Targeting Stat3 reduces leukemia-initiating potential of Cbfb-MYH11/Mpl⁺cells. (A-B) CMM⁺ AML cells were isolated from bone marrows of primary recipient mice treated with CpG siRNAs (5 mg/kg) injected intravenously 6 times every other day or untreated as described in Figure 2. Magnetically enriched c-kit⁺ AML cells pooled from CpG-Stat3 siRNA, CpG-Luc siRNA, or untreated mice were pooled and counted, and identical cell numbers were injected into secondary recipient mice. (A) AML progression in all experimental groups was monitored weekly by using flow cytometry to detect percentages of blood GFP⁺c-Kit⁺ AML cells in the peripheral blood. (B) Survival of mice injected with CpG-Stat3 siRNA–treated AML cells was significantly improved compared with mice that received untreated or CpG-Luc siRNA–treated AML cells. (C) Survival curve showing long-term antitumor effect of systemic administration of CpG-Stat3 siRNA compared with untreated CpG-Luc siRNA–treated group. Statistically significant differences between CpG-Stat3 siRNA– and CpG-Luc siRNA–treated or untreated groups are indicated by asterisks: P = .0002 and P < .0001, respectively. Shown are means ± SEM with n = 8 per group.