Abstract 1420: Microsomal prostaglandin E2 synthase 1 (mPGES-1) is expressed in neuroblastoma and may represent a novel target for therapy

Abstract

Abstract Neuroblastoma (NB) is an embryonic tumor of the sympathetic nervous system and it is the most common extracranial tumor affecting young children. Despite a very intensive treatment regimen high-risk neuroblastoma patients still have a poor prognosis. Neuroblastoma cells are enriched in arachidonic acid, over express COX-2 and produce prostaglandin E2 (PGE2) that acts as an autocrine or paracrine survival and proliferation factor by induction of Akt signaling. Downstream of the COX enzymes, specific synthases converts PGH2 into the different prostaglandins. Microsomal prostaglandin E2 synthase-1 (mPGES-1) specifically converts PGH2 to PGE2 and is thought to primarily couple to COX-2. The aim of this study is to investigate if inhibition of mPGES-1 could represent an alternative therapeutic approach to COX- inhibition in neuroblastoma. We could detect expression of mPGES-1 in a panel of seven human neuroblastoma cell lines. Stable knock down of mPGES-1 expression using shRNA significantly reduced the clonogenic capacity and treatment with the mPGES-1 inhibitor CAY1052 inhibited neuroblastoma cell growth in vitro. By immunohistochemistry and western blot we could also detect expression of COX-1, COX-2 and mPGES-1 in tumors from the transgenic TH-MYCN mouse model of neuroblastoma. Treatment of homozygous TH-MYCN mice with 10 mg/L diclofenac for two weeks, starting at the age of four weeks, significantly reduced tumour weight compared to untreated animals. Ex vivo analysis with LC-MS/MS of tumor tissues from diclofenac treated animals revealed a significant decreased level of COX metabolites compared to control. The expression of mPGES-1was not affected by the treatment. Furthermore the number of cells staining positive for cleaved caspase-3 were higher in the treated tumors indicating induced apoptosis. In conclusion, our results show that mPGES-1 is expressed in neuroblastoma therefore mPGES-1 might represent an alternative way of reducing NB growth through specific PGE2 inhibition. 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 1420. doi:1538-7445.AM2012-1420