AML is induced by the combination of NRAS^G12V and Mll-AF9. (A) Breeding scheme for generating experimental animals. Boxes indicate transgenes present. (B) Kaplan-Meier survival curve. Vav-tTA; TRE-NRAS^G12V; Mll-AF9 triply transgenic (TRM-transgenic) and Vav-tTA; Mll-AF9 doubly transgenic (TM-transgenic) mice developed AML and died significantly earlier than Vav-tTA; TRE-NRAS^G12V doubly transgenic (TR-transgenic) mice (P < .05). The TRM-transgenic mice showed a trend of decreased latency for AML compared with those carrying the TM transgene (P = .072). Bidirectional arrow indicates the prenatal period of Dox treatment. (C) Immunophenotypes of BM and spleen cells in AML mice. Mac1 and Gr1 double-positive cells are greater than those of FBV/n × C57BL/6J F1 mice. (D) NRAS^G12V transcription is repressed by Dox treatment. Vav-tTA-driven TRE-NRAS^G12V expression is found in all Vav-tTA; TRE-NRAS^G12V cotransgenic BM cells with or without Mll-AF9 transgene and mastocytosis tumor cells (lanes 2, 5, 6, and 7). The NRAS^G12V expression is completely repressed by Dox treatment (lane 1). GAPDH is used as a loading control. No RT-PCR products were found in the same procedures without reverse transcriptase (data not shown). The genotypes and cell types along with numbers indicate the transgenic cells used for mRNA preparations. BM indicates bone marrow; MT, mastocytosis tumor; and W, water control.