Distinct effects of IL-6 signaling pathways on Bim and Mcl-1. (A) MM.1s and KMS18 were treated with ABT-737 in combination with 1 ng/mL IL-6 and either 1 μM ruxolitinib, 10 μM U0126, or 10 μM LY294002 for 24 hours. Cell death was measured by flow cytometry after staining with annexin V-FITC and PI. Data are presented as the mean ± SE of 3 independent experiments (*P < .05; **P < .01; ***P < .001; ****P < .0001). (B) MM.1s was treated with 1 ng/mL IL-6 in the presence of 1 μM AZD1480, 10 μM LY294002, 10 μM SB203580, 10 μM SP600125, or 10 μM U0126 for 15 minutes. Protein lysates were prepared and subjected to SDS-PAGE and western blotting with antibodies against serine 69 phosphorylated Bim, total Bim, phosphorylated Erk, and total Erk. (C) KMS18 was treated with 1 ng/mL IL-6 for the indicated times and with 10 μM U0126 followed by western blotting for Mcl-1, Bcl-2, Bcl-xL, serine 69 phosphorylated Bim, total Bim, and actin. (D) KMS18 was treated with 1 ng/mL IL-6 with or without 1 μM ruxolitinb for 24 hours followed by western blotting for Mcl-1, Bcl-2, Bcl-xL, and GAPDH.
