title: Black tea polyphenols inhibit tumor proteasome activity.
abstract: Tea is a widely consumed beverage and its constituent polyphenols have been associated with potential health benefits. Although black tea polyphenols have been reported to possess potent anticancer activities, the effect of its polyphenols, theaflavins on the tumor's cellular proteasome function, an important biological target in cancer prevention, has not been carefully studied. Here black tea extract (T5550) enriched in theaflavins inhibited the chymotrypsin-like (CT) activity of the proteasome and proliferation of human multiple myeloma cells in a dose-dependent manner. Also an isolated theaflavin (TF-1) can bind to, and inhibit the purified 20S proteasome, accompanied by suppression of tumor cell proliferation, suggesting that the tumor proteasome is an important target whose inhibition is at least partially responsible for the anticancer effects of black tea.
authors.affiliation: The Developmental Therapeutics Program, Barbara Ann Karmanos Cancer Institute and Department of Oncology, School of Medicine, Wayne State University, Detroit, MI 48201-2013, USA.
authors.forename: Taskeen
authors.initials: T
authors.lastname: Mujtaba
authors.forename: Q Ping
authors.initials: QP
authors.lastname: Dou
mesh_terms: D016588:Anticarcinogenic Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D044946:Biflavonoids / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D002392:Catechin / Q000031:analogs & derivatives / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D003198:Computer Simulation; D004354:Drug Screening Assays, Antitumor; D005285:Fermentation; D005656:Fungal Proteins / Q000037:antagonists & inhibitors; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D006801:Humans; D008958:Models, Molecular; D015394:Molecular Structure; D009101:Multiple Myeloma / Q000201:enzymology / Q000473:pathology*; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors*; D010936:Plant Extracts / Q000494:pharmacology; D018515:Plant Leaves / Q000737:chemistry; D059808:Polyphenols / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D011480:Protease Inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D061988:Proteasome Inhibitors; D021122:Protein Subunits; D013662:Tea / Q000737:chemistry*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology; D015003:Yeasts / Q000201:enzymology
chemical_list: D016588:Anticarcinogenic Agents; D044946:Biflavonoids; D005656:Fungal Proteins; D009363:Neoplasm Proteins; D010936:Plant Extracts; D059808:Polyphenols; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D021122:Protein Subunits; D013662:Tea; C056068:theaflavin; C088983:theaflavine gallate; C077197:theaflavin digallate; D005707:Gallic Acid; D002392:Catechin; C045651:epigallocatechin gallate