title: Reversal effect of bufalin on multidrug resistance in K562/VCR vincristine-resistant leukemia cell line.
abstract: OBJECTIVE
  To probe insights into the reversal effect of bufalin on vincristine-acquired multidrug resistance (MDR) in human leukemia cell line K562/VCR.
  
  
  METHODS
  Proliferative inhibition rate and the reversal index (RI) of bufalin were determined by Methyl thiazolyl tetrazolium assay. The uptake of Adriamycin (ADM) in K562/VCR cells, cell cycle and apoptosis rate were determined by flow cytometry (FCM). Cell morphologic changes were observed with Wright-Giemsa staining. The expression of P-glycoprotein (P-gp), multidrug-associated protein-1 (MRP1), Bcl-xL and Bax protein were measured by immunocytochemistry.
  
  
  RESULTS
  The human leukemia multidrug resistant K562/VCR cells showed no cross-resistance to bufalin. The RIs of bufalin at concentrations of 0.0002, 0.001 and 0.005 μmol/L were 4.85, 6.94 and 14.77, respectively. Preincubation of 0.001 μmol/L bufalin for 2 h could increase intracellular ADM fluorescence intensity to 28.07% (P < 0.05) and down-regulate MRP1 expression simultaneously, but no remarkable effect was found on P-gp protein. Cell cycle analysis indicated increased apoptosis rate and apparent decreased G2/M phase proportion after treatment with bufalin. When exposed to 0.01 μmol/L bufalin, typical morphological changes of apoptosis could be observed. Down-regulation of Bcl-xL and up-regulation of Bax expression in K562/VCR cells could be detected by immunocytochemistry.
  
  
  CONCLUSIONS
  Bufalin could partly reverse the MDR of K562/VCR cells, with a possible mechanism of down-regulating MRP1 expression and activating apoptosis pathway by altering Bcl-xL/Bax ratio.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Zhai
authors.forename: Jianying
authors.initials: J
authors.lastname: Lu
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.forename: Fanfu
authors.initials: F
authors.lastname: Fang
authors.forename: Bai
authors.initials: B
authors.lastname: Li
authors.forename: Wei
authors.initials: W
authors.lastname: Gu
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics / Q000378:metabolism; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D002018:Bufanolides / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D006801:Humans; D020014:K562 Cells; D007938:Leukemia / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D014750:Vincristine / Q000494:pharmacology*; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002018:Bufanolides; D051028:bcl-2-Associated X Protein; D014750:Vincristine; C022777:bufalin