MM cells also degrade osteoprotegerin (OPG), a soluble decoy receptor for RANKL that antagonizes osteoclastogenesis, after internalizing it via binding to heparan sulfate proteoglycans (HSPGs), such as syndecan-1 (CD138), on the myeloma cell surface [8]. This evidence concerns the gene TNFRSF11B and Miyoshi myopathy.