Assessment of the Parameters of Myeloma Bone Disease Signaling to the Extent of Skeletal Involvement, Bone Mineral Turnover and Activity of Multiple Myeloma

Background: Myeloma bone disease (MBD) is present in up to 80% patients with newly diagnosed multiple myeloma (MM). It is known to be activated by three separate signaling pathways - receptor activator of nuclear factor κB/osteoprotegerin pathway (RANK/OPG), macrophage inflammatory factor pathway (MIP) and Wnt pathway. Except of these, several other factors have been described in relationship to MBD development. The aim of our study was to assess the activity of selected parameters of MBD signaling with respect to macroscopic skeletal changes detectable using imaging techniques, and in comparison with markers of bone turnover and the activity of MM.

Patients and methods: We assessed 92 patients with monoclonal gammopathies: 56 patients with active multiple myeloma, 12 with smoldering myeloma and 24 individuals with monoclonal gammopathy of undetermined significance (MGUS). Following parameters of MBD signaling were measured in the patients´serum: hepatocyte growth factor (HGF, Human HGF Quantine ELISA), macrophage inflammatory factor alpha (MIP-1α, Human CCL3/MIP-1α Quantikine ELISA), syndecan-1 (Human Syndecan-1 (CD138) ELISA), osteoprotegerin (OPG, Human Osteoprotegerin ELISA), Activin A (Human Activin A Quantikine ELISA), Dickkopf-related protein-1 (DKK1, Human Dkk-1 Quantikine ELISA), Annexin A2 (Human Annexin A2 ELISA kit), nuclear factor kappa B (NF-κB, Human Nuclear factor-kappa B). The extent of skeletal involvement was evaluated using whole body magnetic resonance and low-dose computed tomography. The levels of the selected parameters of MBD signaling were compared to serum levels of Ca, P, PINP, ICTP, CTx, parathormone (PTH), calcitonine (CLC), 25-hydroxyvitamin D2 (D2), 1,25dihydroxyvitamin D3 (D3), bone isoenzyme of alkaline phosphatase (bALP) and sclerostin (SCL). The parameters were measured at the time of diagnosis and then after 4 months. In patients with MM we measured selected parameters of MBD in comparison with the stage of the disease according to Durie-Salmon (DS) and according to International Staging System (ISS). In MGUS we assessed the relationship of the parameters to the risk of transformation to MM based on the Mayo clinic stratification system. For statistical estimation we used Kruskal-Wallis test and Mann-Whitney U post hoc test with Bonferroni correction at p < 0,05.

Results: Statistically significant difference between patients with low and high skeletal involvement was found in serum levels of MIP-1α, syndecan-1, DKK-1 and Annexin A2. None of the parameters correlated with the presence of extramedullary disease. With respect to markers of bone turnover we found following significant relationships: HGF to PINP, ICTP, CTx and inverse relationship to D3; MIP-1α to PINP, ICTP, CTx and inverse relationship to D3; Syndecan-1 to ICTP, CTx, and inversely to D2 and D3; OPG to ICTP and SCL; Activin A to PINP, ICTP, CTx and SCL; NF-κB to ICTP and CTx. We found significant differences between MGUS and MM in serum levels of HGF, MIP-1α, syndecan-1, DKK-1 and NF-κB. There was no significant relationship of any of the parameters to DS, however, we found significant relationship of HGF, syndecan-1, OPG and Activin A to ISS. MIP-1α only had a significant relationship to the risk stratification of MGUS. There was no significant change in the parameters in MM patients after 4 months of treatment with respect to treatment response.

Conclusions: We confirmed the relationship of MBD signaling to the extent of skeletal changes using imaging techniques. All three signalling pathways were involved in the development of MBD in MM in comparison with MGUS. Signaling involved in osteoclast activation was more activated than the parameters preventing osteoblast differentiation. There was, however, no significant change in any of the parameters in MM patients with respect to treatment response after 4 months, suggesting that bone reparation processes are delayed after hematological response. Significant relationship to the markers of bone turnover and to the activity of MM suggests possible use of the parameters of MBD signaling as tools for early detection of bone marrow changes and timely indication for anti-resorption therapy.

Supported by the grant NT 14393.