Cell viability assay

Cell viability was monitored either by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay or by phase contract microscopy. For the MTT assay, cells were suspended at 5 × 10⁵ cells/ml, and 100 μl aliquots were dispended into 96-well microtiter plates and exposed to drugs as described using DMSO control. At the end of incubations, 10 μl of a stock solution of 5 mg/ml MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), was added into each well, and the plates were incubated 4 hours at 37°C. Formazan crystals were dissolved with 100 μl of 10% SDS/10 mM HCl solution overnight at 37°C. Absorbance was measured using an ELISA plate reader (Labsystems Multiscan RC) at 590 nm. Short term viability was assessed by phase contrast microscopy.