Abstract 4530: The anti-tumor effect of MDM2 antagonist nutlin-3 in gastric cancer cell in vitro and in vivo

Abstract

Abstract Purpose: The mortality of gastric cancer is still high accounting for an estimated 50,000 deaths in Japan. The chemotherapies based on fluoropyrimidine and platinum complexes are widely used for unresectable advanced gastric cancer, however, development of new strategies including molecular targeting therapies are urgently required to obtain further effectiveness. Recent studies demonstrate that 70% of gastric cancers has wild-type p53 gene and its function thought to be inhibited by over-expression of murine double minute 2 (MDM2), a regulator of p53 turnover by binding p53 and acting as a ubiquitin E3 ligase. Nutlin-3 is a small-molecule MDM2 antagonist that efficiently activates p53 and its tumor suppresser function has been shown in retinoblastoma and hematological malignancy but not in gastrointestinal carcinoma. In this study, we investigated the antitumor effects of nutlin-3 in gastric cancer cells in combination with 5-fluorouracil or cisplatin in vitro and in vivo. Experimental Design: Human gastric cancer cell lines carrying wild-type (4 cell lines) or mutated p53 gene (3 cell lines) were incubated with nutlin-3 alone or combination with 5-fluorouracil or cisplatin in time dependent manner. Cell viability was calculated by WST assay. Western blot analysis for MDM2 and p53 are also performed to investigate protein expression. In vivo study, mice xenografted gastric cancer cells were treated with nutlin-3 alone or combination with 5-fluorouracil intraperitoneally. The tumor size was measured and histochemistry was done after 3 weeks administration. Results: Nutlin-3 showed strong cytotoxicity in gastric cancer cells carrying wild-type p53 gene not mutated p53 gene, regardless of expression level of MDM2 protein. Anti-tumor effect of Nutlin-3 was also observed in xenografted mice model. Histochemical analysis indicated nutlin-3 induced apoptotic cell death in tumor tissue. Furthermore, combined treatment with nutlin-3 and 5-fluorouracil or cisplatin revealed enhanced cytotoxicity in gastric cancer cells with wild-type p53 gene. Conclusions: Our results present new option in exploiting reactivation of p53 as what we believe to be a novel and highly selective treatment for gastric cancer patients with wild-type p53 gene. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4530.