MDM2 Non-Genotoxic Inhibitors as Innovative Therapeutic Approaches for the Treatment of Pediatric Malignancies

V.      Tisato; A.      Norcio; R.      Voltan; C.      Celeghini; D.      Zella; P.      Secchiero

Abstract

Since the discovery of p53 as “guardian of the genome” , a large number of efforts have been put in place in order to find molecular strategies aiming to restore p53 wild-type functions, particularly in the light of the fact that its pathway results ineffective in most tumors even though they have non-mutated p53. In this context, pediatric cancers, that are mostly p53 wild-type at the time of diagnosis, represent an ideal target for such therapeutic approach. Within the several mechanisms and proteins ruling p53 activity, the murine double minute 2 (MDM2) is its crucial negative regulator, frequently found overexpressed in p53-wild-type tumors. The development of new technologies such as nuclear magnetic resonance structure analyses, computational structure-based design studies, and library peptides screening have recently led to the discovery and characterization of a large number of compounds belonging to different chemical families that are able to target the interaction p53-MDM2, rescuing the p53 wild-type pathway with an overall pro-apoptotic and anticancer activity. Within the preclinical assessment of these molecules, the cis-imidazoline analogue Nutlin-3 has definitely attracted great interest for its in vitro and in vivo antitumor activity in several pediatric cancer models, either as single agent on in combination with standard chemotherapy. In this light, the aim of this review is to summarize the main preclinical evidences of the potential of MDM2 inhibitors for the treatment of childhood cancers and the key suggestions coming from their assessment in the treatment of adult cancers as proof of concept for future pediatric clinical studies.

Keywords: Clinical perspectives, innovative therapeutic combinations, MDM2-inhibitors, non genotoxic inhibitors, nutlins family, p53, pediatric tumors, pediatric preclinical testing program.