title: Phosphatidylinositol 3-kinase/Akt stimulates androgen pathway through GSK3beta inhibition and nuclear beta-catenin accumulation.
abstract: PI3K/Akt plays a critical role in prostate cancer cell growth and survival. Recent studies have shown that the effect of PI3K/Akt in prostate cells is mediated through androgen signaling. The PI3K inhibitor, LY294002, and a tumor suppressor, PTEN, negatively regulate the PI3K/Akt pathway and repress AR activity. However, the molecular mechanisms whereby PI3K/Akt and PTEN regulate the androgen pathway are currently unclear. Here, we demonstrate that blocking the PI3K/Akt pathway reduces the expression of an endogenous AR target gene. Moreover, we show that the repression of AR activity by LY294002 is mediated through phosphorylation and inactivation of GSK3beta, a downstream substrate of PI3K/Akt, which results in the nuclear accumulation of beta-catenin. Given the recent evidence that beta-catenin acts as a coactivator of AR, our findings suggest a novel mechanism by which PI3K/Akt modulates androgen signaling. In a PTEN-null prostate cancer cell line, we show that PTEN expression reduces beta-catenin-mediated augmentation of AR transactivation. Using the mutants of beta-catenin, we further demonstrate that the repressive effect of PTEN is mediated by a GSK3beta-regulated degradation of beta-catenin. Our results delineate a novel link among the PI3K, wnt, and androgen pathways and provide fresh insights into the mechanisms of prostate tumor development and progression.
authors.affiliation: Departments of Surgery and Genetics, Stanford University School of Medicine, R135 Edwards Building, Stanford, CA 94305-5328, USA.
authors.forename: Manju
authors.initials: M
authors.lastname: Sharma
authors.forename: William W
authors.initials: WW
authors.lastname: Chuang
authors.forename: Zijie
authors.initials: Z
authors.lastname: Sun
mesh_terms: D000728:Androgens / Q000502:physiology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors* / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism*; D002867:Chromones / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3; D006801:Humans; D008297:Male; D009025:Morpholines / Q000494:pharmacology; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D010744:Phosphoric Monoester Hydrolases / Q000502:physiology; D011471:Prostatic Neoplasms / Q000209:etiology / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000502:physiology; D051176:beta Catenin
chemical_list: D000728:Androgens; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002867:Chromones; D003598:Cytoskeletal Proteins; D038362:Glycogen Synthase Kinase 3; D009025:Morpholines; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D010744:Phosphoric Monoester Hydrolases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D015534:Trans-Activators; D025521:Tumor Suppressor Proteins; D051176:beta Catenin; C495270:CTNNB1 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494918:AKT1 protein, human; C494929:PTEN protein, human