The interaction between myeloma cells and the bone marrow (BM) microenvironment, through vascular cell adhesion molecule-1 (VCAM-1) and α4β1 integrin, stimulates the production of several proosteoclastogenic factors, including the receptor activator of nuclear factor kappa B (NF-κB) ligand (RANKL) [12]. The gene discussed is TNFSF11; the disease is plasma cell myeloma.