title: Effect of tamoxifen on mitoxantrone cytotoxicity in drug-sensitive and multidrug-resistant MCF-7 cells.
abstract: The influence of the antiestrogen tamoxifen (TAM) on the activity of mitoxantrone (MXN), was evaluated against wild-type MCF-7/WT and their multidrug-resistant variant MCF-7/ADR cells. Multidrug resistance (MDR) in this cell line which was selected for resistance to Adriamycin (ADR), is associated with increased expression of P-glycoprotein (P-gp). In a clonogenic assay it was observed that TAM (1-10 microM) significantly enhanced the activity of MXN in the MCF-7/ADR but not in the drug-sensitive cell line. Isobologram analysis indicated that the effect of the combination was additive in the parental MCF-7/WT cells and strongly synergistic in the MDR MCF-7/ADR cells. Also, TAM (10 microM) caused a three-fold increase in the steady-state levels (Css) of MXN in MCF-7/ADR cells but did not modulate MXN levels in MCF-7/WT cells. The observed synergism in MCF-7/ADR cells was perhaps due to the increase in Css of MXN that may involve interaction of TAM with P-gp. The combination of MXN and TAM may be useful in the treatment of drug-sensitive and drug-resistant breast cancer.
authors.affiliation: Division of Medicinal Chemistry and Pharmaceutics, School of Pharmacy, Northeast Louisiana University, Monroe 71209-0470, USA.
authors.forename: P B
authors.initials: PB
authors.lastname: Desai
authors.forename: R
authors.initials: R
authors.lastname: Bhardwaj
authors.forename: B
authors.initials: B
authors.lastname: Damle
mesh_terms: D001943:Breast Neoplasms / Q000188:drug therapy; D002470:Cell Survival / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D018432:Drug Resistance, Multiple; D004357:Drug Synergism; D006801:Humans; D008942:Mitoxantrone / Q000494:pharmacology*; D013629:Tamoxifen / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects*; D014410:Tumor Stem Cell Assay
chemical_list: D013629:Tamoxifen; D008942:Mitoxantrone