title: Simvastatin-induced compartmentalisation of doxorubicin sharpens up nuclear topoisomerase II inhibition in human rhabdomyosarcoma cells.
abstract: Tumours, which are initially sensitive to cytotoxic agents, often develop resistance to a broad spectrum of structurally unrelated drugs. The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors have been shown to inhibit ATP-binding cassette (ABC) transporters but have also impact on glycosylation of such proteins. Doxorubicin is a substrate for ABC transporters like P-glycoprotein (ABCB1) which is present in human RD rhabdomyosarcoma cells. It was therefore the aim of this study to identify the compartmentalisation and action of doxorubicin in simvastatin-treated RD cells. Due to autofluorescence of doxorubicin, intracellular distribution was monitored by confocal microscopy. The biological effects were traced on the level of colony formation, caspase activation and DNA injury. Here we show that simvastatin treatment leads to ABCB1 inhibition and down-regulation of the transporter. Consequently, these cells accumulate significant amounts of doxorubicin, predominantly in the nucleus and lysosomes. While clearance of the anthracycline into lysosomes is not altered by simvastatin treatment, it significantly enhanced nuclear accumulation in a HMG-CoA reductase-independent manner. Thus, in such treated cells, topoisomerase II activity is significantly inhibited, which is further corroborated by augmented double-strand DNA breaks. Moreover, colony formation was synergistically inhibited by the combination of simvastatin and doxorubicin. Given the fact that ABCB1 expression correlates with an adverse prognosis in many tumours, adjuvant chemotherapy including statins might represent a novel therapeutic concept to overcome ABCB1-mediated multidrug resistance by direct inhibition and down-regulation.
authors.affiliation: Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Währingerstraße 13A, 1090 Vienna, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Werner
authors.forename: Bihter
authors.initials: B
authors.lastname: Atil
authors.forename: Evelyn
authors.initials: E
authors.lastname: Sieczkowski
authors.forename: Peter
authors.initials: P
authors.lastname: Chiba
authors.forename: Martin
authors.initials: M
authors.lastname: Hohenegger
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D000277:Adjuvants, Pharmaceutic / Q000008:administration & dosage*; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004317:Doxorubicin / Q000008:administration & dosage*; D006657:Histones / Q000378:metabolism; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000008:administration & dosage*; D008798:Mevalonic Acid / Q000008:administration & dosage; D012208:Rhabdomyosarcoma / Q000378:metabolism; D019821:Simvastatin / Q000008:administration & dosage*; D059005:Topoisomerase II Inhibitors / Q000008:administration & dosage*
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000277:Adjuvants, Pharmaceutic; C468783:H2AX protein, human; D006657:Histones; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D059005:Topoisomerase II Inhibitors; D004317:Doxorubicin; D019821:Simvastatin; D053148:Caspase 3; D053181:Caspase 8; D004250:DNA Topoisomerases, Type II; D008798:Mevalonic Acid
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