YM155 sensitizes ESCC cells to irradiation. A, ESCC cell lines Eca109 and TE13 were seeded in 96-well plates in triplicate and treated with various concentrations of YM155 for 24 or 48 h. Cell viability was determined by CCK8 assay. * and #, P < 0.05 versus control. B, Cell survival curve was established by clonogenic survival assay. The cells were treated with 5 nM or 10 nM YM155 and ionizing radiation as illustrated and harvested after incubation for 10–14 d. Each bar represented mean ± SE from 3 independent experiments. * and #, P < 0.05 versus control; ** and ##, P < 0.01 versus control.