title: D-verapamil downmodulates P170-associated resistance to doxorubicin, daunorubicin and idarubicin.
abstract: Verapamil (VRP) is an effective modulator of P170-associated multidrug resistance (MDR), but its clinical application is limited by cardiovascular side-effects. The D-isomer of VRP (D-VRP) is 10 times less active than the racemic mixture on the cardiovascular system, but retains a MDR modulating activity. Daunorubicin (DNR) and doxorubicin (DX) are two anthracyclines whose cytotoxicity is strongly related with the expression of P170, while their respective lipophylic derivatives idarubicin (IDA) and iododoxorubicin (IDX) are less P170-dependent. We studied the effect of D-VRP on intracellular retention and on the cytotoxicity of these four anthracyclines in two MDR cell systems (LOVO and CEM) by flow cytometry and by a microcultured tetrazolium colorimetric assay (MTT). We found that in MDR cells D-VRP increased intracellular anthracycline concentration and increased the cytotoxicity of DNR, IDA and DX but not of IDX. The effect of D-VRP was dose-related, but it was already consistent at D-VRP concentrations that can be readily maintained in vivo (2-3 microM). These data suggest that at a clinically tolerable concentration D-VRP can downmodulate the resistance to DNR and DX and can restore full sensitivity to IDA.
authors.affiliation: Chair of Anatomy, Udine University School of Medicine, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Damiani
authors.forename: M
authors.initials: M
authors.lastname: Michieli
authors.forename: A
authors.initials: A
authors.lastname: Michelutti
authors.forename: C
authors.initials: C
authors.lastname: Melli
authors.forename: M
authors.initials: M
authors.lastname: Cerno
authors.forename: M
authors.initials: M
authors.lastname: Baccarani
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000230:Adenocarcinoma; D002352:Carrier Proteins / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms; D003630:Daunorubicin / Q000493:pharmacokinetics / Q000494:pharmacology*; D004317:Doxorubicin / Q000493:pharmacokinetics / Q000494:pharmacology*; D004347:Drug Interactions; D004351:Drug Resistance; D004354:Drug Screening Assays, Antitumor; D005434:Flow Cytometry; D006801:Humans; D015255:Idarubicin / Q000493:pharmacokinetics / Q000494:pharmacology*; D015459:Leukemia-Lymphoma, Adult T-Cell; D008562:Membrane Glycoproteins / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000493:pharmacokinetics / Q000494:pharmacology*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D004317:Doxorubicin; D014700:Verapamil; D015255:Idarubicin; D003630:Daunorubicin