MTT Assay for Cell Viability

To assess the treated cells’ metabolic rate as a sign of cell viability, we performed a 3(4,5 dimethylthiazol)-2,5 diphenyltetrazolium (MTT) assay as described by Sehm et al.^{31 (link)} After 24 h, incubation with either 5 or 10 μM sorafenib or erastin, cells were incubated with freshly made MTT solution (Roth, Karlsruhe, Germany) (5 mg/ml) for 4 h at 37 °C, 5% CO₂. We used 100 μl isopropanol, supplemented with 0.1 N HCl for the following cell lysis. The optical density of each well was determined using the microplate reader Tecan Infinite F50 (Crailsheim, Germany) set to 550 nm (wavelength correction set to 690 nm).