TNFSF13B and plasma cell myeloma: The interaction of myeloma cells with stromal and osteoprogenitor cells in the bone marrow leads to the overexpression of multiple OC activating factors (including RANKL, CCL3, IL-3, osteopontin, IL-6 and vascular endothelial growth factor; in turn, OCs also support myeloma proliferation and survival by production of myeloma growth factors such as IL-6, B-cell-activating factor, and a proliferation inducing ligand [4].