CRBN and plasma cell myeloma: The celebron (CRBN) was discovered as a receptor molecule binding to thalidomide15, and the ligand-bounded CRBN is shown to form the CRL4CRBN E3 ubiquitin ligase complex and mediate the ubiquitination of specific substrates including IKZFs 1 and 3 and their subsequent degradation via the proteasome system in multiple myeloma cells16,17 (Supplementary Fig. S2).