2.7. MTS Proliferation Assay

3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assays were used to determine BETi-induced cytotoxicity. Briefly, Calu-3 (~20,000 cells/well), Vero E6 (~10,000/well), or Karpas-299 (~20,000 cells/well) were treated with vehicle (DMSO) or increasing amounts of BETi for 48 h in 96-well plates, and then, the CellTiter 96® AQueous assay (Promega, Madison, WI, USA) was preformed according to the manufacturer’s instructions to determine cell proliferation. Absorbance signals from each well were acquired at 490 nm on a Tecan Infinite® M1000 Pro microplate reader (Männedorf, Switzerland).