title: Molecular pathway for (-)-epigallocatechin-3-gallate-induced cell cycle arrest and apoptosis of human prostate carcinoma cells.
abstract: Epigallocatechin-3-gallate (EGCG), the major polyphenolic constituent present in green tea, is a promising chemopreventive agent. We recently showed that green tea polyphenols exert remarkable preventive effects against prostate cancer in a mouse model and many of these effects are mediated by the ability of polyphenols to induce apoptosis in cancer cells [Proc. Natl. Acad. Sci. USA 98 (2001) 10350]. Earlier, we showed that EGCG causes a G0/G1 phase cell cycle arrest and apoptosis of both androgen-sensitive LNCaP and androgen-insensitive DU145 human prostate carcinoma cells, irrespective of p53 status [Toxicol. Appl. Pharmacol. 164 (2000) 82]. Here, we provide molecular understanding of this effect. We tested a hypothesis that EGCG-mediated cell cycle dysregulation and apoptosis is mediated via modulation of cyclin kinase inhibitor (cki)-cyclin-cyclin-dependent kinase (cdk) machinery. As shown by immunoblot analysis, EGCG treatment of LNCaP and DU145 cells resulted in significant dose- and time-dependent (i) upregulation of the protein expression of WAF1/p21, KIP1/p27, INK4a/p16, and INK4c/p18, (ii) down-modulation of the protein expression of cyclin D1, cyclin E, cdk2, cdk4, and cdk6, but not of cyclin D2, (iii) increase in the binding of cyclin D1 toward WAF1/p21 and KIP1/p27, and (iv) decrease in the binding of cyclin E toward cdk2. Taken together, our results suggest that EGCG causes an induction of G1 phase ckis, which inhibits the cyclin-cdk complexes operative in the G0/G1 phase of the cell cycle, thereby causing an arrest, which may be an irreversible process ultimately leading to apoptotic cell death. This is the first systematic study showing the involvement of each component of cdk inhibitor-cyclin-cdk machinery during cell cycle arrest and apoptosis of human prostate carcinoma cells by EGCG.
authors.affiliation: Department of Urology, Jim & Eillen Dicke Research Laboratory, Case Western Reserve University, The Research Institute of University Hospitals of Cleveland, Cleveland, OH 44106, USA.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Gupta
authors.forename: Tajamul
authors.initials: T
authors.lastname: Hussain
authors.forename: Hasan
authors.initials: H
authors.lastname: Mukhtar
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002277:Carcinoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects* / Q000502:physiology; D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000187:drug effects / Q000378:metabolism; D050763:Cyclin-Dependent Kinase Inhibitor p18; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000187:drug effects / Q000378:metabolism; D016213:Cyclins / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000378:metabolism; D016193:G1 Phase / Q000187:drug effects; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D015398:Signal Transduction; D025521:Tumor Suppressor Proteins / Q000187:drug effects / Q000378:metabolism
chemical_list: D000972:Antineoplastic Agents, Phytogenic; C493956:CDKN1A protein, human; C436291:CDKN1B protein, human; C493971:CDKN2C protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050763:Cyclin-Dependent Kinase Inhibitor p18; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D002392:Catechin; C045651:epigallocatechin gallate; D018844:Cyclin-Dependent Kinases