Increased sensitivity of Myc^V394DAML cells to chemotherapy compared with Myc AML cells. (A-B) Myc- and Myc^V394D-AML cells were seeded into methylcellulose medium for CFU assay with or without Ara-C and DNR treatment. CFUs were counted (A) and imaged (B) on day 7 of culturing. (C-G) Myc/Cre^ERTMyc^fx/fx and Myc^V394D/Cre^ERTMyc^fx/fx AML cells were transplanted into recipient mice. Beginning on day 3 after transplantation, mice were treated with TAM every day for 5 consecutive days to induce the deletion of endogenous Myc. Beginning on day 8 after transplantation, mice were treated with D3+A5 regimen of chemotherapy. A panel of mice was euthanized on day 24 posttransplantation to assess the development of leukemia by examining leukemic blasts in PB smears (C), spleen size (D), liver size (E), and leukemic cell infiltration into livers (F). The other panel of mice was monitored for leukemia-related death (G). *P < .05 compared to Myc-Veh group; **P < .01 compared to Myc-DA group. DA, daunorubicin and cytarabine.