[Myeloma bone disease]

Multiple myeloma (MM) develops and expands almost exclusively in the bone marrow, and generates devastating bone destruction. MM cells produce a variety of cytokines to stimulate RANK ligand-mediated osteoclastogenesis and suppress osteoblastic differentiation from bone marrow stromal cells, leading to extensive bone destruction with rapid loss of bone. Pim-2 kinase as well as growth factor independence-1 (Gfi-1) were found to be up-regulated in bone marrow stromal cells by major inhibitors of bone formation known in myeloma as common downstream mediators for the suppression of osteoblastogenesis. The biology of osteocytes is largely unknown in myeloma bone lesions, but the reduction of viable osteocytes and their correlation with osteoclastogenesis have been demonstrated.