Glycogen Synthase Kinase-3β Activity Is Required for Androgen-Stimulated Gene Expression in Prostate Cancer

• Published in: Endocrinology (Philadelphia) Vol. 145; no. 6; pp. 2941 - 2949
• Main Authors: Liao, Xinbo, Thrasher, J. Brantley, Holzbeierlein, Jeffery, Stanley, Scott, Li, Benyi
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Endocrine Society 01.06.2004
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Vertebrates: endocrinology; Androgen; Glycogen synthase kinase-3β; Malignant tumor; Sex steroid hormone; Gene expression; Urogenital system; Prostate
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/en.2003-1519

Despite the specificity inferred by its name, glycogen synthase kinase (GSK)-3β is an important kinase with a plethora of significant cellular targets, including cytoskeletal proteins and transcription factors, and its activity is regulated by phosphorylation on tyrosine/serine residues. As part of our efforts to dissect the molecular basis responsible for androgen-independent progression of prostate cancer, we investigated the role of GSK-3β in androgen-stimulated gene expression in human prostate cancer cells. Pretreatment of prostate cancer cells harboring wild-type or mutant androgen receptor with the GSK-3β inhibitors, lithium chloride (LiCl), RO318220, or GF109203X, inhibited R1881-stimulated androgen-responsive reporter activity in a dose- and time-dependent manner. In addition, the expression of two endogenous androgen-stimulated gene products, prostate-specific antigen and matrix metalloproteinase-2, was suppressed by the GSK-3β inhibitors in those cells. Most importantly, knocking down GSK-3β expression via a small interference RNA-mediated gene silencing approach also reduced R1881-stimulated gene expression, demonstrating the specificity of GSK-3β involvement. Moreover, R1881 treatment of the cells increased phosphorylation status of GSK-3β on tyrosine residue Y216 but not on serine residue S9. Pretreatment of the cells with phosphatidylinositol 3-kinase inhibitor LY294002 or wortmannin, which blocks androgen action in cells, abolished R1881-induced GSK-3β Y216 phosphorylation. However, the phosphatidylinositol 3kinase or GSK-3β inhibitors did not block R1881-induced nuclear translocation of androgen receptor. Finally, knocking down the expression of Akt or β-catenin, the two GSK-3β-related signaling molecules, via siRNA-mediated gene silencing did not significant affect R1881-stimulated gene expression. These findings suggest that GSK-3β activity is required for androgen-stimulated gene expression in prostate cancer cells.