Inhibition of Wnt-supressing genes regulates non-Canonical Wnt signalling in Pituitary Adenomas (PA)

Abstract

Introduction: The Wnt developmental pathway has been implicated in tumour development in numerous tissues. Both the canonical and non-canonical Wnt pathways, namely the Wnt-Calcium signalling pathway and the Wnt- planar polarity pathway have also been found de-regulated in a number of cancers (Katoh et al, 2017). Microarray analysis on locally resected PAs revealed strong down-regulation of a number of Wnt antagonists. The aim of this study was to functionally assess the role of WIF1 in PA in relation to the different Wnt signalling pathways using two established cell lines in the presence Wnt3, Wnt4 and Wnt5a ligands. Methods: Proliferation analysis was used to assess the effect of Wnt pathway antagonists on cell models of PA. Luciferase reporter, hormone secretion and calcium signalling assays were then used to assess which downstream pathways could mediate these effects. Finally, quantitative expression of target genes was used to identify activated pathways that mediate the effects of non/ canonical Wnt signalling. Results: Preliminary findings indicate that Wnt antagonists reduce GH3 and MMQ proliferation. Additionally, the canonical Wnt pathway appears to be completely inactive in these two PA cell models using real- time PCR and reporter assays. Conversely, free calcium fluxes are clearly influenced by the addition of Wnt ligands and co-treatment with Wnt antagonist Wnt Inhibitor Factor 1 (WIF1) represses these calcium fluctuations, with concomitant effects on hormone secretion. Conclusion: Preliminary data reveals that the Wnt agonists may activate the Wnt-Calcium signalling pathway and WIF1 could play a role in PA by inhibiting specific aspects of this pathway. Disclosures: This study was funded by two independent research funds awarded to JV (University of Malta Research Fund: MEDRP02-05 and the Dean’s Research Fund, Faculty of Medicine and Surgery: MDSIN08-22). RF is funded by the REACH HIGH Scholars Programme – Post-Doctor