title: Blocking telomerase by dietary polyphenols is a major mechanism for limiting the growth of human cancer cells in vitro and in vivo.
abstract: Animal and epidemiological studies reveal that consuming food and beverages rich in polyphenols (e.g., catechins, flavones, and antocyanines) is associated with a lower incidence of cancer, and several molecular mechanisms have been proposed for explaining this effect. However, because most of these mechanisms were observed only under specific and nonphysiological conditions, and in most cases, with practically irrelevant concentrations, there is still no clear-cut or universal explanation for the major events that underlie the anticancer effects of polyphenols. In this study we present clear in vitro and in vivo evidence that the inhibition of the cancer-associated enzyme telomerase is a key mechanism involved in cancer inhibition by epigallocatechin gallate (EGCG), a major tea polyphenol. We demonstrate that EGCG and other selected polyphenols undergo structural rearrangements at physiologically permissible conditions that result in remarkably increased telomerase inhibition. In nude mice models bearing both telomerase-dependent and -independent xenograft tumors cloned from a single human cancer progeny, only the telomerase-dependent tumors responded to prolonged oral administration of EGCG. Thus, EGCG and likely other structurally related dietary polyphenols seem to act as prodrug-like molecules that, once ingested and distributed, undergo structural changes that favor potent activity against telomerase.
authors.affiliation: Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, Kami-Ikebukuro, Toshima-ku, Tokyo 170-8455, Japan. inaasani@biocrystal.com
authors.forename: Imad
authors.initials: I
authors.lastname: Naasani
authors.forename: Fujiko
authors.initials: F
authors.lastname: Oh-Hashi
authors.forename: Tomoko
authors.initials: T
authors.lastname: Oh-Hara
authors.forename: Wan Yong
authors.initials: WY
authors.lastname: Feng
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Johnston
authors.forename: Kenneth
authors.initials: K
authors.lastname: Chan
authors.forename: Takashi
authors.initials: T
authors.lastname: Tsuruo
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D005419:Flavonoids; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D012516:Osteosarcoma / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D010636:Phenols / Q000494:pharmacology*; D011108:Polymers / Q000494:pharmacology*; D019098:Telomerase / Q000037:antagonists & inhibitors*; D014407:Tumor Cells, Cultured; D020298:U937 Cells; D023041:Xenograft Model Antitumor Assays
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D004791:Enzyme Inhibitors; D005419:Flavonoids; D010636:Phenols; D011108:Polymers; D002392:Catechin; C045651:epigallocatechin gallate; D019098:Telomerase