Synergism of energy starvation and dextran-conjugated doxorubicin in the killing of multidrug-resistant KB carcinoma cells.
Here we report that 2-deoxyglucose/Na azide treatment and free/conjugated doxorubicin are synergistic in cell killing. As demonstrated by fluorescence confocal microscopy, KB-V1 cells retained more conjugated doxorubicin than free doxorubicin. Verapamil or 2-deoxyglucose/Na azide enhanced only the retention of the free drug and the small (<70 kDa) conjugates, indicating that P-glycoprotein (P-gp) is not effective against large conjugates. Conjugated doxorubicin was excluded from nuclei. Initially both free and conjugated doxorubicin accumulated in cytoplasmic organelles. Upon 2-deoxyglucose/Na azide treatment, fluorescence labeling of organelles dissipated. Prolonged (24 h) incubation of conjugate-preloaded cells resulted in redistribution of some of the organelle-associated fluorescence to nuclei, suggesting decoupling. The appearance of free doxorubicin was confirmed by capillary electrophoresis. 2-Deoxyglucose/Na azide treatment also retarded decoupling. Our results suggest that energy starvation, in addition to increasing cellular retention of P-gp substrates, may affect cellular fate of conjugated drugs with a possible enhancing effect in cancer cell killing.
Lam
W
W
Department of Biology and Chemistry, City University of Hong Kong, Kowloon.
Chan
H
H
Yang
M
M
Cheng
S
S
Fong
W
W
D000970:Antineoplastic Agents / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003078:Colchicine / Q000494:pharmacology; D003847:Deoxyglucose / Q000494:pharmacology; D003911:Dextrans / Q000494:pharmacology*; D004317:Doxorubicin / Q000378:metabolism / Q000494:pharmacology*; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D004734:Energy Metabolism; D006801:Humans; D007624:KB Cells / Q000187:drug effects* / Q000378:metabolism; D019810:Sodium Azide / Q000494:pharmacology; D013347:Subcellular Fractions; D014407:Tumor Cells, Cultured; D014747:Vinblastine / Q000494:pharmacology
D000970:Antineoplastic Agents; D003911:Dextrans; D014747:Vinblastine; D004317:Doxorubicin; D019810:Sodium Azide; D003847:Deoxyglucose; D003078:Colchicine