Application of Chk2 inhibitor in combination with cisplatin greatly inhibited cell growth. A2780 or Caov-3 cells (around 1000 per well) were seeded in 96-well plates for 24 hrs and pretreated with different concentrations of Chk2 inhibitor II C3742 for 30 min. Subsequently, cells were treated with cisplatin at IC₅₀ dose for 1 hr while continuously exposed to Chk2 inhibitor. After drug removal, cells were washed twice with PBS, and then incubated with fresh medium containing Chk2 inhibitor for 5 days. Cytotoxicity assay was performed following company’s protocol of Cell Proliferation Kit I (Roche) and the complete solubilization of the purple formazan crystals was measured. Optical density was read at 600 nm to determine cell quantity.