Prostaglandin E₂ promotes MYCN non‐amplified neuroblastoma cell survival via β‐catenin stabilization

Abstract

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.

Frizzled2 signaling regulates growth of high-risk neuroblastomas by interfering with β-catenin-dependent and β-catenin-independent signaling pathways

“…Intriguingly, our study revealed higher expression levels of FZD2, LRP6 and cyclin D1 in MYCN -amplified SK-N-DZ NB cells and tumors, while β-catenin (both total and active) and MYC were higher expressed in MYCN -unamplified SK-N-AS cells and tumors. In support of this, other studies reported upregulated β-catenin and β-catenin target genes in high-risk NB tumor tissue without MYCN amplification in comparison to high-risk MYCN -amplified tumor sections [15, 33]. Importantly, FZD2 blockade reduced β-catenin staining intensity in both NB xenografts.…”

Epac1 links prostaglandin E2 to β-catenin-dependent transcription during epithelial-to-mesenchymal transition

“…We and other have previously shown that PGE 2 , through activation of cyclic AMP, is responsible for activating β-catenin, thus making the Gαs-coupled EP 2 and EP 4 receptor the most likely candidates [14]. Here, we observed no effect of specific antagonism of the EP 4 receptor on PGE 2 -induced β-catenin-dependent transcription, whereas antagonism of the EP 2 receptor completely abolished the effect of PGE 2 .…”

“…Earlier studies by us and others have indicated that PGE 2 activates β-catenin-dependent transcription via cyclic AMP [13, 14, 48–52]. When we investigated expression of the cyclic AMP effector Epac, we observed increased expression of the Epac1 subtype by PGE 2 .…”

“…We have shown in other cell models, that PGE 2 stabilizes β-catenin [14]. We therefore studied the role of β-catenin in PGE 2 induced EMT in A549 cells.…”

“…Previous work from our group and others has shown that PGE 2 results in the stabilization of the important oncogene β-catenin in cancer cells [12–14]. β-Catenin has a dual function in the cell; on one hand it is a component of the adherens junction, where it stabilizes E-cadherin/actin cytoskeleton binding, on the other hand, free cytosolic β-catenin can translocate to the nucleus.…”