SOST and plasma cell myeloma: LDN and BMPR1a-FC could inhibit Dkk1 expression in bone marrow mesenchymal stem cells (BMSCs) from myeloma patients, but only BMPR1a-FC reduced sclerostin levels in the bone marrow plasma of myeloma-bearing mice, which may explain the stronger anabolic effect of BMPR1a-FC.