ABSTRACT
Bone marrow monocytes are primarily committed to osteoclast formation. It is, however, unknown whether potential primary alterations are specifically present in bone marrow monocytes from patients with multiple myeloma, smoldering myeloma or monoclonal gammopathy of undetermined significance. We analyzed the immunophenotypic and transcriptional profiles of bone marrow CD14+ monocytes in a cohort of patients with different types of monoclonal gammopathies to identify alterations involved in myeloma-enhanced osteoclastogenesis. The number of bone marrow CD14+CD16+ cells was higher in patients with active myeloma than in those with smoldering myeloma or monoclonal gammopathy of undetermined significance. Interestingly, sorted bone marrow CD14+CD16+ cells from myeloma patients were more pro-osteoclastogenic than CD14+CD16-cells in cultures ex vivo Moreover, transcriptional analysis demonstrated that bone marrow CD14+ cells from patients with multiple myeloma (but neither monoclonal gammopathy of undetermined significance nor smoldering myeloma) significantly upregulated genes involved in osteoclast formation, including IL21RIL21R mRNA over-expression by bone marrow CD14+ cells was independent of the presence of interleukin-21. Consistently, interleukin-21 production by T cells as well as levels of interleukin-21 in the bone marrow were not significantly different among monoclonal gammopathies. Thereafter, we showed that IL21R over-expression in CD14+ cells increased osteoclast formation. Consistently, interleukin-21 receptor signaling inhibition by Janex 1 suppressed osteoclast differentiation from bone marrow CD14+ cells of myeloma patients. Our results indicate that bone marrow monocytes from multiple myeloma patients show distinct features compared to those from patients with indolent monoclonal gammopathies, supporting the role of IL21R over-expression by bone marrow CD14+ cells in enhanced osteoclast formation.
Subject(s)
Gene Expression , Monocytes/metabolism , Multiple Myeloma/genetics , Multiple Myeloma/pathology , Osteoclasts/metabolism , Receptors, Interleukin-21/genetics , Biomarkers , Bone Marrow Cells/metabolism , Bone Marrow Cells/pathology , Cluster Analysis , Cytokines/metabolism , Female , Gene Expression Profiling , Humans , Immunophenotyping , Lipopolysaccharide Receptors/metabolism , Male , Monoclonal Gammopathy of Undetermined Significance/genetics , Monoclonal Gammopathy of Undetermined Significance/metabolism , Monoclonal Gammopathy of Undetermined Significance/pathology , Multiple Myeloma/metabolism , Phenotype , RNA, Messenger/genetics , RNA, Messenger/metabolism , Receptors, IgG/metabolism , Receptors, Interleukin-21/metabolismSubject(s)
Gene Expression Regulation, Neoplastic , Hypoxia-Inducible Factor 1, alpha Subunit/genetics , Immunologic Factors/pharmacology , Multiple Myeloma/therapy , Plasma Cells/drug effects , Thalidomide/analogs & derivatives , Animals , Caspase 3/genetics , Caspase 3/immunology , Cyclin-Dependent Kinase Inhibitor p27/genetics , Cyclin-Dependent Kinase Inhibitor p27/immunology , Disease Models, Animal , Humans , Hypoxia-Inducible Factor 1, alpha Subunit/antagonists & inhibitors , Hypoxia-Inducible Factor 1, alpha Subunit/immunology , Ikaros Transcription Factor/genetics , Ikaros Transcription Factor/immunology , Interferon Regulatory Factors/genetics , Interferon Regulatory Factors/immunology , Lenalidomide , Mice , Mice, Inbred NOD , Mice, SCID , Mitogen-Activated Protein Kinase 1/genetics , Mitogen-Activated Protein Kinase 1/immunology , Mitogen-Activated Protein Kinase 3/genetics , Mitogen-Activated Protein Kinase 3/immunology , Multiple Myeloma/genetics , Multiple Myeloma/immunology , Multiple Myeloma/pathology , Plasma Cells/immunology , Plasma Cells/pathology , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , S-Phase Kinase-Associated Proteins/genetics , S-Phase Kinase-Associated Proteins/immunology , Signal Transduction , Thalidomide/pharmacology , Trans-Activators/genetics , Trans-Activators/immunologyABSTRACT
Multiple myeloma (MM)-induced osteoclast (OC) formation is mainly due to an imbalance of the receptor activator NF-κB ligand (RANKL)-osteoprotegerin (OPG) ratio in favor of RANKL in the bone microenvironment and to the CCL3 production by MM cells. The purpose of the study was to investigate the effect of the immunomodulatory drugs on RANKL/OPG ratio, the production of pro-osteoclastogenic cytokines, and MM-induced OC formation. We found that in vivo concentrations of both lenalidomide (LEN) and pomalidomide (POM) significantly blunted RANKL upregulation normalizing the RANKL/OPG ratio in human osteoprogenitor cells (PreOBs) when co-cultured with MM cells and also inhibited CCL3 production by MM cells. A reduction in CD49d expression, a molecule critically involved in RANKL upregulation in the MM microenvironment, accompanied this effect. Consistently, the pro-osteoclastogenic property of MM cells co-cultured with PreOBs was reduced by both LEN and POM. We further investigated the effect of these drugs on the transcriptional profile of both MM cells and PreOBs by microarray analysis, which showed that adhesion molecules, such as ITGA8 and ICAM2, are significantly downregulated in MM cells. Our data suggest that LEN and POM inhibit MM-induced OC formation through normalization of the RANKL/OPG ratio targeting the expression of adhesion molecules by MM cells.
