Figure 2. Myc augments p53-dependent, CQ-induced cell death.

(A) CQ augments cell death in Eμ-Myc transgenic B cells. B cells cultured from 4-week-old nontransgenic and Eμ-Myc transgenic mice were treated with 50 μM CQ for 24 h. The percentage of viable cells was determined by propidium iodide incorporation. Results shown are the mean of 3 independent B cell cultures. (B) p53 is required for sensitization of Myc-expressing MEFs to CQ. Myc-ER^TAM–expressing MEFs were either left untreated (Unt) or were treated for 24 h with 4-HT alone or with 4-HT and 50 μM CQ. The percentage cell death was determined by staining cells with propidium iodide. Results shown are the mean of 3 independent experiments. Western blot analyses of the indicated cells demonstrated equal levels of expression of the Myc-ER^TAM transgene. (C) Myc sensitizes HCT116 colon cancer cells to p53-dependent, CQ-induced death. Cells were treated for 24 h with 4-HT and were either left untreated or were treated with 50 μM CQ for 24 h. The percentage cell death was determined by staining cells with propidium iodide. Results shown are the mean of 3 independent experiments. (D) CQ treatment leads to clearance of Arf/p53/Puma-expressing precancerous Eμ-Myc B cells. Beginning at 4 weeks, Eμ-Myc transgenic mice and their wild-type littermates were injected with 3.5 mg/kg CQ (in PBS) i.p. every 5 days or with PBS alone. At 7 weeks, mice were sacrificed and B220⁺ B cells analyzed. As controls, lysates were also prepared from primary Arf^–/– and p53^–/– B cells. Protein extracts were prepared and evaluated for their levels of the indicated antibodies.