In myeloma, inhibition of ABCG2 by small molecule drugs, such as cyclosporine analogs and verapamil, proved to be ineffective, despite promising pre-clinical results suggesting that this inhibition may re-sensitize myeloma cells to vincristine, doxorubicin and dexamethasone (VAD) and, thereby, prevent tumor relapse [46]. Here, ABCG2 is linked to plasma cell myeloma.