The backbone myeloma drug lenalidomide (Len) down regulates IRF4 indirectly because it lies downstream of cereblon (CRBN), the primary target of Len, in the CRBN-IKFZ1/3-IRF4-MYC pathway (Lopez-Girona et al., 2011; Zhu et al., 2011, 2014; Greenberg et al., 2013; Schuster et al., 2014). Here, CRBN is linked to plasma cell myeloma.