Inducible deletion of A/E9a phenocopies the effect of panobinostat. (A) Western blot analysis of whole-cell lysates prepared from GFP-positive spleen cells isolated from Tet-off A/E9a;Nras^G12D leukemia recipient mice 72 hours after initiation of treatment with doxycycline or vehicle using an antibody to AML1. β-actin served as loading control. The results shown are representative of 2 independent experiments. (B) Kaplan-Meier survival curves of treated Tet-off A/E9a;Nras^G12D leukemia recipient mice following initiation of therapy (n = 5 for vehicle, n = 4 for doxycycline; median survival benefit 42 days, P = .0051). (C-D) Flow cytometry analysis of c-Kit and CD11b expression in donor GFP-positive spleen cells isolated from Tet-off A/E9a;Nras^G12D leukemia recipient mice at the indicated time after initiation of treatment with doxycycline (2 mg/kg) or vehicle. Each data point represents an individual mouse, and the mean value ± standard error from 2 separate experiments is shown. *P < .001. (E) Mice bearing Tet-off A/E9a;Nras^G12D leukemias were treated with vehicle or doxycycline (dox) for 5 days. Tumors were harvested, and expression of the indicated genes was determined by quantitative real-time PCR. Results (mean and standard error of the mean) shown are from tumors harvested from 5 individual recipient mice for each treatment regimen.