title: Antiproliferative effect of the isoquinoline alkaloid papaverine in hepatocarcinoma HepG-2 cells--inhibition of telomerase and induction of senescence.
abstract: Cancer cells are often immortal through up-regulation of the hTERT gene, which encodes the catalytic subunit of a special reverse transcriptase to overcome end-replication problem of chromosomes. This study demonstrates that papaverine, an isoquinoline alkaloid from the Papaveraceae, can overcome telomerase dependent immortality of HepG-2 cells that was used as a model of hepatocarcinoma. Although this alkaloid does not directly interact with telomeric sequences, papaverine inhibits telomerase through down-regulation of hTERT, which was analysed using thermal FRET and qRT-PCR, respectively. The IC50 values for the reduction of both telomerase activity and hTERT expression was 60 µM, while IC50 for cytotoxicity was 120 µM. Repeated treatments of the cells with very low non-toxic concentrations of papaverine resulted in growth arrest and strong reduction of population doublings after 40 days. This treatment induced senescent morphology in HepG-2 cells, which was evaluated by beta-galactosidase staining. Altogether, papaverine can be regarded as a promising model compound for drug design targeting cancer development.
authors.affiliation: Department of Biology, Faculty of Science, Hakim Sabzevari University, P.O. Box 397, Sabzevar, Iran. kazemibio@gmail.com.
authors.forename: Sakineh Kazemi
authors.initials: SK
authors.lastname: Noureini
authors.affiliation: Department of Biology, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, INF 364, 69120 Heidelberg, Germany. wink@uni-hd.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Wink
mesh_terms: D000375:Aging / Q000187:drug effects; D000470:Alkaloids / Q000008:administration & dosage; D000970:Antineoplastic Agents / Q000008:administration & dosage; D017209:Apoptosis / Q000187:drug effects; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects*; D016922:Cellular Senescence / Q000187:drug effects; D056945:Hep G2 Cells; D006801:Humans; D007546:Isoquinolines / Q000008:administration & dosage; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000473:pathology; D010208:Papaverine / Q000008:administration & dosage*; D019098:Telomerase / Q000037:antagonists & inhibitors; D016615:Telomere / Q000187:drug effects / Q000378:metabolism
chemical_list: D000470:Alkaloids; D000970:Antineoplastic Agents; D007546:Isoquinolines; D010208:Papaverine; D019098:Telomerase; C039109:isoquinoline
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