Figure 1. YM155 inhibits cell growth and induces apoptosis in MM cells.

(A) Chemical structure of YM155. Chemical name, 1-(2-methoxyethyl)-2-methyl-3-(pyrazin-2-ylmethyl) benzo[f]benzimidazol-3-ium-4,9-dione; chloride. (B) Cell growth inhibition by YM155 in human MM cell lines. The cells (U266, KMS11, and KMS12) were incubated with various concentrations of YM155 at 37°c for 72 h. Cell growth inhibition rate was determined by Cell counting Kit as described in Materials and Methods. IC₅₀ was calculated as the mean of three independent experiments with triplicate determinations at each concentration. Error bars represent SD from triplicate experiments. (C) The cells (U266, KMS11, and KMS12) were incubated with 0.1 or 1 μM YM155 for 12 hr followed by Annexin-V and propidium iodide co-staining. (D) The cells (U266, KMS11, and KMS12) were incubated with 10, 30 or 100 nM YM155 for 24 h followed by Annexin-V and propidium iodide co-staining. The left lower quadrant shows live cells, the left upper quadrant necrotic cells, the right lower and the right upper quadrant early and late apoptotic cells, respectively. The percentage of cells in each quadrant is indicated.