Combination effect of puromycin and reactivating p53 and inducing tumor apoptosis (RITA) or doxorubicin in cancer cells. (A) Synergistic effect of puromycin and RITA on cytotoxicity in HCT116 cells. HCT116 cells were treated with various concentrations of puromycin and RITA for 24 h, and cytotoxicity was evaluated by using MTT assay. **, p < 0.001 vs. untreated control. (B) Combination effect of puromycin and RITA on c-Myc, p53, PARP, Bcl-2, and cyclin D1 in HCT116 and H1299 cells. HCT116 and H1299 cells were treated with or without puromycin or/and RITA for 24 h. Western blotting was performed with antibodies of c-Myc, p53, PARP, Bcl-2, cyclin D1, and β-actin. (C) Combination effect of puromycin and doxorubicin on c-Myc, p53 and Bcl-2 in HCT116 cells. HCT116 cells were treated with or without puromycin (0.25 μg/mL) and doxorubicin (1 μM) for 24 h and subjected to Western blotting for c-Myc, p53, Bcl-2, and β-actin. (D) A mechanistic scheme for puromycin-induced p53 dependent apoptosis via interaction between MDM2 and RPL5/RPL11.