fig5

Figure 5. Effect of simvastatin and CHR2863 combinations on cell viability, apoptosis induction and cell cycle distribution in U937/WT, U937/CHR2863^R0.2 and U937/CHR2863^R5 cells. Simvastatin concentrations used for U937/WT cells, U937/CHR2863R0.2 and U937/CHR2863R5 cells were maximal in vitro non-toxic concentrations: 2 µM, 2.5 µM and 2.5 µM, respectively. For CHR2863, minimally cytotoxic (≈ IC10) were selected (from Figure 1), i.e., 25 nM, 250 nM and 5 μM for U937/WT cells, U937/CHR2863^R0.2 and U937/CHR2863^R5 cells, respectively. Cells (3 × 10⁵/mL in 10 mL medium) were incubated for 48 h with the indicated concentrations of simvastatin, CHR2863 and their combination and assessed for the impact on (A) cell viability, (B) apoptosis induction, (C) sub-G1 fraction and (D) cell cycle distribution. Cells incubated for 24 h with bortezomib or 48 h with 6 µM CHR2863 served as a control for cell growth inhibition and apoptosis induction. Percentages of apoptotic cells in control untreated U937/WT, U937/CHR2863^R0.2 and U937/CHR2863^R5 cells were 4.6% ± 1.9%, 5.2% ± 1.2% and 6.1% ± 0.9%, respectively. Sub-G1 fractions in control untreated U937/WT, U937/CHR2863^R0.2 and U937/CHR2863^R5 cells were 4.2% ± 2.0%, 9.1% ± 6.5% and 8.2% ± 2.2%, respectively. The results depicted are the mean ± SD of 4-5 independent experiments. *Combination statistically significant (P < 0.05) different compared to single drugs control cells. CHR2863: (6S)-[(R)-2-((S)-Hydroxy-hydroxycarbamoyl-methoxy-methyl)-4-methyl-pentanoylamino]-3,3 dimethyl-butyric acid cyclopentyl ester.