Cell viability assay

Cells were seeded into 96-well plates (5,000 cells/well) and treated with a dose range of drugs. After 48 h, cells were incubated with PrestoBlue™ Cell Viability Reagent (Thermo Fisher Scientific) for 1 h at 37 °C. Plates were then subjected to fluorescence reading (excitation: 535 nm, emission: 615 nm) using a microplate reader. IC50 drug values were determined using GraphPad Prism 6.0 (GraphPadSoftware, Inc., San Diego, CA) and the combination index (CI) was determined with the CompuSyn 1.0 software.