Zalypsis overcomes the protective effects of IL-6, IGF-I, and adherence to patient BMSCs. (A,B) MM1S cells were treated for 48 hours with the indicated concentrations of Zalypsis in the presence or absence of IL-6 (A) or IGF-I (B), and DNA synthesis was determined by measuring BrdU incorporation during the last 8 hours of 48-hour cultures. (C) MM1S-luc cells were treated for 48 hours with the indicated concentrations of Zalypsis in the presence or absence of BMSCs derived from a MM patient, and proliferation was analyzed by bioluminescence (photons/sec). (D) BMSCs were cultured with different doses of Zalypsis for 48 hours, and the cytotoxicity was analyzed by MTT assay. Data are mean plus or minus SD of quadruplicates.