The MCF-7 and MDA-MB231 human breast cancer cell lines and the PC3 and 22Rv1 prostate cancer cell lines were purchased from the ATCC collection. Cells were cultured in standard high glucose DMEM medium (Hyclone) supplemented with 10% fetal calf serum (FCS) (HyClone) and 0.1 mg/ml sodium pyruvate (Santa Cruz) at 37°C, 5% CO2 and 80–85% humidity (NuAir CO2 incubator). The cell growth was evaluated by the modified MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) (Applichem) test (Iselt et al., 1989) as described in Volkova et al. (2016). Briefly, the cells were seeded at a density of 2.5 × 104 cells per well in 24-well plates (Corning) in 900 μL of the medium. The tested compounds were dissolved in DMSO (Applichem) to 10 mM before experiments and then were diluted in the medium to the required concentrations. Compounds with different concentrations in 100 μL of the medium were added 24 h after the seeding, and the cells were grown for 72 h. After incubation with the compounds, the medium was removed, and the MTT reagent dissolved in the medium was added to the final concentration of 0.2 mg/mL to each well and incubated for 3 h. Then the cell supernatants were removed and the MTT formazan purple crystals were dissolved in 100% DMSO (350 μL per well). Plates were gently shaken and the absorbance was measured at 571 nm with a MultiScan reader (ThermoFisher). The viability of the cells was assessed after subtraction of the blank value (the absorbance in the well w/o cells) from all wells. Dose-response curves were analyzed by regression analysis using sigmoidal curves (Log(concentration) vs. normalized absorbance). The half maximal inhibitory concentrations (IC50) were determined with GraphPad Prism.