title: [miR-34a may regulate sensitivity of breast cancer cells to adriamycin via targeting Notch1].
abstract: OBJECTIVE
  To explore the influence of miR-34a on Notch1 expression in breast cancer cells, and to explore the role of miR-34a in the sensitivity of breast cancer cells to Adriamycin (ADR).
  
  
  METHODS
  The expression of miR-34a in MCF-7 and MCF-7/ADR cells were detected by real-time fluorescence quantitative PCR. Cells were transfected with miR-34a mimics or inhibitor using Lipofectamine 2000. Expression of Notch1 in the two groups before and after transfection was detected by real-time fluorescence quantitative PCR and Western blot. MTT test and apoptosis assay were performed to observe the impact of miR-34a expression on the sensitivity of breast cancer cells to ADR. Statistical analysis of the results was conducted using SPSS 16.0 software. The experiment was repeated independently for at least three times, and had a good reproducibility. The data were shown as mean ± standard deviation. The analysis of variance between groups used one-way ANOVA test. Correlation between groups was analyzed using Spearman rank test. P < 0.05 was considered statistically significant.
  
  
  RESULTS
  Compared with the control MCF-7 cells, the relative expression level of miR-34a in MCF-7/ADR cells was significantly decreased to 0.02 (P < 0.05). In the MCF-7 ADR-resistant cells, Notch1 mRNA expression was increased compared with that in the MCF-7 ADR-sensitive cells (2.10 ± 0.20-fold, P < 0.05). The expression levels of Notch1 mRNA and protein in MCF-7/ADR cells transfected with miR-34a mimics were significantly up-regulated. On the contrary, the expressions of Notch1 mRNA and protein in MCF-7 cells transfected with miR-34a inhibitor were down-regulated. The IC50 value of ADR in the control MCF-7/ADR cells and cells transfected with miR-34a mimics was (116.33 ± 16.80) and (39.28 ± 4.12) µmol/L, respectively (P < 0.05). The IC50 value of ADR in control MCF-7 cells and cells transfected with miR-34a inhibitor was (0.29 ± 0.21) and (0.51 ± 0.03) µmol/L, respectively (P < 0.05). Further, overexpression of miR-34a significantly enhanced apoptosis in the ADR-treated MCF-7/ADR cells, and miR-34a inhibitor reduced apoptosis in the ADR-treated MCF-7 cells.
  
  
  CONCLUSIONS
  miR-34a negatively regulates the expression of Notch1 at both mRNA and protein levels. Overexpression of miR-34a may sensitize MCF-7/ADR cells to adriamycin.
authors.affiliation: Department of General Surgery, Jiangsu Cancer Hospital, Nanjing 210009, China.
authors.forename: Xiujuan
authors.initials: X
authors.lastname: Li
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Email: lxj221356@126.com.
authors.forename: Jinhai
authors.initials: J
authors.lastname: Tang
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis; D001943:Breast Neoplasms; D015536:Down-Regulation; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D006801:Humans; D061986:MCF-7 Cells; D035683:MicroRNAs / Q000378:metabolism*; D051881:Receptor, Notch1 / Q000378:metabolism*; D015203:Reproducibility of Results
chemical_list: D000903:Antibiotics, Antineoplastic; D035683:MicroRNAs; D051881:Receptor, Notch1; D004317:Doxorubicin