Drug synergy testing in cell lines

Human ALL cell lines were incubated at drug concentrations ranging between 1 nM and 50 μM for 72 hours, and cell viability was assessed by Cell-Titer Glo viability assays (Promega). Cells were plated in triplicate in 96-well plates at 50,000 cells/well and treated with drug at the indicated concentrations individually or in combination. Percent cell growth was calculated relative to 0.1% DMSO vehicle treated cells and normalized (using values of vehicle-treated cells set to 100% and medium alone without viable cells set to 0%) and displayed graphically in Prism. IC₅₀ values were determined using GraphPad Prism and Compusyn software. Combination index (CI) values were calculated using Compusyn software (27). Each monotherapy and combination drug assay was repeated at least three times for each studied cell line.