This study has demonstrated for the first time that MM cells inhibit RANKL-induced OC differentiation, OC gene expression, and bone resorption activity from monocytes and repress RANKL-induced NF-κB, ERK, JNK, and p38 MAPK signaling pathways by producing several inhibitory cytokines, such as IL-10. This evidence concerns the gene BGLAP and Miyoshi myopathy.