title: Potent inhibition of human telomerase by helenalin.
abstract: Telomerase activity is repressed in normal human somatic cells, but is activated in most cancers, suggesting that telomerase may be an important target for cancer therapy. Inhibition of telomerase in cancer cells has been shown to limit the growth of human cancer cells in culture. In this study, we report that helenalin, a natural sesquiterpene lactone, is a potent and selective inhibitor for human telomerase. In vitro studies indicate that this drug can inactivate telomerase directly in a manner that is dependent on concentration and time. The inhibitory action of this drug on telomerase is selective since the presence of excessive externally added proteins did not protect the inhibition and all of the other enzymes tested in this study were not inhibited by this drug. Furthermore, we demonstrated that helenalin can inhibit the expression of hTERT and telomerase in hematopoietic cancer cells. Therefore, the anti-tumor activity of helenalin is attributed, at least in part, to the inhibition of telomerase.
authors.affiliation: Department of Molecular and Cellular Biology, Chang Gung University, Kwei-San, Tao-Yuan 333, Taiwan, ROC.
authors.forename: Pei-Rong
authors.initials: PR
authors.lastname: Huang
authors.forename: Yuan-Ming
authors.initials: YM
authors.lastname: Yeh
authors.forename: Tzu-Chien V
authors.initials: TC
authors.lastname: Wang
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D018922:HL-60 Cells / Q000201:enzymology; D006801:Humans; D066298:In Vitro Techniques; D019169:Jurkat Cells / Q000201:enzymology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012717:Sesquiterpenes / Q000494:pharmacology*; D045789:Sesquiterpenes, Guaiane; D019098:Telomerase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D014118:Toxins, Biological
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D012717:Sesquiterpenes; D045789:Sesquiterpenes, Guaiane; D014118:Toxins, Biological; C001329:helenalin; D019098:Telomerase; D012321:DNA-Directed RNA Polymerases; D004259:DNA-Directed DNA Polymerase