Abnormal IGF-Binding Protein Profile in the Bone Marrow of Multiple Myeloma Patients.

Insulin-like growth factor (IGF) signalling plays a key role in homing, progression, and treatment resistance in multiple myeloma (MM). In the extracellular environment, the majority of IGF molecules are bound to one of six IGF-binding proteins (IGFBP1-6), leaving a minor fraction of total IGF free and accessible for receptor activation. In MM, high IGF-receptor type 1 expression levels correlate with a poor prognosis, but the status and role of IGF and IGFBPs in the pathobiology of MM is unknown. Here we measured total IGF1, IGF2, and intact IGFBP levels in blood and bone marrow samples from MM (n = 17), monoclonal gammopathy of undetermined significance (MGUS) (n = 37), and control individuals (n = 15), using ELISA (IGFs) and 125I-IGF1 Western Ligand Blotting (IGFBPs). MGUS and MM patients displayed a significant increase in intact IGFBP-2 (2.5-3.8 fold) and decrease in intact IGFBP-3 (0.6-0.5 fold) in the circulation compared to control individuals. Further, IGFBP-2 as well as total IGFBP levels were significantly lower in bone marrow compared to circulation in MM and MGUS only, whereas IGF1, IGF2, and IGFBP-3 were equally distributed between the two compartments. In conclusion, the profound change in IGFBP profile strongly suggests an increased IGF bioavailability in the bone marrow microenvironment in MGUS and MM, despite no change in growth factor concentration.

Clinicopathological features of plasmablastic multiple myeloma: a population-based cohort.

Multiple myeloma (MM) is a common malignant hematological disease displaying considerable heterogeneity. Historical data indicate a prognostic significance of plasmablastic morphology, proliferation, and adverse cytogenetics, but there is little knowledge on the degree of interdependency of these parameters. The aim of this study was to study the degree of overlap between these variables. In a consecutive population-based cohort of 194 untreated MM patients, morphology, and proliferation index, using immunohistochemical double staining for Ki-67 and CD138, was analyzed. In addition, cytogenetic changes were studied by karyotyping and fluorescence in situ hybridization (FISH). Plasmablastic morphology correlated with unfavorable clinical features, high proliferation index, high percentage of plasma cell infiltration in the bone marrow, abnormal karyotype, and del(13q) detected by karyotyping, which indicates that plasmablastic morphology reflects advanced and highly proliferative disease. However, plasmablastic morphology did not correlate with established adverse prognostic cytogenetics identified by FISH, for example, t(4;14), t(14;16) and del(17p).

Upregulation of Syndecan-1 in the bone marrow microenvironment in multiple myeloma is associated with angiogenesis.

OBJECTIVES: Syndecan-1 (SDC1), hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF) and interleukin-6 (IL6) are expressed by malignant plasma cells and cells in the bone marrow microenvironment and may be involved in the angiogenic process in multiple myeloma (MM). METHODS: In this study, we examined the association between bone marrow angiogenesis estimated as micro-vessel density (MVD) and gene expression of SDC1, HGF, VEGF and IL6 in whole bone marrow biopsies from healthy volunteers (n = 10), patients with monoclonal gammopathy of undetermined significance (MGUS) (n = 35) and MM (n = 65). RESULTS: MVD was significantly higher in patients with MM than MGUS (P = 0.03) and was positively correlated with plasma cell percentage (P = 0.002). SDC1 gene expression increased with increasing MVD in patients with MGUS and MM (P < 0.001). A positive correlation between bone marrow plasma cell percentage and SDC1 gene expression was detected in patients with MM (P < 0.001). Importantly, after adjustment for plasma cell percentage, the association between MVD and SDC1 gene expression remained significant (P = 0.026). No association between bone marrow angiogenesis and gene expression of HGF, VEGF and IL6 was seen. CONCLUSION: Our study indicates that SDC1 expressed by the bone marrow microenvironment is involved in angiogenesis in MM.

Expression of osteoblast and osteoclast regulatory genes in the bone marrow microenvironment in multiple myeloma: only up-regulation of Wnt inhibitors SFRP3 and DKK1 is associated with lytic bone disease.

Multiple myeloma (MM) lytic bone disease (LBD) is caused by osteoclast activation and osteoblast inhibition. RANK/RANKL/OPG play central roles in osteoclast activation and Wnt inhibitor DKK1 in osteoblast inhibition. The role of other Wnt inhibitors is less clear. We evaluated gene expression of osteoclast regulators (RANK, RANKL, OPG, TRAIL, MIP1A), Wnt inhibitors (DKK1, SFRP2, SFRP3, sclerostin, WIF1) and osteoblast transcription factors (RUNX2, osterix) by quantitative reverse transcriptase polymerase chain reaction (RT-PCR) in the bone marrow (BM) microenvironment using snap-frozen BM biopsies, thereby achieving minimal post-sampling manipulation, and gene expression profiling (GEP) data, reflecting the in vivo situation. We analyzed 110 biopsies from newly diagnosed patients with MM and monoclonal gammopathy of unknown significance (MGUS) and healthy volunteers. LBD was evaluated using standard radiographs and the bone resorption marker CTX-1. Protein levels were evaluated by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry. Among Wnt inhibitors, only SFRP3 and DKK1 were significantly overexpressed in advanced LBD, correlating with protein levels. SFRP3 correlated with CTX-1. Our findings support osteoblast inhibition as the driving force behind MM LBD.

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.

Hepatocyte growth factor pathway upregulation in the bone marrow microenvironment in multiple myeloma is associated with lytic bone disease.

Lytic bone disease (LBD) in multiple myeloma (MM) is caused by osteoclast hyperactivation and osteoblast inhibition. Based on in vitro studies, the hepatocyte growth factor (HGF) pathway is thought to be central in osteoblast inhibition. We evaluated the gene expression of the HGF pathway in vivo using bone marrow biopsies (BMBs) of patients with MM and monoclonal gammopathy of undetermined significance (MGUS), and healthy volunteers (HV). BMBs (N = 110) obtained at diagnosis were snap-frozen and used to evaluate gene expression by quantitative reverse transcription polymerase chain reaction. LBD was evaluated using standard radiographs. Enzyme-linked immunosorbent assay (ELISA) was performed on matched bone marrow plasma and immunohistochemistry on matched formalin-fixed paraffin-embedded biopsies. Gene expression of HGF, SDC1, and MET in BMBs were significantly altered in MM versus HV and MGUS, and HGF and MET correlated with the extent of LBD. A significant correlation between gene and protein expression levels was observed for SDC1 (Syndecan-1) and HGF. The HGF bone marrow plasma level was significantly lower in MM patients with no/limited versus advanced LBD. Our novel approach using snap-frozen BMBs seems generally applicable because it allows evaluation of gene expression independent of the extent of MM plasma-cell infiltration. Our study highlights the importance of the HGF pathway in MM LBD.