title: Separate roles for the Golgi apparatus and lysosomes in the sequestration of drugs in the multidrug-resistant human leukemic cell line HL-60.
abstract: The sequestration of drugs away from cellular target sites into cytoplasmic organelles of multidrug-resistant (MDR) cancer cells has been recently shown to be a cause for ineffective drug therapy. This process is poorly understood despite the fact that it has been observed in a large number of MDR cancer cell lines. Analysis of drug sequestration in these cells has traditionally been done using fluorescent anthracycline antibiotics (i.e. daunorubicin, doxorubicin). This narrow selection of substrates has resulted in a limited understanding of sequestration mechanisms and the intracellular compartments that are involved. To better characterize this phenotype, we chose to examine the sequestration of molecules having different acid/base properties in the MDR HL-60 human leukemic cell line. Here we show that weakly basic drug daunorubicin is sequestered into lysosomes according to a pH partitioning type mechanism, whereas sulforhodamime 101, a zwitterionic molecule, is sequestered into the Golgi apparatus through a drug transporter-mediated process. Quantitative intracellular pH measurements reveal that the lysosome-tocytosol pH gradient is expanded in the MDR line. Moreover, the MDR cells overexpress the multidrug resistance-related protein (MRP1), which is localized to the Golgi apparatus. These results demonstrate, for the first time, that two distinct mechanisms for intracellular compartmentalization are operational in a single MDR cell line.
authors.affiliation: Division of Drug Delivery and Disposition, School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
authors.forename: Yuping
authors.initials: Y
authors.lastname: Gong
authors.forename: Muralikrishna
authors.initials: M
authors.lastname: Duvvuri
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: Krise
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D001692:Biological Transport; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D019742:Chemokines, CC / Q000378:metabolism; D004396:Coloring Agents / Q000494:pharmacology; D003630:Daunorubicin / Q000378:metabolism / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D006056:Golgi Apparatus / Q000378:metabolism / Q000502:physiology*; D018922:HL-60 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D020128:Inhibitory Concentration 50; D008247:Lysosomes / Q000378:metabolism / Q000502:physiology*; D008856:Microscopy, Fluorescence; D010641:Phenotype; D012235:Rhodamines / Q000494:pharmacology
chemical_list: D000903:Antibiotics, Antineoplastic; D000970:Antineoplastic Agents; D019742:Chemokines, CC; D004396:Coloring Agents; D012235:Rhodamines; C070959:Ccl6 protein, mouse; C050829:sulforhodamine 101; D003630:Daunorubicin