Pitstop 2 does not affect the growth and viability of non-tumourigenic NIH3T3 fibroblasts. A-B, HeLa (A) and NIH3T3 (B) cells were synchronized in mitosis and then treated with increasing concentrations of the indicated compounds at 24 h intervals. After 48 h, total viable and non-viable cell number (mean ± S.D. from two independent experiments) was assessed by trypan blue. Drug concentrations are indicated in μM units.