Abstract 1768: Enhanced cytotoxicity and apoptosis of cisplatin by p53-reactivating small molecule RITA in head and neck cancer

Abstract

Abstract Overexpression of MDM2 inactivates the tumor suppressive function of p53 and a small-molecule reactivation of p53 and induction of tumor cell apoptosis (RITA) disrupts the MDM2-p53 interaction. We evaluated whether the restoration of p53 function by RITA enhances cytotoxicity and apoptosis of cisplatin in head-and-neck cancer (HNC). RITA was tested in four human HNC cell lines differing in TP53 status. In vitro and in vivo growth suppression, cell cycle arrest, apoptosis after RITA treatment individually or in combination with cisplatin were assessed. RITA induced prominent accumulation and reactivation of p53 in a wild-type TP53-bearing tumor cell line. RITA showed maximal growth suppression in tumor cells showing MDM2-dependent p53 degradation. RITA upregulated p21, BAX, and cleavage of caspase-3 but the p53-dependent apoptosis was blocked by pifithrin-μ. Strong induction of apoptosis rather than G2-phase arrest was observed along with increased dose of RITA. In combination therapy, RITA enhanced the growth inhibition and apoptosis of HNC by cisplatin in vitro and in vivo. Our data suggest that the restoration of p53 tumor suppressive function by RITA enhances cytotoxicity and apoptosis of cisplatin, which may offer an attractive strategy for treating HNC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1768. doi:1538-7445.AM2012-1768