Abstract 2746: Microsomal prostaglandin E2 synthase-1 may provide a novel specific therapeutic target in neuroblastoma.

Abstract

Abstract Background: Neuroblastoma (NB) cells are enriched in the omega-6 fatty acid arachidonic acid, the substrate for the cyclooxygenase (COX) enzymes and prostaglandin biosynthesis. The inducible isoform, COX-2 is overexpressed in NB and NB cells produce prostaglandin E2 (PGE2) that acts as an autocrine and/or paracrine survival and proliferation factor. Downstream of the COX enzymes, specific synthases are responsible for the production of the respective 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 was to investigate if inhibition of mPGES-1 could represent an alternative therapeutic approach to COX- inhibition in NB. Methods: Western blot and immunohistochemistry were used for protein detection. Cell viability of seven NB cell-lines treated with the mPGES-1 inhibitor CAY1052 was determined by MTT-assay. Stable mPGES-1 knockdown SK-N-BE2 clones were established using shRNA and the clonogenic capacity was analysed by clonogenic assay. To study the in vivo effect of COX inhibition, four week old homozygous TH-MYCN mice were treated with 10mg/L diclofenac for two weeks. Ex vivo analyses of COX-metabolites in tumors were performed by LC-MS/MS. Results: Expression of mPGES-1 in human NB tumors and in NB cell lines could be detected. Inhibition of mPGES-1 reduced NB cell growth in vitro and knockdown of mPGES-1 significantly reduced the clonogenic capacity. Expression of COX-1, COX-2 and mPGES-1 in TH-MYCN tumors could be detected and treatment with the dual COX-inhibitor diclofenac significantly reduced tumour weight, compared to untreated animals. Ex vivo analysis of tumor tissues from treated animals revealed a significantly decreased level of COX metabolites compared to controls. The expression of mPGES-1was not affected by the treatment. Furthermore, cells staining positive for cleaved caspase-3 were more prevalent in treated tumors indicating apoptosis Induction. Conclusion: We found that mPGES-1 is expressed in NB, with a potential role for PGE2 synthesis and tumor growth. mPGES-1 represents an alternative therapeutic target for inhibiting NB growth through specific PGE2 inhibition and the TH-MYCN model is well suited for in vivo studies with this purpose. Citation Format: Anna Kock, Agnes Rasmuson, Marina Korotkova, Helena Idborg, John Inge Johnsen, Per-Johan Jakobsson, Per Kogner. Microsomal prostaglandin E2 synthase-1 may provide a novel specific therapeutic target in neuroblastoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2746. doi:10.1158/1538-7445.AM2013-2746