Novel β-carbolines against colorectal cancer cell growth via inhibition of Wnt/β-catenin signaling

X Li,B Mao,J Zhang,J Yan,Z Ye,H Zhou,H Zhu,P Ma,B Bai,Y Li,L Kong,L Liu

doi:10.1038/cddiscovery.2015.33

Abstract

Wnt signaling pathway is aberrantly activated in a variety of cancers, especially in colorectal cancer (CRC), because of mutations in the genes encoding adenomatous polyposis coli (APC), β-catenin and Axin. Small-molecule antagonists of Wnt/β-catenin signaling are attractive candidates for developing effective therapeutics for CRC. In this study, we have identified a novel Wnt signaling inhibitor, isopropyl 9-ethyl-1- (naphthalen-1-yl)-9H-pyrido[3,4-b]indole-3- carboxylate (Z86). Z86 inhibited Wnt reporter activities and the expression of endogenous Wnt signaling target genes in mammalian cells and antagonized the second axis formation of Xenopus embryos induced by Wnt8. We showed that Z86 treatment inhibits GSK3β (Ser9) phosphorylation, leading to its overactivation and promoting the phosphorylation and degradation of β-catenin. In vitro, Z86 selectively inhibited the growth of CRC cells with constitutive Wnt signaling and caused obvious G1-phase arrest of the cell cycle. Notably, in a nude mouse model, Z86 inhibited dramatically the xenografted tumor growth of CRC. Daily intraperitoneal injection of Z86 at 5 mg/kg resulted in >70% reduction in the tumor weight of HCT116 cell origin that was associated with decreased GSK3β (Ser9) phosphorylation and increased β-catenin phosphorylation. Taken together, our findings provide a novel promising chemotype for CRC therapeutics development targeting the canonical Wnt signaling.

Highlights

The Wnt signaling transduction pathway plays a critical role in embryonic developmental processes, tissue homeostasis and tumorigensis.[1] β-Catenin is an important component of the canonical Wnt signaling pathway
The results showed that, consistent with the Topflash reporter assays, isopropyl 9-ethyl-1-(naphthalen-1-yl)-9H-pyrido [3 (Z86) reduced the expression of these Wnt signaling target genes at both the mRNA and protein levels in a dose- and time-dependent manner in these cells (Figures 2b and c), To further confirm the inhibitory activity of Z86 on Wnt signaling, we tested its activity in Xenopus embryos to inhibit secondary axis induced by Wnt[8], a classical model to study Wnt activity
We described the discovery of a novel β-carboline structuretype compound Z86 that interfered with Wnt/β-catenin pathway by overactivation of glycogen synthase kinase-3β (GSK3β), promoted β-catenin degradation and exhibited efficient cell growth inhibition in colon cancer cells both in vitro and in vivo

Summary

INTRODUCTION

The Wnt signaling transduction pathway plays a critical role in embryonic developmental processes, tissue homeostasis and tumorigensis.[1] β-Catenin is an important component of the canonical Wnt signaling pathway. Several other studies have confirmed the effectiveness of suppression of APC mutation-driven colorectal tumor growth through inhibition of Wnt signaling pathway by stabilizing Axin.[20,21,22]. We have identified a novel Wnt signaling inhibitor, isopropyl 9-ethyl-1-(naphthalen-1-yl)-9H-pyrido[3,4-b]indole-3-carboxylate (Z86), that belongs to β-carboline structuretype compound. This type of compounds was first derived from natural alkaloids. Selective inhibitory effects on the proliferation of colon cancer cells, and dramatically suppressed tumor growth of CRC HCT116 xenografts in vivo, both of which were mediated by inhibition of Wnt signaling. We further examined the effects of Z86 on endogenous Wnt signaling in colon cancer cell lines, SW480 (with APC deficiency)

RESULTS

DISCUSSION

Findings

MATERIALS AND METHODS