title: Rapid up-regulation of mdr1 expression by anthracyclines in a classical multidrug-resistant cell line.
abstract: Studies were carried out in a variant human multidrug-resistant (MDR) cell line CEM/A7R, which expresses very low levels of mdr1 mRNA and P-glycoprotein (P-gp). The induction of mdr1 RNA expression by three anthracyclines, (doxorubicin, daunorubicin, epirubicin), VP-16 and two vinca alkaloids (vincristine, vinblastine) was semiquantitatively assessed by scanning Northern blots on a phosphorimager. The relative level of mdr1 expression was expressed as ratio of mdr1 to the internal RNA (actin). A significant increase (P < 0.02) in expression of mdr1 was noted within 4 hrs of exposure to 1.5 micrograms ml-1 daunorubicin or epirubicin. Neither vinblastine nor vincristine had any effect on mdr1 levels after an 8 h exposure. With increasing concentrations of daunorubicin or epirubicin in a fixed 24 h time period, mdr1 expression increased, although a biphasic response was seen. Based on MRK 16 binding, an increase in P-gp levels was seen in the CEM/A7R line after a 24 h exposure to 1 microgram ml-1 daunorubicin or epirubicin. The rapid increase in mdr1 expression after a short period of exposure to doxorubicin, daunorubicin or epirubicin suggests that induction of mdr1 expression may have an important role in the development of drug-resistant tumours.
authors.affiliation: Department of Medical Oncology, Heidelberg Repatriation Hospital, Victoria, Australia.
authors.forename: X F
authors.initials: XF
authors.lastname: Hu
authors.forename: A
authors.initials: A
authors.lastname: Slater
authors.forename: D M
authors.initials: DM
authors.lastname: Wall
authors.forename: P
authors.initials: P
authors.lastname: Kantharidis
authors.forename: J D
authors.initials: JD
authors.lastname: Parkin
authors.forename: A
authors.initials: A
authors.lastname: Cowman
authors.forename: J R
authors.initials: JR
authors.lastname: Zalcberg
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000235:genetics*; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D015152:Blotting, Northern; D003630:Daunorubicin / Q000494:pharmacology; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000235:genetics*; D015251:Epirubicin / Q000494:pharmacology; D005434:Flow Cytometry; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects*; D006801:Humans; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000187:drug effects*; D014747:Vinblastine / Q000494:pharmacology; D014750:Vincristine / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000903:Antibiotics, Antineoplastic; D012333:RNA, Messenger; D015251:Epirubicin; D014750:Vincristine; D014747:Vinblastine; D004317:Doxorubicin; D003630:Daunorubicin