title: [Reversal of multidrug resistance in drug-resistant human breast cancer cell line MCF-7/ADR by calmodulin antagonist O-(4-ethoxyl-butyl)-berbamine].
abstract: OBJECTIVE
  To investigate the reversal effect of O-(4-ethoxyl-butyl)-berbamine (EBB) on multidrug resistance (MDR) in MCF-7/ADR cell.
  
  
  METHODS
  3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium bromide (MTT) assay was used to assess the antitumor effect of EBB and determine the reversal effects of different concentrations ( < or = IC20) of EBB on MCF-7/ADR cell. Flow cytometry was applied to observe the intracellular accumulation of Rh123 and cell cycle in the presence of EBB. The expressions of MDR-related genes mdr 1 and topoisomerase II b (top II b) were evaluated by reverse transcription-polymerase chain reaction.
  
  
  RESULTS
  The sensitivity of MCF-7/ADR to adriamycin (ADR) was enhanced up to 50. 40, 89.80, and 14.88 folds after exposure of the cells to 3 micromol/L EBB, 7.5 micromol/L EBB, and 10 micromol/L verapamil (VPL), respectively. After 2 hours of incubation with 6 micromol/L EBB, intracellular Rh123 accumulation in MCF-7/ADR cells was increased to the level comparable to that in MCF-7 cells. When 6 micromol/L EBB was added together with 2 micromol/L ADR, MCF-7/ ADR cells showed to be arrested in the G2/M phase. The declination of mdr 1 gene expression was observed when 6 micromol/L EBB, 12 micromol/L EBB, and 10 micromol/L VPL were added for 48 hours; meanwhile, the expression of top II b mRNA showed no significant change.
  
  
  CONCLUSIONS
  EBB has a strong reversal effect on MDR in MCF-7/ ADR cell, which may be achieved by enhancing the arrestment of MCF-7/ADR cells at G2/M phase and increasing intracellular drug concentration.
authors.affiliation: National Key Laboratory of Experimental Hematology, Institute of Hematology, CAMS and PUMC, Tianjin 300020, China.
authors.forename: Yan-hong
authors.initials: YH
authors.lastname: Cheng
authors.forename: Jing
authors.initials: J
authors.lastname: Qi
authors.forename: Dong-sheng
authors.initials: DS
authors.lastname: Xiong
authors.forename: Jie-wen
authors.initials: JW
authors.lastname: Liu
authors.forename: Shu-ling
authors.initials: SL
authors.lastname: Qi
authors.forename: Bing
authors.initials: B
authors.lastname: Pan
authors.forename: Chun-zheng
authors.initials: CZ
authors.lastname: Yang
authors.forename: Hui-fang
authors.initials: HF
authors.lastname: Zhu
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000187:drug effects / Q000378:metabolism; D000970:Antineoplastic Agents / Q000493:pharmacokinetics / Q000494:pharmacology; D044182:Benzylisoquinolines / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000473:pathology*; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000493:pharmacokinetics / Q000494:pharmacology; D004347:Drug Interactions; D018432:Drug Resistance, Multiple / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D005260:Female; D006801:Humans
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D044182:Benzylisoquinolines; D002147:Calmodulin; C050387:O-(4-ethoxybutyl)berbamine; D004317:Doxorubicin