YM155 enhances radiation induced apoptosis. Cells were seeded into six-well plates at the concentration of 2 × 105/mL, incubated with 10 nmol/L YM155 or 0.1% DMSO for 24 h, and (or not) irradiated at dose of 10 Gy, respectively. Forty-eight hours after incubation, cells were harvested. A, The cells were stained with AnnexinV/FITC and propidium iodide and examined by flow cytometry for apoptotic cell populations. Data were Mean ± SD (n = 3). **, P < 0.01. B. Western blot analysis of apoptosis-related proteins. Actin was used as a loading control.