title: Isolation and characterization of adriamycin-resistant HL-60 cells which are not defective in the initial intracellular accumulation of drug.
abstract: Two human leukemia cell lines (Molt-4 and HL-60) have been used for establishing cells which exhibit a low level resistance to Adriamycin. Analysis of drug uptake patterns shows that the Molt-4 resistant cells are defective in the initial intracellular accumulation of drug. In contrast to Molt-4 the levels of drug which accumulate in the sensitive and resistant HL-60 cells during a 60-min incubation period are essentially the same. However, when incubations are continued there is a major reduction in intracellular drug levels in the resistant cell. Further studies show that resistant cells incubated in the presence of drug for extended time periods efflux drug at a rate considerably greater than that exhibited by the sensitive parent line. Similar efflux patterns are obtained with nuclei isolated from drug-sensitive and -resistant cells. Additional studies using an in vitro phosphorylation system demonstrate distinct protein changes in membranes of Molt-4 and HL-60 resistant cells. Thus, we have found that a membrane fraction from the Molt-4 resistant line contains a Mr 170,000 protein which is not detected in a similar fraction from cells sensitive to drug. HL-60 resistant membranes contain two proteins with molecular weights of 150,000 and 120,000 which are also not found in membranes from drug-sensitive cells. The results of this study suggest that drug resistance in HL-60 cells is related to an efflux mechanism which is triggered only after cells are exposed to drug for prolonged periods.
mesh_terms: D002460:Cell Line; D004247:DNA / Q000096:biosynthesis; D003630:Daunorubicin / Q000378:metabolism; D004317:Doxorubicin / Q000378:metabolism* / Q000494:pharmacology; D004351:Drug Resistance; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy / Q000378:metabolism*; D008345:Manganese / Q000494:pharmacology; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism; D010766:Phosphorylation; D012313:RNA / Q000096:biosynthesis
chemical_list: D008565:Membrane Proteins; D008345:Manganese; D012313:RNA; D004317:Doxorubicin; D004247:DNA; D003630:Daunorubicin