Dominant-negative TCF4 inhibits leukemic cell growth of Flt3-ITD mutations. (A) Stable 32D/Flt3-ITD or 32D/Flt3-WT cells were either transfected with a dominant-negative TCF4 expression construct (dnTCF4; □) or with control vector (▪) as indicated. Cells were seeded in triplicates in colony assays in the presence of neomycin selection. Colony growth was evaluated on day 10. The bar graph shows the result of 1 of 3 independent experiments (mean and SD). (B) 32D cells stably transfected with Flt3-WT or with Flt3-ITD were grown for 12 hours in the absence of IL-3. Subsequently, cells were stimulated with FL or IL-3 or left without cytokine in the presence or absence of Dkk-1 protein for 6 hours. Either 50% of Wnt3a-conditioned medium or control-conditioned medium was added. Western blot analyses were performed with lysates from these cells using β-catenin or actin antibodies as indicated.