Dex-mediated downregulation of NF-κB DNA binding activity correlates with patients’ clinical response to Dex. FACS-sorted–purified myeloma plasma cells from bone marrow aspirates of MM patients were treated with and without Dex (0.1 μmol/L) for 24 hours. WCEs were prepared and subjected to EMSA for binding to the κB oligonucleotide probe.