Characterization of leukemia models. (A) Example of bone marrow derived from a primary recipient of coinfected cells. The BCR/ABL-transduced cells are detected by GFP expression and the Nup98/HoxA9-infected cells are detected by YFP expression. Panels I and II indicate singly infected populations, whereas panel III shows cells that are successfully transduced with both the BCR/ABL and Nup98/HoxA9 vectors. (B) Example of bone marrow derived from a secondary recipient of coinfected cells. The doubly transduced cells typically outgrow the singly infected populations shown in panel A. (C) GFP⁻/YFP⁻ cells from the secondary recipient in panel B were analyzed with respect to Ly5.1 versus Ly5.2 expression as a means to verify host origin and to establish that potential donor leukemic cells have not lost GFP/YFP expression (host cells in this experiment were of Ly5.2 origin). Fidelity of the system is demonstrated by greater than 99% purity of the host marker.