SOST and plasma cell myeloma: The differentiation of MSCs into bone cells is governed by the activation of two principal transcription factors: runt-related transcription factor 2 (RUNX2) and osterix.352 These transcription factors are vital for the maturation and ossification of osteoblasts and depend on the typical Wnt signaling pathway.353 Whereas, myeloma cells secrete various Wnt antagonists like dickkopf-1 (DKK1) and sclerostin (SOST).