MTT assay

Cells (2×10³ per well) were seeded in 96-well plates, and then incubated with different concentrations of sunitinib on the next day. 48hours later, the metabolically active cells were quantified using MTT (5mg/ml, Sigma-Aldrich) by measuring the Optical Density (OD) value at 570nm in ELISA reader. The proliferation inhibition due to different concentration of sunitinib was calculated by the following formula: proliferation inhibition (%)=(OD_treated-OD_control)/(OD_control-OD_blank)×100. The value of IC₅₀ (the concentration required for a 50% proliferation inhibition) was determined by Graphpad prism 5.0.