Figure 6

Calculation of combination indexes indicates a synergistic cell growth arrest upon treatment of the AML cell line ML-2 with the association of daunorubicin and CK2 inhibitors. (A) Synergistic effect of CX-4945 and daunorubicin on ML-2 cell proliferation. Left graph: dose–response of ML-2 cells incubated for 48 hours with increasing concentrations of daunorubicin (black square) or daunorubicin plus a fixed dose (5 μM) of CX-4945 (white circle). Right graph: dose–response of ML-2 cells incubated for 48 hours with increasing concentrations of CX-4945 (black square) or CX-4945 plus a fixed dose (0.05 μM) of daunorubicin (white square). (B) Synergistic effect of K27 and daunorubicin on ML-2 cell proliferation. Left graph: dose–response of ML-2 cells incubated for 48 hours with increasing concentrations of daunorubicin (black square) or daunorubicin plus a fixed dose (5 μM) of K27 (white circle). Right graph: dose–response of ML-2 cells incubated for 48 hours with increasing concentrations of K27 (black square) or K27 plus a fixed dose (0.05 μM) of daunorubicin (white triangle). The combination index (CI), obtained according to the formula described in the Material and Methods section, was calculated as to be: 0.86 for the daunorubicin plus CX-4945 combination and 0.7 for the daunorubicin plus K27 combination, indicating a synergic effect. In all the experiments data represent mean ± SD, n = 3. * indicates p < 0.01.