title: [Reversal of multidrug-resistance in human leukemia cell line K562/A02 by a cyclosporin D analogue PSC 833].
abstract: OBJECTIVE
  To explore the efficacy of PSC 833 on multidrug resistance (MDR) reversal and its mechanism.
  
  
  METHODS
  Human erythroleukemic cell line K562 and its doxorubicin-resistant counterpart K562/A02 were used in the study. Cytotoxicity was assessed by MTT assay, P-gp expression by direct immunofluorescence and mdr1 mRNA expression by reverse transcriptase polymerase chain reaction (RT-PCR) with beta-actin as internal control. Intracellular DNR retention was measured with flow cytometry.
  
  
  RESULTS
  K562/A02 cells displayed high levels of mdr1 mRNA and P-glycoprotein and reduced DNR retention compared to their parental K562 cells. 1 micromol/L of PSC 833 had no effect on the levels of mdr1 mRNA and P-gp expression in K562/A02 cells (P > 0.05). PSC 833 conferred a dose-dependent increase on chemosensitivity of K562/A02 to DNR, and its effect was at least 3-fold more potent than that of CsA or Ver. PSC 833 could increase DNR retention in K562/A02 cells. A 100.9% restoration of intracellular DNR retention of the level of K562 cells was gained by PSC 833 at 1.0 micromol/L in K562/A02 cells, whereas only a 86.9% restoration of DNR retention was obtained by CsA at 10 micromol/L in the K562/A02 cells. No effect on DNR sensitivity and retention was found in K562 cells (P > 0.05).
  
  
  CONCLUSIONS
  PSC 833 is at least 3 approximately 10 fold more potent than CsA or Ver with respect to MDR reversing activity, and it may function by inhibiting the function of P-gp and not reducing the levels of mdr1 mRNA and P-gp directly.
authors.affiliation: Department of Heamatology, The First Affiliated Hospital, Sun Yat Sen University of Medical Sciences, Guangzhou 510080, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Dai
authors.forename: Shaokai
authors.initials: S
authors.lastname: Luo
authors.forename: Aihua
authors.initials: A
authors.lastname: Yin
authors.forename: Aihua
authors.initials: A
authors.lastname: Peng
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D016572:Cyclosporine / Q000494:pharmacology; D003524:Cyclosporins / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D006801:Humans; D020014:K562 Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002121:Calcium Channel Blockers; D003524:Cyclosporins; D012333:RNA, Messenger; D016572:Cyclosporine; D014700:Verapamil; C070272:valspodar