Systemic administration of CpG-STAT3dODN targets disseminated AML inducing leukemia regression. (A) Biodistribution of systemically injected CpG(D19)-STAT3dODN. MV4-11 AML cells were engrafted into immunodeficient NSG mice. Mice were then injected IV using Cy3-labeled CpG-STAT3dODN (5 mg/kg) and euthanized 3 to 18 hours later. Percentages of Cy3⁺/hCD45⁺ double-positive MV4-11 cells were assessed using flow cytometry in single-cell suspensions prepared from blood, bone marrow (BM), or spleen. Shown are representative results of 2 independent experiments using a total of 6 mice analyzed individually; means ± SEM. (B) Dose-dependent inhibition of STAT3 activity in AML in vivo. AML-bearing mice were treated 3 times using CpG-STAT3 dODN or control CpG-scrODN at indicated dosing every other day and euthanized 1 day after the last treatment. STAT3 activity at the level of Y705 phosphorylation was measured using flow cytometry; means ± SEM (n = 6). (C) Systemic delivery of CpG-STAT3dODN induces regression of human AML in mice. MV4-11ch/luc-bearing NSG mice were treated using daily IV injections (5 mg/kg) for 15 days. Tumor burden was monitored using the bioluminescent imaging (BLI) on an IVIS 100 imaging system. (D) The percentages of human CD45⁺ MV4-11ch/luc cells in various organs were assessed using flow cytometry at the end of the experiment (day 15); means ± SEM (n = 6). % ge, percentage.