DKK1 and plasma cell myeloma: The targeting of DKK1 could be achieved through the treatment with the DKN-01 inhibitor, in a phase I trial (NCT01711671 and NCT01457417) or with the anti-DKK1 monoclonal antibody BHQ880, which has been included in an already completed phase 1 (NCT01302886) and phase 2 trials (NCT01337752 and NCT00741377) showing potential clinical activity in myeloma patients (68).