flavokawain-a and Prostatic-Neoplasms

Flavokawain A (FKA), a major chalcone in kava extracts, has exhibited anti-proliferative and apoptotic effects in the prostate cancer. However, the molecular mechanism of FKA remains unclear. In this study, FKA induces cell apoptosis and cell cycle arrest in a G2M phase to prostate cancer cells. FKA interferes with tubulin polymerization and inhibits survivin expression in PC3 cells. Molecular docking simulation experiment finds that FKA can bind to colchicine binding sites that inhibit tubulin polymerization. FKA treatment regulates the glutamine metabolism pathway in PC3 cells by reducing intracellular glutamine, glutamic and proline. FKA treatment also decreases the GSH content by decreasing the activity of GSH synthetase (GSS) and increasing the activity of glutathione thiol transferase (GSTP1), which subsequently induces ROS production and PC3 cell apoptosis.

Topics: Apoptosis; Binding Sites; Chalcone; Drug Screening Assays, Antitumor; G2 Phase Cell Cycle Checkpoints; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Glutamine; Glutathione; Glutathione S-Transferase pi; Glutathione Synthase; Humans; Male; Metabolic Networks and Pathways; Metabolomics; Molecular Docking Simulation; PC-3 Cells; Prostate; Prostatic Neoplasms; Reactive Oxygen Species; Tubulin

S phase kinase-associated protein 2 (Skp2) has been shown to be required for spontaneous tumor development that occurs in the retinoblastoma protein (pRb) deficient mice. Here we have demonstrated that flavokawain A (FKA), a novel chalcone from the kava plant, selectively inhibited the growth of pRb deficient cell lines and resulted in a proteasome-dependent and ubiquitination-mediated Skp2 degradation. Degradation of Skp2 by FKA was found to be involved in a functional Cullin1, but independent of Cdh1 expression. Further studies have demonstrated that FKA docked into the ATP binding pocket of the precursor cell-expressed developmentally down-regulated 8 (NEDD8)-activating enzyme (NAE) complex, inhibited NEDD8 conjugations to both Cullin1 and Ubc12 in PC3 cells and Ubc12 NEDDylation in an in vitro assay. Finally, dietary feeding of the autochthonous transgenic adenocarcinoma of the mouse prostate (TRAMP) mice with FKA inhibited the formation of high-grade prostatic intra-epithelial neoplasia lesions (HG-PIN) and prostate adenocarcinomas, reduced the tumor burden and completely abolished distant organ metastasis. Immunohistochemistry studies revealed that dietary FKA feeding resulted in marked anti-proliferative and apoptotic effects via down-regulation of Skp2 and NEDD8 and up-regulation of p27/Kip1 in the prostate of TRAMP mice. Our findings therefore provide evidence that FKA is a promising NEDDylation inhibitor for targeting Skp2 degradation in prostate cancer prevention and treatment.

Topics: Adenocarcinoma; Animals; Anticarcinogenic Agents; Apoptosis; Carcinogenesis; Cell Line, Tumor; Cell Proliferation; Chalcone; Cullin Proteins; Disease Models, Animal; Dose-Response Relationship, Drug; Genetic Predisposition to Disease; Humans; Male; Mice, Inbred C57BL; Mice, Transgenic; Molecular Docking Simulation; NEDD8 Protein; Phenotype; Prostatic Neoplasms; Proteasome Endopeptidase Complex; Protein Binding; Protein Processing, Post-Translational; Proteolysis; Retinoblastoma Protein; S-Phase Kinase-Associated Proteins; Time Factors; Transfection; Ubiquitin-Conjugating Enzymes; Ubiquitination; Ubiquitins