FIG. 4.

Tumor growth and morphology are unaffected by p19^ARF deficiency. H & E-stained CP tumors from 20-week-old TgT₁₂₁;p19^ARF+/+ (A) and TgT₁₂₁;p19^ARF−/− (B) mice are similar in size and morphology. In contrast, tumors become life-threatening by 4 weeks of age in TgT₁₂₁;p53^−/− mice (D). Leukemia caused by the p19^ARF−/− mutation is frequently observed invading the brains of TgT₁₂₁;p19^ARF−/− mice (C), a pathology that is present only in mice with compound genotypes and is thought to further reduce survival time (Table 1). Representative leukemia-filled vessels in the brain are indicated by arrows. The bar in panel C is equal to 100 μm. The bar in panel D is equal to 200 μm; panels A, B, and D are of the same magnification. br, brain tissue.