(A) Mice transplanted with BM cells expressing Cdx2 (n = 5) developed AML after a median of 187 days after transplantation, whereas mice transplanted with MSCV-IRES-GFP–transduced BM (n = 3) showed no evidence of disease with a follow-up duration of more than 250 days (P = 0.013). Secondary recipients (n = 5) transplanted with BM from primary leukemic mice developed AML after a median of 52 days after transplantation. BMT, BM transplantation. (B) Diseased mice showed elevated wbc counts (primary recipients versus control mice, P = 0.09; secondary recipients versus control mice, P = 0.019) and splenomegaly (primary recipients versus control mice, P = 0.0029; secondary recipients versus control mice, P < 0.0001). Values are represented as mean ± SD. (C) Microscopic analysis of PB from primary and secondary leukemic animals demonstrated leukocytosis consisting of frequent immature myeloid cells with a high proportion of blast forms that extensively involved the BM, liver, and spleen. Panels display Wright-Giemsa–stained PB smears and H&E-stained tissue sections from representative mice transplanted with BM cells expressing Cdx2. Original magnification, ×400 and ×1,000 (PB); ×100 and ×600 (BM and liver); and ×40 and ×600 (spleen). (D) Flow cytometric analysis of GFP-gated cells from BM and spleen of primary and secondary leukemic animals demonstrated an increased proportion of Mac-1⁺ myeloid cells with variable expression of Gr-1, CD34, and c-Kit and a concomitant reduction in the level of CD3⁺ or B220⁺ lymphoid cells. The percentages of positive cells within the GFP⁺ compartment are indicated.