Dual Targeting of Wild-Type and Mutant p53 by Small Molecule RITA Results in the Inhibition of N-Myc and Key Survival Oncogenes and Kills Neuroblastoma Cells In Vivo and In Vitro

Purpose: Restoration of the p53 function in tumors is a promising therapeutic strategy due to the high potential of p53 as tumor suppressor and the fact that established tumors depend on p53 inactivation for their survival. Here, we addressed the question whether small molecule RITA can reactivate p53 in neuroblastoma and suppress the growth of neuroblastoma cells in vitro and in vivo. Experimental Design: The ability of RITA to inhibit growth and to induce apoptosis was shown in seven neuroblastoma cell lines. Mechanistic studies were carried out to determine the p53 dependence and the molecular mechanism of RITA-induced apoptosis in neuroblastoma, using cell viability assays, RNAi silencing, co-immunoprecipitation, qPCR, and Western blotting analysis. In vivo experiments were conducted to study the effect of RITA on human neuroblastoma xenografts in mice. Results: RITA induced p53-dependent apoptosis in a set of seven neuroblastoma cell lines, carrying wild-type or mutant p53; it activated p53 and triggered the expression of proapoptotic p53 target genes. Importantly, p53 activated by RITA inhibited several key oncogenes that are high-priority targets for pharmacologic anticancer strategies in neuroblastoma, including N-Myc, Aurora kinase, Mcl-1, Bcl-2, Wip-1, MDM2, and MDMX. Moreover, RITA had a strong antitumor effect in vivo. Conclusions: Reactivation of wild-type and mutant p53 resulting in the induction of proapoptotic factors along with ablation of key oncogenes by compounds such as RITA may be a highly effective strategy to treat neuroblastoma. (C) 2013 AACR.