title: Over-expression of miR-451a can enhance the sensitivity of breast cancer cells to tamoxifen by regulating 14-3-3ζ, estrogen receptor α, and autophagy.
abstract: OBJECTIVE
  To investigate the effects and mechanisms of miR-451a in the tamoxifen (TAM) resistance of breast cancer cells.
  
  
  METHODS
  TAM sensitive cells (MCF-7) and resistant cells (LCC2) were employed in the study. The lentivirus vectors of Lv-miR-451a, Lv-miR-451a sponge, and Lv-miR-451a NC were employed to increase or decrease the expression of miR-451a, respectively. SiRNA to 14-3-3ζ was used to inhibit expression of 14-3-3ζ. MTT assay was utilized to detect breast cancer cell proliferation. AnnexinV-FITC binding assay was used to detect apoptosis. Expression of ERα, 14-3-3ζ and miR-451a were measured by qRT-PCR and Western blot analysis. Interactions between 14-3-3ζ and ERα were investigated by co-immunoprecipitation. LC3-II surface expression and intracellular autophagosomes were observed by Western blot and electron microscopy.
  
  
  RESULTS
  Over-expression of miR-451a can enhance MCF-7 and LCC2 cell sensitivity to TAM. Opposite effects were elicited by knocking down miR-451a. TAM treatment can up-regulate 14-3-3ζ expression, and down-regulate ERα expression. 14-3-3ζ and ERα were shown to interact. Over-expression of miR-451a decreased 14-3-3ζ expression and increased ERα expression, suppressing cell proliferation, increasing apoptosis, and reducing activation of p-AKT and p-mTOR. R18 can significantly decrease cell proliferation and increase apoptosis. R18 and 14-3-3ζ siRNA can rescue the effects of down-regulation of ERα by knocking down miR-451a. Over-expression of miR-451a inhibits autophagy, knocking-down miR-451a stimulates autophagy.
  
  
  CONCLUSIONS
  MiR-451a functions as a suppressor of resistance to TAM through regulating autophagy, the expression of 14-3-3ζ and ERα. This suggests miR-451a to be a potential target for reversing resistance to TAM.
authors.affiliation: Department of Pharmacology, West China School of Preclinical and Forensic Medicine, Sichuan University, Chengdu, Sichuan 610041, PR China.
authors.forename: Zhen-Ru
authors.initials: ZR
authors.lastname: Liu
authors.affiliation: Department of Pharmacy, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, PR China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Song
authors.affiliation: Department of Pharmacology, West China School of Preclinical and Forensic Medicine, Sichuan University, Chengdu, Sichuan 610041, PR China.
authors.forename: Li-Hong
authors.initials: LH
authors.lastname: Wan
authors.affiliation: Department of Pharmacology, West China School of Preclinical and Forensic Medicine, Sichuan University, Chengdu, Sichuan 610041, PR China. Electronic address: sarahyyzhang@hotmail.com.
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, West China School of Preclinical and Forensic Medicine, Sichuan University, Chengdu, Sichuan 610041, PR China; 985 Science and Technology Platform for Innovative Drugs, Sichuan University, Chengdu, Sichuan 610041, PR China. Electronic address: zhou1081@hotmail.com.
authors.forename: Li-Mimg
authors.initials: LM
authors.lastname: Zhou
mesh_terms: D048948:14-3-3 Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology / Q000627:therapeutic use; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D047628:Estrogen Receptor alpha / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D061986:MCF-7 Cells; D035683:MicroRNAs / Q000096:biosynthesis*; D013629:Tamoxifen / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D048948:14-3-3 Proteins; D018931:Antineoplastic Agents, Hormonal; C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; C531201:MIRN451 microRNA, human; D035683:MicroRNAs; D013629:Tamoxifen
keywords: 14-3-3ζ; Autophagy; Breast cancer; ERα; MiR-451a; Resistance; Tamoxifen