The Impact of Mast Cell Density on the Progression of Bone Disease in Multiple Myeloma Patients.

Background: Osteolytic bone disease is a major hallmark in multiple myeloma (MM) progression and affects many patients. Several inflammatory cells are involved in MM progression. Among them, mast cells (MCs) accumulated in the bone marrow (BM) microenvironment are known to play an important role in the mechanism of neovascularization.

Methods: In 52 newly diagnosed active MM patients, we measured BM MC density (MCD) using an immunohistochemical stain for tryptase, serum levels of matrix metalloproteinase-9 (MMP-9) and receptor activator of nuclear factor x03BA;B ligand (RANKL) by a solid-phase sandwich enzyme-linked immunosorbent assay, along with urine levels of N-terminal propeptide of procollagen type I (Ntx) by a competitive inhibition enzyme-linked immunosorbent assay, in various clinical stages and skeletal grades.

Results: MCD, RANKL and Ntx were higher in MM patients. All values increased in association with both the clinical stage and skeletal grade. Furthermore, MCD correlated positively with MMP-9, RANKL and Ntx.

Conclusions: Our data suggest that MCs may contribute to osteolytic processes during MM progression. Although the major role of MCs in tumor progression is to enhance angiogenesis, it seems that they may affect MM bone disease and may secrete a plethora of mediators that may directly and indirectly have an impact on osteolysis.