title: Homocamptothecin-daunorubicin association overcomes multidrug-resistance in breast cancer MCF7 cells.
abstract: The multidrug-resistance (MDR) status of a novel camptothecin analogue, homocamptothecin (hCPT), was investigated in human colon adenocarcinoma HT29 cells, myelogenous leukemia K562 cells and breast carcinoma MCF7 cells. The cytotoxicity of hCPT was not sensitive to the MDR status in K562 cell lines. However, its cytotoxicity was altered by MRP1, but not Pgp, in naturally MRP1-expressing HT29 cells, and etoposide- and doxorubicin-resistant MCF7/VP and MCF7/DOX cells, respectively. These cells were sensitized to hCPT in presence of MK571, probenecid but not verapamil. These results led to consider hCPT as a substrate for MRP1 and a potential modulator of MRP1 activity. The relationship between the cytotoxic effect of anthracyclines and their nuclear localization had been previously demonstrated. We show that MRPI mediated the daunorubicin (DNR) efflux in MCF7/VP and MCF7/DOX cells. The combination of sub-toxic doses of hCPT with DNR resulted in the potentiation of DNR activity, well-correlated with an increase in its nuclear accumulation in MCF7/VP cells. Simultaneous pattern was shown to provide higher cytotoxic response than sequential one. In agreement, hCPT increased also the DNR nuclear accumulation in low MRP1-expressing MCF7/DOX cells. However, the enhancement of cytotoxicity in the DNR-hCPT combination was poorly correlated with the nuclear concentration of DNR in MCF7/DOX cells. In addition to the increase in DNR accumulation, the potentiation of DNR activity by hCPT in MCF7/DOX cells implied a synergistic mechanism between both drugs. These data suggest that the present topoisomerase I/II inhibitors combination may be of clinical interest to overcome MDR phenotype in DNR-treated breast cancer patients.
authors.affiliation: Unité Médian, CNRS FRE2141, UFR Pharmacie, IFR53, Reims, France. michel.manfait@univ-riems.fr
authors.forename: David
authors.initials: D
authors.lastname: Chauvier
authors.forename: Hamid
authors.initials: H
authors.lastname: Morjani
authors.forename: Michel
authors.initials: M
authors.lastname: Manfait
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy; D000903:Antibiotics, Antineoplastic / Q000008:administration & dosage; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology* / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D002166:Camptothecin / Q000008:administration & dosage / Q000031:analogs & derivatives*; D002277:Carcinoma / Q000188:drug therapy* / Q000378:metabolism; D003110:Colonic Neoplasms / Q000188:drug therapy; D003630:Daunorubicin / Q000008:administration & dosage; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D005260:Female; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D007951:Leukemia, Myeloid / Q000188:drug therapy; D008826:Microbial Sensitivity Tests; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D016133:Polymerase Chain Reaction; D012334:RNA, Neoplasm / Q000032:analysis; D016896:Treatment Outcome; D014407:Tumor Cells, Cultured
chemical_list: D000903:Antibiotics, Antineoplastic; D002166:Camptothecin; D003630:Daunorubicin; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012334:RNA, Neoplasm; C120029:homocamptothecin; C421109:multidrug resistance-associated protein 1