DKK1 and plasma cell myeloma: Among them, DKK1, ATP-binding cassette subfamily G member 2 (junior blood group) (ABCG2), nuclear receptor-binding SET domain protein 2 (NSD2), and BCL2 apoptosis regulator (BCL2), which are closely related to myeloma progression and bone lesions, were included in the highly elevated genes, and activating transcription factor 3 (ATF3), MAX interactor 1, dimerization protein (MXI1), and stanniocalcin 2 (STC2) are known targets of the hypoxia-inducible factor (HIF)-1α signaling pathway (Fig. 1a).