HOXA9 suppression induces apoptosis in primary MLL-rearranged human AML cells. (A) Analysis of baseline HOXA9 expression before shRNA transduction by quantitative real-time PCR. (B) The mean HOXA9 expression level was found to be significantly higher in primary AML patient samples bearing an MLL translocation (P = .004). (C) Analysis of apoptosis induction by annexin V staining 72 hours after transduction with the 1F3-HOXA9shRNA or control shRNA. (D) Induction of apoptosis is significantly higher in the MLL-rearranged group (P = .010). (E) A significant correlation between baseline HOXA9 expression and impact of HOXA9 knockdown on viability is demonstrated. Samples expressing high-level HOXA9 were found to be especially susceptible to HOXA9 depletion (R = −0.8; P = .005).