Cytotoxicity MTT assay

A375 cells (5000 cells/well) were cultured as described above in the presence of varying concentrations of DG013A (0–30 μM) for 48h. The culture medium was replaced by 100μl of DMEM containing 1mg/ml MTT reagent. After incubation for another 4 h the resultant formazan crystals were dissolved in DMSO (100μl) and the absorbance intensity measured on a TECAN infinite M200 microplate fluorescence reader at 540 nm with reference at 620 nm. All experiments were performed at least three times and the relative cell viability (%) was expressed as a percentage relative to untreated control cells.