Knockdown of Survivin potentiated ABT-869–induced apoptosis in MV4-11-R cells. (A) MV4-11-R cells were treated with nontarget control shRNA or Survivin shRNA pools for 48 hours and then harvested for Western blot analysis. Actin level served as loading controls. Densitometric analysis was performed using Amersham Image Scanner with LabScan ImageQuant TL software. The level of survivin was normalized with each actin level. (B) After knockdown, MV4-11-R cells were treated with ABT-869 at doses of 50, 100, and 200 nM, and MV4-11 parental cells were treated with ABT-869 at doses of 5, 10, and 20 nM for 48 hours. As residual expression of survivin persists after treatment of survivin shRNA, it may provide some level of protection from a full-scale apoptosis. Apoptosis was measured by annexin V–FITC binding assay. P values demonstrate the comparison between survivin shRNA-treated and control shRNA-treated group. All P values of MV4-11-R samples are < .001. All P values of MV4-11 samples are greater than 0.05. Means are for 3 replicated experiments; bars represent SD. (C) Immunoblot analysis of the survivin protein level in MV4-11-Survivin and MV4-11 vector control cells.