Decorin is down-regulated in multiple myeloma and MGUS bone marrow plasma and inhibits HGF-induced myeloma plasma cell viability and migration

OBJECTIVES: Decorin is a stromal-produced small leucine-rich proteoglycan known to attenuate tumour pro-survival, migration, proliferation and angiogenic signalling pathways. Recent studies have shown that decorin interacts with the hepatocyte growth factor (HGF) receptor c-Met, a potential key pathway in multiple myeloma (MM).

METHODS: Decorin levels in paired peripheral blood and bone marrow plasma samples from healthy volunteers (HV) (n = 23), and patients with monoclonal gammopathy of undetermined significance (MGUS) (n = 41) and MM (n = 19) were determined by ELISA. Further, the ability of decorin to inhibit HGF-induced effects on MM cell lines were analysed in vitro using cell viability and Transwell migration assays.

RESULTS: We found that decorin concentrations were significantly higher (P < 0.05) in bone marrow (BM) plasma from HVs (median 35.2 ng/mL; range, 15.3-99.1) compared with MGUS (median 22.5 ng/mL; range, 11.1-59.5) and patients with MM (median 21.5 ng/mL; range, 10.6-35.9). Decorin levels were higher in BM plasma than in peripheral blood in all groups, with a BM/PB ratio of 3.9, 3.4 and 2.5 for HV, MGUS and MM, respectively. A positive correlation (Spearman's ρ = 0.51, P < 0.05) was found between simultaneously measured levels of HGF and decorin in BM plasma in HVs, but not in MGUS or MM samples. Functionally, decorin inhibited HGF-induced migration and viability of INA-6 and ANBL-6 MM cell lines, independent of c-Met down-regulation.

CONCLUSION: Our results show that decorin is down-regulated in MGUS and MM bone marrow plasma and that it inhibits HGF-induced viability and migration of myeloma cell lines in vitro.