Activation of the Wnt Pathway through AR79, a GSK3β Inhibitor, Promotes Prostate Cancer Growth in Soft Tissue and Bone

Abstract

Due to its bone anabolic activity, methods to increase Wnt activity, such as inhibitors of dickkopf-1 and sclerostin, are being clinically explored. Glycogen synthase kinase (GSK3β) inhibits Wnt signaling through inducing β-catenin degradation. Therefore, AR79, an inhibitor of GSK3β, is being evaluated as a bone anabolic agent. However, Wnt activation has potential to promote tumor growth. The goal of this study was to determine if AR79 impacted progression of prostate cancer (PCa). PCa tumors were established in subcutaneous and bone sites of mice followed by AR79 administration. Tumor growth, β-catenin activation, proliferation (Ki67 expression) and apoptosis (caspase 3 activity) were measured. Additionally, PCa and osteoblast cell lines were treated with AR79 and β-catenin status, proliferation (with β-catenin knocked down in some cases) and proportion of the ALDH+CD133+ stem-like cells was determined. AR79 promoted PCa growth, decreased phospho-β-catenin expression and increased total and nuclear β-catenin expression in tumors and increased tumor-induced bone remodeling. Additionally, it decreased caspase 3 and increased Ki67 expression. In addition, AR79 increased bone formation in normal mouse tibiae. AR79 inhibited β-catenin phosphorylation, increased nuclear β-catenin accumulation in PCa and osteoblast cell lines and increased proliferation of PCa cells in vitro through β-catenin. Furthermore, AR79 increased the ALDH+CD133+ cancer stem cell-like proportion of the PCa cell lines. We conclude that AR79, while being bone anabolic, promotes PCa cell growth through Wnt pathway activation.

SOX4 Is Essential for Prostate Tumorigenesis Initiated by PTEN Ablation

“…There is growing evidence that Wnt signaling is important for the progression of CPRC (35–37), with one study demonstrating nuclear β-catenin in 37% of bone metastases (37). SOX4 is important for progenitor cell differentiation and Wnt signaling (38, 39), and SOX4 interacts directly with β-catenin (13, 39).…”

Notch Pathway Inhibition Using PF-03084014, a γ-Secretase Inhibitor (GSI), Enhances the Antitumor Effect of Docetaxel in Prostate Cancer

“…The protein concentration of tumor extracts was determined using BCA Protein Assay Kit (Pierce). Target protein expression was analyzed using Western blot analysis, which was done as previously described (22), with β-actin was used as a loading control. Anti-NICD, Cyclin E, BCL-2, BCL-xl, BAK, BAX, MEK1/2, phosphor-MEK1/2( ser217/221), ERK1/2, phosphor-ERK1/2 ( T202/Y204), AKT, phosphor-AKT(ser473), PI3K, phosphor-PI3K(tyr455/199), EGFR, P52, E-cadherin, Snail, Slug, MDR1, NANOG were obtained from Cell Signaling Technology Company (Beverly, MA);β-actin from Sigma Aldrich (St Louis, MO).…”

“…Ki67 (1:500, Santa Cruz Biotechnology), Cleaved-caspase 3 (1:300, Cell Signaling Biotechnology) and CD31 (1:50, Biocare Medical) were stained as per the manufactures protocols. Sections were examined for positive staining and vessel density that was quantified as previously described (22, 23). Representative fields were photographed under 40× magnification.…”

Wnt1 and SFRP1 as potential prognostic factors and therapeutic targets in cutaneous squamous cell carcinoma

“…A number of studies conducted over the past decade have determined the crucial role of deregulation or constitutive activation of the Wnt signaling pathway in carcinogenesis and the neoplastic transformation of different forms of human cancer, including breast cancer (Holland et al, 2013), colorectal cancer (Spreafico et al, 2013), gastric cancer (Tang et al, 2013), and prostate cancer (Jiang et al, 2013). The Wnt protein family is a family of secreted glycoproteins that regulate cell proliferation, differentiation, migration, and apoptosis, therefore playing a key role in embryo development and maintenance of homeostatic balance in humans (Chang et al, 2004).…”