Myeloid leukemia developed in mice that received transplanted MSCV-Sox4-infected bone marrow cells. (A) Survival curve of lethally irradiated mice that received transplanted MSCV-Sox4-infected marrow, uninfected marrow, or empty MSCV-infected marrow. The area shaded in gray represents the survival of secondary transplant recipient mice (n = 8) that received leukemia cells from a primary recipient. (B) (top) Wright-Giemsa staining of representative leukemic bone marrow. (bottom) Hematoxylin and eosin staining of a representative liver section showing leukemia-cell infiltration. Original magnifications, × 400 (left) and × 100 (bottom). (C) Normal (top) and leukemic (bottom) spleens stained with anti-MPO antibody. Original magnification, × 100. (D) Northern blot analysis of Sox4 expression in 7 myeloid leukemias induced by MSCV-Sox4 infection or normal spleen RNA. β-Actin was included to control for RNA loading. The Sox4 transcript expressed in leukemia 0935 was smaller than expected, suggesting a rearrangement in the MSCV-Sox4 virus present in this leukemia. (E) Southern blotting of leukemic spleen DNA using an MSCV-specific probe. Samples were digested with HindIII, which cuts once in the viral construct. Each band represents a separate Sox4 viral integration.