‐1 correlate with tumour mass and decreased matrix metalloproteinase‐9 activity in the serum of patients with multiple myeloma

Sera from 20 myeloma patients and 12 normal controls were analysed for the presence of syndecan-1 and matrix metalloproteinase-9 (MMP-9). The level of syndecan-1 in the serum was elevated in 7/20 (3 5%) myeloma patients whilst 6/19 patients (31%) had decreased serum MMP-9 activity. The presence of increased syndecan-1 was associated with decreased serum MMP-9. Both elevated syndecan-1 and decreased MMP-9 were associated with higher marrow plasmacytosis, serum beta-2 microglobulin and paraprotein levels. These data provide evidence that the syndecan-1 ectodomain is shed in vivo. Quantitation of serum syndecan-1 may be a useful measure of tumour mass and may have important implications for myeloma biology.