*4.4. Cellular Survival MTS-Based Assay*

STS and GIST cells were seeded in 96-well flat-bottomed plates (Corning Inc., Corning, NY, USA) and were cultured for 24 h. The cells were further incubated for 48–72 h with indicated concentrations of MK-2206, doxorubicin or DMSO (control). To assess the number of living cells, the MTS reagent (Promega, Madison, WI, USA) was added to the culture medium for at least 1 h. Cellular viability was determined using a MultiScan FC plate reader (Thermo Fisher Scientific, Waltham, MA, USA) at 492 nm. Calculated IC50 data were defined as the concentration of compound that inhibits cell growth by 50% at 48–72 h. Data were normalized to the DMSO-treated control group.
