Combined treatment with PD184352 and ATO overcomes the protective effects of human IL-6, IGF-1, and BM microenvironment in MM cells. RPMI 8226, JJN3, and XG-6 cells were cultured with PD and/or ATO in the presence or absence of IL-6 (20 ng/mL), IGF-1 (50 ng/mL), or BMSCs. After 48 hours of treatment, the cells were harvested for annexin V labeling; data represent means plus or minus SD of triplicate cultures. CTR indicates control; PD, PD184352 (1 μM); ATO, arsenic trioxide (2 μM).