Development of small molecules targeting the Wnt pathway for the treatment of colon cancer: a high-throughput screening approach

Dept. of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
AJP Gastrointestinal and Liver Physiology (Impact Factor: 3.74). 08/2010; 299(2):G293-300. DOI: 10.1152/ajpgi.00005.2010
Source: PubMed

ABSTRACT Wnt proteins play major roles in development and differentiation, and abnormalities in their regulation are believed to contribute to the formation of many cancers, including colorectal malignancies. As a result, there has been an interest in identifying small molecule inhibitors of Wnt signaling as tool compounds for research or as precursors to new generations of anticancer drugs. Advancements in robotic technology along with reductions in the costs of equipment, chemical libraries, and information handling have made high-throughput drug discovery programs possible in an academic setting. In this minireview we discuss the most plausible protein targets for inhibiting Wnt signaling in colon cancer therapy, list small molecule Wnt inhibitors that have been identified through recent drug discovery efforts, and provide our laboratory's strategy for identifying novel Wnt signaling antagonists using high-throughput screening. In particular, we summarize the results of a screen of over 1,200 drug and druglike compounds we recently completed in which niclosamide was identified as a Wnt pathway antagonist.

1 Follower
  • [Show abstract] [Hide abstract]
    ABSTRACT: Activating mutations in the Wnt signaling pathway account for the initiation of greater than 90% of all colorectal cancers and this pathway has been implicated in numerous other diseases. Therefore, identifying small molecule inhibitors of this pathway is of critical importance towards identifying clinically relevant drugs. Numerous screens have been employed to identify therapeutic reagents, but none have made it to advanced clinical trials, suggesting that traditional screening methods are ineffective at identifying clinically relevant targets. Here, we describe a novel in vivo screen to identify small molecule inhibitors of the Wnt pathway. Specifically, treatment of zebrafish embryos with LiCl inhibits GSK3 kinase function, resulting in hyperactivation of the signaling pathway and an eyeless phenotype at 1 day post fertilization. Using the small molecule XAV939, a known inhibitor of Wnt signaling, we rescued the LiCl induced eyeless phenotype, confirming efficacy of the screen. We next tested our assay with 400 known small molecule kinase inhibitors, none of which should inhibit Wnt signaling below the level of GSK3 based on their known targets. Accordingly, none of these small molecules rescued the eyeless phenotype, which demonstrates the stringency of the assay. However, several of these small molecule kinase inhibitors did generate a non-Wnt phenotype in accordance with the kinase they targeted. Therefore, combining the efficacy, sensitivity, and stringency of this preliminary screen, this model will provide an alternative to the traditional in vitro screen, generating potentially clinical relevant drugs in a rapid and cost-effective way.
    Experimental Biology and Medicine 01/2014; 239(2). DOI:10.1177/1535370213514322 · 2.23 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Basal-like breast cancers (BLBCs) are poorly differentiated and display aggressive clinical behavior. These tumors become resistant to cytotoxic agents and tumor relapse has been attributed to the presence of cancer stem cells (CSCs). One of the pathways involved in CSC regulation is the Wnt/beta-catenin signaling pathway. LRP6, a Wnt ligand receptor, is one of the critical elements of this pathway and could potentially be an excellent therapeutic target. Niclosamide has been shown to inhibit the Wnt/beta-catenin signaling pathway by causing degradation of LRP6. TRA-8, a monoclonal antibody specific to TRAIL death receptor 5, is cytotoxic to BLBC cell lines and their CSC enriched populations. The goal of this study was to examine whether niclosamide is cytotoxic to BLBCs, specifically the CSC population, and if in combination with TRA-8 could produce increased cytotoxicity. Aldehyde dehydrogenase (ALDH) is a known marker of CSCs. By testing BLBC cells for ALDH expression by flow cytometry, we were able to isolate a non-adherent population of cells that have high ALDH expression. Niclosamide showed cytotoxicity against these non-adherent ALDH expressing cells in addition to adherent cells from four BLBC cell lines: 2LMP, SUM159, HCC1187 and HCC1143. Niclosamide produced reduced levels of LRP6 and beta-catenin, which is a downstream Wnt/beta-catenin signaling protein. The combination of TRA-8 and niclosamide produced additive cytotoxicity and a reduction in Wnt/beta-catenin activity. Niclosamide in combination with TRA-8 suppressed growth of 2LMP orthotopic tumor xenografts. These results suggest that niclosamide or congeners of this agent may be useful for the treatment of BLBC.
    Molecular Cancer Therapeutics 02/2014; 13(4). DOI:10.1158/1535-7163.MCT-13-0555 · 6.11 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Wnt/β-catenin signaling plays an important role in the regulation of embryonic development and tumorigenesis. Since its deregulation results in severe human diseases, especially cancer, the Wnt signaling pathway constitutes a promising platform for pharmacological targeting of cancer. In this study we synthesized a series of imidazo[1,2-a]pyrimidines and imidazo[1,2-a]pyridines and identified some derivatives that were able to inhibit the Wnt/β-catenin signaling pathway in a luciferase reporter assay and cell proliferation in selected cancer cell lines, endowed with APC or β-catenin gene mutations. The most active compounds significantly downregulate the expression of Wnt target genes such as c-myc and cyclin D1. Further studies indicated that these compounds function independently of GSK-3β activity. More importantly, in vivo experiments, carried out on a Wnt-reporter zebrafish model indicate, in particular for compounds 4c and 4i as the most active compounds, an activity comparable to that of the reference compound IWR1, suggesting their potential use not only as small molecule inhibitors of the Wnt/β-catenin signal in Wnt driven cancers, but also in other Wnt-related diseases.
    European Journal of Medicinal Chemistry 06/2014; 83C:45-56. DOI:10.1016/j.ejmech.2014.05.071 · 3.43 Impact Factor