Expression of p53 is induced in T-ALL tumors when NOTCH^IC expression is extinguished. Each primary tumor was transplanted into multiple syngeneic mice, and tumors were allowed to form. When mice were moribund, Dox was added and tissue collected at various time points for analysis. RT-PCR (A), quantitative RT-PCR (B), and Western blot (C) analyses were performed with the indicated specific primers or antibodies on single-cell suspensions from spleens of Top-NOTCH^IC-/MIT-c-MYC tumors.