Inhibition of Wnt/β-Catenin Signaling in Neuroendocrine Tumors in vitro: Antitumoral Effects

Xi-Feng Jin; Gerald Spoettl; Julian Maurer; Svenja Nölting; Christoph Josef Auernhammer

doi:10.3390/cancers12020345

Inhibition of Wnt/β-Catenin Signaling in Neuroendocrine Tumors in vitro: Antitumoral Effects

Cancers (Basel). 2020 Feb 4;12(2):345. doi: 10.3390/cancers12020345.

Authors

Xi-Feng Jin¹, Gerald Spoettl¹, Julian Maurer¹, Svenja Nölting^{1

2}, Christoph Josef Auernhammer^{1

2}

Affiliations

¹ Department of Internal Medicine 4, University-Hospital, Klinikum der Universitaet Muenchen, Ludwig-Maximilians-University of Munich, 81377 Munich, Germany.
² Interdisciplinary Center of Neuroendocrine Tumors of the GastroEnteroPancreatic System (GEPNET-KUM), Klinikum der Universitaet Muenchen, Ludwig-Maximilians-University of Munich, Campus Grosshadern, Marchioninistr. 15, 81377 Munich, Germany.

Abstract

Background and aims: Inhibition of Wnt/β-catenin signaling by specific inhibitors is currently being investigated as an antitumoral strategy for various cancers. The role of Wnt/β-catenin signaling in neuroendocrine tumors still needs to be further investigated.

Methods: This study investigated the antitumor activity of the porcupine (PORCN) inhibitor WNT974 and the β-catenin inhibitor PRI-724 in human neuroendocrine tumor (NET) cell lines BON1, QGP-1, and NCI-H727 in vitro. NET cells were treated with WNT974, PRI-724, or small interfering ribonucleic acids against β-catenin, and subsequent analyses included cell viability assays, flow cytometric cell cycle analysis, caspase3/7 assays and Western blot analysis.

Results: Treatment of NET cells with WNT974 significantly reduced NET cell viability in a dose- and time-dependent manner by inducing NET cell cycle arrest at the G1 and G2/M phases without inducing apoptosis. WNT974 primarily blocked Wnt/β-catenin signaling by the dose- and time-dependent downregulation of low-density lipoprotein receptor-related protein 6 (LRP6) phosphorylation and non-phosphorylated β-catenin and total β-catenin, as well as the genes targeting the latter (c-Myc and cyclinD1). Furthermore, the WNT974-induced reduction of NET cell viability occurred through the inhibition of GSK-3-dependent or independent signaling (including pAKT/mTOR, pEGFR and pIGFR signaling). Similarly, treatment of NET cells with the β-catenin inhibitor PRI-724 caused significant growth inhibition, while the knockdown of β-catenin expression by siRNA reduced NET tumor cell viability of BON1 cells but not of NCI-H727 cells.

Conclusions: The PORCN inhibitor WNT974 possesses antitumor properties in NET cell lines by inhibiting Wnt and related signaling. In addition, the β-catenin inhibitor PRI-724 possesses antitumor properties in NET cell lines. Future studies are needed to determine the role of Wnt/β-catenin signaling in NET as a potential therapeutic target.

Keywords: Wnt/β-catenin signaling; neuroendocrine tumor; porcupine inhibitor; β-catenin inhibitor; β-catenin siRNA.