title: Decreased resistance to N,N-dimethylated anthracyclines in multidrug-resistant Friend erythroleukemia cells.
abstract: Doxorubicin-resistant Friend erythroleukemia cells, line F4-6 ADM2R, were selected by exposure of wild-type F4-6 cells to doxorubicin concentrations of up to 1 microgram/ml. In these cells, increased expression of multidrug resistance (MDR) genes was demonstrated by Northern blot analysis. The growth-inhibitory effect of doxorubicin, daunorubicin, N,N-dimethyldoxorubicin, N,N-dimethyldaunorubicin, morpholinodoxorubicin, and pyrromycin was comparatively investigated in resistant and wild-type cells. The doxorubicin-resistant F4-6 cells showed approx. 200-fold resistance to doxorubicin and about 100-fold resistance to daunorubicin with respect to the drug-sensitive counterpart. A dramatic decrease in resistance was observed for the N,N-dimethylated derivatives of doxorubicin and daunorubicin as well as for the N,N-dimethylated natural anthracycline pyrromycin and for morpholinodoxorubicin. Uptake studies using [14C]-daunorubicin and [14C]-N,N-dimethyldaunorubicin in resistant F4-6 cells showed a decreased accumulation of daunorubicin but no significant reduction in N,N-dimethyldaunorubicin accumulation as compared with the wild-type cells. Treatment with verapamil led to increased intracellular levels of daunorubicin in resistant cells, whereas an excess of N,N-dimethyldaunorubicin did not have this effect. Thus, the decreased resistance of the doxorubicin-resistant F4-6 cells to the N-alkylated anthracyclines may at least in part be due to a reduced affinity of these compounds for the efflux pump. The results indicate that the dimethylation of the amino group of the anthracycline sugar moiety and its incorporation within a morpholinyl ring may overcome MDR by similar mechanisms.
authors.affiliation: Department of Toxicology, University of Hamburg Medical School, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Schaefer
authors.forename: J
authors.initials: J
authors.lastname: Westendorf
authors.forename: K
authors.initials: K
authors.lastname: Lingelbach
authors.forename: C A
authors.initials: CA
authors.lastname: Schmidt
authors.forename: D L
authors.initials: DL
authors.lastname: Mihalache
authors.forename: A
authors.initials: A
authors.lastname: Reymann
authors.forename: H
authors.initials: H
authors.lastname: Marquardt
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000627:therapeutic use*; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D015152:Blotting, Northern; D002455:Cell Division / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D005622:Friend murine leukemia virus / Q000187:drug effects*; D004915:Leukemia, Erythroblastic, Acute / Q000188:drug therapy*; D012334:RNA, Neoplasm / Q000187:drug effects; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured / Q000187:drug effects*
chemical_list: D000903:Antibiotics, Antineoplastic; D000970:Antineoplastic Agents; D012334:RNA, Neoplasm