Combined inhibition of cell cycle and survival eradicate leukemic cell growth. (A) Cells (606HS2 and 931HS2) transducing Stat5-shRNA17 or control ns-shRNA were plated 72 hours after infection at 1 × 105 cells/mL and cultured in the absence (V, vehicle) or in the presence of UO126 (20μM). The number of viable cells was scored at 24 and 48 hours. Data are means ± SEM (n = 3). P < .001 comparing sh-ns + V with sh-ns + UO or sh17 + V and comparing sh-ns + UO or sh17 + V with sh17 + UO (by Student t test). (B) Cells (606HS2 and 931HS2) transducing Shp2-shRNA78 or control ns-shRNA were plated 72 hours after infection at 105 cells/mL and cultured in the absence (V, vehicle) or in the presence of LY294002 (10μM). Viable cells were scored at 24 and 48 hours. Data are means ± SEM (n = 3). P < .001 comparing sh-ns + V with sh-ns + LY or sh78 + V and comparing sh-ns + LY or sh78 + V with sh78 + LY (by Student t test). (C) Cells (606HS2 and 931HS2) were plated at 1 × 105 cells/mL and cultured in the absence (V, vehicle) or in the presence of NVP-BEZ235 (100nM) and/or Obatoclax (OBX; 100nM). Viable cells were scored at 24 and 48 hours. Data are means ± SEM (n = 3). P < .001 comparing control cells with cells grown in the presence of NVP-BEZ235 and/or OBX (by Student t test). (D) The effects of BEZ and OBX on cell proliferation were analyzed according to the Chou-Talalay method using CalcuSyn software.30 Cells (606HS2 and 931HS2) were treated with suboptimal concentrations of BEZ combined with suboptimal concentrations of OBX. The combination index values were determined from these dose-response curves for each combination. Combination index values above 1.1 indicate antagonistic, 0.9-1.1 additive, 0.7-0.9 moderately synergistic, and 0.3-0.7 synergistic effects.
