GFI1B and acute myeloid leukemia: First, Lin- cells from Gfi1bfl/flMxCretg or Gfi1bfl/flMxCrewt mice were transduced with different oncofusion genes (MLL/AF9, AML/ETO, or BCR/ABL) to generate preleukemic cells, and then treated with IFN β to induce Gfi1b deletion (Fig. 4a).