ERK inactivation by AZD6244 enhances cytotoxicity of conventional and novel agents. (A) INA-6 cells were cultured for 2 days with Dex (0-50 nM) in the presence or absence of AZD6244 (0-1 μM), and DNA synthesis was measured. Data represent mean (+ SE) of quadruplicate cultures. MM1S cells were cultured for 2 days with (B) bortezomib (0-7.5 nM) and AZD6244 (0-1 μM) or (C) lenalidomide (0-0.5 μM) and AZD6244 (0-1 μM). (D) CD138⁺ patient MM cells were incubated for 3 days with AZD6244 (0-0.1 μM), perifosine (0-7.5 μM), or the combination. (E) CD138⁺ MM-patient cells were cultured with BMSCs in the presence or absence of AZD6244 (20 nM), perifosine (7.5 μM), or the combination. Cytotoxicity (viability) was measured by MTT assay, expressed as fold change to control.