Chemical-Genetic Screen Identifies Riluzole as an Enhancer of Wnt/β-catenin Signaling in Melanoma

Abstract

SUMMARY To identify new protein and pharmacological regulators of Wnt/β-catenin signaling we used a cell-based reporter assay to screen a collection of 1857 human-experienced compounds for their ability to enhance activation of the β-catenin reporter by a low concentration of WNT3A. This identified 44 unique compounds, including the FDA-approved drug riluzole, which is presently in clinical trials for treating melanoma. We found that treating melanoma cells with riluzole in vitro enhances the ability of WNT3A to regulate gene expression, to promote pigmentation, and to decrease cell proliferation. Furthermore riluzole, like WNT3A, decreases metastases in a mouse melanoma model. Interestingly, siRNAs targeting the metabotropic glutamate receptor, GRM1, a reported indirect target of riluzole, enhance β-catenin signaling. The unexpected regulation of β-catenin signaling by both riluzole and GRM1 has implications for the future uses of this drug.

Amyotrophic Lateral Sclerosis: Role of the Canonical Wnt/Beta- Catenin Pathway and PPAR Gamma

“…Like WNT3A, riluzole decreases metastases in a mouse melanoma model. Moreover, riluzole enhances Wnt/beta-catenin signaling in the primary screen both in HT22 neuronal cells and in adult hippocampal progenitor cells [40]. As the Wnt/beta-catenin pathway is upregulated, at least in genetic ALS mice [32][33][34][35], this can partly explain poor results in trials testing riluzole in ALS as shown previously [12][13][14][15].…”

“…Importantly, riluzole has been found to be an enhancer of the Wnt/beta-catenin signaling in melanoma [40]. For the authors, treating melanoma cells with riluzole in vitro enhances the ability of WNT3A to regulate gene expression, promote pigmentation and decrease cell proliferation.…”

Dynamics and evolution of β-catenin-dependent Wnt signaling revealed through massively parallel clonogenic screening

“…While luminescent reporters (through the use of firefly luciferase as the reporter gene 17 ) remain the most sensitive readout for reporter activation, fluorescent protein-based reporters permit measurement of reporter activation in single, live cells. 18 In an attempt to reduce cell-to-cell variability to permit more sensitive measurements pooled over multiple cells, monoclonal cell lines are often employed for fluorescent reporters. 19–23 Noise from polyclonal variability can also be reduced by averaging measurements over a larger number of cells but this leads to increased reagent consumption, reduced throughput and limited dynamic range.…”

Targeting Wnt Pathways in Disease

“…In another study, a cell-based screen utilizing the BAR reporter of a chemical library of 1857 human-experienced drugs identified 44 compounds that enhanced Wnt3a-mediated stimulation (Pollock et al 2003;Namkoong et al 2007;Biechele et al 2010). One of these activators, riluzole, is an FDA-approved drug for treating amyotrophic lateral sclerosis (ALS).…”

“…One promising approach has been the use of cell-based reporter assays to screen siRNA or chemical libraries. These cell-based reporters provide a rapid, reliable, and quantitative means of interrogating Wnt/b-catenin signaling, and have been critical tools in the identification and subsequent characterization of every Wnt-modulating small molecule identified to date (Biechele and Moon 2008). Genome-wide siRNA and drug library screening approaches are powerful but have many difficulties such as uneven transfection efficiency, the knockdown efficacy of siRNA sequences, or off-target effects leading to false hits.…”