Growth inhibitory effect of YM155 on SK-NEP-1 cells. (A) Molecular Structure of YM155. (B) Proliferation and IC50 analysis of YM155. Sk-NEP-1 cells (2 × 104) were seeded in 96-well plates overnight and incubated with DMSO, 1 nM YM155, or increasing concentrations of YM155 (0.005, 0.01, 0.02, 0.04, 0.08, 0.16, 0.32, 0.64or 1.28 μM) for 24 hours. Compared with the control group, the relative survival rate of remained cells was calculated from the absorbance values. Cell proliferation was calculated as a percentage of the DMSO treated control wells with IC50 values derived after plotting proliferation values on a logarithmic curve. Experiments were performed in quadruplicate and repeated two times.