title: Arsenic trioxide in the mechanism of drug resistance reversal in MCF-7/ADM cell line of human breast cancer.
abstract: OBJECTIVE
  To investigate the effect of drug resistance by arsenic trioxide (As(2)O(3)) and its possible mechanism in human breast cancer cell line MCF-7/ADM.
  
  
  METHODS
  Cytotoxicity of As(2)O(3) and the sensibility to adriamycin (ADM) in MCF-7/ADM cell line, a ADM-resistance cell line of human breast cancer, were studied through MTT assay. The concentration of intracellular ADM was detected by spectrofluorometry. With MCF-7/ADM cells treated with As(2)O(3) in combination with ADM, the glutathione-s-transferase (GST) activity was measured by biochemical method. The expression of GST-pi mRNA was assessed by RT-PCR.
  
  
  RESULTS
  The non-cytotoxic dose of As(2)O(3) was 0.2 micro mol/L and the low cytotoxic dose was 0.8 micro mol/L to MCF-7/ADM cell line. 0.2 micro mol/L As(2)O(3) could significantly increase the intracellular accumulation of ADM in MCF-7/ADM cell line (P < 0.05). The medium inhibition concentration (IC(50)) was obviously reduced from 53.74 micro mol/L to 25.0 micro mol/L, with a reversal ratio of 2.1 as compared to its parental cell line. Before and after 0.2 micro mol/L, 0.8 micro mol/L As(2)O(3) were given, GST activities were decreased from 29.68 +/- 0.29 U/ml to 19.29 +/- 2.10 U/m l and 12.66 +/- 2.78 U/ml (P < 0.05). In addition, MCF-7/ADM cell line had overexpression of GST-pi mRNA. A significant down regulation of GST-pi mRNA was observed in MCF-7/ADM cells when As(2)O(3) and ADM (21.55 micro mol/L) were given for 24 hours.
  
  
  CONCLUSIONS
  As(2)O(3) is able to enhance the cytotoxicity of ADM and partly reverse the ADM resistance of MCF-7/ADM cell line of human breast cancer, which may be related to the variation of GST-pi enzyme.
authors.affiliation: Department of Histoembryology, Dalian Medical University, Dalian 116027, China.
authors.forename: Xiuli
authors.initials: X
authors.lastname: Wang
authors.forename: Li
authors.initials: L
authors.lastname: Kong
authors.forename: Jinyao
authors.initials: J
authors.lastname: Zhao
authors.forename: Peiman
authors.initials: P
authors.lastname: Yang
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology*; D001943:Breast Neoplasms; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000494:pharmacology*; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D005260:Female; D015870:Gene Expression; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase / Q000235:genetics; D006801:Humans; D007527:Isoenzymes / Q000235:genetics; D010087:Oxides / Q000494:pharmacology*; D012333:RNA, Messenger; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D001152:Arsenicals; D007527:Isoenzymes; D010087:Oxides; D012333:RNA, Messenger; D004317:Doxorubicin; C496556:GSTP1 protein, human; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase; D000077237:Arsenic Trioxide