ABL1 promotes myeloid differentiation of BCR-ABL1 leukemia cells. (A) Representative hematoxylin-eosin–stained spleen sections from moribund SCID mice injected with BCR-ABL1 Abl1^−/− [−/−], BCR-ABL1 Abl1^+/+ [+/+] and BCR-ABL1/YFP-ABL1 Abl1^−/− [−/−(+)] cells; magnification, ×20, inset, ×40. (B) Wright-Giemsa staining of BCR-ABL1 Abl1^+/+ [+/+], BCR-ABL1 Abl1^−/− [−/−] and BCR-ABL1/YFP-ABL1 Abl1^−/− [−/−(+)] leukemia cells maintained in the presence of SCF + IL-3 (top panels) or G-CSF (bottom panels). Representative images are shown; magnification, ×100. (C) Mean percentages of Gr-1⁺/Mac-1⁺ cells ± SD in BCR-ABL1 Abl1^−/− and BCR-ABL1 Abl1^+/+ leukemia cells maintained in the presence of SCF + IL-3 or G-CSF; *P < .002. (D) Statistically significant (FDR < 0.05) fold changes (>1.5) of expression of genes regulating myeloid differentiation in BCR-ABL1 Abl1^−/− vs BCR-ABL1 Abl1^+/+ leukemia cells maintained with SCF + IL-3 or G-CSF.