Amplification of MYCN is the most well-known prognostic marker of neuroblastoma risk classification, but still is only observed in 25% of cases. Recent evidence points to the cyclic adenosine monophosphate (cAMP) elevating ligand prostaglandin E2 (PGE2) and β-catenin as two novel players in neuroblastoma. Here, we aimed to define the potential role of PGE2 and cAMP and its potential interplay with β-catenin, both of which may converge on neuroblastoma cell behaviour. Gain and loss of β-catenin function, PGE2, the adenylyl cyclase activator forskolin and pharmacological inhibition of cyclooxygenase-2 (COX-2) were studied in two human neuroblastoma cell lines without MYCN amplification. Our findings show that PGE2 enhanced cell viability through the EP4 receptor and cAMP elevation, whereas COX-2 inhibitors attenuated cell viability. Interestingly, PGE2 and forskolin promoted glycogen synthase kinase 3β inhibition, β-catenin phosphorylation at the protein kinase A target residue ser675, β-catenin nuclear translocation and TCF-dependent gene transcription. Ectopic expression of a degradation-resistant β-catenin mutant enhances neuroblastoma cell viability and inhibition of β-catenin with XAV939 prevented PGE2-induced cell viability. Finally, we show increased β-catenin expression in human high-risk neuroblastoma tissue without MYCN amplification. Our data indicate that PGE2 enhances neuroblastoma cell viability, a process which may involve cAMP-mediated β-catenin stabilization, and suggest that this pathway is of relevance to high-risk neuroblastoma without MYCN amplification.

Neuroblastoma (NBL) is a neural crest derived tumor which accounts for ±15% of pediatric cancer deaths. Despite recent efforts to elucidate the genetic background of NBL, the molecular etiology remains unclear. Recent evidence points to the cyclic‐ AMP (cAMP) elevating ligand prostaglandin E2 (PGE2) and the oncoprotein β‐catenin as two novel players in NBL. Here, we aimed to define a potential role and interplay of PGE2 and β‐catenin in survival of NBL.β‐Catenin expression was analyzed by immunohistochemistry in 41 human NBL biopsies. Further, we studied survival of 8 human NBL cell lines in response to PGE2 and cAMP elevation by the adenylyl cyclase activator forskolin.Our findings show that β‐catenin expression inversely correlates with NBL patient survival. In addition, we show that expression of a degradation‐resistant β‐catenin mutant (S33Y) increased NBL cell proliferation. Similarly, both PGE2 and forskolin enhanced proliferation, promoted GSK‐3 phosphorylation, β‐catenin stabilization and β‐catenin dependent gene transcription. In line with our hypothesis, reduction of endogenous PGE2 by a cyclooxygenase‐2 inhibitor attenuated NBL cell survival, a process being partially reversed by exogenous PGE2. We conclude that PGE2‐induced cAMP stabilizes β‐catenin and promotes NBL tumor cell survival via enhanced β‐catenin target gene transcription.This study is supported by the UMCG.