title: Circumvention of the multidrug-resistance protein (MRP-1) by an antitumor drug through specific inhibition of gene transcription in breast tumor cells.
abstract: Multidrug-resistance protein 1 (MRP-1) confers resistance to a number of clinically important chemotherapeutic agents. The promoter of the mrp-1 gene contains an Sp1-binding site, which we targeted using the antitumor bis-anthracycline WP631. When MCF-7/VP breast cancer cells, which overexpress MRP-1 protein, were incubated with WP631 the expression of the multidrug-resistance protein gene decreased. Conversely, doxorubicin did not alter mrp-1 gene expression. The inhibition of gene expression was followed by a decrease in the activity of the MRP-1 protein. The IC(75) for WP631 (drug concentration required to inhibit cell growth by 75%) circumvented the drug-efflux pump, without addition of resistant modifiers. After treatment with WP631, MCF-7/VP cells were committed to die after entering mitosis (mitotic catastrophe), while treatment with doxorubicin did not affect cell growth. This is the first report on an antitumor drug molecule inhibiting the mrp-1 gene directly, rather than being simply a poor substrate for the transporter-mediated efflux. However, both situations appeared to coexist, thereby a superior cytotoxic effect was attained. Ours results suggest that WP631 offers great potential for the clinical treatment of tumors displaying a multidrug-resistance phenotype.
authors.affiliation: Instituto de Biología Molecular de Barcelona, CSIC, Parc Cientific de Barcelona, Josep Samitier 1-5, E-08028 Barcelona, Spain.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Mansilla
authors.forename: Marta
authors.initials: M
authors.lastname: Rojas
authors.forename: Marc
authors.initials: M
authors.lastname: Bataller
authors.forename: Waldemar
authors.initials: W
authors.lastname: Priebe
authors.forename: José
authors.initials: J
authors.lastname: Portugal
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000473:pathology*; D015536:Down-Regulation; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D014158:Transcription, Genetic / Q000187:drug effects*; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D004317:Doxorubicin